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1 | # Common Trace Format (CTF) Specification (v1.8.2) |
2 | ||
3 | **Author**: Mathieu Desnoyers, [EfficiOS Inc.](http://www.efficios.com/) | |
4 | ||
5 | The goal of the present document is to specify a trace format that suits | |
6 | the needs of the embedded, telecom, high-performance and kernel | |
7 | communities. It is based on the | |
8 | [Common Trace Format Requirements (v1.4)](http://git.efficios.com/?p=ctf.git;a=blob_plain;f=common-trace-format-reqs.txt;hb=master) | |
9 | document. It is designed to allow traces to be natively generated by the | |
10 | Linux kernel, Linux user space applications written in C/C++, and | |
11 | hardware components. One major element of CTF is the Trace Stream | |
12 | Description Language (TSDL) which flexibility enables description of | |
13 | various binary trace stream layouts. | |
14 | ||
15 | The latest version of this document can be found at: | |
16 | ||
17 | * Git: `git clone git://git.efficios.com/ctf.git` | |
18 | * [Gitweb](http://git.efficios.com/?p=ctf.git) | |
19 | ||
20 | A reference implementation of a library to read and write this trace | |
21 | format is being implemented within the | |
22 | [Babeltrace](http://www.efficios.com/babeltrace) project, a converter | |
23 | between trace formats. The development tree is available at: | |
24 | ||
25 | * Git: `git clone git://git.efficios.com/babeltrace.git` | |
26 | * [Gitweb](http://git.efficios.com/?p=babeltrace.git) | |
27 | ||
28 | The [CE Workgroup](http://www.linuxfoundation.org/collaborate/workgroups/celf) | |
29 | of the Linux Foundation, [Ericsson](http://www.ericsson.com/), and | |
30 | [EfficiOS](http://www.efficios.com/) have sponsored this work. | |
31 | ||
32 | **Contents**: | |
33 | ||
34 | 1. Preliminary definitions | |
35 | 2. High-level representation of a trace | |
36 | 3. Event stream | |
37 | 4. Types | |
38 | 4.1 Basic types | |
39 | 4.1.1 Type inheritance | |
40 | 4.1.2 Alignment | |
41 | 4.1.3 Byte order | |
42 | 4.1.4 Size | |
43 | 4.1.5 Integers | |
44 | 4.1.6 GNU/C bitfields | |
45 | 4.1.7 Floating point | |
46 | 4.1.8 Enumerations | |
47 | 4.2 Compound types | |
48 | 4.2.1 Structures | |
49 | 4.2.2 Variants (discriminated/tagged unions) | |
50 | 4.2.3 Arrays | |
51 | 4.2.4 Sequences | |
52 | 4.2.5 Strings | |
53 | 5. Event packet header | |
54 | 5.1 Event packet header description | |
55 | 5.2 Event packet context description | |
56 | 6. Event structure | |
57 | 6.1 Event header | |
58 | 6.1.1 Type 1: few event IDs | |
59 | 6.1.2 Type 2: many event IDs | |
60 | 6.2 Stream event context and event context | |
61 | 6.3 Event payload | |
62 | 6.3.1 Padding | |
63 | 6.3.2 Alignment | |
64 | 7. Trace Stream Description Language (TSDL) | |
65 | 7.1 Metadata | |
66 | 7.2 Declaration vs definition | |
67 | 7.3 TSDL scopes | |
68 | 7.3.1 Lexical scope | |
69 | 7.3.2 Static and dynamic scopes | |
70 | 7.4 TSDL examples | |
71 | 8. Clocks | |
72 | A. Helper macros | |
73 | B. Stream header rationale | |
74 | C. TSDL Grammar | |
75 | C.1 Lexical grammar | |
76 | C.1.1 Lexical elements | |
77 | C.1.2 Keywords | |
78 | C.1.3 Identifiers | |
79 | C.1.4 Universal character names | |
80 | C.1.5 Constants | |
81 | C.1.6 String literals | |
82 | C.1.7 Punctuators | |
83 | C.2 Phrase structure grammar | |
84 | C.2.2 Declarations: | |
85 | C.2.3 CTF-specific declarations | |
86 | ||
87 | ||
88 | ## 1. Preliminary definitions | |
89 | ||
90 | * **Event trace**: an ordered sequence of events. | |
91 | * **Event stream**: an ordered sequence of events, containing a | |
92 | subset of the trace event types. | |
93 | * **Event packet**: a sequence of physically contiguous events within | |
94 | an event stream. | |
95 | * **Event**: this is the basic entry in a trace. Also known as | |
96 | a _trace record_. | |
97 | * An **event identifier** (ID) relates to the class (a type) of | |
98 | event within an event stream, e.g. event `irq_entry`. | |
99 | * An **event** (or event record) relates to a specific instance of | |
100 | an event class, e.g. event `irq_entry`, at time _X_, on CPU _Y_. | |
101 | * Source architecture: architecture writing the trace. | |
102 | * Reader architecture: architecture reading the trace. | |
103 | ||
104 | ||
105 | ## 2. High-level representation of a trace | |
106 | ||
107 | A _trace_ is divided into multiple event streams. Each event stream | |
108 | contains a subset of the trace event types. | |
109 | ||
110 | The final output of the trace, after its generation and optional | |
111 | transport over the network, is expected to be either on permanent or | |
112 | temporary storage in a virtual file system. Because each event stream | |
113 | is appended to while a trace is being recorded, each is associated with | |
114 | a distinct set of files for output. Therefore, a stored trace can be | |
115 | represented as a directory containing zero, one or more files | |
116 | per stream. | |
117 | ||
118 | Metadata description associated with the trace contains information on | |
119 | trace event types expressed in the _Trace Stream Description Language_ | |
120 | (TSDL). This language describes: | |
121 | ||
122 | * Trace version | |
123 | * Types available | |
124 | * Per-trace event header description | |
125 | * Per-stream event header description | |
126 | * Per-stream event context description | |
127 | * Per-event | |
128 | * Event type to stream mapping | |
129 | * Event type to name mapping | |
130 | * Event type to ID mapping | |
131 | * Event context description | |
132 | * Event fields description | |
133 | ||
134 | ||
135 | ## 3. Event stream | |
136 | ||
137 | An _event stream_ can be divided into contiguous event packets of | |
138 | variable size. An event packet can contain a certain amount of padding | |
139 | at the end. The stream header is repeated at the beginning of each | |
140 | event packet. The rationale for the event stream design choices is | |
141 | explained in [Stream header rationale](#specB). | |
142 | ||
143 | The event stream header will therefore be referred to as the | |
144 | _event packet header_ throughout the rest of this document. | |
145 | ||
146 | ||
147 | ## 4. Types | |
148 | ||
149 | Types are organized as type classes. Each type class belong to either | |
150 | of two kind of types: _basic types_ or _compound types_. | |
151 | ||
152 | ||
153 | ### 4.1 Basic types | |
154 | ||
155 | A basic type is a scalar type, as described in this section. It | |
156 | includes integers, GNU/C bitfields, enumerations, and floating | |
157 | point values. | |
158 | ||
159 | ||
160 | #### 4.1.1 Type inheritance | |
161 | ||
162 | Type specifications can be inherited to allow deriving types from a | |
163 | type class. For example, see the uint32_t named type derived from the | |
164 | [_integer_ type](#spec4.1.5) class. Types have a precise binary | |
165 | representation in the trace. A type class has methods to read and write | |
166 | these types, but must be derived into a type to be usable in an event | |
167 | field. | |
168 | ||
169 | ||
170 | #### 4.1.2 Alignment | |
171 | ||
172 | We define _byte-packed_ types as aligned on the byte size, namely 8-bit. | |
173 | We define _bit-packed_ types as following on the next bit, as defined | |
174 | by the [Integers](#spec4.1.5) section. | |
175 | ||
176 | Each basic type must specify its alignment, in bits. Examples of | |
177 | possible alignments are: bit-packed (`align = 1`), byte-packed | |
178 | (`align = 8`), or word-aligned (e.g. `align = 32` or `align = 64`). | |
179 | The choice depends on the architecture preference and compactness vs | |
180 | performance trade-offs of the implementation. Architectures providing | |
181 | fast unaligned write byte-packed basic types to save space, aligning | |
182 | each type on byte boundaries (8-bit). Architectures with slow unaligned | |
183 | writes align types on specific alignment values. If no specific | |
184 | alignment is declared for a type, it is assumed to be bit-packed for | |
185 | integers with size not multiple of 8 bits and for gcc bitfields. All | |
186 | other basic types are byte-packed by default. It is however recommended | |
187 | to always specify the alignment explicitly. Alignment values must be | |
188 | power of two. Compound types are aligned as specified in their | |
189 | individual specification. | |
190 | ||
191 | The base offset used for field alignment is the start of the packet | |
192 | containing the field. For instance, a field aligned on 32-bit needs to | |
193 | be at an offset multiple of 32-bit from the start of the packet that | |
194 | contains it. | |
195 | ||
196 | TSDL metadata attribute representation of a specific alignment: | |
197 | ||
198 | ~~~ tsdl | |
199 | align = /* value in bits */; | |
200 | ~~~ | |
201 | ||
202 | #### 4.1.3 Byte order | |
203 | ||
204 | By default, byte order of a basic type is the byte order described in | |
205 | the trace description. It can be overridden by specifying a | |
206 | `byte_order` attribute for a basic type. Typical use-case is to specify | |
207 | the network byte order (big endian: `be`) to save data captured from | |
208 | the network into the trace without conversion. | |
209 | ||
210 | TSDL metadata representation: | |
211 | ||
212 | ~~~ tsdl | |
213 | /* network and be are aliases */ | |
214 | byte_order = /* native OR network OR be OR le */; | |
215 | ~~~ | |
216 | ||
217 | The `native` keyword selects the byte order described in the trace | |
218 | description. The `network` byte order is an alias for big endian. | |
219 | ||
220 | Even though the trace description section is not per se a type, for | |
221 | sake of clarity, it should be noted that `native` and `network` byte | |
222 | orders are only allowed within type declaration. The `byte_order` | |
223 | specified in the trace description section only accepts `be` or `le` | |
224 | values. | |
225 | ||
226 | ||
227 | #### 4.1.4 Size | |
228 | ||
229 | Type size, in bits, for integers and floats is that returned by | |
230 | `sizeof()` in C multiplied by `CHAR_BIT`. We require the size of `char` | |
231 | and `unsigned char` types (`CHAR_BIT`) to be fixed to 8 bits for | |
232 | cross-endianness compatibility. | |
233 | ||
234 | TSDL metadata representation: | |
235 | ||
236 | ~~~ tsdl | |
237 | size = /* value is in bits */; | |
238 | ~~~ | |
239 | ||
240 | ||
241 | #### 4.1.5 Integers | |
242 | ||
243 | Signed integers are represented in two-complement. Integer alignment, | |
244 | size, signedness and byte ordering are defined in the TSDL metadata. | |
245 | Integers aligned on byte size (8-bit) and with length multiple of byte | |
246 | size (8-bit) correspond to the C99 standard integers. In addition, | |
247 | integers with alignment and/or size that are _not_ a multiple of the | |
248 | byte size are permitted; these correspond to the C99 standard bitfields, | |
249 | with the added specification that the CTF integer bitfields have a fixed | |
250 | binary representation. Integer size needs to be a positive integer. | |
251 | Integers of size 0 are **forbidden**. An MIT-licensed reference | |
252 | implementation of the CTF portable bitfields is available | |
253 | [here](http://git.efficios.com/?p=babeltrace.git;a=blob;f=include/babeltrace/bitfield.h). | |
254 | ||
255 | Binary representation of integers: | |
256 | ||
257 | * On little and big endian: | |
258 | * Within a byte, high bits correspond to an integer high bits, and | |
259 | low bits correspond to low bits | |
260 | * On little endian: | |
261 | * Integer across multiple bytes are placed from the less significant | |
262 | to the most significant | |
263 | * Consecutive integers are placed from lower bits to higher bits | |
264 | (even within a byte) | |
265 | * On big endian: | |
266 | * Integer across multiple bytes are placed from the most significant | |
267 | to the less significant | |
268 | * Consecutive integers are placed from higher bits to lower bits | |
269 | (even within a byte) | |
270 | ||
271 | This binary representation is derived from the bitfield implementation | |
272 | in GCC for little and big endian. However, contrary to what GCC does, | |
273 | integers can cross units boundaries (no padding is required). Padding | |
274 | can be [explicitly added](#spec4.1.6) to follow the GCC layout if needed. | |
275 | ||
276 | TSDL metadata representation: | |
277 | ||
278 | ~~~ tsdl | |
279 | integer { | |
280 | signed = /* true OR false */; /* default: false */ | |
281 | byte_order = /* native OR network OR be OR le */; /* default: native */ | |
282 | size = /* value in bits */; /* no default */ | |
283 | align = /* value in bits */; | |
284 | ||
285 | /* base used for pretty-printing output; default: decimal */ | |
286 | base = /* decimal OR dec OR d OR i OR u OR 10 OR hexadecimal OR hex | |
287 | OR x OR X OR p OR 16 OR octal OR oct OR o OR 8 OR binary | |
288 | OR b OR 2 */; | |
289 | ||
290 | /* character encoding */ | |
291 | encoding = /* none or UTF8 or ASCII */; /* default: none */ | |
292 | } | |
293 | ~~~ | |
294 | ||
295 | Example of type inheritance (creation of a `uint32_t` named type): | |
296 | ||
297 | ~~~ tsdl | |
298 | typealias integer { | |
299 | size = 32; | |
300 | signed = false; | |
301 | align = 32; | |
302 | } := uint32_t; | |
303 | ~~~ | |
304 | ||
305 | Definition of a named 5-bit signed bitfield: | |
306 | ||
307 | ~~~ tsdl | |
308 | typealias integer { | |
309 | size = 5; | |
310 | signed = true; | |
311 | align = 1; | |
312 | } := int5_t; | |
313 | ~~~ | |
314 | ||
315 | The character encoding field can be used to specify that the integer | |
316 | must be printed as a text character when read. e.g.: | |
317 | ||
318 | ~~~ tsdl | |
319 | typealias integer { | |
320 | size = 8; | |
321 | align = 8; | |
322 | signed = false; | |
323 | encoding = UTF8; | |
324 | } := utf_char; | |
325 | ~~~ | |
326 | ||
327 | #### 4.1.6 GNU/C bitfields | |
328 | ||
329 | The GNU/C bitfields follow closely the integer representation, with a | |
330 | particularity on alignment: if a bitfield cannot fit in the current | |
331 | unit, the unit is padded and the bitfield starts at the following unit. | |
332 | The unit size is defined by the size of the type `unit_type`. | |
333 | ||
334 | TSDL metadata representation: | |
335 | ||
336 | ~~~ tsdl | |
337 | unit_type name:size; | |
338 | ~~~ | |
339 | ||
340 | As an example, the following structure declared in C compiled by GCC: | |
341 | ||
342 | ~~~ tsdl | |
343 | struct example { | |
344 | short a:12; | |
345 | short b:5; | |
346 | }; | |
347 | ~~~ | |
348 | ||
349 | The example structure is aligned on the largest element (short). The | |
350 | second bitfield would be aligned on the next unit boundary, because it | |
351 | would not fit in the current unit. | |
352 | ||
353 | ||
354 | #### 4.1.7 Floating point | |
355 | ||
356 | The floating point values byte ordering is defined in the TSDL metadata. | |
357 | ||
358 | Floating point values follow the IEEE 754-2008 standard interchange | |
359 | formats. Description of the floating point values include the exponent | |
360 | and mantissa size in bits. Some requirements are imposed on the | |
361 | floating point values: | |
362 | ||
363 | * `FLT_RADIX` must be 2. | |
364 | * `mant_dig` is the number of digits represented in the mantissa. It is | |
365 | specified by the ISO C99 standard, section 5.2.4, as `FLT_MANT_DIG`, | |
366 | `DBL_MANT_DIG` and `LDBL_MANT_DIG` as defined by `<float.h>`. | |
367 | * `exp_dig` is the number of digits represented in the exponent. Given | |
368 | that `mant_dig` is one bit more than its actual size in bits (leading | |
369 | 1 is not needed) and also given that the sign bit always takes one | |
370 | bit, `exp_dig` can be specified as: | |
371 | * `sizeof(float) * CHAR_BIT - FLT_MANT_DIG` | |
372 | * `sizeof(double) * CHAR_BIT - DBL_MANT_DIG` | |
373 | * `sizeof(long double) * CHAR_BIT - LDBL_MANT_DIG` | |
374 | ||
375 | TSDL metadata representation: | |
376 | ||
377 | ~~~ tsdl | |
378 | floating_point { | |
379 | exp_dig = /* value */; | |
380 | mant_dig = /* value */; | |
381 | byte_order = /* native OR network OR be OR le */; | |
382 | align = /* value */; | |
383 | } | |
384 | ~~~ | |
385 | ||
386 | Example of type inheritance: | |
387 | ||
388 | ~~~ tsdl | |
389 | typealias floating_point { | |
390 | exp_dig = 8; /* sizeof(float) * CHAR_BIT - FLT_MANT_DIG */ | |
391 | mant_dig = 24; /* FLT_MANT_DIG */ | |
392 | byte_order = native; | |
393 | align = 32; | |
394 | } := float; | |
395 | ~~~ | |
396 | ||
397 | TODO: define NaN, +inf, -inf behavior. | |
398 | ||
399 | Bit-packed, byte-packed or larger alignments can be used for floating | |
400 | point values, similarly to integers. | |
401 | ||
402 | ||
403 | #### 4.1.8 Enumerations | |
404 | ||
405 | Enumerations are a mapping between an integer type and a table of | |
406 | strings. The numerical representation of the enumeration follows the | |
407 | integer type specified by the metadata. The enumeration mapping table | |
408 | is detailed in the enumeration description within the metadata. The | |
409 | mapping table maps inclusive value ranges (or single values) to strings. | |
410 | Instead of being limited to simple `value -> string` mappings, these | |
411 | enumerations map `[ start_value ... end_value ] -> string`, which map | |
412 | inclusive ranges of values to strings. An enumeration from the C | |
413 | language can be represented in this format by having the same | |
414 | `start_value` and `end_value` for each mapping, which is in fact a | |
415 | range of size 1. This single-value range is supported without repeating | |
416 | the start and end values with the `value = string` declaration. | |
417 | Enumerations need to contain at least one entry. | |
418 | ||
419 | ~~~ tsdl | |
420 | enum name : integer_type { | |
421 | somestring = /* start_value1 */ ... /* end_value1 */, | |
422 | "other string" = /* start_value2 */ ... /* end_value2 */, | |
423 | yet_another_string, /* will be assigned to end_value2 + 1 */ | |
424 | "some other string" = /* value */, | |
425 | /* ... */ | |
426 | } | |
427 | ~~~ | |
428 | ||
429 | If the values are omitted, the enumeration starts at 0 and increment | |
430 | of 1 for each entry. An entry with omitted value that follows a range | |
431 | entry takes as value the `end_value` of the previous range + 1: | |
432 | ||
433 | ~~~ tsdl | |
434 | enum name : unsigned int { | |
435 | ZERO, | |
436 | ONE, | |
437 | TWO, | |
438 | TEN = 10, | |
439 | ELEVEN, | |
440 | } | |
441 | ~~~ | |
442 | ||
443 | Overlapping ranges within a single enumeration are implementation | |
444 | defined. | |
445 | ||
446 | A nameless enumeration can be declared as a field type or as part of | |
447 | a `typedef`: | |
448 | ||
449 | ~~~ tsdl | |
450 | enum : integer_type { | |
451 | /* ... */ | |
452 | } | |
453 | ~~~ | |
454 | ||
455 | Enumerations omitting the container type `: integer_type` use the `int` | |
456 | type (for compatibility with C99). The `int` type _must be_ previously | |
457 | declared, e.g.: | |
458 | ||
459 | ~~~ tsdl | |
460 | typealias integer { size = 32; align = 32; signed = true; } := int; | |
461 | ||
462 | enum { | |
463 | /* ... */ | |
464 | } | |
465 | ~~~ | |
466 | ||
467 | ### 4.2 Compound types | |
468 | ||
469 | Compound are aggregation of type declarations. Compound types include | |
470 | structures, variant, arrays, sequences, and strings. | |
471 | ||
472 | ||
473 | #### 4.2.1 Structures | |
474 | ||
475 | Structures are aligned on the largest alignment required by basic types | |
476 | contained within the structure. (This follows the ISO/C standard for | |
477 | structures) | |
478 | ||
479 | TSDL metadata representation of a named structure: | |
480 | ||
481 | ~~~ tsdl | |
482 | struct name { | |
483 | field_type field_name; | |
484 | field_type field_name; | |
485 | /* ... */ | |
486 | }; | |
487 | ~~~ | |
488 | ||
489 | Example: | |
490 | ||
491 | ~~~ tsdl | |
492 | struct example { | |
493 | integer { /* nameless type */ | |
494 | size = 16; | |
495 | signed = true; | |
496 | align = 16; | |
497 | } first_field_name; | |
498 | uint64_t second_field_name; /* named type declared in the metadata */ | |
499 | }; | |
500 | ~~~ | |
501 | ||
502 | The fields are placed in a sequence next to each other. They each | |
503 | possess a field name, which is a unique identifier within the structure. | |
504 | The identifier is not allowed to use any [reserved keyword](#specC.1.2). | |
505 | Replacing reserved keywords with underscore-prefixed field names is | |
506 | **recommended**. Fields starting with an underscore should have their | |
507 | leading underscore removed by the CTF trace readers. | |
508 | ||
509 | A nameless structure can be declared as a field type or as part of | |
510 | a `typedef`: | |
511 | ||
512 | ~~~ tsdl | |
513 | struct { | |
514 | /* ... */ | |
515 | } | |
516 | ~~~ | |
517 | ||
518 | Alignment for a structure compound type can be forced to a minimum | |
519 | value by adding an `align` specifier after the declaration of a | |
520 | structure body. This attribute is read as: `align(value)`. The value is | |
521 | specified in bits. The structure will be aligned on the maximum value | |
522 | between this attribute and the alignment required by the basic types | |
523 | contained within the structure. e.g. | |
524 | ||
525 | ~~~ tsdl | |
526 | struct { | |
527 | /* ... */ | |
528 | } align(32) | |
529 | ~~~ | |
530 | ||
531 | #### 4.2.2 Variants (discriminated/tagged unions) | |
532 | ||
533 | A CTF variant is a selection between different types. A CTF variant must | |
534 | always be defined within the scope of a structure or within fields | |
535 | contained within a structure (defined recursively). A _tag_ enumeration | |
536 | field must appear in either the same static scope, prior to the variant | |
537 | field (in field declaration order), in an upper static scope, or in an | |
538 | upper dynamic scope (see [Static and dynamic scopes](#spec7.3.2)). | |
539 | The type selection is indicated by the mapping from the enumeration | |
540 | value to the string used as variant type selector. The field to use as | |
541 | tag is specified by the `tag_field`, specified between `< >` after the | |
542 | `variant` keyword for unnamed variants, and after _variant name_ for | |
543 | named variants. It is not required that each enumeration mapping appears | |
544 | as variant type tag field. It is also not required that each variant | |
545 | type tag appears as enumeration mapping. However, it is required that | |
546 | any enumeration mapping encountered within a stream has a matching | |
547 | variant type tag field. | |
548 | ||
549 | The alignment of the variant is the alignment of the type as selected | |
550 | by the tag value for the specific instance of the variant. The size of | |
551 | the variant is the size as selected by the tag value for the specific | |
552 | instance of the variant. | |
553 | ||
554 | The alignment of the type containing the variant is independent of the | |
555 | variant alignment. For instance, if a structure contains two fields, a | |
556 | 32-bit integer, aligned on 32 bits, and a variant, which contains two | |
557 | choices: either a 32-bit field, aligned on 32 bits, or a 64-bit field, | |
558 | aligned on 64 bits, the alignment of the outmost structure will be | |
559 | 32-bit (the alignment of its largest field, disregarding the alignment | |
560 | of the variant). The alignment of the variant will depend on the | |
561 | selector: if the variant's 32-bit field is selected, its alignment will | |
562 | be 32-bit, or 64-bit otherwise. It is important to note that variants | |
563 | are specifically tailored for compactness in a stream. Therefore, the | |
564 | relative offsets of compound type fields can vary depending on the | |
565 | offset at which the compound type starts if it contains a variant | |
566 | that itself contains a type with alignment larger than the largest field | |
567 | contained within the compound type. This is caused by the fact that the | |
568 | compound type may contain the enumeration that select the variant's | |
569 | choice, and therefore the alignment to be applied to the compound type | |
570 | cannot be determined before encountering the enumeration. | |
571 | ||
572 | Each variant type selector possess a field name, which is a unique | |
573 | identifier within the variant. The identifier is not allowed to use any | |
574 | [reserved keyword](#C.1.2). Replacing reserved keywords with | |
575 | underscore-prefixed field names is recommended. Fields starting with an | |
576 | underscore should have their leading underscore removed by the CTF trace | |
577 | readers. | |
578 | ||
579 | A named variant declaration followed by its definition within a | |
580 | structure declaration: | |
581 | ||
582 | ~~~ tsdl | |
583 | variant name { | |
584 | field_type sel1; | |
585 | field_type sel2; | |
586 | field_type sel3; | |
587 | /* ... */ | |
588 | }; | |
589 | ||
590 | struct { | |
591 | enum : integer_type { sel1, sel2, sel3, /* ... */ } tag_field; | |
592 | /* ... */ | |
593 | variant name <tag_field> v; | |
594 | } | |
595 | ~~~ | |
596 | ||
597 | An unnamed variant definition within a structure is expressed by the | |
598 | following TSDL metadata: | |
599 | ||
600 | ~~~ tsdl | |
601 | struct { | |
602 | enum : integer_type { sel1, sel2, sel3, /* ... */ } tag_field; | |
603 | /* ... */ | |
604 | variant <tag_field> { | |
605 | field_type sel1; | |
606 | field_type sel2; | |
607 | field_type sel3; | |
608 | /* ... */ | |
609 | } v; | |
610 | } | |
611 | ~~~ | |
612 | ||
613 | Example of a named variant within a sequence that refers to a single | |
614 | tag field: | |
615 | ||
616 | ~~~ tsdl | |
617 | variant example { | |
618 | uint32_t a; | |
619 | uint64_t b; | |
620 | short c; | |
621 | }; | |
622 | ||
623 | struct { | |
624 | enum : uint2_t { a, b, c } choice; | |
625 | unsigned int seqlen; | |
626 | variant example <choice> v[seqlen]; | |
627 | } | |
628 | ~~~ | |
629 | ||
630 | Example of an unnamed variant: | |
631 | ||
632 | ~~~ tsdl | |
633 | struct { | |
634 | enum : uint2_t { a, b, c, d } choice; | |
635 | ||
636 | /* Unrelated fields can be added between the variant and its tag */ | |
637 | int32_t somevalue; | |
638 | variant <choice> { | |
639 | uint32_t a; | |
640 | uint64_t b; | |
641 | short c; | |
642 | struct { | |
643 | unsigned int field1; | |
644 | uint64_t field2; | |
645 | } d; | |
646 | } s; | |
647 | } | |
648 | ~~~ | |
649 | ||
650 | Example of an unnamed variant within an array: | |
651 | ||
652 | ~~~ tsdl | |
653 | struct { | |
654 | enum : uint2_t { a, b, c } choice; | |
655 | variant <choice> { | |
656 | uint32_t a; | |
657 | uint64_t b; | |
658 | short c; | |
659 | } v[10]; | |
660 | } | |
661 | ~~~ | |
662 | ||
663 | Example of a variant type definition within a structure, where the | |
664 | defined type is then declared within an array of structures. This | |
665 | variant refers to a tag located in an upper static scope. This example | |
666 | clearly shows that a variant type definition referring to the tag `x` | |
667 | uses the closest preceding field from the static scope of the type | |
668 | definition. | |
669 | ||
670 | ~~~ tsdl | |
671 | struct { | |
672 | enum : uint2_t { a, b, c, d } x; | |
673 | ||
674 | /* | |
675 | * "x" refers to the preceding "x" enumeration in the | |
676 | * static scope of the type definition. | |
677 | */ | |
678 | typedef variant <x> { | |
679 | uint32_t a; | |
680 | uint64_t b; | |
681 | short c; | |
682 | } example_variant; | |
683 | ||
684 | struct { | |
685 | enum : int { x, y, z } x; /* This enumeration is not used by "v". */ | |
686 | ||
687 | /* "v" uses the "enum : uint2_t { a, b, c, d }" tag. */ | |
688 | example_variant v; | |
689 | } a[10]; | |
690 | } | |
691 | ~~~ | |
692 | ||
693 | ||
694 | #### 4.2.3 Arrays | |
695 | ||
696 | Arrays are fixed-length. Their length is declared in the type | |
697 | declaration within the metadata. They contain an array of _inner type_ | |
698 | elements, which can refer to any type not containing the type of the | |
699 | array being declared (no circular dependency). The length is the number | |
700 | of elements in an array. | |
701 | ||
702 | TSDL metadata representation of a named array: | |
703 | ||
704 | ~~~ tsdl | |
705 | typedef elem_type name[/* length */]; | |
706 | ~~~ | |
707 | ||
708 | A nameless array can be declared as a field type within a | |
709 | structure, e.g.: | |
710 | ||
711 | ~~~ tsdl | |
712 | uint8_t field_name[10]; | |
713 | ~~~ | |
714 | ||
715 | Arrays are always aligned on their element alignment requirement. | |
716 | ||
717 | ||
718 | #### 4.2.4 Sequences | |
719 | ||
720 | Sequences are dynamically-sized arrays. They refer to a _length_ | |
721 | unsigned integer field, which must appear in either the same static | |
722 | scope, prior to the sequence field (in field declaration order), | |
723 | in an upper static scope, or in an upper dynamic scope | |
724 | (see [Static and dynamic scopes](#spec7.3.2)). This length field represents | |
725 | the number of elements in the sequence. The sequence per se is an | |
726 | array of _inner type_ elements. | |
727 | ||
728 | TSDL metadata representation for a sequence type definition: | |
729 | ||
730 | ~~~ tsdl | |
731 | struct { | |
732 | unsigned int length_field; | |
733 | typedef elem_type typename[length_field]; | |
734 | typename seq_field_name; | |
735 | } | |
736 | ~~~ | |
737 | ||
738 | A sequence can also be declared as a field type, e.g.: | |
739 | ||
740 | ~~~ tsdl | |
741 | struct { | |
742 | unsigned int length_field; | |
743 | long seq_field_name[length_field]; | |
744 | } | |
745 | ~~~ | |
746 | ||
747 | Multiple sequences can refer to the same length field, and these length | |
748 | fields can be in a different upper dynamic scope, e.g., assuming the | |
749 | `stream.event.header` defines: | |
750 | ||
751 | ~~~ tsdl | |
752 | stream { | |
753 | /* ... */ | |
754 | id = 1; | |
755 | event.header := struct { | |
756 | uint16_t seq_len; | |
757 | }; | |
758 | }; | |
759 | ||
760 | event { | |
761 | /* ... */ | |
762 | stream_id = 1; | |
763 | fields := struct { | |
764 | long seq_a[stream.event.header.seq_len]; | |
765 | char seq_b[stream.event.header.seq_len]; | |
766 | }; | |
767 | }; | |
768 | ~~~ | |
769 | ||
770 | The sequence elements follow the [array](#spec4.2.3) specifications. | |
771 | ||
772 | ||
773 | #### 4.2.5 Strings | |
774 | ||
775 | Strings are an array of _bytes_ of variable size and are terminated by | |
776 | a `'\0'` "NULL" character. Their encoding is described in the TSDL | |
777 | metadata. In absence of encoding attribute information, the default | |
778 | encoding is UTF-8. | |
779 | ||
780 | TSDL metadata representation of a named string type: | |
781 | ||
782 | ~~~ tsdl | |
783 | typealias string { | |
784 | encoding = /* UTF8 OR ASCII */; | |
785 | } := name; | |
786 | ~~~ | |
787 | ||
788 | A nameless string type can be declared as a field type: | |
789 | ||
790 | ~~~ tsdl | |
791 | string field_name; /* use default UTF8 encoding */ | |
792 | ~~~ | |
793 | ||
794 | Strings are always aligned on byte size. | |
795 | ||
796 | ||
797 | ## 5. Event packet header | |
798 | ||
799 | The event packet header consists of two parts: the | |
800 | _event packet header_ is the same for all streams of a trace. The | |
801 | second part, the _event packet context_, is described on a per-stream | |
802 | basis. Both are described in the TSDL metadata. | |
803 | ||
804 | Event packet header (all fields are optional, specified by | |
805 | TSDL metadata): | |
806 | ||
807 | * **Magic number** (CTF magic number: 0xC1FC1FC1) specifies that this is | |
808 | a CTF packet. This magic number is optional, but when present, it | |
809 | should come at the very beginning of the packet. | |
810 | * **Trace UUID**, used to ensure the event packet match the metadata used. | |
811 | Note: we cannot use a metadata checksum in every cases instead of a | |
812 | UUID because metadata can be appended to while tracing is active. | |
813 | This field is optional. | |
814 | * **Stream ID**, used as reference to stream description in metadata. | |
815 | This field is optional if there is only one stream description in | |
816 | the metadata, but becomes required if there are more than one | |
817 | stream in the TSDL metadata description. | |
818 | ||
819 | Event packet context (all fields are optional, specified by | |
820 | TSDL metadata): | |
821 | ||
822 | * Event packet **content size** (in bits). | |
823 | * Event packet **size** (in bits, includes padding). | |
824 | * Event packet content checksum. Checksum excludes the event packet | |
825 | header. | |
826 | * Per-stream event **packet sequence count** (to deal with UDP packet | |
827 | loss). The number of significant sequence counter bits should also | |
828 | be present, so wrap-arounds are dealt with correctly. | |
829 | * Time-stamp at the beginning and timestamp at the end of the event | |
830 | packet. Both timestamps are written in the packet header, but | |
831 | sampled respectively while (or before) writing the first event and | |
832 | while (or after) writing the last event in the packet. The inclusive | |
833 | range between these timestamps should include all event timestamps | |
834 | assigned to events contained within the packet. The timestamp at the | |
835 | beginning of an event packet is guaranteed to be below or equal the | |
836 | timestamp at the end of that event packet. The timestamp at the end | |
837 | of an event packet is guaranteed to be below or equal the | |
838 | timestamps at the end of any following packet within the same stream. | |
839 | See [Clocks](#spec8) for more detail. | |
840 | * **Events discarded count**. Snapshot of a per-stream | |
841 | free-running counter, counting the number of events discarded that | |
842 | were supposed to be written in the stream after the last event in | |
843 | the event packet. Note: producer-consumer buffer full condition can | |
844 | fill the current event packet with padding so we know exactly where | |
845 | events have been discarded. However, if the buffer full condition | |
846 | chooses not to fill the current event packet with padding, all we | |
847 | know about the timestamp range in which the events have been | |
848 | discarded is that it is somewhere between the beginning and the end | |
849 | of the packet. | |
850 | * Lossless **compression scheme** used for the event packet content. | |
851 | Applied directly to raw data. New types of compression can be added | |
852 | in following versions of the format. | |
853 | * 0: no compression scheme | |
854 | * 1: bzip2 | |
855 | * 2: gzip | |
856 | * 3: xz | |
857 | * **Cypher** used for the event packet content. Applied after | |
858 | compression. | |
859 | * 0: no encryption | |
860 | * 1: AES | |
861 | * **Checksum scheme** used for the event packet content. Applied after | |
862 | encryption. | |
863 | * 0: no checksum | |
864 | * 1: md5 | |
865 | * 2: sha1 | |
866 | * 3: crc32 | |
867 | ||
868 | ||
869 | ### 5.1 Event packet header description | |
870 | ||
871 | The event packet header layout is indicated by the | |
872 | `trace.packet.header` field. Here is a recommended structure type for | |
873 | the packet header with the fields typically expected (although these | |
874 | fields are each optional): | |
875 | ||
876 | ~~~ tsdl | |
877 | struct event_packet_header { | |
878 | uint32_t magic; | |
879 | uint8_t uuid[16]; | |
880 | uint32_t stream_id; | |
881 | }; | |
882 | ||
883 | trace { | |
884 | /* ... */ | |
885 | packet.header := struct event_packet_header; | |
886 | }; | |
887 | ~~~ | |
888 | ||
9ab09151 PP |
889 | If the magic number (`magic` field) is not present, |
890 | tools such as `file` will have no mean to discover the file type. | |
941a19cf | 891 | |
9ab09151 PP |
892 | If the `uuid` field is not present, no validation that the metadata |
893 | actually corresponds to the stream is performed. | |
941a19cf | 894 | |
9ab09151 | 895 | If the `stream_id` packet header field is missing, the trace can only |
941a19cf PP |
896 | contain a single stream. Its `id` field can be left out, and its events |
897 | don't need to declare a `stream_id` field. | |
898 | ||
899 | ||
900 | ### 5.2 Event packet context description | |
901 | ||
902 | Event packet context example. These are declared within the stream | |
903 | declaration in the metadata. All these fields are optional. If the | |
904 | packet size field is missing, the whole stream only contains a single | |
905 | packet. If the content size field is missing, the packet is filled | |
906 | (no padding). The content and packet sizes include all headers. | |
907 | ||
908 | An example event packet context type: | |
909 | ||
910 | ~~~ tsdl | |
911 | struct event_packet_context { | |
912 | uint64_t timestamp_begin; | |
913 | uint64_t timestamp_end; | |
914 | uint32_t checksum; | |
915 | uint32_t stream_packet_count; | |
916 | uint32_t events_discarded; | |
917 | uint32_t cpu_id; | |
918 | uint64_t content_size; | |
919 | uint64_t packet_size; | |
920 | uint8_t compression_scheme; | |
921 | uint8_t encryption_scheme; | |
922 | uint8_t checksum_scheme; | |
923 | }; | |
924 | ~~~ | |
925 | ||
926 | ||
927 | ## 6. Event Structure | |
928 | ||
929 | The overall structure of an event is: | |
930 | ||
931 | 1. Event header (as specified by the stream metadata) | |
932 | 2. Stream event context (as specified by the stream metadata) | |
933 | 3. Event context (as specified by the event metadata) | |
934 | 4. Event payload (as specified by the event metadata) | |
935 | ||
936 | This structure defines an implicit dynamic scoping, where variants | |
937 | located in inner structures (those with a higher number in the listing | |
938 | above) can refer to the fields of outer structures (with lower number | |
939 | in the listing above). See [TSDL scopes](#spec7.3) for more detail. | |
940 | ||
941 | The total length of an event is defined as the difference between the | |
942 | end of its event payload and the end of the previous event's event | |
943 | payload. Therefore, it includes the event header alignment padding, and | |
944 | all its fields and their respective alignment padding. Events of length | |
945 | 0 are forbidden. | |
946 | ||
947 | ||
948 | ### 6.1 Event header | |
949 | ||
950 | Event headers can be described within the metadata. We hereby propose, | |
951 | as an example, two types of events headers. Type 1 accommodates streams | |
952 | with less than 31 event IDs. Type 2 accommodates streams with 31 or | |
953 | more event IDs. | |
954 | ||
955 | One major factor can vary between streams: the number of event IDs | |
956 | assigned to a stream. Luckily, this information tends to stay | |
957 | relatively constant (modulo event registration while trace is being | |
958 | recorded), so we can specify different representations for streams | |
959 | containing few event IDs and streams containing many event IDs, so we | |
960 | end up representing the event ID and timestamp as densely as possible | |
961 | in each case. | |
962 | ||
963 | The header is extended in the rare occasions where the information | |
964 | cannot be represented in the ranges available in the standard event | |
965 | header. They are also used in the rare occasions where the data | |
966 | required for a field could not be collected: the flag corresponding to | |
967 | the missing field within the `missing_fields` array is then set to 1. | |
968 | ||
969 | Types `uintX_t` represent an `X`-bit unsigned integer, as declared with | |
970 | either: | |
971 | ||
972 | ~~~ tsdl | |
973 | typealias integer { | |
974 | size = /* X */; | |
975 | align = /* X */; | |
976 | signed = false; | |
977 | } := uintX_t; | |
978 | ~~~ | |
979 | ||
980 | or | |
981 | ||
982 | ~~~ tsdl | |
983 | typealias integer { | |
984 | size = /* X */; | |
985 | align = 1; | |
986 | signed = false; | |
987 | } := uintX_t; | |
988 | ~~~ | |
989 | ||
990 | For more information about timestamp fields, see [Clocks](#spec8). | |
991 | ||
992 | ||
993 | #### 6.1.1 Type 1: few event IDs | |
994 | ||
995 | * Aligned on 32-bit (or 8-bit if byte-packed, depending on the | |
996 | architecture preference) | |
997 | * Native architecture byte ordering | |
998 | * For `compact` selection, fixed size of 32 bits | |
999 | * For "extended" selection, size depends on the architecture and | |
1000 | variant alignment | |
1001 | ||
1002 | ~~~ tsdl | |
1003 | struct event_header_1 { | |
1004 | /* | |
1005 | * id: range: 0 - 30. | |
1006 | * id 31 is reserved to indicate an extended header. | |
1007 | */ | |
1008 | enum : uint5_t { compact = 0 ... 30, extended = 31 } id; | |
1009 | variant <id> { | |
1010 | struct { | |
1011 | uint27_t timestamp; | |
1012 | } compact; | |
1013 | struct { | |
1014 | uint32_t id; /* 32-bit event IDs */ | |
1015 | uint64_t timestamp; /* 64-bit timestamps */ | |
1016 | } extended; | |
1017 | } v; | |
1018 | } align(32); /* or align(8) */ | |
1019 | ~~~ | |
1020 | ||
1021 | ||
1022 | #### 6.1.2 Type 2: many event IDs | |
1023 | ||
1024 | * Aligned on 16-bit (or 8-bit if byte-packed, depending on the | |
1025 | architecture preference) | |
1026 | * Native architecture byte ordering | |
1027 | * For `compact` selection, size depends on the architecture and | |
1028 | variant alignment | |
1029 | * For `extended` selection, size depends on the architecture and | |
1030 | variant alignment | |
1031 | ||
1032 | ~~~ tsdl | |
1033 | struct event_header_2 { | |
1034 | /* | |
1035 | * id: range: 0 - 65534. | |
1036 | * id 65535 is reserved to indicate an extended header. | |
1037 | */ | |
1038 | enum : uint16_t { compact = 0 ... 65534, extended = 65535 } id; | |
1039 | variant <id> { | |
1040 | struct { | |
1041 | uint32_t timestamp; | |
1042 | } compact; | |
1043 | struct { | |
1044 | uint32_t id; /* 32-bit event IDs */ | |
1045 | uint64_t timestamp; /* 64-bit timestamps */ | |
1046 | } extended; | |
1047 | } v; | |
1048 | } align(16); /* or align(8) */ | |
1049 | ~~~ | |
1050 | ||
1051 | ||
1052 | ### 6.2 Stream event context and event context | |
1053 | ||
1054 | The event context contains information relative to the current event. | |
1055 | The choice and meaning of this information is specified by the TSDL | |
1056 | stream and event metadata descriptions. The stream context is applied | |
1057 | to all events within the stream. The stream context structure follows | |
1058 | the event header. The event context is applied to specific events. Its | |
1059 | structure follows the stream context structure. | |
1060 | ||
1061 | An example of stream-level event context is to save the event payload | |
1062 | size with each event, or to save the current PID with each event. | |
1063 | These are declared within the stream declaration within the metadata: | |
1064 | ||
1065 | ~~~ tsdl | |
1066 | stream { | |
1067 | /* ... */ | |
1068 | event.context := struct { | |
1069 | uint pid; | |
1070 | uint16_t payload_size; | |
1071 | }; | |
1072 | }; | |
1073 | ~~~ | |
1074 | ||
1075 | An example of event-specific event context is to declare a bitmap of | |
1076 | missing fields, only appended after the stream event context if the | |
1077 | extended event header is selected. `NR_FIELDS` is the number of fields | |
1078 | within the event (a numeric value). | |
1079 | ||
1080 | ~~~ tsdl | |
1081 | event { | |
1082 | context := struct { | |
1083 | variant <id> { | |
1084 | struct { } compact; | |
1085 | struct { | |
1086 | /* missing event fields bitmap */ | |
1087 | uint1_t missing_fields[NR_FIELDS]; | |
1088 | } extended; | |
1089 | } v; | |
1090 | }; | |
1091 | /* ... */ | |
1092 | } | |
1093 | ~~~ | |
1094 | ||
1095 | ||
1096 | ### 6.3 Event payload | |
1097 | ||
1098 | An event payload contains fields specific to a given event type. The | |
1099 | fields belonging to an event type are described in the event-specific | |
1100 | metadata within a structure type. | |
1101 | ||
1102 | ||
1103 | #### 6.3.1 Padding | |
1104 | ||
1105 | No padding at the end of the event payload. This differs from the ISO/C | |
1106 | standard for structures, but follows the CTF standard for structures. | |
1107 | In a trace, even though it makes sense to align the beginning of a | |
1108 | structure, it really makes no sense to add padding at the end of the | |
1109 | structure, because structures are usually not followed by a structure | |
1110 | of the same type. | |
1111 | ||
1112 | This trick can be done by adding a zero-length `end` field at the end | |
1113 | of the C structures, and by using the offset of this field rather than | |
1114 | using `sizeof()` when calculating the size of a structure | |
1115 | (see [Helper macros](#specA)). | |
1116 | ||
1117 | ||
1118 | #### 6.3.2 Alignment | |
1119 | ||
1120 | The event payload is aligned on the largest alignment required by types | |
1121 | contained within the payload. This follows the ISO/C standard for | |
1122 | structures. | |
1123 | ||
1124 | ||
1125 | ## 7. Trace Stream Description Language (TSDL) | |
1126 | ||
1127 | The Trace Stream Description Language (TSDL) allows expression of the | |
1128 | binary trace streams layout in a C99-like Domain Specific Language | |
1129 | (DSL). | |
1130 | ||
1131 | ||
1132 | ### 7.1 Meta-data | |
1133 | ||
1134 | The trace stream layout description is located in the trace metadata. | |
1135 | The metadata is itself located in a stream identified by its name: | |
1136 | `metadata`. | |
1137 | ||
1138 | The metadata description can be expressed in two different formats: | |
1139 | text-only and packet-based. The text-only description facilitates | |
1140 | generation of metadata and provides a convenient way to enter the | |
1141 | metadata information by hand. The packet-based metadata provides the | |
1142 | CTF stream packet facilities (checksumming, compression, encryption, | |
1143 | network-readiness) for metadata stream generated and transported by a | |
1144 | tracer. | |
1145 | ||
1146 | The text-only metadata file is a plain-text TSDL description. This file | |
1147 | must begin with the following characters to identify the file as a CTF | |
1148 | TSDL text-based metadata file (without the double-quotes): | |
1149 | ||
1150 | ~~~ text | |
1151 | "/* CTF" | |
1152 | ~~~ | |
1153 | ||
1154 | It must be followed by a space, and the version of the specification | |
1155 | followed by the CTF trace, e.g.: | |
1156 | ||
1157 | ~~~ text | |
1158 | " 1.8" | |
1159 | ~~~ | |
1160 | ||
1161 | These characters allow automated discovery of file type and CTF | |
1162 | specification version. They are interpreted as a the beginning of a | |
1163 | comment by the TSDL metadata parser. The comment can be continued to | |
1164 | contain extra commented characters before it is closed. | |
1165 | ||
1166 | The packet-based metadata is made of _metadata packets_, which each | |
1167 | start with a metadata packet header. The packet-based metadata | |
1168 | description is detected by reading the magic number 0x75D11D57 at the | |
1169 | beginning of the file. This magic number is also used to detect the | |
1170 | endianness of the architecture by trying to read the CTF magic number | |
1171 | and its counterpart in reversed endianness. The events within the | |
1172 | metadata stream have no event header nor event context. Each event only | |
1173 | contains a special _sequence_ payload, which is a sequence of bits which | |
1174 | length is implicitly calculated by using the | |
1175 | `trace.packet.header.content_size` field, minus the packet header size. | |
1176 | The formatting of this sequence of bits is a plain-text representation | |
1177 | of the TSDL description. Each metadata packet start with a special | |
1178 | packet header, specific to the metadata stream, which contains, | |
1179 | exactly: | |
1180 | ||
1181 | ~~~ tsdl | |
1182 | struct metadata_packet_header { | |
1183 | uint32_t magic; /* 0x75D11D57 */ | |
1184 | uint8_t uuid[16]; /* Unique Universal Identifier */ | |
1185 | uint32_t checksum; /* 0 if unused */ | |
1186 | uint32_t content_size; /* in bits */ | |
1187 | uint32_t packet_size; /* in bits */ | |
1188 | uint8_t compression_scheme; /* 0 if unused */ | |
1189 | uint8_t encryption_scheme; /* 0 if unused */ | |
1190 | uint8_t checksum_scheme; /* 0 if unused */ | |
1191 | uint8_t major; /* CTF spec version major number */ | |
1192 | uint8_t minor; /* CTF spec version minor number */ | |
1193 | }; | |
1194 | ~~~ | |
1195 | ||
1196 | The packet-based metadata can be converted to a text-only metadata by | |
1197 | concatenating all the strings it contains. | |
1198 | ||
1199 | In the textual representation of the metadata, the text contained | |
1200 | within `/*` and `*/`, as well as within `//` and end of line, are | |
1201 | treated as comments. Boolean values can be represented as `true`, | |
1202 | `TRUE`, or `1` for true, and `false`, `FALSE`, or `0` for false. Within | |
1203 | the string-based metadata description, the trace UUID is represented as | |
1204 | a string of hexadecimal digits and dashes `-`. In the event packet | |
1205 | header, the trace UUID is represented as an array of bytes. | |
1206 | ||
1207 | ||
1208 | ### 7.2 Declaration vs definition | |
1209 | ||
1210 | A declaration associates a layout to a type, without specifying where | |
1211 | this type is located in the event [structure hierarchy](#spec6). | |
1212 | This therefore includes `typedef`, `typealias`, as well as all type | |
1213 | specifiers. In certain circumstances (`typedef`, structure field and | |
1214 | variant field), a declaration is followed by a declarator, which specify | |
1215 | the newly defined type name (for `typedef`), or the field name (for | |
1216 | declarations located within structure and variants). Array and sequence, | |
1217 | declared with square brackets (`[` `]`), are part of the declarator, | |
1218 | similarly to C99. The enumeration base type is specified by | |
1219 | `: enum_base`, which is part of the type specifier. The variant tag | |
1220 | name, specified between `<` `>`, is also part of the type specifier. | |
1221 | ||
1222 | A definition associates a type to a location in the event | |
1223 | [structure hierarchy](#spec6). This association is denoted by `:=`, | |
1224 | as shown in [TSDL scopes](#spec7.3). | |
1225 | ||
1226 | ||
1227 | ### 7.3 TSDL scopes | |
1228 | ||
1229 | TSDL uses three different types of scoping: a lexical scope is used for | |
1230 | declarations and type definitions, and static and dynamic scopes are | |
1231 | used for variants references to tag fields (with relative and absolute | |
1232 | path lookups) and for sequence references to length fields. | |
1233 | ||
1234 | ||
1235 | #### 7.3.1 Lexical Scope | |
1236 | ||
1237 | Each of `trace`, `env`, `stream`, `event`, `struct` and `variant` have | |
1238 | their own nestable declaration scope, within which types can be declared | |
1239 | using `typedef` and `typealias`. A root declaration scope also contains | |
1240 | all declarations located outside of any of the aforementioned | |
1241 | declarations. An inner declaration scope can refer to type declared | |
1242 | within its container lexical scope prior to the inner declaration scope. | |
1243 | Redefinition of a typedef or typealias is not valid, although hiding an | |
1244 | upper scope typedef or typealias is allowed within a sub-scope. | |
1245 | ||
1246 | ||
1247 | #### 7.3.2 Static and dynamic scopes | |
1248 | ||
1249 | A local static scope consists in the scope generated by the declaration | |
1250 | of fields within a compound type. A static scope is a local static scope | |
1251 | augmented with the nested sub-static-scopes it contains. | |
1252 | ||
1253 | A dynamic scope consists in the static scope augmented with the | |
1254 | implicit [event structure](#spec6) definition hierarchy. | |
1255 | ||
1256 | Multiple declarations of the same field name within a local static scope | |
1257 | is not valid. It is however valid to re-use the same field name in | |
1258 | different local scopes. | |
1259 | ||
1260 | Nested static and dynamic scopes form lookup paths. These are used for | |
1261 | variant tag and sequence length references. They are used at the variant | |
1262 | and sequence definition site to look up the location of the tag field | |
1263 | associated with a variant, and to lookup up the location of the length | |
1264 | field associated with a sequence. | |
1265 | ||
1266 | Variants and sequences can refer to a tag field either using a relative | |
1267 | path or an absolute path. The relative path is relative to the scope in | |
1268 | which the variant or sequence performing the lookup is located. | |
1269 | Relative paths are only allowed to lookup within the same static scope, | |
1270 | which includes its nested static scopes. Lookups targeting parent static | |
1271 | scopes need to be performed with an absolute path. | |
1272 | ||
1273 | Absolute path lookups use the full path including the dynamic scope | |
1274 | followed by a `.` and then the static scope. Therefore, variants (or | |
1275 | sequences) in lower levels in the dynamic scope (e.g., event context) | |
1276 | can refer to a tag (or length) field located in upper levels | |
1277 | (e.g., in the event header) by specifying, in this case, the associated | |
1278 | tag with `<stream.event.header.field_name>`. This allows, for instance, | |
1279 | the event context to define a variant referring to the `id` field of | |
1280 | the event header as selector. | |
1281 | ||
1282 | The dynamic scope prefixes are thus: | |
1283 | ||
1284 | * Trace environment: `<env. >` | |
1285 | * Trace packet header: `<trace.packet.header. >` | |
1286 | * Stream packet context: `<stream.packet.context. >` | |
1287 | * Event header: `<stream.event.header. >` | |
1288 | * Stream event context: `<stream.event.context. >` | |
1289 | * Event context: `<event.context. >` | |
1290 | * Event payload: `<event.fields. >` | |
1291 | ||
1292 | The target dynamic scope must be specified explicitly when referring to | |
1293 | a field outside of the static scope (absolute scope reference). No | |
1294 | conflict can occur between relative and dynamic paths, because the | |
1295 | keywords `trace`, `stream`, and `event` are reserved, and thus not | |
1296 | permitted as field names. It is recommended that field names clashing | |
1297 | with CTF and C99 reserved keywords use an underscore prefix to | |
1298 | eliminate the risk of generating a description containing an invalid | |
1299 | field name. Consequently, fields starting with an underscore should have | |
1300 | their leading underscore removed by the CTF trace readers. | |
1301 | ||
1302 | The information available in the dynamic scopes can be thought of as the | |
1303 | current tracing context. At trace production, information about the | |
1304 | current context is saved into the specified scope field levels. At trace | |
1305 | consumption, for each event, the current trace context is therefore | |
1306 | readable by accessing the upper dynamic scopes. | |
1307 | ||
1308 | ||
1309 | ### 7.4 TSDL examples | |
1310 | ||
1311 | The grammar representing the TSDL metadata is presented in | |
1312 | [TSDL grammar](#specC). This section presents a rather lighter reading that | |
1313 | consists in examples of TSDL metadata, with template values. | |
1314 | ||
1315 | The stream ID can be left out if there is only one stream in the | |
1316 | trace. The event `id` field can be left out if there is only one event | |
1317 | in a stream. | |
1318 | ||
1319 | ~~~ tsdl | |
1320 | trace { | |
1321 | major = /* value */; /* CTF spec version major number */ | |
1322 | minor = /* value */; /* CTF spec version minor number */ | |
1323 | uuid = "aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa"; /* Trace UUID */ | |
1324 | byte_order = /* be OR le */; /* Endianness (required) */ | |
1325 | packet.header := struct { | |
1326 | uint32_t magic; | |
1327 | uint8_t uuid[16]; | |
1328 | uint32_t stream_id; | |
1329 | }; | |
1330 | }; | |
1331 | ||
1332 | /* | |
1333 | * The "env" (environment) scope contains assignment expressions. The | |
1334 | * field names and content are implementation-defined. | |
1335 | */ | |
1336 | env { | |
1337 | pid = /* value */; /* example */ | |
1338 | proc_name = "name"; /* example */ | |
1339 | /* ... */ | |
1340 | }; | |
1341 | ||
1342 | stream { | |
1343 | id = /* stream_id */; | |
1344 | /* Type 1 - Few event IDs; Type 2 - Many event IDs. See section 6.1. */ | |
1345 | event.header := /* event_header_1 OR event_header_2 */; | |
1346 | event.context := struct { | |
1347 | /* ... */ | |
1348 | }; | |
1349 | packet.context := struct { | |
1350 | /* ... */ | |
1351 | }; | |
1352 | }; | |
1353 | ||
1354 | event { | |
1355 | name = "event_name"; | |
1356 | id = /* value */; /* Numeric identifier within the stream */ | |
1357 | stream_id = /* stream_id */; | |
1358 | loglevel = /* value */; | |
1359 | model.emf.uri = "string"; | |
1360 | context := struct { | |
1361 | /* ... */ | |
1362 | }; | |
1363 | fields := struct { | |
1364 | /* ... */ | |
1365 | }; | |
1366 | }; | |
1367 | ||
1368 | callsite { | |
1369 | name = "event_name"; | |
1370 | func = "func_name"; | |
1371 | file = "myfile.c"; | |
1372 | line = 39; | |
1373 | ip = 0x40096c; | |
1374 | }; | |
1375 | ~~~ | |
1376 | ||
1377 | More detail on [types](#spec4): | |
1378 | ||
1379 | ~~~ tsdl | |
1380 | /* | |
1381 | * Named types: | |
1382 | * | |
1383 | * Type declarations behave similarly to the C standard. | |
1384 | */ | |
1385 | ||
1386 | typedef aliased_type_specifiers new_type_declarators; | |
1387 | ||
1388 | /* e.g.: typedef struct example new_type_name[10]; */ | |
1389 | ||
1390 | /* | |
1391 | * typealias | |
1392 | * | |
1393 | * The "typealias" declaration can be used to give a name (including | |
1394 | * pointer declarator specifier) to a type. It should also be used to | |
1395 | * map basic C types (float, int, unsigned long, ...) to a CTF type. | |
1396 | * Typealias is a superset of "typedef": it also allows assignment of a | |
1397 | * simple variable identifier to a type. | |
1398 | */ | |
1399 | ||
1400 | typealias type_class { | |
1401 | /* ... */ | |
1402 | } := type_specifiers type_declarator; | |
1403 | ||
1404 | /* | |
1405 | * e.g.: | |
1406 | * typealias integer { | |
1407 | * size = 32; | |
1408 | * align = 32; | |
1409 | * signed = false; | |
1410 | * } := struct page *; | |
1411 | * | |
1412 | * typealias integer { | |
1413 | * size = 32; | |
1414 | * align = 32; | |
1415 | * signed = true; | |
1416 | * } := int; | |
1417 | */ | |
1418 | ||
1419 | struct name { | |
1420 | /* ... */ | |
1421 | }; | |
1422 | ||
1423 | variant name { | |
1424 | /* ... */ | |
1425 | }; | |
1426 | ||
1427 | enum name : integer_type { | |
1428 | /* ... */ | |
1429 | }; | |
1430 | ~~~ | |
1431 | ||
1432 | Unnamed types, contained within compound type fields, `typedef` or | |
1433 | `typealias`: | |
1434 | ||
1435 | ~~~ tsdl | |
1436 | struct { | |
1437 | /* ... */ | |
1438 | } | |
1439 | ~~~ | |
1440 | ||
1441 | ~~~ tsdl | |
1442 | struct { | |
1443 | /* ... */ | |
1444 | } align(value) | |
1445 | ~~~ | |
1446 | ||
1447 | ~~~ tsdl | |
1448 | variant { | |
1449 | /* ... */ | |
1450 | } | |
1451 | ~~~ | |
1452 | ||
1453 | ~~~ tsdl | |
1454 | enum : integer_type { | |
1455 | /* ... */ | |
1456 | } | |
1457 | ~~~ | |
1458 | ||
1459 | ~~~ tsdl | |
1460 | typedef type new_type[length]; | |
1461 | ||
1462 | struct { | |
1463 | type field_name[length]; | |
1464 | } | |
1465 | ~~~ | |
1466 | ||
1467 | ~~~ tsdl | |
1468 | typedef type new_type[length_type]; | |
1469 | ||
1470 | struct { | |
1471 | type field_name[length_type]; | |
1472 | } | |
1473 | ~~~ | |
1474 | ||
1475 | ~~~ tsdl | |
1476 | integer { | |
1477 | /* ... */ | |
1478 | } | |
1479 | ~~~ | |
1480 | ||
1481 | ~~~ tsdl | |
1482 | floating_point { | |
1483 | /* ... */ | |
1484 | } | |
1485 | ~~~ | |
1486 | ||
1487 | ~~~ tsdl | |
1488 | struct { | |
1489 | integer_type field_name:size; /* GNU/C bitfield */ | |
1490 | } | |
1491 | ~~~ | |
1492 | ||
1493 | ~~~ tsdl | |
1494 | struct { | |
1495 | string field_name; | |
1496 | } | |
1497 | ~~~ | |
1498 | ||
1499 | ||
1500 | ## 8. Clocks | |
1501 | ||
1502 | Clock metadata allows to describe the clock topology of the system, as | |
1503 | well as to detail each clock parameter. In absence of clock description, | |
1504 | it is assumed that all fields named `timestamp` use the same clock | |
1505 | source, which increments once per nanosecond. | |
1506 | ||
1507 | Describing a clock and how it is used by streams is threefold: first, | |
1508 | the clock and clock topology should be described in a `clock` | |
1509 | description block, e.g.: | |
1510 | ||
1511 | ~~~ tsdl | |
1512 | clock { | |
1513 | name = cycle_counter_sync; | |
1514 | uuid = "62189bee-96dc-11e0-91a8-cfa3d89f3923"; | |
1515 | description = "Cycle counter synchronized across CPUs"; | |
1516 | freq = 1000000000; /* frequency, in Hz */ | |
1517 | /* precision in seconds is: 1000 * (1/freq) */ | |
1518 | precision = 1000; | |
1519 | /* | |
1520 | * clock value offset from Epoch is: | |
1521 | * offset_s + (offset * (1/freq)) | |
1522 | */ | |
1523 | offset_s = 1326476837; | |
1524 | offset = 897235420; | |
1525 | absolute = FALSE; | |
1526 | }; | |
1527 | ~~~ | |
1528 | ||
1529 | The mandatory `name` field specifies the name of the clock identifier, | |
1530 | which can later be used as a reference. The optional field `uuid` is | |
1531 | the unique identifier of the clock. It can be used to correlate | |
1532 | different traces that use the same clock. An optional textual | |
1533 | description string can be added with the `description` field. The | |
1534 | `freq` field is the initial frequency of the clock, in Hz. If the | |
1535 | `freq` field is not present, the frequency is assumed to be 1000000000 | |
1536 | (providing clock increment of 1 ns). The optional `precision` field | |
1537 | details the uncertainty on the clock measurements, in (1/freq) units. | |
1538 | The `offset_s` and `offset` fields indicate the offset from | |
1539 | POSIX.1 Epoch, 1970-01-01 00:00:00 +0000 (UTC), to the zero of value | |
1540 | of the clock. The `offset_s` field is in seconds. The `offset` field is | |
1541 | in (1/freq) units. If any of the `offset_s` or `offset` field is not | |
1542 | present, it is assigned the 0 value. The field `absolute` is `TRUE` if | |
1543 | the clock is a global reference across different clock UUID | |
1544 | (e.g. NTP time). Otherwise, `absolute` is `FALSE`, and the clock can | |
1545 | be considered as synchronized only with other clocks that have the same | |
1546 | UUID. | |
1547 | ||
1548 | Secondly, a reference to this clock should be added within an integer | |
1549 | type: | |
1550 | ||
1551 | ~~~ tsdl | |
1552 | typealias integer { | |
1553 | size = 64; align = 1; signed = false; | |
1554 | map = clock.cycle_counter_sync.value; | |
1555 | } := uint64_ccnt_t; | |
1556 | ~~~ | |
1557 | ||
1558 | Thirdly, stream declarations can reference the clock they use as a | |
1559 | timestamp source: | |
1560 | ||
1561 | ~~~ tsdl | |
1562 | struct packet_context { | |
1563 | uint64_ccnt_t ccnt_begin; | |
1564 | uint64_ccnt_t ccnt_end; | |
1565 | /* ... */ | |
1566 | }; | |
1567 | ||
1568 | stream { | |
1569 | /* ... */ | |
1570 | event.header := struct { | |
1571 | uint64_ccnt_t timestamp; | |
1572 | /* ... */ | |
1573 | }; | |
1574 | packet.context := struct packet_context; | |
1575 | }; | |
1576 | ~~~ | |
1577 | ||
1578 | For a N-bit integer type referring to a clock, if the integer overflows | |
1579 | compared to the N low order bits of the clock prior value found in the | |
1580 | same stream, then it is assumed that one, and only one, overflow | |
1581 | occurred. It is therefore important that events encoding time on a small | |
1582 | number of bits happen frequently enough to detect when more than one | |
1583 | N-bit overflow occurs. | |
1584 | ||
1585 | In a packet context, clock field names ending with `_begin` and `_end` | |
1586 | have a special meaning: this refers to the timestamps at, respectively, | |
1587 | the beginning and the end of each packet. | |
1588 | ||
1589 | ||
1590 | ## A. Helper macros | |
1591 | ||
1592 | The two following macros keep track of the size of a GNU/C structure | |
1593 | without padding at the end by placing HEADER_END as the last field. | |
1594 | A one byte end field is used for C90 compatibility (C99 flexible arrays | |
1595 | could be used here). Note that this does not affect the effective | |
1596 | structure size, which should always be calculated with the | |
1597 | `header_sizeof()` helper. | |
1598 | ||
1599 | ~~~ c | |
1600 | #define HEADER_END char end_field | |
1601 | #define header_sizeof(type) offsetof(typeof(type), end_field) | |
1602 | ~~~ | |
1603 | ||
1604 | ## B. Stream header rationale | |
1605 | ||
1606 | An event stream is divided in contiguous event packets of variable | |
1607 | size. These subdivisions allow the trace analyzer to perform a fast | |
1608 | binary search by time within the stream (typically requiring to index | |
1609 | only the event packet headers) without reading the whole stream. These | |
1610 | subdivisions have a variable size to eliminate the need to transfer the | |
1611 | event packet padding when partially filled event packets must be sent | |
1612 | when streaming a trace for live viewing/analysis. An event packet can | |
1613 | contain a certain amount of padding at the end. Dividing streams into | |
1614 | event packets is also useful for network streaming over UDP and flight | |
1615 | recorder mode tracing (a whole event packet can be swapped out of the | |
1616 | buffer atomically for reading). | |
1617 | ||
1618 | The stream header is repeated at the beginning of each event packet to | |
1619 | allow flexibility in terms of: | |
1620 | ||
1621 | * streaming support | |
1622 | * allowing arbitrary buffers to be discarded without making the trace | |
1623 | unreadable | |
1624 | * allow UDP packet loss handling by either dealing with missing event packet | |
1625 | or asking for re-transmission | |
1626 | * transparently support flight recorder mode | |
1627 | * transparently support crash dump | |
1628 | ||
1629 | ||
1630 | ## C. TSDL Grammar | |
1631 | ||
1632 | ~~~ c | |
1633 | /* | |
1634 | * Common Trace Format (CTF) Trace Stream Description Language (TSDL) Grammar. | |
1635 | * | |
1636 | * Inspired from the C99 grammar: | |
1637 | * http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1124.pdf (Annex A) | |
1638 | * and c++1x grammar (draft) | |
1639 | * http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2011/n3291.pdf (Annex A) | |
1640 | * | |
1641 | * Specialized for CTF needs by including only constant and declarations from | |
1642 | * C99 (excluding function declarations), and by adding support for variants, | |
1643 | * sequences and CTF-specific specifiers. Enumeration container types | |
1644 | * semantic is inspired from c++1x enum-base. | |
1645 | */ | |
1646 | ~~~ | |
1647 | ||
1648 | ||
1649 | ### C.1 Lexical grammar | |
1650 | ||
1651 | ||
1652 | #### C.1.1 Lexical elements | |
1653 | ||
1654 | ~~~ text | |
1655 | token: | |
1656 | keyword | |
1657 | identifier | |
1658 | constant | |
1659 | string-literal | |
1660 | punctuator | |
1661 | ~~~ | |
1662 | ||
1663 | #### C.1.2 Keywords | |
1664 | ||
1665 | ~~~ text | |
1666 | keyword: is one of | |
1667 | ||
1668 | align | |
1669 | callsite | |
1670 | const | |
1671 | char | |
1672 | clock | |
1673 | double | |
1674 | enum | |
1675 | env | |
1676 | event | |
1677 | floating_point | |
1678 | float | |
1679 | integer | |
1680 | int | |
1681 | long | |
1682 | short | |
1683 | signed | |
1684 | stream | |
1685 | string | |
1686 | struct | |
1687 | trace | |
1688 | typealias | |
1689 | typedef | |
1690 | unsigned | |
1691 | variant | |
1692 | void | |
1693 | _Bool | |
1694 | _Complex | |
1695 | _Imaginary | |
1696 | ~~~ | |
1697 | ||
1698 | ||
1699 | #### C.1.3 Identifiers | |
1700 | ||
1701 | ~~~ text | |
1702 | identifier: | |
1703 | identifier-nondigit | |
1704 | identifier identifier-nondigit | |
1705 | identifier digit | |
1706 | ||
1707 | identifier-nondigit: | |
1708 | nondigit | |
1709 | universal-character-name | |
1710 | any other implementation-defined characters | |
1711 | ||
1712 | nondigit: | |
1713 | _ | |
1714 | [a-zA-Z] /* regular expression */ | |
1715 | ||
1716 | digit: | |
1717 | [0-9] /* regular expression */ | |
1718 | ~~~ | |
1719 | ||
1720 | ||
1721 | #### C.1.4 Universal character names | |
1722 | ||
1723 | ~~~ text | |
1724 | universal-character-name: | |
1725 | \u hex-quad | |
1726 | \U hex-quad hex-quad | |
1727 | ||
1728 | hex-quad: | |
1729 | hexadecimal-digit hexadecimal-digit hexadecimal-digit hexadecimal-digit | |
1730 | ~~~ | |
1731 | ||
1732 | ||
1733 | ##### C.1.5 Constants | |
1734 | ||
1735 | ~~~ text | |
1736 | constant: | |
1737 | integer-constant | |
1738 | enumeration-constant | |
1739 | character-constant | |
1740 | ||
1741 | integer-constant: | |
1742 | decimal-constant integer-suffix-opt | |
1743 | octal-constant integer-suffix-opt | |
1744 | hexadecimal-constant integer-suffix-opt | |
1745 | ||
1746 | decimal-constant: | |
1747 | nonzero-digit | |
1748 | decimal-constant digit | |
1749 | ||
1750 | octal-constant: | |
1751 | 0 | |
1752 | octal-constant octal-digit | |
1753 | ||
1754 | hexadecimal-constant: | |
1755 | hexadecimal-prefix hexadecimal-digit | |
1756 | hexadecimal-constant hexadecimal-digit | |
1757 | ||
1758 | hexadecimal-prefix: | |
1759 | 0x | |
1760 | 0X | |
1761 | ||
1762 | nonzero-digit: | |
1763 | [1-9] | |
1764 | ||
1765 | integer-suffix: | |
1766 | unsigned-suffix long-suffix-opt | |
1767 | unsigned-suffix long-long-suffix | |
1768 | long-suffix unsigned-suffix-opt | |
1769 | long-long-suffix unsigned-suffix-opt | |
1770 | ||
1771 | unsigned-suffix: | |
1772 | u | |
1773 | U | |
1774 | ||
1775 | long-suffix: | |
1776 | l | |
1777 | L | |
1778 | ||
1779 | long-long-suffix: | |
1780 | ll | |
1781 | LL | |
1782 | ||
1783 | enumeration-constant: | |
1784 | identifier | |
1785 | string-literal | |
1786 | ||
1787 | character-constant: | |
1788 | ' c-char-sequence ' | |
1789 | L' c-char-sequence ' | |
1790 | ||
1791 | c-char-sequence: | |
1792 | c-char | |
1793 | c-char-sequence c-char | |
1794 | ||
1795 | c-char: | |
1796 | any member of source charset except single-quote ('), backslash | |
1797 | (\), or new-line character. | |
1798 | escape-sequence | |
1799 | ||
1800 | escape-sequence: | |
1801 | simple-escape-sequence | |
1802 | octal-escape-sequence | |
1803 | hexadecimal-escape-sequence | |
1804 | universal-character-name | |
1805 | ||
1806 | simple-escape-sequence: one of | |
1807 | \' \" \? \\ \a \b \f \n \r \t \v | |
1808 | ||
1809 | octal-escape-sequence: | |
1810 | \ octal-digit | |
1811 | \ octal-digit octal-digit | |
1812 | \ octal-digit octal-digit octal-digit | |
1813 | ||
1814 | hexadecimal-escape-sequence: | |
1815 | \x hexadecimal-digit | |
1816 | hexadecimal-escape-sequence hexadecimal-digit | |
1817 | ~~~ | |
1818 | ||
1819 | ||
1820 | #### C.1.6 String literals | |
1821 | ||
1822 | ~~~ text | |
1823 | string-literal: | |
1824 | " s-char-sequence-opt " | |
1825 | L" s-char-sequence-opt " | |
1826 | ||
1827 | s-char-sequence: | |
1828 | s-char | |
1829 | s-char-sequence s-char | |
1830 | ||
1831 | s-char: | |
1832 | any member of source charset except double-quote ("), backslash | |
1833 | (\), or new-line character. | |
1834 | escape-sequence | |
1835 | ~~~ | |
1836 | ||
1837 | ||
1838 | #### C.1.7 Punctuators | |
1839 | ||
1840 | ~~~ text | |
1841 | punctuator: one of | |
1842 | [ ] ( ) { } . -> * + - < > : ; ... = , | |
1843 | ~~~ | |
1844 | ||
1845 | ||
1846 | ### C.2 Phrase structure grammar | |
1847 | ||
1848 | ~~~ text | |
1849 | primary-expression: | |
1850 | identifier | |
1851 | constant | |
1852 | string-literal | |
1853 | ( unary-expression ) | |
1854 | ||
1855 | postfix-expression: | |
1856 | primary-expression | |
1857 | postfix-expression [ unary-expression ] | |
1858 | postfix-expression . identifier | |
1859 | postfix-expressoin -> identifier | |
1860 | ||
1861 | unary-expression: | |
1862 | postfix-expression | |
1863 | unary-operator postfix-expression | |
1864 | ||
1865 | unary-operator: one of | |
1866 | + - | |
1867 | ||
1868 | assignment-operator: | |
1869 | = | |
1870 | ||
1871 | type-assignment-operator: | |
1872 | := | |
1873 | ||
1874 | constant-expression-range: | |
1875 | unary-expression ... unary-expression | |
1876 | ~~~ | |
1877 | ||
1878 | ||
1879 | #### C.2.2 Declarations: | |
1880 | ||
1881 | ~~~ text | |
1882 | declaration: | |
1883 | declaration-specifiers declarator-list-opt ; | |
1884 | ctf-specifier ; | |
1885 | ||
1886 | declaration-specifiers: | |
1887 | storage-class-specifier declaration-specifiers-opt | |
1888 | type-specifier declaration-specifiers-opt | |
1889 | type-qualifier declaration-specifiers-opt | |
1890 | ||
1891 | declarator-list: | |
1892 | declarator | |
1893 | declarator-list , declarator | |
1894 | ||
1895 | abstract-declarator-list: | |
1896 | abstract-declarator | |
1897 | abstract-declarator-list , abstract-declarator | |
1898 | ||
1899 | storage-class-specifier: | |
1900 | typedef | |
1901 | ||
1902 | type-specifier: | |
1903 | void | |
1904 | char | |
1905 | short | |
1906 | int | |
1907 | long | |
1908 | float | |
1909 | double | |
1910 | signed | |
1911 | unsigned | |
1912 | _Bool | |
1913 | _Complex | |
1914 | _Imaginary | |
1915 | struct-specifier | |
1916 | variant-specifier | |
1917 | enum-specifier | |
1918 | typedef-name | |
1919 | ctf-type-specifier | |
1920 | ||
1921 | align-attribute: | |
1922 | align ( unary-expression ) | |
1923 | ||
1924 | struct-specifier: | |
1925 | struct identifier-opt { struct-or-variant-declaration-list-opt } align-attribute-opt | |
1926 | struct identifier align-attribute-opt | |
1927 | ||
1928 | struct-or-variant-declaration-list: | |
1929 | struct-or-variant-declaration | |
1930 | struct-or-variant-declaration-list struct-or-variant-declaration | |
1931 | ||
1932 | struct-or-variant-declaration: | |
1933 | specifier-qualifier-list struct-or-variant-declarator-list ; | |
1934 | declaration-specifiers-opt storage-class-specifier declaration-specifiers-opt declarator-list ; | |
1935 | typealias declaration-specifiers abstract-declarator-list type-assignment-operator declaration-specifiers abstract-declarator-list ; | |
1936 | typealias declaration-specifiers abstract-declarator-list type-assignment-operator declarator-list ; | |
1937 | ||
1938 | specifier-qualifier-list: | |
1939 | type-specifier specifier-qualifier-list-opt | |
1940 | type-qualifier specifier-qualifier-list-opt | |
1941 | ||
1942 | struct-or-variant-declarator-list: | |
1943 | struct-or-variant-declarator | |
1944 | struct-or-variant-declarator-list , struct-or-variant-declarator | |
1945 | ||
1946 | struct-or-variant-declarator: | |
1947 | declarator | |
1948 | declarator-opt : unary-expression | |
1949 | ||
1950 | variant-specifier: | |
1951 | variant identifier-opt variant-tag-opt { struct-or-variant-declaration-list } | |
1952 | variant identifier variant-tag | |
1953 | ||
1954 | variant-tag: | |
1955 | < unary-expression > | |
1956 | ||
1957 | enum-specifier: | |
1958 | enum identifier-opt { enumerator-list } | |
1959 | enum identifier-opt { enumerator-list , } | |
1960 | enum identifier | |
1961 | enum identifier-opt : declaration-specifiers { enumerator-list } | |
1962 | enum identifier-opt : declaration-specifiers { enumerator-list , } | |
1963 | ||
1964 | enumerator-list: | |
1965 | enumerator | |
1966 | enumerator-list , enumerator | |
1967 | ||
1968 | enumerator: | |
1969 | enumeration-constant | |
1970 | enumeration-constant assignment-operator unary-expression | |
1971 | enumeration-constant assignment-operator constant-expression-range | |
1972 | ||
1973 | type-qualifier: | |
1974 | const | |
1975 | ||
1976 | declarator: | |
1977 | pointer-opt direct-declarator | |
1978 | ||
1979 | direct-declarator: | |
1980 | identifier | |
1981 | ( declarator ) | |
1982 | direct-declarator [ unary-expression ] | |
1983 | ||
1984 | abstract-declarator: | |
1985 | pointer-opt direct-abstract-declarator | |
1986 | ||
1987 | direct-abstract-declarator: | |
1988 | identifier-opt | |
1989 | ( abstract-declarator ) | |
1990 | direct-abstract-declarator [ unary-expression ] | |
1991 | direct-abstract-declarator [ ] | |
1992 | ||
1993 | pointer: | |
1994 | * type-qualifier-list-opt | |
1995 | * type-qualifier-list-opt pointer | |
1996 | ||
1997 | type-qualifier-list: | |
1998 | type-qualifier | |
1999 | type-qualifier-list type-qualifier | |
2000 | ||
2001 | typedef-name: | |
2002 | identifier | |
2003 | ~~~ | |
2004 | ||
2005 | ||
2006 | #### C.2.3 CTF-specific declarations | |
2007 | ||
2008 | ~~~ text | |
2009 | ctf-specifier: | |
2010 | clock { ctf-assignment-expression-list-opt } | |
2011 | event { ctf-assignment-expression-list-opt } | |
2012 | stream { ctf-assignment-expression-list-opt } | |
2013 | env { ctf-assignment-expression-list-opt } | |
2014 | trace { ctf-assignment-expression-list-opt } | |
2015 | callsite { ctf-assignment-expression-list-opt } | |
2016 | typealias declaration-specifiers abstract-declarator-list type-assignment-operator declaration-specifiers abstract-declarator-list | |
2017 | typealias declaration-specifiers abstract-declarator-list type-assignment-operator declarator-list | |
2018 | ||
2019 | ctf-type-specifier: | |
2020 | floating_point { ctf-assignment-expression-list-opt } | |
2021 | integer { ctf-assignment-expression-list-opt } | |
2022 | string { ctf-assignment-expression-list-opt } | |
2023 | string | |
2024 | ||
2025 | ctf-assignment-expression-list: | |
2026 | ctf-assignment-expression ; | |
2027 | ctf-assignment-expression-list ctf-assignment-expression ; | |
2028 | ||
2029 | ctf-assignment-expression: | |
2030 | unary-expression assignment-operator unary-expression | |
2031 | unary-expression type-assignment-operator type-specifier | |
2032 | declaration-specifiers-opt storage-class-specifier declaration-specifiers-opt declarator-list | |
2033 | typealias declaration-specifiers abstract-declarator-list type-assignment-operator declaration-specifiers abstract-declarator-list | |
2034 | typealias declaration-specifiers abstract-declarator-list type-assignment-operator declarator-list | |
2035 | ~~~ |