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