Clarify alignment requirements
[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 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 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 - Events discarded count
721 - Snapshot of a per-stream free-running counter, counting the number of
722 events discarded that were supposed to be written in the stream after
723 the last event in the event packet.
724 * Note: producer-consumer buffer full condition can fill the current
725 event packet with padding so we know exactly where events have been
726 discarded. However, if the buffer full condition chooses not
727 to fill the current event packet with padding, all we know
728 about the timestamp range in which the events have been
729 discarded is that it is somewhere between the beginning and
730 the end of the packet.
731 - Lossless compression scheme used for the event packet content. Applied
732 directly to raw data. New types of compression can be added in following
733 versions of the format.
734 0: no compression scheme
735 1: bzip2
736 2: gzip
737 3: xz
738 - Cypher used for the event packet content. Applied after compression.
739 0: no encryption
740 1: AES
741 - Checksum scheme used for the event packet content. Applied after encryption.
742 0: no checksum
743 1: md5
744 2: sha1
745 3: crc32
746
747 5.1 Event Packet Header Description
748
749 The event packet header layout is indicated by the trace packet.header
750 field. Here is a recommended structure type for the packet header with
751 the fields typically expected (although these fields are each optional):
752
753 struct event_packet_header {
754 uint32_t magic;
755 uint8_t uuid[16];
756 uint32_t stream_id;
757 };
758
759 trace {
760 ...
761 packet.header := struct event_packet_header;
762 };
763
764 If the magic number is not present, tools such as "file" will have no
765 mean to discover the file type.
766
767 If the uuid is not present, no validation that the meta-data actually
768 corresponds to the stream is performed.
769
770 If the stream_id packet header field is missing, the trace can only
771 contain a single stream. Its "id" field can be left out, and its events
772 don't need to declare a "stream_id" field.
773
774
775 5.2 Event Packet Context Description
776
777 Event packet context example. These are declared within the stream declaration
778 in the meta-data. All these fields are optional. If the packet size field is
779 missing, the whole stream only contains a single packet. If the content
780 size field is missing, the packet is filled (no padding). The content
781 and packet sizes include all headers.
782
783 An example event packet context type:
784
785 struct event_packet_context {
786 uint64_t timestamp_begin;
787 uint64_t timestamp_end;
788 uint32_t checksum;
789 uint32_t stream_packet_count;
790 uint32_t events_discarded;
791 uint32_t cpu_id;
792 uint64_t/uint32_t/uint16_t content_size;
793 uint64_t/uint32_t/uint16_t packet_size;
794 uint8_t compression_scheme;
795 uint8_t encryption_scheme;
796 uint8_t checksum_scheme;
797 };
798
799
800 6. Event Structure
801
802 The overall structure of an event is:
803
804 1 - Stream Packet Context (as specified by the stream meta-data)
805 2 - Event Header (as specified by the stream meta-data)
806 3 - Stream Event Context (as specified by the stream meta-data)
807 4 - Event Context (as specified by the event meta-data)
808 5 - Event Payload (as specified by the event meta-data)
809
810 This structure defines an implicit dynamic scoping, where variants
811 located in inner structures (those with a higher number in the listing
812 above) can refer to the fields of outer structures (with lower number in
813 the listing above). See Section 7.3 TSDL Scopes for more detail.
814
815 6.1 Event Header
816
817 Event headers can be described within the meta-data. We hereby propose, as an
818 example, two types of events headers. Type 1 accommodates streams with less than
819 31 event IDs. Type 2 accommodates streams with 31 or more event IDs.
820
821 One major factor can vary between streams: the number of event IDs assigned to
822 a stream. Luckily, this information tends to stay relatively constant (modulo
823 event registration while trace is being recorded), so we can specify different
824 representations for streams containing few event IDs and streams containing
825 many event IDs, so we end up representing the event ID and time-stamp as
826 densely as possible in each case.
827
828 The header is extended in the rare occasions where the information cannot be
829 represented in the ranges available in the standard event header. They are also
830 used in the rare occasions where the data required for a field could not be
831 collected: the flag corresponding to the missing field within the missing_fields
832 array is then set to 1.
833
834 Types uintX_t represent an X-bit unsigned integer, as declared with
835 either:
836
837 typealias integer { size = X; align = X; signed = false; } := uintX_t;
838
839 or
840
841 typealias integer { size = X; align = 1; signed = false; } := uintX_t;
842
843 6.1.1 Type 1 - Few event IDs
844
845 - Aligned on 32-bit (or 8-bit if byte-packed, depending on the architecture
846 preference).
847 - Native architecture byte ordering.
848 - For "compact" selection
849 - Fixed size: 32 bits.
850 - For "extended" selection
851 - Size depends on the architecture and variant alignment.
852
853 struct event_header_1 {
854 /*
855 * id: range: 0 - 30.
856 * id 31 is reserved to indicate an extended header.
857 */
858 enum : uint5_t { compact = 0 ... 30, extended = 31 } id;
859 variant <id> {
860 struct {
861 uint27_t timestamp;
862 } compact;
863 struct {
864 uint32_t id; /* 32-bit event IDs */
865 uint64_t timestamp; /* 64-bit timestamps */
866 } extended;
867 } v;
868 } align(32); /* or align(8) */
869
870
871 6.1.2 Type 2 - Many event IDs
872
873 - Aligned on 16-bit (or 8-bit if byte-packed, depending on the architecture
874 preference).
875 - Native architecture byte ordering.
876 - For "compact" selection
877 - Size depends on the architecture and variant alignment.
878 - For "extended" selection
879 - Size depends on the architecture and variant alignment.
880
881 struct event_header_2 {
882 /*
883 * id: range: 0 - 65534.
884 * id 65535 is reserved to indicate an extended header.
885 */
886 enum : uint16_t { compact = 0 ... 65534, extended = 65535 } id;
887 variant <id> {
888 struct {
889 uint32_t timestamp;
890 } compact;
891 struct {
892 uint32_t id; /* 32-bit event IDs */
893 uint64_t timestamp; /* 64-bit timestamps */
894 } extended;
895 } v;
896 } align(16); /* or align(8) */
897
898
899 6.2 Event Context
900
901 The event context contains information relative to the current event.
902 The choice and meaning of this information is specified by the TSDL
903 stream and event meta-data descriptions. The stream context is applied
904 to all events within the stream. The stream context structure follows
905 the event header. The event context is applied to specific events. Its
906 structure follows the stream context structure.
907
908 An example of stream-level event context is to save the event payload size with
909 each event, or to save the current PID with each event. These are declared
910 within the stream declaration within the meta-data:
911
912 stream {
913 ...
914 event.context := struct {
915 uint pid;
916 uint16_t payload_size;
917 };
918 };
919
920 An example of event-specific event context is to declare a bitmap of missing
921 fields, only appended after the stream event context if the extended event
922 header is selected. NR_FIELDS is the number of fields within the event (a
923 numeric value).
924
925 event {
926 context = struct {
927 variant <id> {
928 struct { } compact;
929 struct {
930 uint1_t missing_fields[NR_FIELDS]; /* missing event fields bitmap */
931 } extended;
932 } v;
933 };
934 ...
935 }
936
937 6.3 Event Payload
938
939 An event payload contains fields specific to a given event type. The fields
940 belonging to an event type are described in the event-specific meta-data
941 within a structure type.
942
943 6.3.1 Padding
944
945 No padding at the end of the event payload. This differs from the ISO/C standard
946 for structures, but follows the CTF standard for structures. In a trace, even
947 though it makes sense to align the beginning of a structure, it really makes no
948 sense to add padding at the end of the structure, because structures are usually
949 not followed by a structure of the same type.
950
951 This trick can be done by adding a zero-length "end" field at the end of the C
952 structures, and by using the offset of this field rather than using sizeof()
953 when calculating the size of a structure (see Appendix "A. Helper macros").
954
955 6.3.2 Alignment
956
957 The event payload is aligned on the largest alignment required by types
958 contained within the payload. (This follows the ISO/C standard for structures)
959
960
961 7. Trace Stream Description Language (TSDL)
962
963 The Trace Stream Description Language (TSDL) allows expression of the
964 binary trace streams layout in a C99-like Domain Specific Language
965 (DSL).
966
967
968 7.1 Meta-data
969
970 The trace stream layout description is located in the trace meta-data.
971 The meta-data is itself located in a stream identified by its name:
972 "metadata".
973
974 The meta-data description can be expressed in two different formats:
975 text-only and packet-based. The text-only description facilitates
976 generation of meta-data and provides a convenient way to enter the
977 meta-data information by hand. The packet-based meta-data provides the
978 CTF stream packet facilities (checksumming, compression, encryption,
979 network-readiness) for meta-data stream generated and transported by a
980 tracer.
981
982 The text-only meta-data file is a plain-text TSDL description. This file
983 must begin with the following characters to identify the file as a CTF
984 TSDL text-based metadata file (without the double-quotes) :
985
986 "/* CTF"
987
988 It must be followed by a space, and the version of the specification
989 followed by the CTF trace, e.g.:
990
991 " 1.8"
992
993 These characters allow automated discovery of file type and CTF
994 specification version. They are interpreted as a the beginning of a
995 comment by the TSDL metadata parser. The comment can be continued to
996 contain extra commented characters before it is closed.
997
998 The packet-based meta-data is made of "meta-data packets", which each
999 start with a meta-data packet header. The packet-based meta-data
1000 description is detected by reading the magic number "0x75D11D57" at the
1001 beginning of the file. This magic number is also used to detect the
1002 endianness of the architecture by trying to read the CTF magic number
1003 and its counterpart in reversed endianness. The events within the
1004 meta-data stream have no event header nor event context. Each event only
1005 contains a special "sequence" payload, which is a sequence of bits which
1006 length is implicitly calculated by using the
1007 "trace.packet.header.content_size" field, minus the packet header size.
1008 The formatting of this sequence of bits is a plain-text representation
1009 of the TSDL description. Each meta-data packet start with a special
1010 packet header, specific to the meta-data stream, which contains,
1011 exactly:
1012
1013 struct metadata_packet_header {
1014 uint32_t magic; /* 0x75D11D57 */
1015 uint8_t uuid[16]; /* Unique Universal Identifier */
1016 uint32_t checksum; /* 0 if unused */
1017 uint32_t content_size; /* in bits */
1018 uint32_t packet_size; /* in bits */
1019 uint8_t compression_scheme; /* 0 if unused */
1020 uint8_t encryption_scheme; /* 0 if unused */
1021 uint8_t checksum_scheme; /* 0 if unused */
1022 uint8_t major; /* CTF spec version major number */
1023 uint8_t minor; /* CTF spec version minor number */
1024 };
1025
1026 The packet-based meta-data can be converted to a text-only meta-data by
1027 concatenating all the strings it contains.
1028
1029 In the textual representation of the meta-data, the text contained
1030 within "/*" and "*/", as well as within "//" and end of line, are
1031 treated as comments. Boolean values can be represented as true, TRUE,
1032 or 1 for true, and false, FALSE, or 0 for false. Within the string-based
1033 meta-data description, the trace UUID is represented as a string of
1034 hexadecimal digits and dashes "-". In the event packet header, the trace
1035 UUID is represented as an array of bytes.
1036
1037
1038 7.2 Declaration vs Definition
1039
1040 A declaration associates a layout to a type, without specifying where
1041 this type is located in the event structure hierarchy (see Section 6).
1042 This therefore includes typedef, typealias, as well as all type
1043 specifiers. In certain circumstances (typedef, structure field and
1044 variant field), a declaration is followed by a declarator, which specify
1045 the newly defined type name (for typedef), or the field name (for
1046 declarations located within structure and variants). Array and sequence,
1047 declared with square brackets ("[" "]"), are part of the declarator,
1048 similarly to C99. The enumeration base type is specified by
1049 ": enum_base", which is part of the type specifier. The variant tag
1050 name, specified between "<" ">", is also part of the type specifier.
1051
1052 A definition associates a type to a location in the event structure
1053 hierarchy (see Section 6). This association is denoted by ":=", as shown
1054 in Section 7.3.
1055
1056
1057 7.3 TSDL Scopes
1058
1059 TSDL uses three different types of scoping: a lexical scope is used for
1060 declarations and type definitions, and static and dynamic scopes are
1061 used for variants references to tag fields (with relative and absolute
1062 path lookups) and for sequence references to length fields.
1063
1064 7.3.1 Lexical Scope
1065
1066 Each of "trace", "env", "stream", "event", "struct" and "variant" have
1067 their own nestable declaration scope, within which types can be declared
1068 using "typedef" and "typealias". A root declaration scope also contains
1069 all declarations located outside of any of the aforementioned
1070 declarations. An inner declaration scope can refer to type declared
1071 within its container lexical scope prior to the inner declaration scope.
1072 Redefinition of a typedef or typealias is not valid, although hiding an
1073 upper scope typedef or typealias is allowed within a sub-scope.
1074
1075 7.3.2 Static and Dynamic Scopes
1076
1077 A local static scope consists in the scope generated by the declaration
1078 of fields within a compound type. A static scope is a local static scope
1079 augmented with the nested sub-static-scopes it contains.
1080
1081 A dynamic scope consists in the static scope augmented with the
1082 implicit event structure definition hierarchy presented at Section 6.
1083
1084 Multiple declarations of the same field name within a local static scope
1085 is not valid. It is however valid to re-use the same field name in
1086 different local scopes.
1087
1088 Nested static and dynamic scopes form lookup paths. These are used for
1089 variant tag and sequence length references. They are used at the variant
1090 and sequence definition site to look up the location of the tag field
1091 associated with a variant, and to lookup up the location of the length
1092 field associated with a sequence.
1093
1094 Variants and sequences can refer to a tag field either using a relative
1095 path or an absolute path. The relative path is relative to the scope in
1096 which the variant or sequence performing the lookup is located.
1097 Relative paths are only allowed to lookup within the same static scope,
1098 which includes its nested static scopes. Lookups targeting parent static
1099 scopes need to be performed with an absolute path.
1100
1101 Absolute path lookups use the full path including the dynamic scope
1102 followed by a "." and then the static scope. Therefore, variants (or
1103 sequences) in lower levels in the dynamic scope (e.g. event context) can
1104 refer to a tag (or length) field located in upper levels (e.g. in the
1105 event header) by specifying, in this case, the associated tag with
1106 <stream.event.header.field_name>. This allows, for instance, the event
1107 context to define a variant referring to the "id" field of the event
1108 header as selector.
1109
1110 The dynamic scope prefixes are thus:
1111
1112 - Trace Environment: <env. >,
1113 - Trace Packet Header: <trace.packet.header. >,
1114 - Stream Packet Context: <stream.packet.context. >,
1115 - Event Header: <stream.event.header. >,
1116 - Stream Event Context: <stream.event.context. >,
1117 - Event Context: <event.context. >,
1118 - Event Payload: <event.fields. >.
1119
1120
1121 The target dynamic scope must be specified explicitly when referring to
1122 a field outside of the static scope (absolute scope reference). No
1123 conflict can occur between relative and dynamic paths, because the
1124 keywords "trace", "stream", and "event" are reserved, and thus
1125 not permitted as field names. It is recommended that field names
1126 clashing with CTF and C99 reserved keywords use an underscore prefix to
1127 eliminate the risk of generating a description containing an invalid
1128 field name. Consequently, fields starting with an underscore should have
1129 their leading underscore removed by the CTF trace readers.
1130
1131
1132 The information available in the dynamic scopes can be thought of as the
1133 current tracing context. At trace production, information about the
1134 current context is saved into the specified scope field levels. At trace
1135 consumption, for each event, the current trace context is therefore
1136 readable by accessing the upper dynamic scopes.
1137
1138
1139 7.4 TSDL Examples
1140
1141 The grammar representing the TSDL meta-data is presented in Appendix C.
1142 TSDL Grammar. This section presents a rather lighter reading that
1143 consists in examples of TSDL meta-data, with template values.
1144
1145 The stream "id" can be left out if there is only one stream in the
1146 trace. The event "id" field can be left out if there is only one event
1147 in a stream.
1148
1149 trace {
1150 major = value; /* CTF spec version major number */
1151 minor = value; /* CTF spec version minor number */
1152 uuid = "aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa"; /* Trace UUID */
1153 byte_order = be OR le; /* Endianness (required) */
1154 packet.header := struct {
1155 uint32_t magic;
1156 uint8_t uuid[16];
1157 uint32_t stream_id;
1158 };
1159 };
1160
1161 /*
1162 * The "env" (environment) scope contains assignment expressions. The
1163 * field names and content are implementation-defined.
1164 */
1165 env {
1166 pid = value; /* example */
1167 proc_name = "name"; /* example */
1168 ...
1169 };
1170
1171 stream {
1172 id = stream_id;
1173 /* Type 1 - Few event IDs; Type 2 - Many event IDs. See section 6.1. */
1174 event.header := event_header_1 OR event_header_2;
1175 event.context := struct {
1176 ...
1177 };
1178 packet.context := struct {
1179 ...
1180 };
1181 };
1182
1183 event {
1184 name = "event_name";
1185 id = value; /* Numeric identifier within the stream */
1186 stream_id = stream_id;
1187 loglevel = value;
1188 model.emf.uri = "string";
1189 context := struct {
1190 ...
1191 };
1192 fields := struct {
1193 ...
1194 };
1195 };
1196
1197 callsite {
1198 name = "event_name";
1199 func = "func_name";
1200 file = "myfile.c";
1201 line = 39;
1202 ip = 0x40096c;
1203 };
1204
1205 /* More detail on types in section 4. Types */
1206
1207 /*
1208 * Named types:
1209 *
1210 * Type declarations behave similarly to the C standard.
1211 */
1212
1213 typedef aliased_type_specifiers new_type_declarators;
1214
1215 /* e.g.: typedef struct example new_type_name[10]; */
1216
1217 /*
1218 * typealias
1219 *
1220 * The "typealias" declaration can be used to give a name (including
1221 * pointer declarator specifier) to a type. It should also be used to
1222 * map basic C types (float, int, unsigned long, ...) to a CTF type.
1223 * Typealias is a superset of "typedef": it also allows assignment of a
1224 * simple variable identifier to a type.
1225 */
1226
1227 typealias type_class {
1228 ...
1229 } := type_specifiers type_declarator;
1230
1231 /*
1232 * e.g.:
1233 * typealias integer {
1234 * size = 32;
1235 * align = 32;
1236 * signed = false;
1237 * } := struct page *;
1238 *
1239 * typealias integer {
1240 * size = 32;
1241 * align = 32;
1242 * signed = true;
1243 * } := int;
1244 */
1245
1246 struct name {
1247 ...
1248 };
1249
1250 variant name {
1251 ...
1252 };
1253
1254 enum name : integer_type {
1255 ...
1256 };
1257
1258
1259 /*
1260 * Unnamed types, contained within compound type fields, typedef or typealias.
1261 */
1262
1263 struct {
1264 ...
1265 }
1266
1267 struct {
1268 ...
1269 } align(value)
1270
1271 variant {
1272 ...
1273 }
1274
1275 enum : integer_type {
1276 ...
1277 }
1278
1279 typedef type new_type[length];
1280
1281 struct {
1282 type field_name[length];
1283 }
1284
1285 typedef type new_type[length_type];
1286
1287 struct {
1288 type field_name[length_type];
1289 }
1290
1291 integer {
1292 ...
1293 }
1294
1295 floating_point {
1296 ...
1297 }
1298
1299 struct {
1300 integer_type field_name:size; /* GNU/C bitfield */
1301 }
1302
1303 struct {
1304 string field_name;
1305 }
1306
1307
1308 8. Clocks
1309
1310 Clock metadata allows to describe the clock topology of the system, as
1311 well as to detail each clock parameter. In absence of clock description,
1312 it is assumed that all fields named "timestamp" use the same clock
1313 source, which increments once per nanosecond.
1314
1315 Describing a clock and how it is used by streams is threefold: first,
1316 the clock and clock topology should be described in a "clock"
1317 description block, e.g.:
1318
1319 clock {
1320 name = cycle_counter_sync;
1321 uuid = "62189bee-96dc-11e0-91a8-cfa3d89f3923";
1322 description = "Cycle counter synchronized across CPUs";
1323 freq = 1000000000; /* frequency, in Hz */
1324 /* precision in seconds is: 1000 * (1/freq) */
1325 precision = 1000;
1326 /*
1327 * clock value offset from Epoch is:
1328 * offset_s + (offset * (1/freq))
1329 */
1330 offset_s = 1326476837;
1331 offset = 897235420;
1332 absolute = FALSE;
1333 };
1334
1335 The mandatory "name" field specifies the name of the clock identifier,
1336 which can later be used as a reference. The optional field "uuid" is the
1337 unique identifier of the clock. It can be used to correlate different
1338 traces that use the same clock. An optional textual description string
1339 can be added with the "description" field. The "freq" field is the
1340 initial frequency of the clock, in Hz. If the "freq" field is not
1341 present, the frequency is assumed to be 1000000000 (providing clock
1342 increment of 1 ns). The optional "precision" field details the
1343 uncertainty on the clock measurements, in (1/freq) units. The "offset_s"
1344 and "offset" fields indicate the offset from POSIX.1 Epoch, 1970-01-01
1345 00:00:00 +0000 (UTC), to the zero of value of the clock. The "offset_s"
1346 field is in seconds. The "offset" field is in (1/freq) units. If any of
1347 the "offset_s" or "offset" field is not present, it is assigned the 0
1348 value. The field "absolute" is TRUE if the clock is a global reference
1349 across different clock uuid (e.g. NTP time). Otherwise, "absolute" is
1350 FALSE, and the clock can be considered as synchronized only with other
1351 clocks that have the same uuid.
1352
1353
1354 Secondly, a reference to this clock should be added within an integer
1355 type:
1356
1357 typealias integer {
1358 size = 64; align = 1; signed = false;
1359 map = clock.cycle_counter_sync.value;
1360 } := uint64_ccnt_t;
1361
1362 Thirdly, stream declarations can reference the clock they use as a
1363 time-stamp source:
1364
1365 struct packet_context {
1366 uint64_ccnt_t ccnt_begin;
1367 uint64_ccnt_t ccnt_end;
1368 /* ... */
1369 };
1370
1371 stream {
1372 /* ... */
1373 event.header := struct {
1374 uint64_ccnt_t timestamp;
1375 /* ... */
1376 }
1377 packet.context := struct packet_context;
1378 };
1379
1380 For a N-bit integer type referring to a clock, if the integer overflows
1381 compared to the N low order bits of the clock prior value, then it is
1382 assumed that one, and only one, overflow occurred. It is therefore
1383 important that events encoding time on a small number of bits happen
1384 frequently enough to detect when more than one N-bit overflow occurs.
1385
1386 In a packet context, clock field names ending with "_begin" and "_end"
1387 have a special meaning: this refers to the time-stamps at, respectively,
1388 the beginning and the end of each packet.
1389
1390
1391 A. Helper macros
1392
1393 The two following macros keep track of the size of a GNU/C structure without
1394 padding at the end by placing HEADER_END as the last field. A one byte end field
1395 is used for C90 compatibility (C99 flexible arrays could be used here). Note
1396 that this does not affect the effective structure size, which should always be
1397 calculated with the header_sizeof() helper.
1398
1399 #define HEADER_END char end_field
1400 #define header_sizeof(type) offsetof(typeof(type), end_field)
1401
1402
1403 B. Stream Header Rationale
1404
1405 An event stream is divided in contiguous event packets of variable size. These
1406 subdivisions allow the trace analyzer to perform a fast binary search by time
1407 within the stream (typically requiring to index only the event packet headers)
1408 without reading the whole stream. These subdivisions have a variable size to
1409 eliminate the need to transfer the event packet padding when partially filled
1410 event packets must be sent when streaming a trace for live viewing/analysis.
1411 An event packet can contain a certain amount of padding at the end. Dividing
1412 streams into event packets is also useful for network streaming over UDP and
1413 flight recorder mode tracing (a whole event packet can be swapped out of the
1414 buffer atomically for reading).
1415
1416 The stream header is repeated at the beginning of each event packet to allow
1417 flexibility in terms of:
1418
1419 - streaming support,
1420 - allowing arbitrary buffers to be discarded without making the trace
1421 unreadable,
1422 - allow UDP packet loss handling by either dealing with missing event packet
1423 or asking for re-transmission.
1424 - transparently support flight recorder mode,
1425 - transparently support crash dump.
1426
1427
1428 C. TSDL Grammar
1429
1430 /*
1431 * Common Trace Format (CTF) Trace Stream Description Language (TSDL) Grammar.
1432 *
1433 * Inspired from the C99 grammar:
1434 * http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1124.pdf (Annex A)
1435 * and c++1x grammar (draft)
1436 * http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2011/n3291.pdf (Annex A)
1437 *
1438 * Specialized for CTF needs by including only constant and declarations from
1439 * C99 (excluding function declarations), and by adding support for variants,
1440 * sequences and CTF-specific specifiers. Enumeration container types
1441 * semantic is inspired from c++1x enum-base.
1442 */
1443
1444 1) Lexical grammar
1445
1446 1.1) Lexical elements
1447
1448 token:
1449 keyword
1450 identifier
1451 constant
1452 string-literal
1453 punctuator
1454
1455 1.2) Keywords
1456
1457 keyword: is one of
1458
1459 align
1460 callsite
1461 const
1462 char
1463 clock
1464 double
1465 enum
1466 env
1467 event
1468 floating_point
1469 float
1470 integer
1471 int
1472 long
1473 short
1474 signed
1475 stream
1476 string
1477 struct
1478 trace
1479 typealias
1480 typedef
1481 unsigned
1482 variant
1483 void
1484 _Bool
1485 _Complex
1486 _Imaginary
1487
1488
1489 1.3) Identifiers
1490
1491 identifier:
1492 identifier-nondigit
1493 identifier identifier-nondigit
1494 identifier digit
1495
1496 identifier-nondigit:
1497 nondigit
1498 universal-character-name
1499 any other implementation-defined characters
1500
1501 nondigit:
1502 _
1503 [a-zA-Z] /* regular expression */
1504
1505 digit:
1506 [0-9] /* regular expression */
1507
1508 1.4) Universal character names
1509
1510 universal-character-name:
1511 \u hex-quad
1512 \U hex-quad hex-quad
1513
1514 hex-quad:
1515 hexadecimal-digit hexadecimal-digit hexadecimal-digit hexadecimal-digit
1516
1517 1.5) Constants
1518
1519 constant:
1520 integer-constant
1521 enumeration-constant
1522 character-constant
1523
1524 integer-constant:
1525 decimal-constant integer-suffix-opt
1526 octal-constant integer-suffix-opt
1527 hexadecimal-constant integer-suffix-opt
1528
1529 decimal-constant:
1530 nonzero-digit
1531 decimal-constant digit
1532
1533 octal-constant:
1534 0
1535 octal-constant octal-digit
1536
1537 hexadecimal-constant:
1538 hexadecimal-prefix hexadecimal-digit
1539 hexadecimal-constant hexadecimal-digit
1540
1541 hexadecimal-prefix:
1542 0x
1543 0X
1544
1545 nonzero-digit:
1546 [1-9]
1547
1548 integer-suffix:
1549 unsigned-suffix long-suffix-opt
1550 unsigned-suffix long-long-suffix
1551 long-suffix unsigned-suffix-opt
1552 long-long-suffix unsigned-suffix-opt
1553
1554 unsigned-suffix:
1555 u
1556 U
1557
1558 long-suffix:
1559 l
1560 L
1561
1562 long-long-suffix:
1563 ll
1564 LL
1565
1566 enumeration-constant:
1567 identifier
1568 string-literal
1569
1570 character-constant:
1571 ' c-char-sequence '
1572 L' c-char-sequence '
1573
1574 c-char-sequence:
1575 c-char
1576 c-char-sequence c-char
1577
1578 c-char:
1579 any member of source charset except single-quote ('), backslash
1580 (\), or new-line character.
1581 escape-sequence
1582
1583 escape-sequence:
1584 simple-escape-sequence
1585 octal-escape-sequence
1586 hexadecimal-escape-sequence
1587 universal-character-name
1588
1589 simple-escape-sequence: one of
1590 \' \" \? \\ \a \b \f \n \r \t \v
1591
1592 octal-escape-sequence:
1593 \ octal-digit
1594 \ octal-digit octal-digit
1595 \ octal-digit octal-digit octal-digit
1596
1597 hexadecimal-escape-sequence:
1598 \x hexadecimal-digit
1599 hexadecimal-escape-sequence hexadecimal-digit
1600
1601 1.6) String literals
1602
1603 string-literal:
1604 " s-char-sequence-opt "
1605 L" s-char-sequence-opt "
1606
1607 s-char-sequence:
1608 s-char
1609 s-char-sequence s-char
1610
1611 s-char:
1612 any member of source charset except double-quote ("), backslash
1613 (\), or new-line character.
1614 escape-sequence
1615
1616 1.7) Punctuators
1617
1618 punctuator: one of
1619 [ ] ( ) { } . -> * + - < > : ; ... = ,
1620
1621
1622 2) Phrase structure grammar
1623
1624 primary-expression:
1625 identifier
1626 constant
1627 string-literal
1628 ( unary-expression )
1629
1630 postfix-expression:
1631 primary-expression
1632 postfix-expression [ unary-expression ]
1633 postfix-expression . identifier
1634 postfix-expressoin -> identifier
1635
1636 unary-expression:
1637 postfix-expression
1638 unary-operator postfix-expression
1639
1640 unary-operator: one of
1641 + -
1642
1643 assignment-operator:
1644 =
1645
1646 type-assignment-operator:
1647 :=
1648
1649 constant-expression-range:
1650 unary-expression ... unary-expression
1651
1652 2.2) Declarations:
1653
1654 declaration:
1655 declaration-specifiers declarator-list-opt ;
1656 ctf-specifier ;
1657
1658 declaration-specifiers:
1659 storage-class-specifier declaration-specifiers-opt
1660 type-specifier declaration-specifiers-opt
1661 type-qualifier declaration-specifiers-opt
1662
1663 declarator-list:
1664 declarator
1665 declarator-list , declarator
1666
1667 abstract-declarator-list:
1668 abstract-declarator
1669 abstract-declarator-list , abstract-declarator
1670
1671 storage-class-specifier:
1672 typedef
1673
1674 type-specifier:
1675 void
1676 char
1677 short
1678 int
1679 long
1680 float
1681 double
1682 signed
1683 unsigned
1684 _Bool
1685 _Complex
1686 _Imaginary
1687 struct-specifier
1688 variant-specifier
1689 enum-specifier
1690 typedef-name
1691 ctf-type-specifier
1692
1693 align-attribute:
1694 align ( unary-expression )
1695
1696 struct-specifier:
1697 struct identifier-opt { struct-or-variant-declaration-list-opt } align-attribute-opt
1698 struct identifier align-attribute-opt
1699
1700 struct-or-variant-declaration-list:
1701 struct-or-variant-declaration
1702 struct-or-variant-declaration-list struct-or-variant-declaration
1703
1704 struct-or-variant-declaration:
1705 specifier-qualifier-list struct-or-variant-declarator-list ;
1706 declaration-specifiers-opt storage-class-specifier declaration-specifiers-opt declarator-list ;
1707 typealias declaration-specifiers abstract-declarator-list type-assignment-operator declaration-specifiers abstract-declarator-list ;
1708 typealias declaration-specifiers abstract-declarator-list type-assignment-operator declarator-list ;
1709
1710 specifier-qualifier-list:
1711 type-specifier specifier-qualifier-list-opt
1712 type-qualifier specifier-qualifier-list-opt
1713
1714 struct-or-variant-declarator-list:
1715 struct-or-variant-declarator
1716 struct-or-variant-declarator-list , struct-or-variant-declarator
1717
1718 struct-or-variant-declarator:
1719 declarator
1720 declarator-opt : unary-expression
1721
1722 variant-specifier:
1723 variant identifier-opt variant-tag-opt { struct-or-variant-declaration-list }
1724 variant identifier variant-tag
1725
1726 variant-tag:
1727 < unary-expression >
1728
1729 enum-specifier:
1730 enum identifier-opt { enumerator-list }
1731 enum identifier-opt { enumerator-list , }
1732 enum identifier
1733 enum identifier-opt : declaration-specifiers { enumerator-list }
1734 enum identifier-opt : declaration-specifiers { enumerator-list , }
1735
1736 enumerator-list:
1737 enumerator
1738 enumerator-list , enumerator
1739
1740 enumerator:
1741 enumeration-constant
1742 enumeration-constant assignment-operator unary-expression
1743 enumeration-constant assignment-operator constant-expression-range
1744
1745 type-qualifier:
1746 const
1747
1748 declarator:
1749 pointer-opt direct-declarator
1750
1751 direct-declarator:
1752 identifier
1753 ( declarator )
1754 direct-declarator [ unary-expression ]
1755
1756 abstract-declarator:
1757 pointer-opt direct-abstract-declarator
1758
1759 direct-abstract-declarator:
1760 identifier-opt
1761 ( abstract-declarator )
1762 direct-abstract-declarator [ unary-expression ]
1763 direct-abstract-declarator [ ]
1764
1765 pointer:
1766 * type-qualifier-list-opt
1767 * type-qualifier-list-opt pointer
1768
1769 type-qualifier-list:
1770 type-qualifier
1771 type-qualifier-list type-qualifier
1772
1773 typedef-name:
1774 identifier
1775
1776 2.3) CTF-specific declarations
1777
1778 ctf-specifier:
1779 clock { ctf-assignment-expression-list-opt }
1780 event { ctf-assignment-expression-list-opt }
1781 stream { ctf-assignment-expression-list-opt }
1782 env { ctf-assignment-expression-list-opt }
1783 trace { ctf-assignment-expression-list-opt }
1784 callsite { ctf-assignment-expression-list-opt }
1785 typealias declaration-specifiers abstract-declarator-list type-assignment-operator declaration-specifiers abstract-declarator-list
1786 typealias declaration-specifiers abstract-declarator-list type-assignment-operator declarator-list
1787
1788 ctf-type-specifier:
1789 floating_point { ctf-assignment-expression-list-opt }
1790 integer { ctf-assignment-expression-list-opt }
1791 string { ctf-assignment-expression-list-opt }
1792 string
1793
1794 ctf-assignment-expression-list:
1795 ctf-assignment-expression ;
1796 ctf-assignment-expression-list ctf-assignment-expression ;
1797
1798 ctf-assignment-expression:
1799 unary-expression assignment-operator unary-expression
1800 unary-expression type-assignment-operator type-specifier
1801 declaration-specifiers-opt storage-class-specifier declaration-specifiers-opt declarator-list
1802 typealias declaration-specifiers abstract-declarator-list type-assignment-operator declaration-specifiers abstract-declarator-list
1803 typealias declaration-specifiers abstract-declarator-list type-assignment-operator declarator-list
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