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