Specify that trace readers (and not parser) should remove leading field underscores
[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. Fields starting with an
424 underscore should have their leading underscore removed by the CTF trace
425 readers.
426
427 A nameless structure can be declared as a field type or as part of a typedef:
428
429 struct {
430 ...
431 }
432
433 Alignment for a structure compound type can be forced to a minimum value
434 by adding an "align" specifier after the declaration of a structure
435 body. This attribute is read as: align(value). The value is specified in
436 bits. The structure will be aligned on the maximum value between this
437 attribute and the alignment required by the basic types contained within
438 the structure. e.g.
439
440 struct {
441 ...
442 } align(32)
443
444 4.2.2 Variants (Discriminated/Tagged Unions)
445
446 A CTF variant is a selection between different types. A CTF variant must
447 always be defined within the scope of a structure or within fields
448 contained within a structure (defined recursively). A "tag" enumeration
449 field must appear in either the same static scope, prior to the variant
450 field (in field declaration order), in an upper static scope , or in an
451 upper dynamic scope (see Section 7.3.2). The type selection is indicated
452 by the mapping from the enumeration value to the string used as variant
453 type selector. The field to use as tag is specified by the "tag_field",
454 specified between "< >" after the "variant" keyword for unnamed
455 variants, and after "variant name" for named variants.
456
457 The alignment of the variant is the alignment of the type as selected by the tag
458 value for the specific instance of the variant. The alignment of the type
459 containing the variant is independent of the variant alignment. The size of the
460 variant is the size as selected by the tag value for the specific instance of
461 the variant.
462
463 Each variant type selector possess a field name, which is a unique
464 identifier within the variant. The identifier is not allowed to use any
465 reserved keyword (see Section C.1.2). Replacing reserved keywords with
466 underscore-prefixed field names is recommended. Fields starting with an
467 underscore should have their leading underscore removed by the CTF trace
468 readers.
469
470
471 A named variant declaration followed by its definition within a structure
472 declaration:
473
474 variant name {
475 field_type sel1;
476 field_type sel2;
477 field_type sel3;
478 ...
479 };
480
481 struct {
482 enum : integer_type { sel1, sel2, sel3, ... } tag_field;
483 ...
484 variant name <tag_field> v;
485 }
486
487 An unnamed variant definition within a structure is expressed by the following
488 TSDL meta-data:
489
490 struct {
491 enum : integer_type { sel1, sel2, sel3, ... } tag_field;
492 ...
493 variant <tag_field> {
494 field_type sel1;
495 field_type sel2;
496 field_type sel3;
497 ...
498 } v;
499 }
500
501 Example of a named variant within a sequence that refers to a single tag field:
502
503 variant example {
504 uint32_t a;
505 uint64_t b;
506 short c;
507 };
508
509 struct {
510 enum : uint2_t { a, b, c } choice;
511 unsigned int seqlen;
512 variant example <choice> v[seqlen];
513 }
514
515 Example of an unnamed variant:
516
517 struct {
518 enum : uint2_t { a, b, c, d } choice;
519 /* Unrelated fields can be added between the variant and its tag */
520 int32_t somevalue;
521 variant <choice> {
522 uint32_t a;
523 uint64_t b;
524 short c;
525 struct {
526 unsigned int field1;
527 uint64_t field2;
528 } d;
529 } s;
530 }
531
532 Example of an unnamed variant within an array:
533
534 struct {
535 enum : uint2_t { a, b, c } choice;
536 variant <choice> {
537 uint32_t a;
538 uint64_t b;
539 short c;
540 } v[10];
541 }
542
543 Example of a variant type definition within a structure, where the defined type
544 is then declared within an array of structures. This variant refers to a tag
545 located in an upper static scope. This example clearly shows that a variant
546 type definition referring to the tag "x" uses the closest preceding field from
547 the static scope of the type definition.
548
549 struct {
550 enum : uint2_t { a, b, c, d } x;
551
552 typedef variant <x> { /*
553 * "x" refers to the preceding "x" enumeration in the
554 * static scope of the type definition.
555 */
556 uint32_t a;
557 uint64_t b;
558 short c;
559 } example_variant;
560
561 struct {
562 enum : int { x, y, z } x; /* This enumeration is not used by "v". */
563 example_variant v; /*
564 * "v" uses the "enum : uint2_t { a, b, c, d }"
565 * tag.
566 */
567 } a[10];
568 }
569
570 4.2.3 Arrays
571
572 Arrays are fixed-length. Their length is declared in the type
573 declaration within the meta-data. They contain an array of "inner type"
574 elements, which can refer to any type not containing the type of the
575 array being declared (no circular dependency). The length is the number
576 of elements in an array.
577
578 TSDL meta-data representation of a named array:
579
580 typedef elem_type name[length];
581
582 A nameless array can be declared as a field type within a structure, e.g.:
583
584 uint8_t field_name[10];
585
586 Arrays are always aligned on their element alignment requirement.
587
588 4.2.4 Sequences
589
590 Sequences are dynamically-sized arrays. They refer to a a "length"
591 unsigned integer field, which must appear in either the same static scope,
592 prior to the sequence field (in field declaration order), in an upper
593 static scope, or in an upper dynamic scope (see Section 7.3.2). This
594 length field represents the number of elements in the sequence. The
595 sequence per se is an array of "inner type" elements.
596
597 TSDL meta-data representation for a sequence type definition:
598
599 struct {
600 unsigned int length_field;
601 typedef elem_type typename[length_field];
602 typename seq_field_name;
603 }
604
605 A sequence can also be declared as a field type, e.g.:
606
607 struct {
608 unsigned int length_field;
609 long seq_field_name[length_field];
610 }
611
612 Multiple sequences can refer to the same length field, and these length
613 fields can be in a different upper dynamic scope:
614
615 e.g., assuming the stream.event.header defines:
616
617 stream {
618 ...
619 id = 1;
620 event.header := struct {
621 uint16_t seq_len;
622 };
623 };
624
625 event {
626 ...
627 stream_id = 1;
628 fields := struct {
629 long seq_a[stream.event.header.seq_len];
630 char seq_b[stream.event.header.seq_len];
631 };
632 };
633
634 The sequence elements follow the "array" specifications.
635
636 4.2.5 Strings
637
638 Strings are an array of bytes of variable size and are terminated by a '\0'
639 "NULL" character. Their encoding is described in the TSDL meta-data. In
640 absence of encoding attribute information, the default encoding is
641 UTF-8.
642
643 TSDL meta-data representation of a named string type:
644
645 typealias string {
646 encoding = UTF8 OR ASCII;
647 } := name;
648
649 A nameless string type can be declared as a field type:
650
651 string field_name; /* Use default UTF8 encoding */
652
653 Strings are always aligned on byte size.
654
655 5. Event Packet Header
656
657 The event packet header consists of two parts: the "event packet header"
658 is the same for all streams of a trace. The second part, the "event
659 packet context", is described on a per-stream basis. Both are described
660 in the TSDL meta-data. The packets are aligned on architecture-page-sized
661 addresses.
662
663 Event packet header (all fields are optional, specified by TSDL meta-data):
664
665 - Magic number (CTF magic number: 0xC1FC1FC1) specifies that this is a
666 CTF packet. This magic number is optional, but when present, it should
667 come at the very beginning of the packet.
668 - Trace UUID, used to ensure the event packet match the meta-data used.
669 (note: we cannot use a meta-data checksum in every cases instead of a
670 UUID because meta-data can be appended to while tracing is active)
671 This field is optional.
672 - Stream ID, used as reference to stream description in meta-data.
673 This field is optional if there is only one stream description in the
674 meta-data, but becomes required if there are more than one stream in
675 the TSDL meta-data description.
676
677 Event packet context (all fields are optional, specified by TSDL meta-data):
678
679 - Event packet content size (in bits).
680 - Event packet size (in bits, includes padding).
681 - Event packet content checksum. Checksum excludes the event packet
682 header.
683 - Per-stream event packet sequence count (to deal with UDP packet loss). The
684 number of significant sequence counter bits should also be present, so
685 wrap-arounds are dealt with correctly.
686 - Time-stamp at the beginning and time-stamp at the end of the event packet.
687 Both timestamps are written in the packet header, but sampled respectively
688 while (or before) writing the first event and while (or after) writing the
689 last event in the packet. The inclusive range between these timestamps should
690 include all event timestamps assigned to events contained within the packet.
691 - Events discarded count
692 - Snapshot of a per-stream free-running counter, counting the number of
693 events discarded that were supposed to be written in the stream prior to
694 the first event in the event packet.
695 * Note: producer-consumer buffer full condition should fill the current
696 event packet with padding so we know exactly where events have been
697 discarded.
698 - Lossless compression scheme used for the event packet content. Applied
699 directly to raw data. New types of compression can be added in following
700 versions of the format.
701 0: no compression scheme
702 1: bzip2
703 2: gzip
704 3: xz
705 - Cypher used for the event packet content. Applied after compression.
706 0: no encryption
707 1: AES
708 - Checksum scheme used for the event packet content. Applied after encryption.
709 0: no checksum
710 1: md5
711 2: sha1
712 3: crc32
713
714 5.1 Event Packet Header Description
715
716 The event packet header layout is indicated by the trace packet.header
717 field. Here is a recommended structure type for the packet header with
718 the fields typically expected (although these fields are each optional):
719
720 struct event_packet_header {
721 uint32_t magic;
722 uint8_t uuid[16];
723 uint32_t stream_id;
724 };
725
726 trace {
727 ...
728 packet.header := struct event_packet_header;
729 };
730
731 If the magic number is not present, tools such as "file" will have no
732 mean to discover the file type.
733
734 If the uuid is not present, no validation that the meta-data actually
735 corresponds to the stream is performed.
736
737 If the stream_id packet header field is missing, the trace can only
738 contain a single stream. Its "id" field can be left out, and its events
739 don't need to declare a "stream_id" field.
740
741
742 5.2 Event Packet Context Description
743
744 Event packet context example. These are declared within the stream declaration
745 in the meta-data. All these fields are optional. If the packet size field is
746 missing, the whole stream only contains a single packet. If the content
747 size field is missing, the packet is filled (no padding). The content
748 and packet sizes include all headers.
749
750 An example event packet context type:
751
752 struct event_packet_context {
753 uint64_t timestamp_begin;
754 uint64_t timestamp_end;
755 uint32_t checksum;
756 uint32_t stream_packet_count;
757 uint32_t events_discarded;
758 uint32_t cpu_id;
759 uint32_t/uint16_t content_size;
760 uint32_t/uint16_t packet_size;
761 uint8_t compression_scheme;
762 uint8_t encryption_scheme;
763 uint8_t checksum_scheme;
764 };
765
766
767 6. Event Structure
768
769 The overall structure of an event is:
770
771 1 - Stream Packet Context (as specified by the stream meta-data)
772 2 - Event Header (as specified by the stream meta-data)
773 3 - Stream Event Context (as specified by the stream meta-data)
774 4 - Event Context (as specified by the event meta-data)
775 5 - Event Payload (as specified by the event meta-data)
776
777 This structure defines an implicit dynamic scoping, where variants
778 located in inner structures (those with a higher number in the listing
779 above) can refer to the fields of outer structures (with lower number in
780 the listing above). See Section 7.3 TSDL Scopes for more detail.
781
782 6.1 Event Header
783
784 Event headers can be described within the meta-data. We hereby propose, as an
785 example, two types of events headers. Type 1 accommodates streams with less than
786 31 event IDs. Type 2 accommodates streams with 31 or more event IDs.
787
788 One major factor can vary between streams: the number of event IDs assigned to
789 a stream. Luckily, this information tends to stay relatively constant (modulo
790 event registration while trace is being recorded), so we can specify different
791 representations for streams containing few event IDs and streams containing
792 many event IDs, so we end up representing the event ID and time-stamp as
793 densely as possible in each case.
794
795 The header is extended in the rare occasions where the information cannot be
796 represented in the ranges available in the standard event header. They are also
797 used in the rare occasions where the data required for a field could not be
798 collected: the flag corresponding to the missing field within the missing_fields
799 array is then set to 1.
800
801 Types uintX_t represent an X-bit unsigned integer, as declared with
802 either:
803
804 typealias integer { size = X; align = X; signed = false } := uintX_t;
805
806 or
807
808 typealias integer { size = X; align = 1; signed = false } := uintX_t;
809
810 6.1.1 Type 1 - Few event IDs
811
812 - Aligned on 32-bit (or 8-bit if byte-packed, depending on the architecture
813 preference).
814 - Native architecture byte ordering.
815 - For "compact" selection
816 - Fixed size: 32 bits.
817 - For "extended" selection
818 - Size depends on the architecture and variant alignment.
819
820 struct event_header_1 {
821 /*
822 * id: range: 0 - 30.
823 * id 31 is reserved to indicate an extended header.
824 */
825 enum : uint5_t { compact = 0 ... 30, extended = 31 } id;
826 variant <id> {
827 struct {
828 uint27_t timestamp;
829 } compact;
830 struct {
831 uint32_t id; /* 32-bit event IDs */
832 uint64_t timestamp; /* 64-bit timestamps */
833 } extended;
834 } v;
835 } align(32); /* or align(8) */
836
837
838 6.1.2 Type 2 - Many event IDs
839
840 - Aligned on 16-bit (or 8-bit if byte-packed, depending on the architecture
841 preference).
842 - Native architecture byte ordering.
843 - For "compact" selection
844 - Size depends on the architecture and variant alignment.
845 - For "extended" selection
846 - Size depends on the architecture and variant alignment.
847
848 struct event_header_2 {
849 /*
850 * id: range: 0 - 65534.
851 * id 65535 is reserved to indicate an extended header.
852 */
853 enum : uint16_t { compact = 0 ... 65534, extended = 65535 } id;
854 variant <id> {
855 struct {
856 uint32_t timestamp;
857 } compact;
858 struct {
859 uint32_t id; /* 32-bit event IDs */
860 uint64_t timestamp; /* 64-bit timestamps */
861 } extended;
862 } v;
863 } align(16); /* or align(8) */
864
865
866 6.2 Event Context
867
868 The event context contains information relative to the current event.
869 The choice and meaning of this information is specified by the TSDL
870 stream and event meta-data descriptions. The stream context is applied
871 to all events within the stream. The stream context structure follows
872 the event header. The event context is applied to specific events. Its
873 structure follows the stream context structure.
874
875 An example of stream-level event context is to save the event payload size with
876 each event, or to save the current PID with each event. These are declared
877 within the stream declaration within the meta-data:
878
879 stream {
880 ...
881 event.context := struct {
882 uint pid;
883 uint16_t payload_size;
884 };
885 };
886
887 An example of event-specific event context is to declare a bitmap of missing
888 fields, only appended after the stream event context if the extended event
889 header is selected. NR_FIELDS is the number of fields within the event (a
890 numeric value).
891
892 event {
893 context = struct {
894 variant <id> {
895 struct { } compact;
896 struct {
897 uint1_t missing_fields[NR_FIELDS]; /* missing event fields bitmap */
898 } extended;
899 } v;
900 };
901 ...
902 }
903
904 6.3 Event Payload
905
906 An event payload contains fields specific to a given event type. The fields
907 belonging to an event type are described in the event-specific meta-data
908 within a structure type.
909
910 6.3.1 Padding
911
912 No padding at the end of the event payload. This differs from the ISO/C standard
913 for structures, but follows the CTF standard for structures. In a trace, even
914 though it makes sense to align the beginning of a structure, it really makes no
915 sense to add padding at the end of the structure, because structures are usually
916 not followed by a structure of the same type.
917
918 This trick can be done by adding a zero-length "end" field at the end of the C
919 structures, and by using the offset of this field rather than using sizeof()
920 when calculating the size of a structure (see Appendix "A. Helper macros").
921
922 6.3.2 Alignment
923
924 The event payload is aligned on the largest alignment required by types
925 contained within the payload. (This follows the ISO/C standard for structures)
926
927
928 7. Trace Stream Description Language (TSDL)
929
930 The Trace Stream Description Language (TSDL) allows expression of the
931 binary trace streams layout in a C99-like Domain Specific Language
932 (DSL).
933
934
935 7.1 Meta-data
936
937 The trace stream layout description is located in the trace meta-data.
938 The meta-data is itself located in a stream identified by its name:
939 "metadata".
940
941 The meta-data description can be expressed in two different formats:
942 text-only and packet-based. The text-only description facilitates
943 generation of meta-data and provides a convenient way to enter the
944 meta-data information by hand. The packet-based meta-data provides the
945 CTF stream packet facilities (checksumming, compression, encryption,
946 network-readiness) for meta-data stream generated and transported by a
947 tracer.
948
949 The text-only meta-data file is a plain-text TSDL description. This file
950 must begin with the following characters to identify the file as a CTF
951 TSDL text-based metadata file (without the double-quotes) :
952
953 "/* CTF"
954
955 It must be followed by a space, and the version of the specification
956 followed by the CTF trace, e.g.:
957
958 " 1.8"
959
960 These characters allow automated discovery of file type and CTF
961 specification version. They are interpreted as a the beginning of a
962 comment by the TSDL metadata parser. The comment can be continued to
963 contain extra commented characters before it is closed.
964
965 The packet-based meta-data is made of "meta-data packets", which each
966 start with a meta-data packet header. The packet-based meta-data
967 description is detected by reading the magic number "0x75D11D57" at the
968 beginning of the file. This magic number is also used to detect the
969 endianness of the architecture by trying to read the CTF magic number
970 and its counterpart in reversed endianness. The events within the
971 meta-data stream have no event header nor event context. Each event only
972 contains a "sequence" payload, which is a sequence of bits using the
973 "trace.packet.header.content_size" field as a placeholder for its length
974 (the packet header size should be substracted). The formatting of this
975 sequence of bits is a plain-text representation of the TSDL description.
976 Each meta-data packet start with a special packet header, specific to
977 the meta-data stream, which contains, exactly:
978
979 struct metadata_packet_header {
980 uint32_t magic; /* 0x75D11D57 */
981 uint8_t uuid[16]; /* Unique Universal Identifier */
982 uint32_t checksum; /* 0 if unused */
983 uint32_t content_size; /* in bits */
984 uint32_t packet_size; /* in bits */
985 uint8_t compression_scheme; /* 0 if unused */
986 uint8_t encryption_scheme; /* 0 if unused */
987 uint8_t checksum_scheme; /* 0 if unused */
988 uint8_t major; /* CTF spec version major number */
989 uint8_t minor; /* CTF spec version minor number */
990 };
991
992 The packet-based meta-data can be converted to a text-only meta-data by
993 concatenating all the strings in contains.
994
995 In the textual representation of the meta-data, the text contained
996 within "/*" and "*/", as well as within "//" and end of line, are
997 treated as comments. Boolean values can be represented as true, TRUE,
998 or 1 for true, and false, FALSE, or 0 for false. Within the string-based
999 meta-data description, the trace UUID is represented as a string of
1000 hexadecimal digits and dashes "-". In the event packet header, the trace
1001 UUID is represented as an array of bytes.
1002
1003
1004 7.2 Declaration vs Definition
1005
1006 A declaration associates a layout to a type, without specifying where
1007 this type is located in the event structure hierarchy (see Section 6).
1008 This therefore includes typedef, typealias, as well as all type
1009 specifiers. In certain circumstances (typedef, structure field and
1010 variant field), a declaration is followed by a declarator, which specify
1011 the newly defined type name (for typedef), or the field name (for
1012 declarations located within structure and variants). Array and sequence,
1013 declared with square brackets ("[" "]"), are part of the declarator,
1014 similarly to C99. The enumeration base type is specified by
1015 ": enum_base", which is part of the type specifier. The variant tag
1016 name, specified between "<" ">", is also part of the type specifier.
1017
1018 A definition associates a type to a location in the event structure
1019 hierarchy (see Section 6). This association is denoted by ":=", as shown
1020 in Section 7.3.
1021
1022
1023 7.3 TSDL Scopes
1024
1025 TSDL uses three different types of scoping: a lexical scope is used for
1026 declarations and type definitions, and static and dynamic scopes are
1027 used for variants references to tag fields (with relative and absolute
1028 path lookups) and for sequence references to length fields.
1029
1030 7.3.1 Lexical Scope
1031
1032 Each of "trace", "stream", "event", "struct" and "variant" have their own
1033 nestable declaration scope, within which types can be declared using "typedef"
1034 and "typealias". A root declaration scope also contains all declarations
1035 located outside of any of the aforementioned declarations. An inner
1036 declaration scope can refer to type declared within its container
1037 lexical scope prior to the inner declaration scope. Redefinition of a
1038 typedef or typealias is not valid, although hiding an upper scope
1039 typedef or typealias is allowed within a sub-scope.
1040
1041 7.3.2 Static and Dynamic Scopes
1042
1043 A local static scope consists in the scope generated by the declaration
1044 of fields within a compound type. A static scope is a local static scope
1045 augmented with the nested sub-static-scopes it contains.
1046
1047 A dynamic scope consists in the static scope augmented with the
1048 implicit event structure definition hierarchy presented at Section 6.
1049
1050 Multiple declarations of the same field name within a local static scope
1051 is not valid. It is however valid to re-use the same field name in
1052 different local scopes.
1053
1054 Nested static and dynamic scopes form lookup paths. These are used for
1055 variant tag and sequence length references. They are used at the variant
1056 and sequence definition site to look up the location of the tag field
1057 associated with a variant, and to lookup up the location of the length
1058 field associated with a sequence.
1059
1060 Variants and sequences can refer to a tag field either using a relative
1061 path or an absolute path. The relative path is relative to the scope in
1062 which the variant or sequence performing the lookup is located.
1063 Relative paths are only allowed to lookup within the same static scope,
1064 which includes its nested static scopes. Lookups targeting parent static
1065 scopes need to be performed with an absolute path.
1066
1067 Absolute path lookups use the full path including the dynamic scope
1068 followed by a "." and then the static scope. Therefore, variants (or
1069 sequences) in lower levels in the dynamic scope (e.g. event context) can
1070 refer to a tag (or length) field located in upper levels (e.g. in the
1071 event header) by specifying, in this case, the associated tag with
1072 <stream.event.header.field_name>. This allows, for instance, the event
1073 context to define a variant referring to the "id" field of the event
1074 header as selector.
1075
1076 The dynamic scope prefixes are thus:
1077
1078 - Trace Packet Header: <trace.packet.header. >,
1079 - Stream Packet Context: <stream.packet.context. >,
1080 - Event Header: <stream.event.header. >,
1081 - Stream Event Context: <stream.event.context. >,
1082 - Event Context: <event.context. >,
1083 - Event Payload: <event.fields. >.
1084
1085
1086 The target dynamic scope must be specified explicitly when referring to
1087 a field outside of the static scope (absolute scope reference). No
1088 conflict can occur between relative and dynamic paths, because the
1089 keywords "trace", "stream", and "event" are reserved, and thus
1090 not permitted as field names. It is recommended that field names
1091 clashing with CTF and C99 reserved keywords use an underscore prefix to
1092 eliminate the risk of generating a description containing an invalid
1093 field name. Consequently, fields starting with an underscore should have
1094 their leading underscore removed by the CTF trace readers.
1095
1096
1097 The information available in the dynamic scopes can be thought of as the
1098 current tracing context. At trace production, information about the
1099 current context is saved into the specified scope field levels. At trace
1100 consumption, for each event, the current trace context is therefore
1101 readable by accessing the upper dynamic scopes.
1102
1103
1104 7.4 TSDL Examples
1105
1106 The grammar representing the TSDL meta-data is presented in Appendix C.
1107 TSDL Grammar. This section presents a rather lighter reading that
1108 consists in examples of TSDL meta-data, with template values.
1109
1110 The stream "id" can be left out if there is only one stream in the
1111 trace. The event "id" field can be left out if there is only one event
1112 in a stream.
1113
1114 trace {
1115 major = value; /* Trace format version */
1116 minor = value;
1117 uuid = "aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa"; /* Trace UUID */
1118 byte_order = be OR le; /* Endianness (required) */
1119 packet.header := struct {
1120 uint32_t magic;
1121 uint8_t uuid[16];
1122 uint32_t stream_id;
1123 };
1124 };
1125
1126 stream {
1127 id = stream_id;
1128 /* Type 1 - Few event IDs; Type 2 - Many event IDs. See section 6.1. */
1129 event.header := event_header_1 OR event_header_2;
1130 event.context := struct {
1131 ...
1132 };
1133 packet.context := struct {
1134 ...
1135 };
1136 };
1137
1138 event {
1139 name = "event_name";
1140 id = value; /* Numeric identifier within the stream */
1141 stream_id = stream_id;
1142 loglevel.identifier = "loglevel_identifier";
1143 loglevel.value = value;
1144 context := struct {
1145 ...
1146 };
1147 fields := struct {
1148 ...
1149 };
1150 };
1151
1152 /* More detail on types in section 4. Types */
1153
1154 /*
1155 * Named types:
1156 *
1157 * Type declarations behave similarly to the C standard.
1158 */
1159
1160 typedef aliased_type_specifiers new_type_declarators;
1161
1162 /* e.g.: typedef struct example new_type_name[10]; */
1163
1164 /*
1165 * typealias
1166 *
1167 * The "typealias" declaration can be used to give a name (including
1168 * pointer declarator specifier) to a type. It should also be used to
1169 * map basic C types (float, int, unsigned long, ...) to a CTF type.
1170 * Typealias is a superset of "typedef": it also allows assignment of a
1171 * simple variable identifier to a type.
1172 */
1173
1174 typealias type_class {
1175 ...
1176 } := type_specifiers type_declarator;
1177
1178 /*
1179 * e.g.:
1180 * typealias integer {
1181 * size = 32;
1182 * align = 32;
1183 * signed = false;
1184 * } := struct page *;
1185 *
1186 * typealias integer {
1187 * size = 32;
1188 * align = 32;
1189 * signed = true;
1190 * } := int;
1191 */
1192
1193 struct name {
1194 ...
1195 };
1196
1197 variant name {
1198 ...
1199 };
1200
1201 enum name : integer_type {
1202 ...
1203 };
1204
1205
1206 /*
1207 * Unnamed types, contained within compound type fields, typedef or typealias.
1208 */
1209
1210 struct {
1211 ...
1212 }
1213
1214 struct {
1215 ...
1216 } align(value)
1217
1218 variant {
1219 ...
1220 }
1221
1222 enum : integer_type {
1223 ...
1224 }
1225
1226 typedef type new_type[length];
1227
1228 struct {
1229 type field_name[length];
1230 }
1231
1232 typedef type new_type[length_type];
1233
1234 struct {
1235 type field_name[length_type];
1236 }
1237
1238 integer {
1239 ...
1240 }
1241
1242 floating_point {
1243 ...
1244 }
1245
1246 struct {
1247 integer_type field_name:size; /* GNU/C bitfield */
1248 }
1249
1250 struct {
1251 string field_name;
1252 }
1253
1254
1255 8. Clocks
1256
1257 Clock metadata allows to describe the clock topology of the system, as
1258 well as to detail each clock parameter. In absence of clock description,
1259 it is assumed that all fields named "timestamp" use the same clock
1260 source, which increments once per nanosecond.
1261
1262 Describing a clock and how it is used by streams is threefold: first,
1263 the clock and clock topology should be described in a "clock"
1264 description block, e.g.:
1265
1266 clock {
1267 name = cycle_counter_sync;
1268 uuid = "62189bee-96dc-11e0-91a8-cfa3d89f3923";
1269 description = "Cycle counter synchronized across CPUs";
1270 freq = 1000000000; /* frequency, in Hz */
1271 /* precision in seconds is: 1000 * (1/freq) */
1272 precision = 1000;
1273 /*
1274 * clock value offset from Epoch is:
1275 * offset_s + (offset * (1/freq))
1276 */
1277 offset_s = 1326476837;
1278 offset = 897235420;
1279 absolute = FALSE;
1280 };
1281
1282 The mandatory "name" field specifies the name of the clock identifier,
1283 which can later be used as a reference. The optional field "uuid" is the
1284 unique identifier of the clock. It can be used to correlate different
1285 traces that use the same clock. An optional textual description string
1286 can be added with the "description" field. The "freq" field is the
1287 initial frequency of the clock, in Hz. If the "freq" field is not
1288 present, the frequency is assumed to be 1000000000 (providing clock
1289 increment of 1 ns). The optional "precision" field details the
1290 uncertainty on the clock measurements, in (1/freq) units. The "offset_s"
1291 and "offset" fields indicate the offset from POSIX.1 Epoch, 1970-01-01
1292 00:00:00 +0000 (UTC), to the zero of value of the clock. The "offset_s"
1293 field is in seconds. The "offset" field is in (1/freq) units. If any of
1294 the "offset_s" or "offset" field is not present, it is assigned the 0
1295 value. The field "absolute" is TRUE if the clock is a global reference
1296 across different clock uuid (e.g. NTP time). Otherwise, "absolute" is
1297 FALSE, and the clock can be considered as synchronized only with other
1298 clocks that have the same uuid.
1299
1300
1301 Secondly, a reference to this clock should be added within an integer
1302 type:
1303
1304 typealias integer {
1305 size = 64; align = 1; signed = false;
1306 map = clock.cycle_counter_sync.value;
1307 } := uint64_ccnt_t;
1308
1309 Thirdly, stream declarations can reference the clock they use as a
1310 time-stamp source:
1311
1312 struct packet_context {
1313 uint64_ccnt_t ccnt_begin;
1314 uint64_ccnt_t ccnt_end;
1315 /* ... */
1316 };
1317
1318 stream {
1319 /* ... */
1320 event.header := struct {
1321 uint64_ccnt_t timestamp;
1322 /* ... */
1323 }
1324 packet.context := struct packet_context;
1325 };
1326
1327 For a N-bit integer type referring to a clock, if the integer overflows
1328 compared to the N low order bits of the clock prior value, then it is
1329 assumed that one, and only one, overflow occurred. It is therefore
1330 important that events encoding time on a small number of bits happen
1331 frequently enough to detect when more than one N-bit overflow occurs.
1332
1333 In a packet context, clock field names ending with "_begin" and "_end"
1334 have a special meaning: this refers to the time-stamps at, respectively,
1335 the beginning and the end of each packet.
1336
1337
1338 A. Helper macros
1339
1340 The two following macros keep track of the size of a GNU/C structure without
1341 padding at the end by placing HEADER_END as the last field. A one byte end field
1342 is used for C90 compatibility (C99 flexible arrays could be used here). Note
1343 that this does not affect the effective structure size, which should always be
1344 calculated with the header_sizeof() helper.
1345
1346 #define HEADER_END char end_field
1347 #define header_sizeof(type) offsetof(typeof(type), end_field)
1348
1349
1350 B. Stream Header Rationale
1351
1352 An event stream is divided in contiguous event packets of variable size. These
1353 subdivisions allow the trace analyzer to perform a fast binary search by time
1354 within the stream (typically requiring to index only the event packet headers)
1355 without reading the whole stream. These subdivisions have a variable size to
1356 eliminate the need to transfer the event packet padding when partially filled
1357 event packets must be sent when streaming a trace for live viewing/analysis.
1358 An event packet can contain a certain amount of padding at the end. Dividing
1359 streams into event packets is also useful for network streaming over UDP and
1360 flight recorder mode tracing (a whole event packet can be swapped out of the
1361 buffer atomically for reading).
1362
1363 The stream header is repeated at the beginning of each event packet to allow
1364 flexibility in terms of:
1365
1366 - streaming support,
1367 - allowing arbitrary buffers to be discarded without making the trace
1368 unreadable,
1369 - allow UDP packet loss handling by either dealing with missing event packet
1370 or asking for re-transmission.
1371 - transparently support flight recorder mode,
1372 - transparently support crash dump.
1373
1374
1375 C. TSDL Grammar
1376
1377 /*
1378 * Common Trace Format (CTF) Trace Stream Description Language (TSDL) Grammar.
1379 *
1380 * Inspired from the C99 grammar:
1381 * http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1124.pdf (Annex A)
1382 * and c++1x grammar (draft)
1383 * http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2011/n3291.pdf (Annex A)
1384 *
1385 * Specialized for CTF needs by including only constant and declarations from
1386 * C99 (excluding function declarations), and by adding support for variants,
1387 * sequences and CTF-specific specifiers. Enumeration container types
1388 * semantic is inspired from c++1x enum-base.
1389 */
1390
1391 1) Lexical grammar
1392
1393 1.1) Lexical elements
1394
1395 token:
1396 keyword
1397 identifier
1398 constant
1399 string-literal
1400 punctuator
1401
1402 1.2) Keywords
1403
1404 keyword: is one of
1405
1406 align
1407 const
1408 char
1409 clock
1410 double
1411 enum
1412 event
1413 floating_point
1414 float
1415 integer
1416 int
1417 long
1418 short
1419 signed
1420 stream
1421 string
1422 struct
1423 trace
1424 typealias
1425 typedef
1426 unsigned
1427 variant
1428 void
1429 _Bool
1430 _Complex
1431 _Imaginary
1432
1433
1434 1.3) Identifiers
1435
1436 identifier:
1437 identifier-nondigit
1438 identifier identifier-nondigit
1439 identifier digit
1440
1441 identifier-nondigit:
1442 nondigit
1443 universal-character-name
1444 any other implementation-defined characters
1445
1446 nondigit:
1447 _
1448 [a-zA-Z] /* regular expression */
1449
1450 digit:
1451 [0-9] /* regular expression */
1452
1453 1.4) Universal character names
1454
1455 universal-character-name:
1456 \u hex-quad
1457 \U hex-quad hex-quad
1458
1459 hex-quad:
1460 hexadecimal-digit hexadecimal-digit hexadecimal-digit hexadecimal-digit
1461
1462 1.5) Constants
1463
1464 constant:
1465 integer-constant
1466 enumeration-constant
1467 character-constant
1468
1469 integer-constant:
1470 decimal-constant integer-suffix-opt
1471 octal-constant integer-suffix-opt
1472 hexadecimal-constant integer-suffix-opt
1473
1474 decimal-constant:
1475 nonzero-digit
1476 decimal-constant digit
1477
1478 octal-constant:
1479 0
1480 octal-constant octal-digit
1481
1482 hexadecimal-constant:
1483 hexadecimal-prefix hexadecimal-digit
1484 hexadecimal-constant hexadecimal-digit
1485
1486 hexadecimal-prefix:
1487 0x
1488 0X
1489
1490 nonzero-digit:
1491 [1-9]
1492
1493 integer-suffix:
1494 unsigned-suffix long-suffix-opt
1495 unsigned-suffix long-long-suffix
1496 long-suffix unsigned-suffix-opt
1497 long-long-suffix unsigned-suffix-opt
1498
1499 unsigned-suffix:
1500 u
1501 U
1502
1503 long-suffix:
1504 l
1505 L
1506
1507 long-long-suffix:
1508 ll
1509 LL
1510
1511 enumeration-constant:
1512 identifier
1513 string-literal
1514
1515 character-constant:
1516 ' c-char-sequence '
1517 L' c-char-sequence '
1518
1519 c-char-sequence:
1520 c-char
1521 c-char-sequence c-char
1522
1523 c-char:
1524 any member of source charset except single-quote ('), backslash
1525 (\), or new-line character.
1526 escape-sequence
1527
1528 escape-sequence:
1529 simple-escape-sequence
1530 octal-escape-sequence
1531 hexadecimal-escape-sequence
1532 universal-character-name
1533
1534 simple-escape-sequence: one of
1535 \' \" \? \\ \a \b \f \n \r \t \v
1536
1537 octal-escape-sequence:
1538 \ octal-digit
1539 \ octal-digit octal-digit
1540 \ octal-digit octal-digit octal-digit
1541
1542 hexadecimal-escape-sequence:
1543 \x hexadecimal-digit
1544 hexadecimal-escape-sequence hexadecimal-digit
1545
1546 1.6) String literals
1547
1548 string-literal:
1549 " s-char-sequence-opt "
1550 L" s-char-sequence-opt "
1551
1552 s-char-sequence:
1553 s-char
1554 s-char-sequence s-char
1555
1556 s-char:
1557 any member of source charset except double-quote ("), backslash
1558 (\), or new-line character.
1559 escape-sequence
1560
1561 1.7) Punctuators
1562
1563 punctuator: one of
1564 [ ] ( ) { } . -> * + - < > : ; ... = ,
1565
1566
1567 2) Phrase structure grammar
1568
1569 primary-expression:
1570 identifier
1571 constant
1572 string-literal
1573 ( unary-expression )
1574
1575 postfix-expression:
1576 primary-expression
1577 postfix-expression [ unary-expression ]
1578 postfix-expression . identifier
1579 postfix-expressoin -> identifier
1580
1581 unary-expression:
1582 postfix-expression
1583 unary-operator postfix-expression
1584
1585 unary-operator: one of
1586 + -
1587
1588 assignment-operator:
1589 =
1590
1591 type-assignment-operator:
1592 :=
1593
1594 constant-expression-range:
1595 unary-expression ... unary-expression
1596
1597 2.2) Declarations:
1598
1599 declaration:
1600 declaration-specifiers declarator-list-opt ;
1601 ctf-specifier ;
1602
1603 declaration-specifiers:
1604 storage-class-specifier declaration-specifiers-opt
1605 type-specifier declaration-specifiers-opt
1606 type-qualifier declaration-specifiers-opt
1607
1608 declarator-list:
1609 declarator
1610 declarator-list , declarator
1611
1612 abstract-declarator-list:
1613 abstract-declarator
1614 abstract-declarator-list , abstract-declarator
1615
1616 storage-class-specifier:
1617 typedef
1618
1619 type-specifier:
1620 void
1621 char
1622 short
1623 int
1624 long
1625 float
1626 double
1627 signed
1628 unsigned
1629 _Bool
1630 _Complex
1631 _Imaginary
1632 struct-specifier
1633 variant-specifier
1634 enum-specifier
1635 typedef-name
1636 ctf-type-specifier
1637
1638 align-attribute:
1639 align ( unary-expression )
1640
1641 struct-specifier:
1642 struct identifier-opt { struct-or-variant-declaration-list-opt } align-attribute-opt
1643 struct identifier align-attribute-opt
1644
1645 struct-or-variant-declaration-list:
1646 struct-or-variant-declaration
1647 struct-or-variant-declaration-list struct-or-variant-declaration
1648
1649 struct-or-variant-declaration:
1650 specifier-qualifier-list struct-or-variant-declarator-list ;
1651 declaration-specifiers-opt storage-class-specifier declaration-specifiers-opt declarator-list ;
1652 typealias declaration-specifiers abstract-declarator-list type-assignment-operator declaration-specifiers abstract-declarator-list ;
1653 typealias declaration-specifiers abstract-declarator-list type-assignment-operator declarator-list ;
1654
1655 specifier-qualifier-list:
1656 type-specifier specifier-qualifier-list-opt
1657 type-qualifier specifier-qualifier-list-opt
1658
1659 struct-or-variant-declarator-list:
1660 struct-or-variant-declarator
1661 struct-or-variant-declarator-list , struct-or-variant-declarator
1662
1663 struct-or-variant-declarator:
1664 declarator
1665 declarator-opt : unary-expression
1666
1667 variant-specifier:
1668 variant identifier-opt variant-tag-opt { struct-or-variant-declaration-list }
1669 variant identifier variant-tag
1670
1671 variant-tag:
1672 < unary-expression >
1673
1674 enum-specifier:
1675 enum identifier-opt { enumerator-list }
1676 enum identifier-opt { enumerator-list , }
1677 enum identifier
1678 enum identifier-opt : declaration-specifiers { enumerator-list }
1679 enum identifier-opt : declaration-specifiers { enumerator-list , }
1680
1681 enumerator-list:
1682 enumerator
1683 enumerator-list , enumerator
1684
1685 enumerator:
1686 enumeration-constant
1687 enumeration-constant assignment-operator unary-expression
1688 enumeration-constant assignment-operator constant-expression-range
1689
1690 type-qualifier:
1691 const
1692
1693 declarator:
1694 pointer-opt direct-declarator
1695
1696 direct-declarator:
1697 identifier
1698 ( declarator )
1699 direct-declarator [ unary-expression ]
1700
1701 abstract-declarator:
1702 pointer-opt direct-abstract-declarator
1703
1704 direct-abstract-declarator:
1705 identifier-opt
1706 ( abstract-declarator )
1707 direct-abstract-declarator [ unary-expression ]
1708 direct-abstract-declarator [ ]
1709
1710 pointer:
1711 * type-qualifier-list-opt
1712 * type-qualifier-list-opt pointer
1713
1714 type-qualifier-list:
1715 type-qualifier
1716 type-qualifier-list type-qualifier
1717
1718 typedef-name:
1719 identifier
1720
1721 2.3) CTF-specific declarations
1722
1723 ctf-specifier:
1724 event { ctf-assignment-expression-list-opt }
1725 stream { ctf-assignment-expression-list-opt }
1726 trace { ctf-assignment-expression-list-opt }
1727 typealias declaration-specifiers abstract-declarator-list type-assignment-operator declaration-specifiers abstract-declarator-list
1728 typealias declaration-specifiers abstract-declarator-list type-assignment-operator declarator-list
1729
1730 ctf-type-specifier:
1731 floating_point { ctf-assignment-expression-list-opt }
1732 integer { ctf-assignment-expression-list-opt }
1733 string { ctf-assignment-expression-list-opt }
1734 string
1735
1736 ctf-assignment-expression-list:
1737 ctf-assignment-expression ;
1738 ctf-assignment-expression-list ctf-assignment-expression ;
1739
1740 ctf-assignment-expression:
1741 unary-expression assignment-operator unary-expression
1742 unary-expression type-assignment-operator type-specifier
1743 declaration-specifiers-opt storage-class-specifier declaration-specifiers-opt declarator-list
1744 typealias declaration-specifiers abstract-declarator-list type-assignment-operator declaration-specifiers abstract-declarator-list
1745 typealias declaration-specifiers abstract-declarator-list type-assignment-operator declarator-list
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