cb28d6afee7aecb7a730aed9a605bf6c75a54b68
[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 parser.
425
426 A nameless structure can be declared as a field type or as part of a typedef:
427
428 struct {
429 ...
430 }
431
432 Alignment for a structure compound type can be forced to a minimum value
433 by adding an "align" specifier after the declaration of a structure
434 body. This attribute is read as: align(value). The value is specified in
435 bits. The structure will be aligned on the maximum value between this
436 attribute and the alignment required by the basic types contained within
437 the structure. e.g.
438
439 struct {
440 ...
441 } align(32)
442
443 4.2.2 Variants (Discriminated/Tagged Unions)
444
445 A CTF variant is a selection between different types. A CTF variant must
446 always be defined within the scope of a structure or within fields
447 contained within a structure (defined recursively). A "tag" enumeration
448 field must appear in either the same static scope, prior to the variant
449 field (in field declaration order), in an upper static scope , or in an
450 upper dynamic scope (see Section 7.3.2). The type selection is indicated
451 by the mapping from the enumeration value to the string used as variant
452 type selector. The field to use as tag is specified by the "tag_field",
453 specified between "< >" after the "variant" keyword for unnamed
454 variants, and after "variant name" for named variants.
455
456 The alignment of the variant is the alignment of the type as selected by the tag
457 value for the specific instance of the variant. The alignment of the type
458 containing the variant is independent of the variant alignment. The size of the
459 variant is the size as selected by the tag value for the specific instance of
460 the variant.
461
462 Each variant type selector possess a field name, which is a unique
463 identifier within the variant. The identifier is not allowed to use any
464 reserved keyword (see Section C.1.2). Replacing reserved keywords with
465 underscore-prefixed field names is recommended. Fields starting with an
466 underscore should have their leading underscore removed by the CTF parser.
467
468
469 A named variant declaration followed by its definition within a structure
470 declaration:
471
472 variant name {
473 field_type sel1;
474 field_type sel2;
475 field_type sel3;
476 ...
477 };
478
479 struct {
480 enum : integer_type { sel1, sel2, sel3, ... } tag_field;
481 ...
482 variant name <tag_field> v;
483 }
484
485 An unnamed variant definition within a structure is expressed by the following
486 TSDL meta-data:
487
488 struct {
489 enum : integer_type { sel1, sel2, sel3, ... } tag_field;
490 ...
491 variant <tag_field> {
492 field_type sel1;
493 field_type sel2;
494 field_type sel3;
495 ...
496 } v;
497 }
498
499 Example of a named variant within a sequence that refers to a single tag field:
500
501 variant example {
502 uint32_t a;
503 uint64_t b;
504 short c;
505 };
506
507 struct {
508 enum : uint2_t { a, b, c } choice;
509 unsigned int seqlen;
510 variant example <choice> v[seqlen];
511 }
512
513 Example of an unnamed variant:
514
515 struct {
516 enum : uint2_t { a, b, c, d } choice;
517 /* Unrelated fields can be added between the variant and its tag */
518 int32_t somevalue;
519 variant <choice> {
520 uint32_t a;
521 uint64_t b;
522 short c;
523 struct {
524 unsigned int field1;
525 uint64_t field2;
526 } d;
527 } s;
528 }
529
530 Example of an unnamed variant within an array:
531
532 struct {
533 enum : uint2_t { a, b, c } choice;
534 variant <choice> {
535 uint32_t a;
536 uint64_t b;
537 short c;
538 } v[10];
539 }
540
541 Example of a variant type definition within a structure, where the defined type
542 is then declared within an array of structures. This variant refers to a tag
543 located in an upper static scope. This example clearly shows that a variant
544 type definition referring to the tag "x" uses the closest preceding field from
545 the static scope of the type definition.
546
547 struct {
548 enum : uint2_t { a, b, c, d } x;
549
550 typedef variant <x> { /*
551 * "x" refers to the preceding "x" enumeration in the
552 * static scope of the type definition.
553 */
554 uint32_t a;
555 uint64_t b;
556 short c;
557 } example_variant;
558
559 struct {
560 enum : int { x, y, z } x; /* This enumeration is not used by "v". */
561 example_variant v; /*
562 * "v" uses the "enum : uint2_t { a, b, c, d }"
563 * tag.
564 */
565 } a[10];
566 }
567
568 4.2.3 Arrays
569
570 Arrays are fixed-length. Their length is declared in the type
571 declaration within the meta-data. They contain an array of "inner type"
572 elements, which can refer to any type not containing the type of the
573 array being declared (no circular dependency). The length is the number
574 of elements in an array.
575
576 TSDL meta-data representation of a named array:
577
578 typedef elem_type name[length];
579
580 A nameless array can be declared as a field type within a structure, e.g.:
581
582 uint8_t field_name[10];
583
584 Arrays are always aligned on their element alignment requirement.
585
586 4.2.4 Sequences
587
588 Sequences are dynamically-sized arrays. They refer to a a "length"
589 unsigned integer field, which must appear in either the same static scope,
590 prior to the sequence field (in field declaration order), in an upper
591 static scope, or in an upper dynamic scope (see Section 7.3.2). This
592 length field represents the number of elements in the sequence. The
593 sequence per se is an array of "inner type" elements.
594
595 TSDL meta-data representation for a sequence type definition:
596
597 struct {
598 unsigned int length_field;
599 typedef elem_type typename[length_field];
600 typename seq_field_name;
601 }
602
603 A sequence can also be declared as a field type, e.g.:
604
605 struct {
606 unsigned int length_field;
607 long seq_field_name[length_field];
608 }
609
610 Multiple sequences can refer to the same length field, and these length
611 fields can be in a different upper dynamic scope:
612
613 e.g., assuming the stream.event.header defines:
614
615 stream {
616 ...
617 id = 1;
618 event.header := struct {
619 uint16_t seq_len;
620 };
621 };
622
623 event {
624 ...
625 stream_id = 1;
626 fields := struct {
627 long seq_a[stream.event.header.seq_len];
628 char seq_b[stream.event.header.seq_len];
629 };
630 };
631
632 The sequence elements follow the "array" specifications.
633
634 4.2.5 Strings
635
636 Strings are an array of bytes of variable size and are terminated by a '\0'
637 "NULL" character. Their encoding is described in the TSDL meta-data. In
638 absence of encoding attribute information, the default encoding is
639 UTF-8.
640
641 TSDL meta-data representation of a named string type:
642
643 typealias string {
644 encoding = UTF8 OR ASCII;
645 } := name;
646
647 A nameless string type can be declared as a field type:
648
649 string field_name; /* Use default UTF8 encoding */
650
651 Strings are always aligned on byte size.
652
653 5. Event Packet Header
654
655 The event packet header consists of two parts: the "event packet header"
656 is the same for all streams of a trace. The second part, the "event
657 packet context", is described on a per-stream basis. Both are described
658 in the TSDL meta-data. The packets are aligned on architecture-page-sized
659 addresses.
660
661 Event packet header (all fields are optional, specified by TSDL meta-data):
662
663 - Magic number (CTF magic number: 0xC1FC1FC1) specifies that this is a
664 CTF packet. This magic number is optional, but when present, it should
665 come at the very beginning of the packet.
666 - Trace UUID, used to ensure the event packet match the meta-data used.
667 (note: we cannot use a meta-data checksum in every cases instead of a
668 UUID because meta-data can be appended to while tracing is active)
669 This field is optional.
670 - Stream ID, used as reference to stream description in meta-data.
671 This field is optional if there is only one stream description in the
672 meta-data, but becomes required if there are more than one stream in
673 the TSDL meta-data description.
674
675 Event packet context (all fields are optional, specified by TSDL meta-data):
676
677 - Event packet content size (in bits).
678 - Event packet size (in bits, includes padding).
679 - Event packet content checksum. Checksum excludes the event packet
680 header.
681 - Per-stream event packet sequence count (to deal with UDP packet loss). The
682 number of significant sequence counter bits should also be present, so
683 wrap-arounds are dealt with correctly.
684 - Time-stamp at the beginning and time-stamp at the end of the event packet.
685 Both timestamps are written in the packet header, but sampled respectively
686 while (or before) writing the first event and while (or after) writing the
687 last event in the packet. The inclusive range between these timestamps should
688 include all event timestamps assigned to events contained within the packet.
689 - Events discarded count
690 - Snapshot of a per-stream free-running counter, counting the number of
691 events discarded that were supposed to be written in the stream prior to
692 the first event in the event packet.
693 * Note: producer-consumer buffer full condition should fill the current
694 event packet with padding so we know exactly where events have been
695 discarded.
696 - Lossless compression scheme used for the event packet content. Applied
697 directly to raw data. New types of compression can be added in following
698 versions of the format.
699 0: no compression scheme
700 1: bzip2
701 2: gzip
702 3: xz
703 - Cypher used for the event packet content. Applied after compression.
704 0: no encryption
705 1: AES
706 - Checksum scheme used for the event packet content. Applied after encryption.
707 0: no checksum
708 1: md5
709 2: sha1
710 3: crc32
711
712 5.1 Event Packet Header Description
713
714 The event packet header layout is indicated by the trace packet.header
715 field. Here is a recommended structure type for the packet header with
716 the fields typically expected (although these fields are each optional):
717
718 struct event_packet_header {
719 uint32_t magic;
720 uint8_t uuid[16];
721 uint32_t stream_id;
722 };
723
724 trace {
725 ...
726 packet.header := struct event_packet_header;
727 };
728
729 If the magic number is not present, tools such as "file" will have no
730 mean to discover the file type.
731
732 If the uuid is not present, no validation that the meta-data actually
733 corresponds to the stream is performed.
734
735 If the stream_id packet header field is missing, the trace can only
736 contain a single stream. Its "id" field can be left out, and its events
737 don't need to declare a "stream_id" field.
738
739
740 5.2 Event Packet Context Description
741
742 Event packet context example. These are declared within the stream declaration
743 in the meta-data. All these fields are optional. If the packet size field is
744 missing, the whole stream only contains a single packet. If the content
745 size field is missing, the packet is filled (no padding). The content
746 and packet sizes include all headers.
747
748 An example event packet context type:
749
750 struct event_packet_context {
751 uint64_t timestamp_begin;
752 uint64_t timestamp_end;
753 uint32_t checksum;
754 uint32_t stream_packet_count;
755 uint32_t events_discarded;
756 uint32_t cpu_id;
757 uint32_t/uint16_t content_size;
758 uint32_t/uint16_t packet_size;
759 uint8_t compression_scheme;
760 uint8_t encryption_scheme;
761 uint8_t checksum_scheme;
762 };
763
764
765 6. Event Structure
766
767 The overall structure of an event is:
768
769 1 - Stream Packet Context (as specified by the stream meta-data)
770 2 - Event Header (as specified by the stream meta-data)
771 3 - Stream Event Context (as specified by the stream meta-data)
772 4 - Event Context (as specified by the event meta-data)
773 5 - Event Payload (as specified by the event meta-data)
774
775 This structure defines an implicit dynamic scoping, where variants
776 located in inner structures (those with a higher number in the listing
777 above) can refer to the fields of outer structures (with lower number in
778 the listing above). See Section 7.3 TSDL Scopes for more detail.
779
780 6.1 Event Header
781
782 Event headers can be described within the meta-data. We hereby propose, as an
783 example, two types of events headers. Type 1 accommodates streams with less than
784 31 event IDs. Type 2 accommodates streams with 31 or more event IDs.
785
786 One major factor can vary between streams: the number of event IDs assigned to
787 a stream. Luckily, this information tends to stay relatively constant (modulo
788 event registration while trace is being recorded), so we can specify different
789 representations for streams containing few event IDs and streams containing
790 many event IDs, so we end up representing the event ID and time-stamp as
791 densely as possible in each case.
792
793 The header is extended in the rare occasions where the information cannot be
794 represented in the ranges available in the standard event header. They are also
795 used in the rare occasions where the data required for a field could not be
796 collected: the flag corresponding to the missing field within the missing_fields
797 array is then set to 1.
798
799 Types uintX_t represent an X-bit unsigned integer, as declared with
800 either:
801
802 typealias integer { size = X; align = X; signed = false } := uintX_t;
803
804 or
805
806 typealias integer { size = X; align = 1; signed = false } := uintX_t;
807
808 6.1.1 Type 1 - Few event IDs
809
810 - Aligned on 32-bit (or 8-bit if byte-packed, depending on the architecture
811 preference).
812 - Native architecture byte ordering.
813 - For "compact" selection
814 - Fixed size: 32 bits.
815 - For "extended" selection
816 - Size depends on the architecture and variant alignment.
817
818 struct event_header_1 {
819 /*
820 * id: range: 0 - 30.
821 * id 31 is reserved to indicate an extended header.
822 */
823 enum : uint5_t { compact = 0 ... 30, extended = 31 } id;
824 variant <id> {
825 struct {
826 uint27_t timestamp;
827 } compact;
828 struct {
829 uint32_t id; /* 32-bit event IDs */
830 uint64_t timestamp; /* 64-bit timestamps */
831 } extended;
832 } v;
833 } align(32); /* or align(8) */
834
835
836 6.1.2 Type 2 - Many event IDs
837
838 - Aligned on 16-bit (or 8-bit if byte-packed, depending on the architecture
839 preference).
840 - Native architecture byte ordering.
841 - For "compact" selection
842 - Size depends on the architecture and variant alignment.
843 - For "extended" selection
844 - Size depends on the architecture and variant alignment.
845
846 struct event_header_2 {
847 /*
848 * id: range: 0 - 65534.
849 * id 65535 is reserved to indicate an extended header.
850 */
851 enum : uint16_t { compact = 0 ... 65534, extended = 65535 } id;
852 variant <id> {
853 struct {
854 uint32_t timestamp;
855 } compact;
856 struct {
857 uint32_t id; /* 32-bit event IDs */
858 uint64_t timestamp; /* 64-bit timestamps */
859 } extended;
860 } v;
861 } align(16); /* or align(8) */
862
863
864 6.2 Event Context
865
866 The event context contains information relative to the current event.
867 The choice and meaning of this information is specified by the TSDL
868 stream and event meta-data descriptions. The stream context is applied
869 to all events within the stream. The stream context structure follows
870 the event header. The event context is applied to specific events. Its
871 structure follows the stream context structure.
872
873 An example of stream-level event context is to save the event payload size with
874 each event, or to save the current PID with each event. These are declared
875 within the stream declaration within the meta-data:
876
877 stream {
878 ...
879 event.context := struct {
880 uint pid;
881 uint16_t payload_size;
882 };
883 };
884
885 An example of event-specific event context is to declare a bitmap of missing
886 fields, only appended after the stream event context if the extended event
887 header is selected. NR_FIELDS is the number of fields within the event (a
888 numeric value).
889
890 event {
891 context = struct {
892 variant <id> {
893 struct { } compact;
894 struct {
895 uint1_t missing_fields[NR_FIELDS]; /* missing event fields bitmap */
896 } extended;
897 } v;
898 };
899 ...
900 }
901
902 6.3 Event Payload
903
904 An event payload contains fields specific to a given event type. The fields
905 belonging to an event type are described in the event-specific meta-data
906 within a structure type.
907
908 6.3.1 Padding
909
910 No padding at the end of the event payload. This differs from the ISO/C standard
911 for structures, but follows the CTF standard for structures. In a trace, even
912 though it makes sense to align the beginning of a structure, it really makes no
913 sense to add padding at the end of the structure, because structures are usually
914 not followed by a structure of the same type.
915
916 This trick can be done by adding a zero-length "end" field at the end of the C
917 structures, and by using the offset of this field rather than using sizeof()
918 when calculating the size of a structure (see Appendix "A. Helper macros").
919
920 6.3.2 Alignment
921
922 The event payload is aligned on the largest alignment required by types
923 contained within the payload. (This follows the ISO/C standard for structures)
924
925
926 7. Trace Stream Description Language (TSDL)
927
928 The Trace Stream Description Language (TSDL) allows expression of the
929 binary trace streams layout in a C99-like Domain Specific Language
930 (DSL).
931
932
933 7.1 Meta-data
934
935 The trace stream layout description is located in the trace meta-data.
936 The meta-data is itself located in a stream identified by its name:
937 "metadata".
938
939 The meta-data description can be expressed in two different formats:
940 text-only and packet-based. The text-only description facilitates
941 generation of meta-data and provides a convenient way to enter the
942 meta-data information by hand. The packet-based meta-data provides the
943 CTF stream packet facilities (checksumming, compression, encryption,
944 network-readiness) for meta-data stream generated and transported by a
945 tracer.
946
947 The text-only meta-data file is a plain-text TSDL description. This file
948 must begin with the following characters to identify the file as a CTF
949 TSDL text-based metadata file (without the double-quotes) :
950
951 "/* CTF"
952
953 It must be followed by a space, and the version of the specification
954 followed by the CTF trace, e.g.:
955
956 " 1.8"
957
958 These characters allow automated discovery of file type and CTF
959 specification version. They are interpreted as a the beginning of a
960 comment by the TSDL metadata parser. The comment can be continued to
961 contain extra commented characters before it is closed.
962
963 The packet-based meta-data is made of "meta-data packets", which each
964 start with a meta-data packet header. The packet-based meta-data
965 description is detected by reading the magic number "0x75D11D57" at the
966 beginning of the file. This magic number is also used to detect the
967 endianness of the architecture by trying to read the CTF magic number
968 and its counterpart in reversed endianness. The events within the
969 meta-data stream have no event header nor event context. Each event only
970 contains a "sequence" payload, which is a sequence of bits using the
971 "trace.packet.header.content_size" field as a placeholder for its length
972 (the packet header size should be substracted). The formatting of this
973 sequence of bits is a plain-text representation of the TSDL description.
974 Each meta-data packet start with a special packet header, specific to
975 the meta-data stream, which contains, exactly:
976
977 struct metadata_packet_header {
978 uint32_t magic; /* 0x75D11D57 */
979 uint8_t uuid[16]; /* Unique Universal Identifier */
980 uint32_t checksum; /* 0 if unused */
981 uint32_t content_size; /* in bits */
982 uint32_t packet_size; /* in bits */
983 uint8_t compression_scheme; /* 0 if unused */
984 uint8_t encryption_scheme; /* 0 if unused */
985 uint8_t checksum_scheme; /* 0 if unused */
986 uint8_t major; /* CTF spec version major number */
987 uint8_t minor; /* CTF spec version minor number */
988 };
989
990 The packet-based meta-data can be converted to a text-only meta-data by
991 concatenating all the strings in contains.
992
993 In the textual representation of the meta-data, the text contained
994 within "/*" and "*/", as well as within "//" and end of line, are
995 treated as comments. Boolean values can be represented as true, TRUE,
996 or 1 for true, and false, FALSE, or 0 for false. Within the string-based
997 meta-data description, the trace UUID is represented as a string of
998 hexadecimal digits and dashes "-". In the event packet header, the trace
999 UUID is represented as an array of bytes.
1000
1001
1002 7.2 Declaration vs Definition
1003
1004 A declaration associates a layout to a type, without specifying where
1005 this type is located in the event structure hierarchy (see Section 6).
1006 This therefore includes typedef, typealias, as well as all type
1007 specifiers. In certain circumstances (typedef, structure field and
1008 variant field), a declaration is followed by a declarator, which specify
1009 the newly defined type name (for typedef), or the field name (for
1010 declarations located within structure and variants). Array and sequence,
1011 declared with square brackets ("[" "]"), are part of the declarator,
1012 similarly to C99. The enumeration base type is specified by
1013 ": enum_base", which is part of the type specifier. The variant tag
1014 name, specified between "<" ">", is also part of the type specifier.
1015
1016 A definition associates a type to a location in the event structure
1017 hierarchy (see Section 6). This association is denoted by ":=", as shown
1018 in Section 7.3.
1019
1020
1021 7.3 TSDL Scopes
1022
1023 TSDL uses three different types of scoping: a lexical scope is used for
1024 declarations and type definitions, and static and dynamic scopes are
1025 used for variants references to tag fields (with relative and absolute
1026 path lookups) and for sequence references to length fields.
1027
1028 7.3.1 Lexical Scope
1029
1030 Each of "trace", "stream", "event", "struct" and "variant" have their own
1031 nestable declaration scope, within which types can be declared using "typedef"
1032 and "typealias". A root declaration scope also contains all declarations
1033 located outside of any of the aforementioned declarations. An inner
1034 declaration scope can refer to type declared within its container
1035 lexical scope prior to the inner declaration scope. Redefinition of a
1036 typedef or typealias is not valid, although hiding an upper scope
1037 typedef or typealias is allowed within a sub-scope.
1038
1039 7.3.2 Static and Dynamic Scopes
1040
1041 A local static scope consists in the scope generated by the declaration
1042 of fields within a compound type. A static scope is a local static scope
1043 augmented with the nested sub-static-scopes it contains.
1044
1045 A dynamic scope consists in the static scope augmented with the
1046 implicit event structure definition hierarchy presented at Section 6.
1047
1048 Multiple declarations of the same field name within a local static scope
1049 is not valid. It is however valid to re-use the same field name in
1050 different local scopes.
1051
1052 Nested static and dynamic scopes form lookup paths. These are used for
1053 variant tag and sequence length references. They are used at the variant
1054 and sequence definition site to look up the location of the tag field
1055 associated with a variant, and to lookup up the location of the length
1056 field associated with a sequence.
1057
1058 Variants and sequences can refer to a tag field either using a relative
1059 path or an absolute path. The relative path is relative to the scope in
1060 which the variant or sequence performing the lookup is located.
1061 Relative paths are only allowed to lookup within the same static scope,
1062 which includes its nested static scopes. Lookups targeting parent static
1063 scopes need to be performed with an absolute path.
1064
1065 Absolute path lookups use the full path including the dynamic scope
1066 followed by a "." and then the static scope. Therefore, variants (or
1067 sequences) in lower levels in the dynamic scope (e.g. event context) can
1068 refer to a tag (or length) field located in upper levels (e.g. in the
1069 event header) by specifying, in this case, the associated tag with
1070 <stream.event.header.field_name>. This allows, for instance, the event
1071 context to define a variant referring to the "id" field of the event
1072 header as selector.
1073
1074 The dynamic scope prefixes are thus:
1075
1076 - Trace Packet Header: <trace.packet.header. >,
1077 - Stream Packet Context: <stream.packet.context. >,
1078 - Event Header: <stream.event.header. >,
1079 - Stream Event Context: <stream.event.context. >,
1080 - Event Context: <event.context. >,
1081 - Event Payload: <event.fields. >.
1082
1083
1084 The target dynamic scope must be specified explicitly when referring to
1085 a field outside of the static scope (absolute scope reference). No
1086 conflict can occur between relative and dynamic paths, because the
1087 keywords "trace", "stream", and "event" are reserved, and thus
1088 not permitted as field names. It is recommended that field names
1089 clashing with CTF and C99 reserved keywords use an underscore prefix to
1090 eliminate the risk of generating a description containing an invalid
1091 field name. Consequently, fields starting with an underscore should have
1092 their leading underscore removed by the CTF parser.
1093
1094
1095 The information available in the dynamic scopes can be thought of as the
1096 current tracing context. At trace production, information about the
1097 current context is saved into the specified scope field levels. At trace
1098 consumption, for each event, the current trace context is therefore
1099 readable by accessing the upper dynamic scopes.
1100
1101
1102 7.4 TSDL Examples
1103
1104 The grammar representing the TSDL meta-data is presented in Appendix C.
1105 TSDL Grammar. This section presents a rather lighter reading that
1106 consists in examples of TSDL meta-data, with template values.
1107
1108 The stream "id" can be left out if there is only one stream in the
1109 trace. The event "id" field can be left out if there is only one event
1110 in a stream.
1111
1112 trace {
1113 major = value; /* Trace format version */
1114 minor = value;
1115 uuid = "aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa"; /* Trace UUID */
1116 byte_order = be OR le; /* Endianness (required) */
1117 packet.header := struct {
1118 uint32_t magic;
1119 uint8_t uuid[16];
1120 uint32_t stream_id;
1121 };
1122 };
1123
1124 stream {
1125 id = stream_id;
1126 /* Type 1 - Few event IDs; Type 2 - Many event IDs. See section 6.1. */
1127 event.header := event_header_1 OR event_header_2;
1128 event.context := struct {
1129 ...
1130 };
1131 packet.context := struct {
1132 ...
1133 };
1134 };
1135
1136 event {
1137 name = "event_name";
1138 id = value; /* Numeric identifier within the stream */
1139 stream_id = stream_id;
1140 loglevel.identifier = "loglevel_identifier";
1141 loglevel.value = value;
1142 context := struct {
1143 ...
1144 };
1145 fields := struct {
1146 ...
1147 };
1148 };
1149
1150 /* More detail on types in section 4. Types */
1151
1152 /*
1153 * Named types:
1154 *
1155 * Type declarations behave similarly to the C standard.
1156 */
1157
1158 typedef aliased_type_specifiers new_type_declarators;
1159
1160 /* e.g.: typedef struct example new_type_name[10]; */
1161
1162 /*
1163 * typealias
1164 *
1165 * The "typealias" declaration can be used to give a name (including
1166 * pointer declarator specifier) to a type. It should also be used to
1167 * map basic C types (float, int, unsigned long, ...) to a CTF type.
1168 * Typealias is a superset of "typedef": it also allows assignment of a
1169 * simple variable identifier to a type.
1170 */
1171
1172 typealias type_class {
1173 ...
1174 } := type_specifiers type_declarator;
1175
1176 /*
1177 * e.g.:
1178 * typealias integer {
1179 * size = 32;
1180 * align = 32;
1181 * signed = false;
1182 * } := struct page *;
1183 *
1184 * typealias integer {
1185 * size = 32;
1186 * align = 32;
1187 * signed = true;
1188 * } := int;
1189 */
1190
1191 struct name {
1192 ...
1193 };
1194
1195 variant name {
1196 ...
1197 };
1198
1199 enum name : integer_type {
1200 ...
1201 };
1202
1203
1204 /*
1205 * Unnamed types, contained within compound type fields, typedef or typealias.
1206 */
1207
1208 struct {
1209 ...
1210 }
1211
1212 struct {
1213 ...
1214 } align(value)
1215
1216 variant {
1217 ...
1218 }
1219
1220 enum : integer_type {
1221 ...
1222 }
1223
1224 typedef type new_type[length];
1225
1226 struct {
1227 type field_name[length];
1228 }
1229
1230 typedef type new_type[length_type];
1231
1232 struct {
1233 type field_name[length_type];
1234 }
1235
1236 integer {
1237 ...
1238 }
1239
1240 floating_point {
1241 ...
1242 }
1243
1244 struct {
1245 integer_type field_name:size; /* GNU/C bitfield */
1246 }
1247
1248 struct {
1249 string field_name;
1250 }
1251
1252
1253 8. Clocks
1254
1255 Clock metadata allows to describe the clock topology of the system, as
1256 well as to detail each clock parameter. In absence of clock description,
1257 it is assumed that all fields named "timestamp" use the same clock
1258 source, which increments once per nanosecond.
1259
1260 Describing a clock and how it is used by streams is threefold: first,
1261 the clock and clock topology should be described in a "clock"
1262 description block, e.g.:
1263
1264 clock {
1265 name = cycle_counter_sync;
1266 uuid = "62189bee-96dc-11e0-91a8-cfa3d89f3923";
1267 description = "Cycle counter synchronized across CPUs";
1268 freq = 1000000000; /* frequency, in Hz */
1269 /* precision in seconds is: 1000 * (1/freq) */
1270 precision = 1000;
1271 /*
1272 * clock value offset from Epoch is:
1273 * offset_s + (offset * (1/freq))
1274 */
1275 offset_s = 1326476837;
1276 offset = 897235420;
1277 absolute = FALSE;
1278 };
1279
1280 The mandatory "name" field specifies the name of the clock identifier,
1281 which can later be used as a reference. The optional field "uuid" is the
1282 unique identifier of the clock. It can be used to correlate different
1283 traces that use the same clock. An optional textual description string
1284 can be added with the "description" field. The "freq" field is the
1285 initial frequency of the clock, in Hz. If the "freq" field is not
1286 present, the frequency is assumed to be 1000000000 (providing clock
1287 increment of 1 ns). The optional "precision" field details the
1288 uncertainty on the clock measurements, in (1/freq) units. The "offset_s"
1289 and "offset" fields indicate the offset from POSIX.1 Epoch, 1970-01-01
1290 00:00:00 +0000 (UTC), to the zero of value of the clock. The "offset_s"
1291 field is in seconds. The "offset" field is in (1/freq) units. If any of
1292 the "offset_s" or "offset" field is not present, it is assigned the 0
1293 value. The field "absolute" is TRUE if the clock is a global reference
1294 across different clock uuid (e.g. NTP time). Otherwise, "absolute" is
1295 FALSE, and the clock can be considered as synchronized only with other
1296 clocks that have the same uuid.
1297
1298
1299 Secondly, a reference to this clock should be added within an integer
1300 type:
1301
1302 typealias integer {
1303 size = 64; align = 1; signed = false;
1304 map = clock.cycle_counter_sync.value;
1305 } := uint64_ccnt_t;
1306
1307 Thirdly, stream declarations can reference the clock they use as a
1308 time-stamp source:
1309
1310 struct packet_context {
1311 uint64_ccnt_t ccnt_begin;
1312 uint64_ccnt_t ccnt_end;
1313 /* ... */
1314 };
1315
1316 stream {
1317 /* ... */
1318 event.header := struct {
1319 uint64_ccnt_t timestamp;
1320 /* ... */
1321 }
1322 packet.context := struct packet_context;
1323 };
1324
1325 For a N-bit integer type referring to a clock, if the integer overflows
1326 compared to the N low order bits of the clock prior value, then it is
1327 assumed that one, and only one, overflow occurred. It is therefore
1328 important that events encoding time on a small number of bits happen
1329 frequently enough to detect when more than one N-bit overflow occurs.
1330
1331 In a packet context, clock field names ending with "_begin" and "_end"
1332 have a special meaning: this refers to the time-stamps at, respectively,
1333 the beginning and the end of each packet.
1334
1335
1336 A. Helper macros
1337
1338 The two following macros keep track of the size of a GNU/C structure without
1339 padding at the end by placing HEADER_END as the last field. A one byte end field
1340 is used for C90 compatibility (C99 flexible arrays could be used here). Note
1341 that this does not affect the effective structure size, which should always be
1342 calculated with the header_sizeof() helper.
1343
1344 #define HEADER_END char end_field
1345 #define header_sizeof(type) offsetof(typeof(type), end_field)
1346
1347
1348 B. Stream Header Rationale
1349
1350 An event stream is divided in contiguous event packets of variable size. These
1351 subdivisions allow the trace analyzer to perform a fast binary search by time
1352 within the stream (typically requiring to index only the event packet headers)
1353 without reading the whole stream. These subdivisions have a variable size to
1354 eliminate the need to transfer the event packet padding when partially filled
1355 event packets must be sent when streaming a trace for live viewing/analysis.
1356 An event packet can contain a certain amount of padding at the end. Dividing
1357 streams into event packets is also useful for network streaming over UDP and
1358 flight recorder mode tracing (a whole event packet can be swapped out of the
1359 buffer atomically for reading).
1360
1361 The stream header is repeated at the beginning of each event packet to allow
1362 flexibility in terms of:
1363
1364 - streaming support,
1365 - allowing arbitrary buffers to be discarded without making the trace
1366 unreadable,
1367 - allow UDP packet loss handling by either dealing with missing event packet
1368 or asking for re-transmission.
1369 - transparently support flight recorder mode,
1370 - transparently support crash dump.
1371
1372
1373 C. TSDL Grammar
1374
1375 /*
1376 * Common Trace Format (CTF) Trace Stream Description Language (TSDL) Grammar.
1377 *
1378 * Inspired from the C99 grammar:
1379 * http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1124.pdf (Annex A)
1380 * and c++1x grammar (draft)
1381 * http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2011/n3291.pdf (Annex A)
1382 *
1383 * Specialized for CTF needs by including only constant and declarations from
1384 * C99 (excluding function declarations), and by adding support for variants,
1385 * sequences and CTF-specific specifiers. Enumeration container types
1386 * semantic is inspired from c++1x enum-base.
1387 */
1388
1389 1) Lexical grammar
1390
1391 1.1) Lexical elements
1392
1393 token:
1394 keyword
1395 identifier
1396 constant
1397 string-literal
1398 punctuator
1399
1400 1.2) Keywords
1401
1402 keyword: is one of
1403
1404 align
1405 const
1406 char
1407 clock
1408 double
1409 enum
1410 event
1411 floating_point
1412 float
1413 integer
1414 int
1415 long
1416 short
1417 signed
1418 stream
1419 string
1420 struct
1421 trace
1422 typealias
1423 typedef
1424 unsigned
1425 variant
1426 void
1427 _Bool
1428 _Complex
1429 _Imaginary
1430
1431
1432 1.3) Identifiers
1433
1434 identifier:
1435 identifier-nondigit
1436 identifier identifier-nondigit
1437 identifier digit
1438
1439 identifier-nondigit:
1440 nondigit
1441 universal-character-name
1442 any other implementation-defined characters
1443
1444 nondigit:
1445 _
1446 [a-zA-Z] /* regular expression */
1447
1448 digit:
1449 [0-9] /* regular expression */
1450
1451 1.4) Universal character names
1452
1453 universal-character-name:
1454 \u hex-quad
1455 \U hex-quad hex-quad
1456
1457 hex-quad:
1458 hexadecimal-digit hexadecimal-digit hexadecimal-digit hexadecimal-digit
1459
1460 1.5) Constants
1461
1462 constant:
1463 integer-constant
1464 enumeration-constant
1465 character-constant
1466
1467 integer-constant:
1468 decimal-constant integer-suffix-opt
1469 octal-constant integer-suffix-opt
1470 hexadecimal-constant integer-suffix-opt
1471
1472 decimal-constant:
1473 nonzero-digit
1474 decimal-constant digit
1475
1476 octal-constant:
1477 0
1478 octal-constant octal-digit
1479
1480 hexadecimal-constant:
1481 hexadecimal-prefix hexadecimal-digit
1482 hexadecimal-constant hexadecimal-digit
1483
1484 hexadecimal-prefix:
1485 0x
1486 0X
1487
1488 nonzero-digit:
1489 [1-9]
1490
1491 integer-suffix:
1492 unsigned-suffix long-suffix-opt
1493 unsigned-suffix long-long-suffix
1494 long-suffix unsigned-suffix-opt
1495 long-long-suffix unsigned-suffix-opt
1496
1497 unsigned-suffix:
1498 u
1499 U
1500
1501 long-suffix:
1502 l
1503 L
1504
1505 long-long-suffix:
1506 ll
1507 LL
1508
1509 enumeration-constant:
1510 identifier
1511 string-literal
1512
1513 character-constant:
1514 ' c-char-sequence '
1515 L' c-char-sequence '
1516
1517 c-char-sequence:
1518 c-char
1519 c-char-sequence c-char
1520
1521 c-char:
1522 any member of source charset except single-quote ('), backslash
1523 (\), or new-line character.
1524 escape-sequence
1525
1526 escape-sequence:
1527 simple-escape-sequence
1528 octal-escape-sequence
1529 hexadecimal-escape-sequence
1530 universal-character-name
1531
1532 simple-escape-sequence: one of
1533 \' \" \? \\ \a \b \f \n \r \t \v
1534
1535 octal-escape-sequence:
1536 \ octal-digit
1537 \ octal-digit octal-digit
1538 \ octal-digit octal-digit octal-digit
1539
1540 hexadecimal-escape-sequence:
1541 \x hexadecimal-digit
1542 hexadecimal-escape-sequence hexadecimal-digit
1543
1544 1.6) String literals
1545
1546 string-literal:
1547 " s-char-sequence-opt "
1548 L" s-char-sequence-opt "
1549
1550 s-char-sequence:
1551 s-char
1552 s-char-sequence s-char
1553
1554 s-char:
1555 any member of source charset except double-quote ("), backslash
1556 (\), or new-line character.
1557 escape-sequence
1558
1559 1.7) Punctuators
1560
1561 punctuator: one of
1562 [ ] ( ) { } . -> * + - < > : ; ... = ,
1563
1564
1565 2) Phrase structure grammar
1566
1567 primary-expression:
1568 identifier
1569 constant
1570 string-literal
1571 ( unary-expression )
1572
1573 postfix-expression:
1574 primary-expression
1575 postfix-expression [ unary-expression ]
1576 postfix-expression . identifier
1577 postfix-expressoin -> identifier
1578
1579 unary-expression:
1580 postfix-expression
1581 unary-operator postfix-expression
1582
1583 unary-operator: one of
1584 + -
1585
1586 assignment-operator:
1587 =
1588
1589 type-assignment-operator:
1590 :=
1591
1592 constant-expression-range:
1593 unary-expression ... unary-expression
1594
1595 2.2) Declarations:
1596
1597 declaration:
1598 declaration-specifiers declarator-list-opt ;
1599 ctf-specifier ;
1600
1601 declaration-specifiers:
1602 storage-class-specifier declaration-specifiers-opt
1603 type-specifier declaration-specifiers-opt
1604 type-qualifier declaration-specifiers-opt
1605
1606 declarator-list:
1607 declarator
1608 declarator-list , declarator
1609
1610 abstract-declarator-list:
1611 abstract-declarator
1612 abstract-declarator-list , abstract-declarator
1613
1614 storage-class-specifier:
1615 typedef
1616
1617 type-specifier:
1618 void
1619 char
1620 short
1621 int
1622 long
1623 float
1624 double
1625 signed
1626 unsigned
1627 _Bool
1628 _Complex
1629 _Imaginary
1630 struct-specifier
1631 variant-specifier
1632 enum-specifier
1633 typedef-name
1634 ctf-type-specifier
1635
1636 align-attribute:
1637 align ( unary-expression )
1638
1639 struct-specifier:
1640 struct identifier-opt { struct-or-variant-declaration-list-opt } align-attribute-opt
1641 struct identifier align-attribute-opt
1642
1643 struct-or-variant-declaration-list:
1644 struct-or-variant-declaration
1645 struct-or-variant-declaration-list struct-or-variant-declaration
1646
1647 struct-or-variant-declaration:
1648 specifier-qualifier-list struct-or-variant-declarator-list ;
1649 declaration-specifiers-opt storage-class-specifier declaration-specifiers-opt declarator-list ;
1650 typealias declaration-specifiers abstract-declarator-list type-assignment-operator declaration-specifiers abstract-declarator-list ;
1651 typealias declaration-specifiers abstract-declarator-list type-assignment-operator declarator-list ;
1652
1653 specifier-qualifier-list:
1654 type-specifier specifier-qualifier-list-opt
1655 type-qualifier specifier-qualifier-list-opt
1656
1657 struct-or-variant-declarator-list:
1658 struct-or-variant-declarator
1659 struct-or-variant-declarator-list , struct-or-variant-declarator
1660
1661 struct-or-variant-declarator:
1662 declarator
1663 declarator-opt : unary-expression
1664
1665 variant-specifier:
1666 variant identifier-opt variant-tag-opt { struct-or-variant-declaration-list }
1667 variant identifier variant-tag
1668
1669 variant-tag:
1670 < unary-expression >
1671
1672 enum-specifier:
1673 enum identifier-opt { enumerator-list }
1674 enum identifier-opt { enumerator-list , }
1675 enum identifier
1676 enum identifier-opt : declaration-specifiers { enumerator-list }
1677 enum identifier-opt : declaration-specifiers { enumerator-list , }
1678
1679 enumerator-list:
1680 enumerator
1681 enumerator-list , enumerator
1682
1683 enumerator:
1684 enumeration-constant
1685 enumeration-constant assignment-operator unary-expression
1686 enumeration-constant assignment-operator constant-expression-range
1687
1688 type-qualifier:
1689 const
1690
1691 declarator:
1692 pointer-opt direct-declarator
1693
1694 direct-declarator:
1695 identifier
1696 ( declarator )
1697 direct-declarator [ unary-expression ]
1698
1699 abstract-declarator:
1700 pointer-opt direct-abstract-declarator
1701
1702 direct-abstract-declarator:
1703 identifier-opt
1704 ( abstract-declarator )
1705 direct-abstract-declarator [ unary-expression ]
1706 direct-abstract-declarator [ ]
1707
1708 pointer:
1709 * type-qualifier-list-opt
1710 * type-qualifier-list-opt pointer
1711
1712 type-qualifier-list:
1713 type-qualifier
1714 type-qualifier-list type-qualifier
1715
1716 typedef-name:
1717 identifier
1718
1719 2.3) CTF-specific declarations
1720
1721 ctf-specifier:
1722 event { ctf-assignment-expression-list-opt }
1723 stream { ctf-assignment-expression-list-opt }
1724 trace { ctf-assignment-expression-list-opt }
1725 typealias declaration-specifiers abstract-declarator-list type-assignment-operator declaration-specifiers abstract-declarator-list
1726 typealias declaration-specifiers abstract-declarator-list type-assignment-operator declarator-list
1727
1728 ctf-type-specifier:
1729 floating_point { ctf-assignment-expression-list-opt }
1730 integer { ctf-assignment-expression-list-opt }
1731 string { ctf-assignment-expression-list-opt }
1732 string
1733
1734 ctf-assignment-expression-list:
1735 ctf-assignment-expression ;
1736 ctf-assignment-expression-list ctf-assignment-expression ;
1737
1738 ctf-assignment-expression:
1739 unary-expression assignment-operator unary-expression
1740 unary-expression type-assignment-operator type-specifier
1741 declaration-specifiers-opt storage-class-specifier declaration-specifiers-opt declarator-list
1742 typealias declaration-specifiers abstract-declarator-list type-assignment-operator declaration-specifiers abstract-declarator-list
1743 typealias declaration-specifiers abstract-declarator-list type-assignment-operator declarator-list
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