2 RFC: Common Trace Format (CTF) Proposal (pre-v1.7)
4 Mathieu Desnoyers, EfficiOS Inc.
6 The goal of the present document is to propose a trace format that suits the
7 needs of the embedded, telecom, high-performance and kernel communities. It is
8 based on the Common Trace Format Requirements (v1.4) document. It is designed to
9 allow traces to be natively generated by the Linux kernel, Linux user-space
10 applications written in C/C++, and hardware components.
12 The latest version of this document can be found at:
14 git tree: git://git.efficios.com/ctf.git
15 gitweb: http://git.efficios.com/?p=ctf.git
17 A reference implementation of a library to read and write this trace format is
18 being implemented within the BabelTrace project, a converter between trace
19 formats. The development tree is available at:
21 git tree: git://git.efficios.com/babeltrace.git
22 gitweb: http://git.efficios.com/?p=babeltrace.git
25 1. Preliminary definitions
27 - Event Trace: An ordered sequence of events.
28 - Event Stream: An ordered sequence of events, containing a subset of the
30 - Event Packet: A sequence of physically contiguous events within an event
32 - Event: This is the basic entry in a trace. (aka: a trace record).
33 - An event identifier (ID) relates to the class (a type) of event within
35 e.g. event: irq_entry.
36 - An event (or event record) relates to a specific instance of an event
38 e.g. event: irq_entry, at time X, on CPU Y
39 - Source Architecture: Architecture writing the trace.
40 - Reader Architecture: Architecture reading the trace.
43 2. High-level representation of a trace
45 A trace is divided into multiple event streams. Each event stream contains a
46 subset of the trace event types.
48 The final output of the trace, after its generation and optional transport over
49 the network, is expected to be either on permanent or temporary storage in a
50 virtual file system. Because each event stream is appended to while a trace is
51 being recorded, each is associated with a separate file for output. Therefore,
52 a stored trace can be represented as a directory containing one file per stream.
54 A metadata event stream contains information on trace event types. It describes:
58 - Per-stream event header description.
59 - Per-stream event header selection.
60 - Per-stream event context fields.
62 - Event type to stream mapping.
63 - Event type to name mapping.
64 - Event type to ID mapping.
65 - Event fields description.
70 An event stream is divided in contiguous event packets of variable size. These
71 subdivisions have a variable size. An event packet can contain a certain amount
72 of padding at the end. The rationale for the event stream design choices is
73 explained in Appendix B. Stream Header Rationale.
75 An event stream is divided in contiguous event packets of variable size. These
76 subdivisions have a variable size. An event packet can contain a certain amount
77 of padding at the end. The stream header is repeated at the beginning of each
80 The event stream header will therefore be referred to as the "event packet
81 header" throughout the rest of this document.
88 A basic type is a scalar type, as described in this section.
90 4.1.1 Type inheritance
92 Type specifications can be inherited to allow deriving types from a
93 type class. For example, see the uint32_t named type derived from the "integer"
94 type class below ("Integers" section). Types have a precise binary
95 representation in the trace. A type class has methods to read and write these
96 types, but must be derived into a type to be usable in an event field.
100 We define "byte-packed" types as aligned on the byte size, namely 8-bit.
101 We define "bit-packed" types as following on the next bit, as defined by the
104 All basic types, except bitfields, are either aligned on an architecture-defined
105 specific alignment or byte-packed, depending on the architecture preference.
106 Architectures providing fast unaligned write byte-packed basic types to save
107 space, aligning each type on byte boundaries (8-bit). Architectures with slow
108 unaligned writes align types on specific alignment values. If no specific
109 alignment is declared for a type nor its parents, it is assumed to be bit-packed
110 for bitfields and byte-packed for other types.
112 Metadata attribute representation of a specific alignment:
114 align = value; /* value in bits */
118 By default, the native endianness of the source architecture the trace is used.
119 Byte order can be overridden for a basic type by specifying a "byte_order"
120 attribute. Typical use-case is to specify the network byte order (big endian:
121 "be") to save data captured from the network into the trace without conversion.
122 If not specified, the byte order is native.
124 Metadata representation:
126 byte_order = native OR network OR be OR le; /* network and be are aliases */
130 Type size, in bits, for integers and floats is that returned by "sizeof()" in C
131 multiplied by CHAR_BIT.
132 We require the size of "char" and "unsigned char" types (CHAR_BIT) to be fixed
133 to 8 bits for cross-endianness compatibility.
135 Metadata representation:
137 size = value; (value is in bits)
141 Signed integers are represented in two-complement. Integer alignment, size,
142 signedness and byte ordering are defined in the metadata. Integers aligned on
143 byte size (8-bit) and with length multiple of byte size (8-bit) correspond to
144 the C99 standard integers. In addition, integers with alignment and/or size that
145 are _not_ a multiple of the byte size are permitted; these correspond to the C99
146 standard bitfields, with the added specification that the CTF integer bitfields
147 have a fixed binary representation. A MIT-licensed reference implementation of
148 the CTF portable bitfields is available at:
150 http://git.efficios.com/?p=babeltrace.git;a=blob;f=include/babeltrace/bitfield.h
152 Binary representation of integers:
154 - On little and big endian:
155 - Within a byte, high bits correspond to an integer high bits, and low bits
156 correspond to low bits.
158 - Integer across multiple bytes are placed from the less significant to the
160 - Consecutive integers are placed from lower bits to higher bits (even within
163 - Integer across multiple bytes are placed from the most significant to the
165 - Consecutive integers are placed from higher bits to lower bits (even within
168 This binary representation is derived from the bitfield implementation in GCC
169 for little and big endian. However, contrary to what GCC does, integers can
170 cross units boundaries (no padding is required). Padding can be explicitely
171 added (see 4.1.6 GNU/C bitfields) to follow the GCC layout if needed.
173 Metadata representation:
176 signed = true OR false; /* default false */
177 byte_order = native OR network OR be OR le; /* default native */
178 size = value; /* value in bits, no default */
179 align = value; /* value in bits */
182 Example of type inheritance (creation of a uint32_t named type):
190 Definition of a named 5-bit signed bitfield:
198 4.1.6 GNU/C bitfields
200 The GNU/C bitfields follow closely the integer representation, with a
201 particularity on alignment: if a bitfield cannot fit in the current unit, the
202 unit is padded and the bitfield starts at the following unit. The unit size is
203 defined by the size of the type "unit_type".
205 Metadata representation:
209 As an example, the following structure declared in C compiled by GCC:
216 The example structure is aligned on the largest element (short). The second
217 bitfield would be aligned on the next unit boundary, because it would not fit in
222 The floating point values byte ordering is defined in the metadata.
224 Floating point values follow the IEEE 754-2008 standard interchange formats.
225 Description of the floating point values include the exponent and mantissa size
226 in bits. Some requirements are imposed on the floating point values:
228 - FLT_RADIX must be 2.
229 - mant_dig is the number of digits represented in the mantissa. It is specified
230 by the ISO C99 standard, section 5.2.4, as FLT_MANT_DIG, DBL_MANT_DIG and
231 LDBL_MANT_DIG as defined by <float.h>.
232 - exp_dig is the number of digits represented in the exponent. Given that
233 mant_dig is one bit more than its actual size in bits (leading 1 is not
234 needed) and also given that the sign bit always takes one bit, exp_dig can be
237 - sizeof(float) * CHAR_BIT - FLT_MANT_DIG
238 - sizeof(double) * CHAR_BIT - DBL_MANT_DIG
239 - sizeof(long double) * CHAR_BIT - LDBL_MANT_DIG
241 Metadata representation:
246 byte_order = native OR network OR be OR le;
249 Example of type inheritance:
251 typedef floating_point {
252 exp_dig = 8; /* sizeof(float) * CHAR_BIT - FLT_MANT_DIG */
253 mant_dig = 24; /* FLT_MANT_DIG */
257 TODO: define NaN, +inf, -inf behavior.
261 Enumerations are a mapping between an integer type and a table of strings. The
262 numerical representation of the enumeration follows the integer type specified
263 by the metadata. The enumeration mapping table is detailed in the enumeration
264 description within the metadata. The mapping table maps inclusive value ranges
265 (or single values) to strings. Instead of being limited to simple
266 "value -> string" mappings, these enumerations map
267 "[ start_value ... end_value ] -> string", which map inclusive ranges of
268 values to strings. An enumeration from the C language can be represented in
269 this format by having the same start_value and end_value for each element, which
270 is in fact a range of size 1. This single-value range is supported without
271 repeating the start and end values with the value = string declaration.
273 If a numeric value is encountered between < >, it represents the integer type
274 size used to hold the enumeration, in bits.
276 enum <integer_type OR size> name {
277 string = start_value1 ... end_value1,
278 "other string" = start_value2 ... end_value2,
279 yet_another_string, /* will be assigned to end_value2 + 1 */
280 "some other string" = value,
284 If the values are omitted, the enumeration starts at 0 and increment of 1 for
295 Overlapping ranges within a single enumeration are implementation defined.
297 A nameless enumeration can be declared as a field type or as part of a typedef:
299 enum <integer_type> {
307 Structures are aligned on the largest alignment required by basic types
308 contained within the structure. (This follows the ISO/C standard for structures)
310 Metadata representation of a named structure:
313 field_type field_name;
314 field_type field_name;
321 integer { /* Nameless type */
326 uint64_t second_field_name; /* Named type declared in the metadata */
329 The fields are placed in a sequence next to each other. They each possess a
330 field name, which is a unique identifier within the structure.
332 A nameless structure can be declared as a field type or as part of a typedef:
338 4.2.2 Variants (Discriminated/Tagged Unions)
340 A CTF variant is a selection between different types. A CTF variant must always
341 be defined within the scope of a structure or within fields contained within a
342 structure (defined recursively). A "tag" enumeration field must appear in either
343 the same lexical scope or an uppermost scope, prior to the variant field (in
344 field declaration order). The type selection is indicated by the mapping from
345 the enumeration value to the string used as variant type selector. The field to
346 use as tag is specified by the "tag_field", specified between "< >" after the
347 "variant" keyword for unnamed variants, and after "variant name" for named
350 The alignment of the variant is the alignment of the type as selected by the tag
351 value for the specific instance of the variant. The alignment of the type
352 containing the variant is independent of the variant alignment. The size of the
353 variant is the size as selected by the tag value for the specific instance of
356 A named variant declaration followed by its definition within a structure
367 enum <integer_type or size> { sel1, sel2, sel3, ... } tag_field;
369 variant name <tag_field> v;
372 An unnamed variant definition within a structure is expressed by the following
376 enum <integer_type or size> { sel1, sel2, sel3, ... } tag_field;
378 variant <tag_field> {
386 Example of a named variant within a sequence that refers to a single tag field:
395 enum <uint2_t> { a, b, c } choice;
396 variant example <choice> v[unsigned int];
399 Example of an unnamed variant:
402 enum <uint2_t> { a, b, c, d } choice;
403 /* Unrelated fields can be added between the variant and its tag */
416 Example of an unnamed variant within an array:
419 enum <uint2_t> { a, b, c } choice;
427 Example of a variant type definition within a structure, where the defined type
428 is then declared within an array of structures. This variant refers to a tag
429 located in an upper lexical scope. This example clearly shows that a variant
430 type definition referring to the tag "x" uses the closest preceding field from
431 the lexical scope of the type definition.
434 enum <uint2_t> { a, b, c, d } x;
436 typedef variant <x> { /*
437 * "x" refers to the preceding "x" enumeration in the
438 * lexical scope of the type definition.
446 enum <int> { x, y, z } x; /* This enumeration is not used by "v". */
447 example_variant v; /*
448 * "v" uses the "enum <uint2_t> { a, b, c, d }"
456 Arrays are fixed-length. Their length is declared in the type declaration within
457 the metadata. They contain an array of "inner type" elements, which can refer to
458 any type not containing the type of the array being declared (no circular
459 dependency). The length is the number of elements in an array.
461 Metadata representation of a named array:
463 typedef elem_type name[length];
465 A nameless array can be declared as a field type within a structure, e.g.:
467 uint8_t field_name[10];
472 Sequences are dynamically-sized arrays. They start with an integer that specify
473 the length of the sequence, followed by an array of "inner type" elements.
474 The length is the number of elements in the sequence.
476 Metadata representation for a named sequence:
478 typedef elem_type name[length_type];
480 A nameless sequence can be declared as a field type, e.g.:
482 long field_name[int];
484 The length type follows the integer types specifications, and the sequence
485 elements follow the "array" specifications.
489 Strings are an array of bytes of variable size and are terminated by a '\0'
490 "NULL" character. Their encoding is described in the metadata. In absence of
491 encoding attribute information, the default encoding is UTF-8.
493 Metadata representation of a named string type:
496 encoding = UTF8 OR ASCII;
499 A nameless string type can be declared as a field type:
501 string field_name; /* Use default UTF8 encoding */
503 5. Event Packet Header
505 The event packet header consists of two part: one is mandatory and have a fixed
506 layout. The second part, the "event packet context", has its layout described in
509 - Aligned on page size. Fixed size. Fields either aligned or packed (depending
510 on the architecture preference).
511 No padding at the end of the event packet header. Native architecture byte
514 Fixed layout (event packet header):
516 - Magic number (CTF magic numbers: 0xC1FC1FC1 and its reverse endianness
517 representation: 0xC11FFCC1) It needs to have a non-symmetric bytewise
518 representation. Used to distinguish between big and little endian traces (this
519 information is determined by knowing the endianness of the architecture
520 reading the trace and comparing the magic number against its value and the
521 reverse, 0xC11FFCC1). This magic number specifies that we use the CTF metadata
522 description language described in this document. Different magic numbers
523 should be used for other metadata description languages.
524 - Trace UUID, used to ensure the event packet match the metadata used.
525 (note: we cannot use a metadata checksum because metadata can be appended to
526 while tracing is active)
527 - Stream ID, used as reference to stream description in metadata.
529 Metadata-defined layout (event packet context):
531 - Event packet content size (in bytes).
532 - Event packet size (in bytes, includes padding).
533 - Event packet content checksum (optional). Checksum excludes the event packet
535 - Per-stream event packet sequence count (to deal with UDP packet loss). The
536 number of significant sequence counter bits should also be present, so
537 wrap-arounds are deal with correctly.
538 - Timestamp at the beginning and timestamp at the end of the event packet.
539 Both timestamps are written in the packet header, but sampled respectively
540 while (or before) writing the first event and while (or after) writing the
541 last event in the packet. The inclusive range between these timestamps should
542 include all event timestamps assigned to events contained within the packet.
543 - Events discarded count
544 - Snapshot of a per-stream free-running counter, counting the number of
545 events discarded that were supposed to be written in the stream prior to
546 the first event in the event packet.
547 * Note: producer-consumer buffer full condition should fill the current
548 event packet with padding so we know exactly where events have been
550 - Lossless compression scheme used for the event packet content. Applied
551 directly to raw data. New types of compression can be added in following
552 versions of the format.
553 0: no compression scheme
557 - Cypher used for the event packet content. Applied after compression.
560 - Checksum scheme used for the event packet content. Applied after encryption.
566 5.1 Event Packet Header Fixed Layout Description
568 struct event_packet_header {
570 uint8_t trace_uuid[16];
574 5.2 Event Packet Context Description
576 Event packet context example. These are declared within the stream declaration
577 in the metadata. All these fields are optional except for "content_size" and
578 "packet_size", which must be present in the context.
580 An example event packet context type:
582 struct event_packet_context {
583 uint64_t timestamp_begin;
584 uint64_t timestamp_end;
586 uint32_t stream_packet_count;
587 uint32_t events_discarded;
589 uint32_t/uint16_t content_size;
590 uint32_t/uint16_t packet_size;
591 uint8_t stream_packet_count_bits; /* Significant counter bits */
592 uint8_t compression_scheme;
593 uint8_t encryption_scheme;
600 The overall structure of an event is:
602 1 - Stream Packet Context (as specified by the stream metadata)
603 2 - Event Header (as specifed by the stream metadata)
604 3 - Stream Event Context (as specified by the stream metadata)
605 4 - Event Context (as specified by the event metadata)
606 5 - Event Payload (as specified by the event metadata)
610 The lexical scope of each structure (stream packet context, header, stream event
611 context, event context and payload) is extended in the following way: lower
612 levels (e.g. 3) can refer to fields defined in prior levels (e.g. 2 and 1). The
613 field in the closest level has priority in case of field name conflict.
615 This allows, for instance, the event context to define a variant refering to the
616 "id" field of the event header as selector.
620 Event headers can be described within the metadata. We hereby propose, as an
621 example, two types of events headers. Type 1 accommodates streams with less than
622 31 event IDs. Type 2 accommodates streams with 31 or more event IDs.
624 One major factor can vary between streams: the number of event IDs assigned to
625 a stream. Luckily, this information tends to stay relatively constant (modulo
626 event registration while trace is being recorded), so we can specify different
627 representations for streams containing few event IDs and streams containing
628 many event IDs, so we end up representing the event ID and timestamp as densely
629 as possible in each case.
631 The header is extended in the rare occasions where the information cannot be
632 represented in the ranges available in the standard event header. They are also
633 used in the rare occasions where the data required for a field could not be
634 collected: the flag corresponding to the missing field within the missing_fields
635 array is then set to 1.
637 Types uintX_t represent an X-bit unsigned integer.
640 6.2.1 Type 1 - Few event IDs
642 - Aligned on 32-bit (or 8-bit if byte-packed, depending on the architecture
644 - Native architecture byte ordering.
645 - For "compact" selection
646 - Fixed size: 32 bits.
647 - For "extended" selection
648 - Size depends on the architecture and variant alignment.
650 struct event_header_1 {
653 * id 31 is reserved to indicate an extended header.
655 enum <uint5_t> { compact = 0 ... 30, extended = 31 } id;
661 uint32_t id; /* 32-bit event IDs */
662 uint64_t timestamp; /* 64-bit timestamps */
668 6.2.2 Type 2 - Many event IDs
670 - Aligned on 16-bit (or 8-bit if byte-packed, depending on the architecture
672 - Native architecture byte ordering.
673 - For "compact" selection
674 - Size depends on the architecture and variant alignment.
675 - For "extended" selection
676 - Size depends on the architecture and variant alignment.
678 struct event_header_2 {
680 * id: range: 0 - 65534.
681 * id 65535 is reserved to indicate an extended header.
683 enum <uint16_t> { compact = 0 ... 65534, extended = 65535 } id;
689 uint32_t id; /* 32-bit event IDs */
690 uint64_t timestamp; /* 64-bit timestamps */
698 The event context contains information relative to the current event. The choice
699 and meaning of this information is specified by the metadata "stream" and
700 "event" information. The "stream" context is applied to all events within the
701 stream. The "stream" context structure follows the event header. The "event"
702 context is applied to specific events. Its structure follows the "stream"
705 An example of stream-level event context is to save the event payload size with
706 each event, or to save the current PID with each event. These are declared
707 within the stream declaration within the metadata:
715 uint16_t payload_size;
720 An example of event-specific event context is to declare a bitmap of missing
721 fields, only appended after the stream event context if the extended event
722 header is selected. NR_FIELDS is the number of fields within the event (a
730 uint1_t missing_fields[NR_FIELDS]; /* missing event fields bitmap */
739 An event payload contains fields specific to a given event type. The fields
740 belonging to an event type are described in the event-specific metadata
741 within a structure type.
745 No padding at the end of the event payload. This differs from the ISO/C standard
746 for structures, but follows the CTF standard for structures. In a trace, even
747 though it makes sense to align the beginning of a structure, it really makes no
748 sense to add padding at the end of the structure, because structures are usually
749 not followed by a structure of the same type.
751 This trick can be done by adding a zero-length "end" field at the end of the C
752 structures, and by using the offset of this field rather than using sizeof()
753 when calculating the size of a structure (see Appendix "A. Helper macros").
757 The event payload is aligned on the largest alignment required by types
758 contained within the payload. (This follows the ISO/C standard for structures)
763 The meta-data is located in a stream named "metadata". It is made of "event
764 packets", which each start with an event packet header. The event type within
765 the metadata stream have no event header nor event context. Each event only
766 contains a null-terminated "string" payload, which is a metadata description
767 entry. The events are packed one next to another. Each event packet start with
768 an event packet header, which contains, amongst other fields, the magic number
771 The metadata can be parsed by reading through the metadata strings, skipping
772 newlines and null-characters. Type names are made of a single identifier, and
773 can be surrounded by prefix/postfix. Text contained within "/*" and "*/", as
774 well as within "//" and end of line, are treated as comments. Boolean values can
775 be represented as true, TRUE, or 1 for true, and false, FALSE, or 0 for false.
777 The grammar representing the CTF metadata is presented in
778 Appendix C. CTF Metadata Grammar.
781 major = value; /* Trace format version */
783 uuid = value; /* Trace UUID */
789 /* Type 1 - Few event IDs; Type 2 - Many event IDs. See section 6.2. */
790 event.header := event_header_1 OR event_header_2;
791 event.context := struct {
794 packet.context := struct {
801 id = value; /* Numeric identifier within the stream */
811 /* More detail on types in section 4. Types */
816 * Type declarations behave similarly to the C standard.
819 typedef aliased_type_prefix aliased_type new_type aliased_type_postfix;
821 /* e.g.: typedef struct example new_type_name[10]; */
826 * The "typealias" declaration can be used to give a name (including
827 * prefix/postfix) to a type.
830 typealias type_class {
832 } : new_type_prefix new_type new_type_postfix;
836 * typealias integer {
851 enum <integer_type or size> name {
857 * Unnamed types, contained within compound type fields, typedef or typealias.
868 enum <integer_type or size> {
872 typedef type new_type[length];
875 type field_name[length];
878 typedef type new_type[length_type];
881 type field_name[length_type];
893 integer_type field_name:size; /* GNU/C bitfield */
903 The two following macros keep track of the size of a GNU/C structure without
904 padding at the end by placing HEADER_END as the last field. A one byte end field
905 is used for C90 compatibility (C99 flexible arrays could be used here). Note
906 that this does not affect the effective structure size, which should always be
907 calculated with the header_sizeof() helper.
909 #define HEADER_END char end_field
910 #define header_sizeof(type) offsetof(typeof(type), end_field)
913 B. Stream Header Rationale
915 An event stream is divided in contiguous event packets of variable size. These
916 subdivisions allow the trace analyzer to perform a fast binary search by time
917 within the stream (typically requiring to index only the event packet headers)
918 without reading the whole stream. These subdivisions have a variable size to
919 eliminate the need to transfer the event packet padding when partially filled
920 event packets must be sent when streaming a trace for live viewing/analysis.
921 An event packet can contain a certain amount of padding at the end. Dividing
922 streams into event packets is also useful for network streaming over UDP and
923 flight recorder mode tracing (a whole event packet can be swapped out of the
924 buffer atomically for reading).
926 The stream header is repeated at the beginning of each event packet to allow
927 flexibility in terms of:
930 - allowing arbitrary buffers to be discarded without making the trace
932 - allow UDP packet loss handling by either dealing with missing event packet
933 or asking for re-transmission.
934 - transparently support flight recorder mode,
935 - transparently support crash dump.
937 The event stream header will therefore be referred to as the "event packet
938 header" throughout the rest of this document.
940 C. CTF Metadata Grammar
943 * Common Trace Format (CTF) Metadata Grammar.
945 * Inspired from the C99 grammar:
946 * http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1124.pdf (Annex A)
948 * Specialized for CTF needs by including only constant and declarations from
949 * C99 (excluding function declarations), and by adding support for variants,
950 * sequences and CTF-specific specifiers.
955 1.1) Lexical elements
997 identifier identifier-nondigit
1000 identifier-nondigit:
1002 universal-character-name
1003 any other implementation-defined characters
1007 [a-zA-Z] /* regular expression */
1010 [0-9] /* regular expression */
1012 1.4) Universal character names
1014 universal-character-name:
1016 \U hex-quad hex-quad
1019 hexadecimal-digit hexadecimal-digit hexadecimal-digit hexadecimal-digit
1025 enumeration-constant
1029 decimal-constant integer-suffix-opt
1030 octal-constant integer-suffix-opt
1031 hexadecimal-constant integer-suffix-opt
1035 decimal-constant digit
1039 octal-constant octal-digit
1041 hexadecimal-constant:
1042 hexadecimal-prefix hexadecimal-digit
1043 hexadecimal-constant hexadecimal-digit
1053 unsigned-suffix long-suffix-opt
1054 unsigned-suffix long-long-suffix
1055 long-suffix unsigned-suffix-opt
1056 long-long-suffix unsigned-suffix-opt
1072 digit-sequence digit
1074 hexadecimal-digit-sequence:
1076 hexadecimal-digit-sequence hexadecimal-digit
1078 enumeration-constant:
1084 L' c-char-sequence '
1088 c-char-sequence c-char
1091 any member of source charset except single-quote ('), backslash
1092 (\), or new-line character.
1096 simple-escape-sequence
1097 octal-escape-sequence
1098 hexadecimal-escape-sequence
1099 universal-character-name
1101 simple-escape-sequence: one of
1102 \' \" \? \\ \a \b \f \n \r \t \v
1104 octal-escape-sequence:
1106 \ octal-digit octal-digit
1107 \ octal-digit octal-digit octal-digit
1109 hexadecimal-escape-sequence:
1110 \x hexadecimal-digit
1111 hexadecimal-escape-sequence hexadecimal-digit
1113 1.6) String literals
1116 " s-char-sequence-opt "
1117 L" s-char-sequence-opt "
1121 s-char-sequence s-char
1124 any member of source charset except double-quote ("), backslash
1125 (\), or new-line character.
1131 [ ] ( ) { } . -> * + - < > : ; ... = ,
1134 2) Phrase structure grammar
1140 ( unary-expression )
1144 postfix-expression [ unary-expression ]
1145 postfix-expression . identifier
1146 postfix-expressoin -> identifier
1150 unary-operator postfix-expression
1152 unary-operator: one of
1155 assignment-expression:
1156 unary-expression assignment-operator unary-expression
1158 assignment-operator:
1161 constant-expression:
1164 constant-expression-range:
1165 constant-expression ... constant-expression
1170 declaration-specifiers declarator-list-opt ;
1173 declaration-specifiers:
1174 storage-class-specifier declaration-specifiers-opt
1175 type-specifier declaration-specifiers-opt
1176 type-qualifier declaration-specifiers-opt
1180 declarator-list , declarator
1182 storage-class-specifier:
1197 struct-or-variant-specifier
1203 struct identifier-opt { struct-or-variant-declaration-list }
1206 struct-or-variant-declaration-list:
1207 struct-or-variant-declaration
1208 struct-or-variant-declaration-list struct-or-variant-declaration
1210 struct-or-variant-declaration:
1211 specifier-qualifier-list struct-or-variant-declarator-list ;
1213 specifier-qualifier-list:
1214 type-specifier specifier-qualifier-list-opt
1215 type-qualifier specifier-qualifier-list-opt
1217 struct-or-variant-declarator-list:
1218 struct-or-variant-declarator
1219 struct-or-variant-declarator-list , struct-or-variant-declarator
1221 struct-or-variant-declarator:
1223 declarator-opt : constant-expression
1226 variant identifier-opt variant-tag-opt { struct-or-variant-declaration-list }
1227 variant identifier variant-tag
1233 enum identifier-opt { enumerator-list }
1234 enum identifier-opt { enumerator-list , }
1236 enum identifier-opt < type-specifier > { enumerator-list }
1237 enum identifier-opt < type-specifier > { enumerator-list , }
1238 enum identifier < type-specifier >
1239 enum identifier-opt < integer-constant > { enumerator-list }
1240 enum identifier-opt < integer-constant > { enumerator-list , }
1241 enum identifier < integer-constant >
1245 enumerator-list , enumerator
1248 enumeration-constant
1249 enumeration-constant = constant-expression
1250 enumeration-constant = constant-expression-range
1256 pointer-opt direct-declarator
1261 direct-declarator [ type-specifier ]
1262 direct-declarator [ constant-expression ]
1265 type-qualifier-list-opt
1266 type-qualifier-list-opt pointer
1268 type-qualifier-list:
1270 type-qualifier-list type-qualifier
1274 identifier-list , identifier
1279 2.3) CTF-specific declarations
1282 event { ctf-assignment-expression-list-opt }
1283 stream { ctf-assignment-expression-list-opt }
1284 trace { ctf-assignment-expression-list-opt }
1287 floating_point { ctf-assignment-expression-list-opt }
1288 integer { ctf-assignment-expression-list-opt }
1289 string { ctf-assignment-expression-list-opt }
1291 ctf-assignment-expression-list:
1292 ctf-assignment-expression
1293 ctf-assignment-expression-list ; ctf-assignment-expression
1295 ctf-assignment-expression:
1296 unary-expression assignment-operator unary-expression
1297 unary-expression type-assignment-operator type-specifier