Update version to 1.8.2 (minor fix)
[ctf.git] / common-trace-format-specification.txt
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f5cb0e57 1Common Trace Format (CTF) Specification (v1.8.2)
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2
3Mathieu Desnoyers, EfficiOS Inc.
4
339a7dde 5The goal of the present document is to specify a trace format that suits the
cc089c3a 6needs of the embedded, telecom, high-performance and kernel communities. It is
5ba9f198 7based on the Common Trace Format Requirements (v1.4) document. It is designed to
cc089c3a 8allow traces to be natively generated by the Linux kernel, Linux user-space
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9applications written in C/C++, and hardware components. One major element of
10CTF is the Trace Stream Description Language (TSDL) which flexibility
11enables description of various binary trace stream layouts.
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12
13The 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
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17
18A reference implementation of a library to read and write this trace format is
19being implemented within the BabelTrace project, a converter between trace
20formats. 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
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25The CE Workgroup of the Linux Foundation, Ericsson, and EfficiOS have
26sponsored this work.
27
5ba9f198 28
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29Table of Contents
30
311. Preliminary definitions
322. High-level representation of a trace
333. Event stream
344. 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
444.2 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
505. Event Packet Header
51 5.1 Event Packet Header Description
52 5.2 Event Packet Context Description
536. 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
617. 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
37ab95c3 66 7.3.2 Static and Dynamic Scopes
beabf088 67 7.4 TSDL Examples
2fa70eba 688. Clocks
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69
70
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711. Preliminary definitions
72
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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.
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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
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80 an event stream.
81 e.g. event: irq_entry.
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82 - An event (or event record) relates to a specific instance of an event
83 class.
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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.
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87
88
892. High-level representation of a trace
90
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91A trace is divided into multiple event streams. Each event stream contains a
92subset of the trace event types.
5ba9f198 93
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94The final output of the trace, after its generation and optional transport over
95the network, is expected to be either on permanent or temporary storage in a
96virtual file system. Because each event stream is appended to while a trace is
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97being recorded, each is associated with a distinct set of files for
98output. Therefore, a stored trace can be represented as a directory
99containing zero, one or more files per stream.
5ba9f198 100
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101Meta-data description associated with the trace contains information on
102trace event types expressed in the Trace Stream Description Language
103(TSDL). This language describes:
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104
105- Trace version.
106- Types available.
6672e9e1 107- Per-trace event header description.
3bf79539 108- Per-stream event header description.
6672e9e1 109- Per-stream event context description.
5ba9f198 110- Per-event
3bf79539 111 - Event type to stream mapping.
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112 - Event type to name mapping.
113 - Event type to ID mapping.
6672e9e1 114 - Event context description.
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115 - Event fields description.
116
117
3bf79539 1183. Event stream
5ba9f198 119
6672e9e1 120An event stream can be divided into contiguous event packets of variable
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121size. An event packet can contain a certain amount of padding at the
122end. The stream header is repeated at the beginning of each event
123packet. The rationale for the event stream design choices is explained
124in Appendix B. Stream Header Rationale.
5ba9f198 125
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126The event stream header will therefore be referred to as the "event packet
127header" throughout the rest of this document.
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128
129
1304. Types
131
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132Types are organized as type classes. Each type class belong to either of two
133kind of types: basic types or compound types.
134
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1354.1 Basic types
136
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137A basic type is a scalar type, as described in this section. It includes
138integers, GNU/C bitfields, enumerations, and floating point values.
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139
1404.1.1 Type inheritance
141
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142Type specifications can be inherited to allow deriving types from a
143type class. For example, see the uint32_t named type derived from the "integer"
144type class below ("Integers" section). Types have a precise binary
145representation in the trace. A type class has methods to read and write these
146types, but must be derived into a type to be usable in an event field.
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147
1484.1.2 Alignment
149
150We define "byte-packed" types as aligned on the byte size, namely 8-bit.
151We define "bit-packed" types as following on the next bit, as defined by the
370eae99 152"Integers" section.
5ba9f198 153
6672e9e1 154Each basic type must specify its alignment, in bits. Examples of
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155possible alignments are: bit-packed (align = 1), byte-packed (align =
1568), or word-aligned (e.g. align = 32 or align = 64). The choice depends
157on the architecture preference and compactness vs performance trade-offs
158of the implementation. Architectures providing fast unaligned write
159byte-packed basic types to save space, aligning each type on byte
160boundaries (8-bit). Architectures with slow unaligned writes align types
161on specific alignment values. If no specific alignment is declared for a
162type, it is assumed to be bit-packed for integers with size not multiple
163of 8 bits and for gcc bitfields. All other basic types are byte-packed
164by default. It is however recommended to always specify the alignment
165explicitly. Alignment values must be power of two. Compound types are
166aligned as specified in their individual specification.
5ba9f198 167
6672e9e1 168TSDL meta-data attribute representation of a specific alignment:
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169
170 align = value; /* value in bits */
171
1724.1.3 Byte order
173
9f296be4 174By default, the native endianness of the source architecture is used.
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175Byte order can be overridden for a basic type by specifying a "byte_order"
176attribute. Typical use-case is to specify the network byte order (big endian:
177"be") to save data captured from the network into the trace without conversion.
178If not specified, the byte order is native.
5ba9f198 179
6672e9e1 180TSDL meta-data representation:
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181
182 byte_order = native OR network OR be OR le; /* network and be are aliases */
183
1844.1.4 Size
185
186Type size, in bits, for integers and floats is that returned by "sizeof()" in C
187multiplied by CHAR_BIT.
188We require the size of "char" and "unsigned char" types (CHAR_BIT) to be fixed
189to 8 bits for cross-endianness compatibility.
190
6672e9e1 191TSDL meta-data representation:
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192
193 size = value; (value is in bits)
194
1954.1.5 Integers
196
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197Signed integers are represented in two-complement. Integer alignment,
198size, signedness and byte ordering are defined in the TSDL meta-data.
199Integers aligned on byte size (8-bit) and with length multiple of byte
200size (8-bit) correspond to the C99 standard integers. In addition,
201integers with alignment and/or size that are _not_ a multiple of the
202byte size are permitted; these correspond to the C99 standard bitfields,
203with the added specification that the CTF integer bitfields have a fixed
204binary representation. A MIT-licensed reference implementation of the
205CTF portable bitfields is available at:
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206
207 http://git.efficios.com/?p=babeltrace.git;a=blob;f=include/babeltrace/bitfield.h
208
209Binary representation of integers:
210
211- On little and big endian:
212 - Within a byte, high bits correspond to an integer high bits, and low bits
213 correspond to low bits.
214- On little endian:
215 - Integer across multiple bytes are placed from the less significant to the
216 most significant.
217 - Consecutive integers are placed from lower bits to higher bits (even within
218 a byte).
219- On big endian:
220 - Integer across multiple bytes are placed from the most significant to the
221 less significant.
222 - Consecutive integers are placed from higher bits to lower bits (even within
223 a byte).
224
225This binary representation is derived from the bitfield implementation in GCC
226for little and big endian. However, contrary to what GCC does, integers can
6672e9e1 227cross units boundaries (no padding is required). Padding can be explicitly
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228added (see 4.1.6 GNU/C bitfields) to follow the GCC layout if needed.
229
6672e9e1 230TSDL meta-data representation:
5ba9f198 231
80fd2569 232 integer {
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233 signed = true OR false; /* default false */
234 byte_order = native OR network OR be OR le; /* default native */
235 size = value; /* value in bits, no default */
236 align = value; /* value in bits */
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237 /* based used for pretty-printing output, default: decimal. */
238 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
239 OR octal OR oct OR o OR 8 OR binary OR b OR 2;
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240 /* character encoding, default: none */
241 encoding = none or UTF8 or ASCII;
2152348f 242 }
5ba9f198 243
80fd2569 244Example of type inheritance (creation of a uint32_t named type):
5ba9f198 245
359894ac 246typealias integer {
9e4e34e9 247 size = 32;
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248 signed = false;
249 align = 32;
38b8da21 250} := uint32_t;
5ba9f198 251
80fd2569 252Definition of a named 5-bit signed bitfield:
5ba9f198 253
359894ac 254typealias integer {
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255 size = 5;
256 signed = true;
257 align = 1;
38b8da21 258} := int5_t;
5ba9f198 259
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260The character encoding field can be used to specify that the integer
261must be printed as a text character when read. e.g.:
262
263typealias integer {
264 size = 8;
265 align = 8;
266 signed = false;
267 encoding = UTF8;
268} := utf_char;
269
270
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2714.1.6 GNU/C bitfields
272
273The GNU/C bitfields follow closely the integer representation, with a
274particularity on alignment: if a bitfield cannot fit in the current unit, the
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275unit is padded and the bitfield starts at the following unit. The unit size is
276defined by the size of the type "unit_type".
5ba9f198 277
6672e9e1 278TSDL meta-data representation:
80fd2569 279
d674f4b8 280 unit_type name:size;
80fd2569 281
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282As an example, the following structure declared in C compiled by GCC:
283
284struct example {
285 short a:12;
286 short b:5;
287};
288
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289The example structure is aligned on the largest element (short). The second
290bitfield would be aligned on the next unit boundary, because it would not fit in
291the current unit.
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292
2934.1.7 Floating point
294
6672e9e1 295The floating point values byte ordering is defined in the TSDL meta-data.
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296
297Floating point values follow the IEEE 754-2008 standard interchange formats.
298Description of the floating point values include the exponent and mantissa size
299in bits. Some requirements are imposed on the floating point values:
300
301- FLT_RADIX must be 2.
302- mant_dig is the number of digits represented in the mantissa. It is specified
303 by the ISO C99 standard, section 5.2.4, as FLT_MANT_DIG, DBL_MANT_DIG and
304 LDBL_MANT_DIG as defined by <float.h>.
305- exp_dig is the number of digits represented in the exponent. Given that
306 mant_dig is one bit more than its actual size in bits (leading 1 is not
307 needed) and also given that the sign bit always takes one bit, exp_dig can be
308 specified as:
309
310 - sizeof(float) * CHAR_BIT - FLT_MANT_DIG
311 - sizeof(double) * CHAR_BIT - DBL_MANT_DIG
312 - sizeof(long double) * CHAR_BIT - LDBL_MANT_DIG
313
6672e9e1 314TSDL meta-data representation:
5ba9f198 315
80fd2569 316floating_point {
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317 exp_dig = value;
318 mant_dig = value;
319 byte_order = native OR network OR be OR le;
320 align = value;
2152348f 321}
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322
323Example of type inheritance:
324
359894ac 325typealias floating_point {
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326 exp_dig = 8; /* sizeof(float) * CHAR_BIT - FLT_MANT_DIG */
327 mant_dig = 24; /* FLT_MANT_DIG */
328 byte_order = native;
ec4404a7 329 align = 32;
38b8da21 330} := float;
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331
332TODO: define NaN, +inf, -inf behavior.
333
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334Bit-packed, byte-packed or larger alignments can be used for floating
335point values, similarly to integers.
336
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3374.1.8 Enumerations
338
339Enumerations are a mapping between an integer type and a table of strings. The
340numerical representation of the enumeration follows the integer type specified
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341by the meta-data. The enumeration mapping table is detailed in the enumeration
342description within the meta-data. The mapping table maps inclusive value
343ranges (or single values) to strings. Instead of being limited to simple
3bf79539 344"value -> string" mappings, these enumerations map
80fd2569 345"[ start_value ... end_value ] -> string", which map inclusive ranges of
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346values to strings. An enumeration from the C language can be represented in
347this format by having the same start_value and end_value for each element, which
348is in fact a range of size 1. This single-value range is supported without
4767a9e7 349repeating the start and end values with the value = string declaration.
80fd2569 350
a9b83695 351enum name : integer_type {
359894ac 352 somestring = start_value1 ... end_value1,
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353 "other string" = start_value2 ... end_value2,
354 yet_another_string, /* will be assigned to end_value2 + 1 */
355 "some other string" = value,
356 ...
357};
358
359If the values are omitted, the enumeration starts at 0 and increment of 1 for
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360each entry. An entry with omitted value that follows a range entry takes
361as value the end_value of the previous range + 1:
80fd2569 362
a9b83695 363enum name : unsigned int {
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364 ZERO,
365 ONE,
366 TWO,
367 TEN = 10,
368 ELEVEN,
3bf79539 369};
5ba9f198 370
80fd2569 371Overlapping ranges within a single enumeration are implementation defined.
5ba9f198 372
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373A nameless enumeration can be declared as a field type or as part of a typedef:
374
a9b83695 375enum : integer_type {
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376 ...
377}
378
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379Enumerations omitting the container type ": integer_type" use the "int"
380type (for compatibility with C99). The "int" type must be previously
381declared. E.g.:
382
383typealias integer { size = 32; align = 32; signed = true } := int;
384
385enum {
386 ...
387}
388
1fad7a85 389
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3904.2 Compound types
391
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392Compound are aggregation of type declarations. Compound types include
393structures, variant, arrays, sequences, and strings.
394
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3954.2.1 Structures
396
397Structures are aligned on the largest alignment required by basic types
398contained within the structure. (This follows the ISO/C standard for structures)
399
6672e9e1 400TSDL meta-data representation of a named structure:
5ba9f198 401
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402struct name {
403 field_type field_name;
404 field_type field_name;
405 ...
406};
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407
408Example:
409
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410struct example {
411 integer { /* Nameless type */
412 size = 16;
413 signed = true;
414 align = 16;
415 } first_field_name;
6672e9e1 416 uint64_t second_field_name; /* Named type declared in the meta-data */
3bf79539 417};
5ba9f198 418
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419The fields are placed in a sequence next to each other. They each
420possess a field name, which is a unique identifier within the structure.
421The identifier is not allowed to use any reserved keyword
422(see Section C.1.2). Replacing reserved keywords with
70375f92 423underscore-prefixed field names is recommended. Fields starting with an
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424underscore should have their leading underscore removed by the CTF trace
425readers.
5ba9f198 426
2152348f 427A nameless structure can be declared as a field type or as part of a typedef:
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428
429struct {
430 ...
2152348f 431}
80fd2569 432
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433Alignment for a structure compound type can be forced to a minimum value
434by adding an "align" specifier after the declaration of a structure
435body. This attribute is read as: align(value). The value is specified in
436bits. The structure will be aligned on the maximum value between this
437attribute and the alignment required by the basic types contained within
438the structure. e.g.
439
440struct {
441 ...
442} align(32)
443
77a98c82 4444.2.2 Variants (Discriminated/Tagged Unions)
fcba70d4 445
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446A CTF variant is a selection between different types. A CTF variant must
447always be defined within the scope of a structure or within fields
448contained within a structure (defined recursively). A "tag" enumeration
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449field must appear in either the same static scope, prior to the variant
450field (in field declaration order), in an upper static scope , or in an
451upper dynamic scope (see Section 7.3.2). The type selection is indicated
452by the mapping from the enumeration value to the string used as variant
453type selector. The field to use as tag is specified by the "tag_field",
454specified between "< >" after the "variant" keyword for unnamed
455variants, and after "variant name" for named variants.
fcba70d4 456
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457The alignment of the variant is the alignment of the type as selected by
458the tag value for the specific instance of the variant. The size of the
459variant is the size as selected by the tag value for the specific
460instance of the variant.
461
462The alignment of the type containing the variant is independent of the
463variant alignment. For instance, if a structure contains two fields, a
46432-bit integer, aligned on 32 bits, and a variant, which contains two
465choices: either a 32-bit field, aligned on 32 bits, or a 64-bit field,
466aligned on 64 bits, the alignment of the outmost structure will be
46732-bit (the alignment of its largest field, disregarding the alignment
468of the variant). The alignment of the variant will depend on the
469selector: if the variant's 32-bit field is selected, its alignment will
470be 32-bit, or 64-bit otherwise. It is important to note that variants
471are specifically tailored for compactness in a stream. Therefore, the
472relative offsets of compound type fields can vary depending on
473the offset at which the compound type starts if it contains a variant
474that itself contains a type with alignment larger than the largest field
475contained within the compound type. This is caused by the fact that the
476compound type may contain the enumeration that select the variant's
477choice, and therefore the alignment to be applied to the compound type
478cannot be determined before encountering the enumeration.
fcba70d4 479
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480Each variant type selector possess a field name, which is a unique
481identifier within the variant. The identifier is not allowed to use any
482reserved keyword (see Section C.1.2). Replacing reserved keywords with
70375f92 483underscore-prefixed field names is recommended. Fields starting with an
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484underscore should have their leading underscore removed by the CTF trace
485readers.
70375f92 486
4cac83ee 487
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488A named variant declaration followed by its definition within a structure
489declaration:
490
491variant name {
492 field_type sel1;
493 field_type sel2;
494 field_type sel3;
495 ...
496};
497
498struct {
a9b83695 499 enum : integer_type { sel1, sel2, sel3, ... } tag_field;
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500 ...
501 variant name <tag_field> v;
502}
503
504An unnamed variant definition within a structure is expressed by the following
6672e9e1 505TSDL meta-data:
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506
507struct {
a9b83695 508 enum : integer_type { sel1, sel2, sel3, ... } tag_field;
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509 ...
510 variant <tag_field> {
511 field_type sel1;
512 field_type sel2;
513 field_type sel3;
514 ...
515 } v;
516}
517
518Example of a named variant within a sequence that refers to a single tag field:
519
520variant example {
521 uint32_t a;
522 uint64_t b;
523 short c;
524};
525
526struct {
a9b83695 527 enum : uint2_t { a, b, c } choice;
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528 unsigned int seqlen;
529 variant example <choice> v[seqlen];
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530}
531
532Example of an unnamed variant:
533
534struct {
a9b83695 535 enum : uint2_t { a, b, c, d } choice;
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536 /* Unrelated fields can be added between the variant and its tag */
537 int32_t somevalue;
538 variant <choice> {
539 uint32_t a;
540 uint64_t b;
541 short c;
542 struct {
543 unsigned int field1;
544 uint64_t field2;
545 } d;
546 } s;
547}
548
549Example of an unnamed variant within an array:
550
551struct {
a9b83695 552 enum : uint2_t { a, b, c } choice;
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553 variant <choice> {
554 uint32_t a;
555 uint64_t b;
556 short c;
15850440 557 } v[10];
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558}
559
560Example of a variant type definition within a structure, where the defined type
561is then declared within an array of structures. This variant refers to a tag
37ab95c3 562located in an upper static scope. This example clearly shows that a variant
fcba70d4 563type definition referring to the tag "x" uses the closest preceding field from
37ab95c3 564the static scope of the type definition.
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565
566struct {
a9b83695 567 enum : uint2_t { a, b, c, d } x;
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568
569 typedef variant <x> { /*
570 * "x" refers to the preceding "x" enumeration in the
37ab95c3 571 * static scope of the type definition.
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572 */
573 uint32_t a;
574 uint64_t b;
575 short c;
576 } example_variant;
577
578 struct {
a9b83695 579 enum : int { x, y, z } x; /* This enumeration is not used by "v". */
fcba70d4 580 example_variant v; /*
a9b83695 581 * "v" uses the "enum : uint2_t { a, b, c, d }"
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582 * tag.
583 */
584 } a[10];
585}
586
5874.2.3 Arrays
5ba9f198 588
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589Arrays are fixed-length. Their length is declared in the type
590declaration within the meta-data. They contain an array of "inner type"
591elements, which can refer to any type not containing the type of the
592array being declared (no circular dependency). The length is the number
593of elements in an array.
5ba9f198 594
6672e9e1 595TSDL meta-data representation of a named array:
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596
597typedef elem_type name[length];
5ba9f198 598
2152348f 599A nameless array can be declared as a field type within a structure, e.g.:
5ba9f198 600
2152348f 601 uint8_t field_name[10];
80fd2569 602
ec4404a7 603Arrays are always aligned on their element alignment requirement.
5ba9f198 604
fcba70d4 6054.2.4 Sequences
5ba9f198 606
1ab22b2a 607Sequences are dynamically-sized arrays. They refer to a a "length"
37ab95c3 608unsigned integer field, which must appear in either the same static scope,
1ab22b2a 609prior to the sequence field (in field declaration order), in an upper
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610static scope, or in an upper dynamic scope (see Section 7.3.2). This
611length field represents the number of elements in the sequence. The
612sequence per se is an array of "inner type" elements.
5ba9f198 613
1ab22b2a 614TSDL meta-data representation for a sequence type definition:
80fd2569 615
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616struct {
617 unsigned int length_field;
618 typedef elem_type typename[length_field];
619 typename seq_field_name;
620}
621
622A sequence can also be declared as a field type, e.g.:
80fd2569 623
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624struct {
625 unsigned int length_field;
626 long seq_field_name[length_field];
627}
80fd2569 628
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629Multiple sequences can refer to the same length field, and these length
630fields can be in a different upper dynamic scope:
631
632e.g., assuming the stream.event.header defines:
633
634stream {
635 ...
636 id = 1;
637 event.header := struct {
638 uint16_t seq_len;
639 };
640};
641
642event {
643 ...
644 stream_id = 1;
645 fields := struct {
646 long seq_a[stream.event.header.seq_len];
647 char seq_b[stream.event.header.seq_len];
648 };
649};
80fd2569 650
1ab22b2a 651The sequence elements follow the "array" specifications.
5ba9f198 652
fcba70d4 6534.2.5 Strings
5ba9f198
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654
655Strings are an array of bytes of variable size and are terminated by a '\0'
6672e9e1
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656"NULL" character. Their encoding is described in the TSDL meta-data. In
657absence of encoding attribute information, the default encoding is
658UTF-8.
5ba9f198 659
6672e9e1 660TSDL meta-data representation of a named string type:
80fd2569 661
359894ac 662typealias string {
5ba9f198 663 encoding = UTF8 OR ASCII;
38b8da21 664} := name;
5ba9f198 665
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666A nameless string type can be declared as a field type:
667
668string field_name; /* Use default UTF8 encoding */
5ba9f198 669
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670Strings are always aligned on byte size.
671
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6725. Event Packet Header
673
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674The event packet header consists of two parts: the "event packet header"
675is the same for all streams of a trace. The second part, the "event
676packet context", is described on a per-stream basis. Both are described
677in the TSDL meta-data. The packets are aligned on architecture-page-sized
678addresses.
3bf79539 679
6672e9e1 680Event packet header (all fields are optional, specified by TSDL meta-data):
3bf79539 681
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682- Magic number (CTF magic number: 0xC1FC1FC1) specifies that this is a
683 CTF packet. This magic number is optional, but when present, it should
684 come at the very beginning of the packet.
685- Trace UUID, used to ensure the event packet match the meta-data used.
686 (note: we cannot use a meta-data checksum in every cases instead of a
687 UUID because meta-data can be appended to while tracing is active)
688 This field is optional.
689- Stream ID, used as reference to stream description in meta-data.
690 This field is optional if there is only one stream description in the
691 meta-data, but becomes required if there are more than one stream in
692 the TSDL meta-data description.
3bf79539 693
6672e9e1 694Event packet context (all fields are optional, specified by TSDL meta-data):
3bf79539 695
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696- Event packet content size (in bits).
697- Event packet size (in bits, includes padding).
cda89682 698- Event packet content checksum. Checksum excludes the event packet
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699 header.
700- Per-stream event packet sequence count (to deal with UDP packet loss). The
701 number of significant sequence counter bits should also be present, so
b11853af 702 wrap-arounds are dealt with correctly.
6672e9e1 703- Time-stamp at the beginning and time-stamp at the end of the event packet.
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704 Both timestamps are written in the packet header, but sampled respectively
705 while (or before) writing the first event and while (or after) writing the
706 last event in the packet. The inclusive range between these timestamps should
707 include all event timestamps assigned to events contained within the packet.
5ba9f198 708- Events discarded count
3bf79539 709 - Snapshot of a per-stream free-running counter, counting the number of
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710 events discarded that were supposed to be written in the stream after
711 the last event in the event packet.
712 * Note: producer-consumer buffer full condition can fill the current
3bf79539 713 event packet with padding so we know exactly where events have been
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714 discarded. However, if the buffer full condition chooses not
715 to fill the current event packet with padding, all we know
716 about the timestamp range in which the events have been
717 discarded is that it is somewhere between the beginning and
718 the end of the packet.
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719- Lossless compression scheme used for the event packet content. Applied
720 directly to raw data. New types of compression can be added in following
721 versions of the format.
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722 0: no compression scheme
723 1: bzip2
724 2: gzip
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725 3: xz
726- Cypher used for the event packet content. Applied after compression.
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727 0: no encryption
728 1: AES
3bf79539 729- Checksum scheme used for the event packet content. Applied after encryption.
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730 0: no checksum
731 1: md5
732 2: sha1
733 3: crc32
734
6672e9e1 7355.1 Event Packet Header Description
3bf79539 736
fc5425db 737The event packet header layout is indicated by the trace packet.header
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738field. Here is a recommended structure type for the packet header with
739the fields typically expected (although these fields are each optional):
fc5425db 740
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741struct event_packet_header {
742 uint32_t magic;
3fde5da1 743 uint8_t uuid[16];
3bf79539 744 uint32_t stream_id;
80fd2569 745};
5ba9f198 746
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747trace {
748 ...
749 packet.header := struct event_packet_header;
750};
751
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752If the magic number is not present, tools such as "file" will have no
753mean to discover the file type.
754
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755If the uuid is not present, no validation that the meta-data actually
756corresponds to the stream is performed.
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757
758If the stream_id packet header field is missing, the trace can only
759contain a single stream. Its "id" field can be left out, and its events
760don't need to declare a "stream_id" field.
761
762
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7635.2 Event Packet Context Description
764
765Event packet context example. These are declared within the stream declaration
6672e9e1 766in the meta-data. All these fields are optional. If the packet size field is
6a7c61df 767missing, the whole stream only contains a single packet. If the content
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768size field is missing, the packet is filled (no padding). The content
769and packet sizes include all headers.
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770
771An example event packet context type:
772
80fd2569 773struct event_packet_context {
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774 uint64_t timestamp_begin;
775 uint64_t timestamp_end;
776 uint32_t checksum;
777 uint32_t stream_packet_count;
778 uint32_t events_discarded;
779 uint32_t cpu_id;
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780 uint64_t/uint32_t/uint16_t content_size;
781 uint64_t/uint32_t/uint16_t packet_size;
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782 uint8_t compression_scheme;
783 uint8_t encryption_scheme;
3b0f8e4d 784 uint8_t checksum_scheme;
3bf79539 785};
5ba9f198 786
fcba70d4 787
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7886. Event Structure
789
790The overall structure of an event is:
791
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7921 - Stream Packet Context (as specified by the stream meta-data)
793 2 - Event Header (as specified by the stream meta-data)
794 3 - Stream Event Context (as specified by the stream meta-data)
795 4 - Event Context (as specified by the event meta-data)
796 5 - Event Payload (as specified by the event meta-data)
5ba9f198 797
fdf2bb05 798This structure defines an implicit dynamic scoping, where variants
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799located in inner structures (those with a higher number in the listing
800above) can refer to the fields of outer structures (with lower number in
6c7226e9 801the listing above). See Section 7.3 TSDL Scopes for more detail.
5ba9f198 802
fdf2bb05 8036.1 Event Header
fcba70d4 804
6672e9e1 805Event headers can be described within the meta-data. We hereby propose, as an
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806example, two types of events headers. Type 1 accommodates streams with less than
80731 event IDs. Type 2 accommodates streams with 31 or more event IDs.
5ba9f198 808
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809One major factor can vary between streams: the number of event IDs assigned to
810a stream. Luckily, this information tends to stay relatively constant (modulo
5ba9f198 811event registration while trace is being recorded), so we can specify different
3bf79539 812representations for streams containing few event IDs and streams containing
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813many event IDs, so we end up representing the event ID and time-stamp as
814densely as possible in each case.
5ba9f198 815
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816The header is extended in the rare occasions where the information cannot be
817represented in the ranges available in the standard event header. They are also
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818used in the rare occasions where the data required for a field could not be
819collected: the flag corresponding to the missing field within the missing_fields
820array is then set to 1.
5ba9f198 821
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822Types uintX_t represent an X-bit unsigned integer, as declared with
823either:
5ba9f198 824
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MD
825 typealias integer { size = X; align = X; signed = false } := uintX_t;
826
827 or
828
829 typealias integer { size = X; align = 1; signed = false } := uintX_t;
5ba9f198 830
fdf2bb05 8316.1.1 Type 1 - Few event IDs
5ba9f198
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832
833 - Aligned on 32-bit (or 8-bit if byte-packed, depending on the architecture
834 preference).
5ba9f198 835 - Native architecture byte ordering.
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836 - For "compact" selection
837 - Fixed size: 32 bits.
838 - For "extended" selection
839 - Size depends on the architecture and variant alignment.
5ba9f198 840
80fd2569 841struct event_header_1 {
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842 /*
843 * id: range: 0 - 30.
844 * id 31 is reserved to indicate an extended header.
845 */
a9b83695 846 enum : uint5_t { compact = 0 ... 30, extended = 31 } id;
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847 variant <id> {
848 struct {
849 uint27_t timestamp;
850 } compact;
851 struct {
852 uint32_t id; /* 32-bit event IDs */
853 uint64_t timestamp; /* 64-bit timestamps */
854 } extended;
855 } v;
cb108fea 856} align(32); /* or align(8) */
5ba9f198 857
5ba9f198 858
fdf2bb05 8596.1.2 Type 2 - Many event IDs
5ba9f198 860
fcba70d4 861 - Aligned on 16-bit (or 8-bit if byte-packed, depending on the architecture
5ba9f198 862 preference).
5ba9f198 863 - Native architecture byte ordering.
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MD
864 - For "compact" selection
865 - Size depends on the architecture and variant alignment.
866 - For "extended" selection
867 - Size depends on the architecture and variant alignment.
5ba9f198 868
80fd2569 869struct event_header_2 {
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MD
870 /*
871 * id: range: 0 - 65534.
872 * id 65535 is reserved to indicate an extended header.
873 */
a9b83695 874 enum : uint16_t { compact = 0 ... 65534, extended = 65535 } id;
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875 variant <id> {
876 struct {
877 uint32_t timestamp;
878 } compact;
879 struct {
880 uint32_t id; /* 32-bit event IDs */
881 uint64_t timestamp; /* 64-bit timestamps */
882 } extended;
883 } v;
cb108fea 884} align(16); /* or align(8) */
5ba9f198 885
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MD
886
8876.2 Event Context
888
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MD
889The event context contains information relative to the current event.
890The choice and meaning of this information is specified by the TSDL
891stream and event meta-data descriptions. The stream context is applied
892to all events within the stream. The stream context structure follows
893the event header. The event context is applied to specific events. Its
894structure follows the stream context structure.
5ba9f198 895
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896An example of stream-level event context is to save the event payload size with
897each event, or to save the current PID with each event. These are declared
6672e9e1 898within the stream declaration within the meta-data:
5ba9f198 899
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900 stream {
901 ...
6672e9e1 902 event.context := struct {
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MD
903 uint pid;
904 uint16_t payload_size;
6672e9e1 905 };
fcba70d4
MD
906 };
907
908An example of event-specific event context is to declare a bitmap of missing
909fields, only appended after the stream event context if the extended event
910header is selected. NR_FIELDS is the number of fields within the event (a
911numeric value).
5ba9f198 912
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913 event {
914 context = struct {
915 variant <id> {
916 struct { } compact;
917 struct {
918 uint1_t missing_fields[NR_FIELDS]; /* missing event fields bitmap */
919 } extended;
920 } v;
921 };
922 ...
923 }
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MD
924
9256.3 Event Payload
926
927An event payload contains fields specific to a given event type. The fields
6672e9e1 928belonging to an event type are described in the event-specific meta-data
5ba9f198
MD
929within a structure type.
930
9316.3.1 Padding
932
933No padding at the end of the event payload. This differs from the ISO/C standard
934for structures, but follows the CTF standard for structures. In a trace, even
935though it makes sense to align the beginning of a structure, it really makes no
936sense to add padding at the end of the structure, because structures are usually
937not followed by a structure of the same type.
938
939This trick can be done by adding a zero-length "end" field at the end of the C
940structures, and by using the offset of this field rather than using sizeof()
3bf79539 941when calculating the size of a structure (see Appendix "A. Helper macros").
5ba9f198
MD
942
9436.3.2 Alignment
944
945The event payload is aligned on the largest alignment required by types
946contained within the payload. (This follows the ISO/C standard for structures)
947
948
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MD
9497. Trace Stream Description Language (TSDL)
950
951The Trace Stream Description Language (TSDL) allows expression of the
952binary trace streams layout in a C99-like Domain Specific Language
953(DSL).
954
955
6672e9e1 9567.1 Meta-data
6c7226e9
MD
957
958The trace stream layout description is located in the trace meta-data.
959The meta-data is itself located in a stream identified by its name:
960"metadata".
5ba9f198 961
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MD
962The meta-data description can be expressed in two different formats:
963text-only and packet-based. The text-only description facilitates
964generation of meta-data and provides a convenient way to enter the
965meta-data information by hand. The packet-based meta-data provides the
966CTF stream packet facilities (checksumming, compression, encryption,
967network-readiness) for meta-data stream generated and transported by a
968tracer.
969
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970The text-only meta-data file is a plain-text TSDL description. This file
971must begin with the following characters to identify the file as a CTF
9486a18c 972TSDL text-based metadata file (without the double-quotes) :
1b4d35eb 973
ec2b4db8 974"/* CTF"
1b4d35eb 975
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MD
976It must be followed by a space, and the version of the specification
977followed by the CTF trace, e.g.:
978
979" 1.8"
980
981These characters allow automated discovery of file type and CTF
982specification version. They are interpreted as a the beginning of a
983comment by the TSDL metadata parser. The comment can be continued to
984contain extra commented characters before it is closed.
6672e9e1
MD
985
986The packet-based meta-data is made of "meta-data packets", which each
987start with a meta-data packet header. The packet-based meta-data
988description is detected by reading the magic number "0x75D11D57" at the
989beginning of the file. This magic number is also used to detect the
990endianness of the architecture by trying to read the CTF magic number
991and its counterpart in reversed endianness. The events within the
992meta-data stream have no event header nor event context. Each event only
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993contains a special "sequence" payload, which is a sequence of bits which
994length is implicitly calculated by using the
995"trace.packet.header.content_size" field, minus the packet header size.
996The formatting of this sequence of bits is a plain-text representation
997of the TSDL description. Each meta-data packet start with a special
998packet header, specific to the meta-data stream, which contains,
999exactly:
6672e9e1
MD
1000
1001struct metadata_packet_header {
2daeaa3a 1002 uint32_t magic; /* 0x75D11D57 */
3fde5da1 1003 uint8_t uuid[16]; /* Unique Universal Identifier */
6672e9e1
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1004 uint32_t checksum; /* 0 if unused */
1005 uint32_t content_size; /* in bits */
1006 uint32_t packet_size; /* in bits */
1007 uint8_t compression_scheme; /* 0 if unused */
1008 uint8_t encryption_scheme; /* 0 if unused */
1009 uint8_t checksum_scheme; /* 0 if unused */
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1010 uint8_t major; /* CTF spec version major number */
1011 uint8_t minor; /* CTF spec version minor number */
6672e9e1
MD
1012};
1013
1014The packet-based meta-data can be converted to a text-only meta-data by
3568031f 1015concatenating all the strings it contains.
4fafe1ad 1016
6672e9e1
MD
1017In the textual representation of the meta-data, the text contained
1018within "/*" and "*/", as well as within "//" and end of line, are
1019treated as comments. Boolean values can be represented as true, TRUE,
1020or 1 for true, and false, FALSE, or 0 for false. Within the string-based
1021meta-data description, the trace UUID is represented as a string of
1022hexadecimal digits and dashes "-". In the event packet header, the trace
1023UUID is represented as an array of bytes.
fcba70d4 1024
fdf2bb05 1025
6c7226e9 10267.2 Declaration vs Definition
fdf2bb05
MD
1027
1028A declaration associates a layout to a type, without specifying where
1029this type is located in the event structure hierarchy (see Section 6).
1030This therefore includes typedef, typealias, as well as all type
1031specifiers. In certain circumstances (typedef, structure field and
1032variant field), a declaration is followed by a declarator, which specify
1033the newly defined type name (for typedef), or the field name (for
1034declarations located within structure and variants). Array and sequence,
1035declared with square brackets ("[" "]"), are part of the declarator,
a9b83695 1036similarly to C99. The enumeration base type is specified by
6c7226e9 1037": enum_base", which is part of the type specifier. The variant tag
a9b83695 1038name, specified between "<" ">", is also part of the type specifier.
fdf2bb05
MD
1039
1040A definition associates a type to a location in the event structure
b9606a77
MD
1041hierarchy (see Section 6). This association is denoted by ":=", as shown
1042in Section 7.3.
fdf2bb05
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1043
1044
6c7226e9 10457.3 TSDL Scopes
fdf2bb05 1046
37ab95c3
MD
1047TSDL uses three different types of scoping: a lexical scope is used for
1048declarations and type definitions, and static and dynamic scopes are
1049used for variants references to tag fields (with relative and absolute
1050path lookups) and for sequence references to length fields.
fdf2bb05 1051
6c7226e9 10527.3.1 Lexical Scope
fdf2bb05 1053
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1054Each of "trace", "env", "stream", "event", "struct" and "variant" have
1055their own nestable declaration scope, within which types can be declared
1056using "typedef" and "typealias". A root declaration scope also contains
1057all declarations located outside of any of the aforementioned
1058declarations. An inner declaration scope can refer to type declared
1059within its container lexical scope prior to the inner declaration scope.
1060Redefinition of a typedef or typealias is not valid, although hiding an
1061upper scope typedef or typealias is allowed within a sub-scope.
fdf2bb05 1062
37ab95c3 10637.3.2 Static and Dynamic Scopes
fdf2bb05 1064
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MD
1065A local static scope consists in the scope generated by the declaration
1066of fields within a compound type. A static scope is a local static scope
1067augmented with the nested sub-static-scopes it contains.
1068
1069A dynamic scope consists in the static scope augmented with the
7d9d7e92 1070implicit event structure definition hierarchy presented at Section 6.
fdf2bb05 1071
37ab95c3
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1072Multiple declarations of the same field name within a local static scope
1073is not valid. It is however valid to re-use the same field name in
1074different local scopes.
1075
1076Nested static and dynamic scopes form lookup paths. These are used for
1077variant tag and sequence length references. They are used at the variant
1078and sequence definition site to look up the location of the tag field
1079associated with a variant, and to lookup up the location of the length
1080field associated with a sequence.
1081
1082Variants and sequences can refer to a tag field either using a relative
4cac83ee
MD
1083path or an absolute path. The relative path is relative to the scope in
1084which the variant or sequence performing the lookup is located.
37ab95c3
MD
1085Relative paths are only allowed to lookup within the same static scope,
1086which includes its nested static scopes. Lookups targeting parent static
1087scopes need to be performed with an absolute path.
1088
1089Absolute path lookups use the full path including the dynamic scope
1090followed by a "." and then the static scope. Therefore, variants (or
1091sequences) in lower levels in the dynamic scope (e.g. event context) can
1092refer to a tag (or length) field located in upper levels (e.g. in the
1093event header) by specifying, in this case, the associated tag with
1094<stream.event.header.field_name>. This allows, for instance, the event
1095context to define a variant referring to the "id" field of the event
1096header as selector.
1097
284724ae 1098The dynamic scope prefixes are thus:
fdf2bb05 1099
570ecabe 1100 - Trace Environment: <env. >,
e0d9e2c7 1101 - Trace Packet Header: <trace.packet.header. >,
7d9d7e92
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1102 - Stream Packet Context: <stream.packet.context. >,
1103 - Event Header: <stream.event.header. >,
1104 - Stream Event Context: <stream.event.context. >,
1105 - Event Context: <event.context. >,
1106 - Event Payload: <event.fields. >.
fdf2bb05 1107
37ab95c3
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1108
1109The target dynamic scope must be specified explicitly when referring to
4cac83ee
MD
1110a field outside of the static scope (absolute scope reference). No
1111conflict can occur between relative and dynamic paths, because the
1112keywords "trace", "stream", and "event" are reserved, and thus
1113not permitted as field names. It is recommended that field names
1114clashing with CTF and C99 reserved keywords use an underscore prefix to
1115eliminate the risk of generating a description containing an invalid
70375f92 1116field name. Consequently, fields starting with an underscore should have
92250c71 1117their leading underscore removed by the CTF trace readers.
70375f92 1118
fdf2bb05 1119
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1120The information available in the dynamic scopes can be thought of as the
1121current tracing context. At trace production, information about the
1122current context is saved into the specified scope field levels. At trace
1123consumption, for each event, the current trace context is therefore
1124readable by accessing the upper dynamic scopes.
1125
fdf2bb05 1126
6c7226e9 11277.4 TSDL Examples
d285084f 1128
6672e9e1 1129The grammar representing the TSDL meta-data is presented in Appendix C.
7df6b93a 1130TSDL Grammar. This section presents a rather lighter reading that
6672e9e1 1131consists in examples of TSDL meta-data, with template values.
969f30c0 1132
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MD
1133The stream "id" can be left out if there is only one stream in the
1134trace. The event "id" field can be left out if there is only one event
1135in a stream.
1136
5ba9f198 1137trace {
1e9de2d1
MD
1138 major = value; /* CTF spec version major number */
1139 minor = value; /* CTF spec version minor number */
fdf2bb05 1140 uuid = "aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa"; /* Trace UUID */
58997e9e 1141 byte_order = be OR le; /* Endianness (required) */
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MD
1142 packet.header := struct {
1143 uint32_t magic;
3fde5da1 1144 uint8_t uuid[16];
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MD
1145 uint32_t stream_id;
1146 };
3bf79539 1147};
5ba9f198 1148
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MD
1149/*
1150 * The "env" (environment) scope contains assignment expressions. The
1151 * field names and content are implementation-defined.
1152 */
1153env {
1154 pid = value; /* example */
1155 proc_name = "name"; /* example */
1156 ...
1157};
1158
3bf79539
MD
1159stream {
1160 id = stream_id;
fdf2bb05 1161 /* Type 1 - Few event IDs; Type 2 - Many event IDs. See section 6.1. */
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1162 event.header := event_header_1 OR event_header_2;
1163 event.context := struct {
77a98c82 1164 ...
3bf79539 1165 };
4fa992a5 1166 packet.context := struct {
77a98c82 1167 ...
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MD
1168 };
1169};
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1170
1171event {
980015f9 1172 name = "event_name";
3bf79539 1173 id = value; /* Numeric identifier within the stream */
67f02e24 1174 stream_id = stream_id;
dc56f167 1175 loglevel = value;
8e9060f2 1176 model.emf.uri = "string";
4fa992a5 1177 context := struct {
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1178 ...
1179 };
4fa992a5 1180 fields := struct {
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1181 ...
1182 };
3bf79539 1183};
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1184
1185/* More detail on types in section 4. Types */
1186
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1187/*
1188 * Named types:
1189 *
4fa992a5 1190 * Type declarations behave similarly to the C standard.
3d13ef1a
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1191 */
1192
80af8ac6 1193typedef aliased_type_specifiers new_type_declarators;
2152348f 1194
3d13ef1a 1195/* e.g.: typedef struct example new_type_name[10]; */
80fd2569 1196
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1197/*
1198 * typealias
1199 *
1200 * The "typealias" declaration can be used to give a name (including
80af8ac6
MD
1201 * pointer declarator specifier) to a type. It should also be used to
1202 * map basic C types (float, int, unsigned long, ...) to a CTF type.
1203 * Typealias is a superset of "typedef": it also allows assignment of a
38b8da21 1204 * simple variable identifier to a type.
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1205 */
1206
1207typealias type_class {
80fd2569 1208 ...
38b8da21 1209} := type_specifiers type_declarator;
2152348f 1210
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1211/*
1212 * e.g.:
4fa992a5 1213 * typealias integer {
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1214 * size = 32;
1215 * align = 32;
1216 * signed = false;
38b8da21 1217 * } := struct page *;
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1218 *
1219 * typealias integer {
1220 * size = 32;
1221 * align = 32;
1222 * signed = true;
38b8da21 1223 * } := int;
3d13ef1a 1224 */
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1225
1226struct name {
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1227 ...
1228};
5ba9f198 1229
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1230variant name {
1231 ...
1232};
1233
a9b83695 1234enum name : integer_type {
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1235 ...
1236};
1237
2152348f 1238
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1239/*
1240 * Unnamed types, contained within compound type fields, typedef or typealias.
1241 */
2152348f 1242
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1243struct {
1244 ...
2152348f 1245}
5ba9f198 1246
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1247struct {
1248 ...
1249} align(value)
1250
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1251variant {
1252 ...
1253}
1254
a9b83695 1255enum : integer_type {
80fd2569 1256 ...
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1257}
1258
1259typedef type new_type[length];
3bf79539 1260
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1261struct {
1262 type field_name[length];
1263}
1264
1265typedef type new_type[length_type];
1266
1267struct {
1268 type field_name[length_type];
1269}
1270
1271integer {
80fd2569 1272 ...
2152348f 1273}
3bf79539 1274
2152348f 1275floating_point {
80fd2569 1276 ...
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MD
1277}
1278
1279struct {
1280 integer_type field_name:size; /* GNU/C bitfield */
1281}
1282
1283struct {
1284 string field_name;
1285}
3bf79539 1286
fcba70d4 1287
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12888. Clocks
1289
1290Clock metadata allows to describe the clock topology of the system, as
1291well as to detail each clock parameter. In absence of clock description,
1292it is assumed that all fields named "timestamp" use the same clock
aed18b5e 1293source, which increments once per nanosecond.
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1294
1295Describing a clock and how it is used by streams is threefold: first,
1296the clock and clock topology should be described in a "clock"
1297description block, e.g.:
1298
d803bfcb 1299clock {
58262d97 1300 name = cycle_counter_sync;
2fa70eba 1301 uuid = "62189bee-96dc-11e0-91a8-cfa3d89f3923";
58262d97 1302 description = "Cycle counter synchronized across CPUs";
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1303 freq = 1000000000; /* frequency, in Hz */
1304 /* precision in seconds is: 1000 * (1/freq) */
1305 precision = 1000;
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MD
1306 /*
1307 * clock value offset from Epoch is:
1308 * offset_s + (offset * (1/freq))
1309 */
1310 offset_s = 1326476837;
1311 offset = 897235420;
ce0fadbd 1312 absolute = FALSE;
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1313};
1314
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1315The mandatory "name" field specifies the name of the clock identifier,
1316which can later be used as a reference. The optional field "uuid" is the
1317unique identifier of the clock. It can be used to correlate different
1318traces that use the same clock. An optional textual description string
1319can be added with the "description" field. The "freq" field is the
1320initial frequency of the clock, in Hz. If the "freq" field is not
1321present, the frequency is assumed to be 1000000000 (providing clock
1322increment of 1 ns). The optional "precision" field details the
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1323uncertainty on the clock measurements, in (1/freq) units. The "offset_s"
1324and "offset" fields indicate the offset from POSIX.1 Epoch, 1970-01-01
132500:00:00 +0000 (UTC), to the zero of value of the clock. The "offset_s"
1326field is in seconds. The "offset" field is in (1/freq) units. If any of
1327the "offset_s" or "offset" field is not present, it is assigned the 0
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MD
1328value. The field "absolute" is TRUE if the clock is a global reference
1329across different clock uuid (e.g. NTP time). Otherwise, "absolute" is
1330FALSE, and the clock can be considered as synchronized only with other
1331clocks that have the same uuid.
1332
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1333
1334Secondly, a reference to this clock should be added within an integer
1335type:
1336
1337typealias integer {
1338 size = 64; align = 1; signed = false;
58262d97 1339 map = clock.cycle_counter_sync.value;
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MD
1340} := uint64_ccnt_t;
1341
1342Thirdly, stream declarations can reference the clock they use as a
1343time-stamp source:
1344
1345struct packet_context {
1346 uint64_ccnt_t ccnt_begin;
1347 uint64_ccnt_t ccnt_end;
1348 /* ... */
1349};
1350
1351stream {
1352 /* ... */
1353 event.header := struct {
1354 uint64_ccnt_t timestamp;
1355 /* ... */
1356 }
1357 packet.context := struct packet_context;
1358};
1359
1360For a N-bit integer type referring to a clock, if the integer overflows
1361compared to the N low order bits of the clock prior value, then it is
1362assumed that one, and only one, overflow occurred. It is therefore
1363important that events encoding time on a small number of bits happen
1364frequently enough to detect when more than one N-bit overflow occurs.
1365
1366In a packet context, clock field names ending with "_begin" and "_end"
1367have a special meaning: this refers to the time-stamps at, respectively,
1368the beginning and the end of each packet.
1369
1370
3bf79539 1371A. Helper macros
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1372
1373The two following macros keep track of the size of a GNU/C structure without
1374padding at the end by placing HEADER_END as the last field. A one byte end field
1375is used for C90 compatibility (C99 flexible arrays could be used here). Note
1376that this does not affect the effective structure size, which should always be
1377calculated with the header_sizeof() helper.
1378
1379#define HEADER_END char end_field
1380#define header_sizeof(type) offsetof(typeof(type), end_field)
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1381
1382
1383B. Stream Header Rationale
1384
1385An event stream is divided in contiguous event packets of variable size. These
1386subdivisions allow the trace analyzer to perform a fast binary search by time
1387within the stream (typically requiring to index only the event packet headers)
1388without reading the whole stream. These subdivisions have a variable size to
1389eliminate the need to transfer the event packet padding when partially filled
1390event packets must be sent when streaming a trace for live viewing/analysis.
1391An event packet can contain a certain amount of padding at the end. Dividing
1392streams into event packets is also useful for network streaming over UDP and
1393flight recorder mode tracing (a whole event packet can be swapped out of the
1394buffer atomically for reading).
1395
1396The stream header is repeated at the beginning of each event packet to allow
1397flexibility in terms of:
1398
1399 - streaming support,
1400 - allowing arbitrary buffers to be discarded without making the trace
1401 unreadable,
1402 - allow UDP packet loss handling by either dealing with missing event packet
1403 or asking for re-transmission.
1404 - transparently support flight recorder mode,
1405 - transparently support crash dump.
1406
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MD
1407
1408C. TSDL Grammar
fcba70d4 1409
4fa992a5 1410/*
6c7226e9 1411 * Common Trace Format (CTF) Trace Stream Description Language (TSDL) Grammar.
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1412 *
1413 * Inspired from the C99 grammar:
1414 * http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1124.pdf (Annex A)
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1415 * and c++1x grammar (draft)
1416 * http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2011/n3291.pdf (Annex A)
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1417 *
1418 * Specialized for CTF needs by including only constant and declarations from
1419 * C99 (excluding function declarations), and by adding support for variants,
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MD
1420 * sequences and CTF-specific specifiers. Enumeration container types
1421 * semantic is inspired from c++1x enum-base.
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MD
1422 */
1423
14241) Lexical grammar
1425
14261.1) Lexical elements
1427
1428token:
1429 keyword
1430 identifier
1431 constant
1432 string-literal
1433 punctuator
1434
14351.2) Keywords
1436
1437keyword: is one of
1438
ec4404a7 1439align
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MD
1440const
1441char
2fa70eba 1442clock
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MD
1443double
1444enum
570ecabe 1445env
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MD
1446event
1447floating_point
1448float
1449integer
1450int
1451long
1452short
1453signed
1454stream
1455string
1456struct
1457trace
3e1e1a78 1458typealias
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MD
1459typedef
1460unsigned
1461variant
1462void
1463_Bool
1464_Complex
1465_Imaginary
1466
1467
14681.3) Identifiers
1469
1470identifier:
1471 identifier-nondigit
1472 identifier identifier-nondigit
1473 identifier digit
1474
1475identifier-nondigit:
1476 nondigit
1477 universal-character-name
1478 any other implementation-defined characters
1479
1480nondigit:
1481 _
1482 [a-zA-Z] /* regular expression */
1483
1484digit:
1485 [0-9] /* regular expression */
1486
14871.4) Universal character names
1488
1489universal-character-name:
1490 \u hex-quad
1491 \U hex-quad hex-quad
1492
1493hex-quad:
1494 hexadecimal-digit hexadecimal-digit hexadecimal-digit hexadecimal-digit
1495
14961.5) Constants
1497
1498constant:
1499 integer-constant
1500 enumeration-constant
1501 character-constant
1502
1503integer-constant:
1504 decimal-constant integer-suffix-opt
1505 octal-constant integer-suffix-opt
1506 hexadecimal-constant integer-suffix-opt
1507
1508decimal-constant:
1509 nonzero-digit
1510 decimal-constant digit
1511
1512octal-constant:
1513 0
1514 octal-constant octal-digit
1515
1516hexadecimal-constant:
1517 hexadecimal-prefix hexadecimal-digit
1518 hexadecimal-constant hexadecimal-digit
1519
1520hexadecimal-prefix:
1521 0x
1522 0X
1523
1524nonzero-digit:
1525 [1-9]
1526
1527integer-suffix:
1528 unsigned-suffix long-suffix-opt
1529 unsigned-suffix long-long-suffix
1530 long-suffix unsigned-suffix-opt
1531 long-long-suffix unsigned-suffix-opt
1532
1533unsigned-suffix:
1534 u
1535 U
1536
1537long-suffix:
1538 l
1539 L
1540
1541long-long-suffix:
1542 ll
1543 LL
1544
4fa992a5
MD
1545enumeration-constant:
1546 identifier
1547 string-literal
1548
1549character-constant:
1550 ' c-char-sequence '
1551 L' c-char-sequence '
1552
1553c-char-sequence:
1554 c-char
1555 c-char-sequence c-char
1556
1557c-char:
1558 any member of source charset except single-quote ('), backslash
1559 (\), or new-line character.
1560 escape-sequence
1561
1562escape-sequence:
1563 simple-escape-sequence
1564 octal-escape-sequence
1565 hexadecimal-escape-sequence
1566 universal-character-name
1567
1568simple-escape-sequence: one of
1569 \' \" \? \\ \a \b \f \n \r \t \v
1570
1571octal-escape-sequence:
1572 \ octal-digit
1573 \ octal-digit octal-digit
1574 \ octal-digit octal-digit octal-digit
1575
1576hexadecimal-escape-sequence:
1577 \x hexadecimal-digit
1578 hexadecimal-escape-sequence hexadecimal-digit
1579
15801.6) String literals
1581
1582string-literal:
1583 " s-char-sequence-opt "
1584 L" s-char-sequence-opt "
1585
1586s-char-sequence:
1587 s-char
1588 s-char-sequence s-char
1589
1590s-char:
1591 any member of source charset except double-quote ("), backslash
1592 (\), or new-line character.
1593 escape-sequence
1594
15951.7) Punctuators
1596
1597punctuator: one of
1598 [ ] ( ) { } . -> * + - < > : ; ... = ,
1599
1600
16012) Phrase structure grammar
1602
1603primary-expression:
1604 identifier
1605 constant
1606 string-literal
1607 ( unary-expression )
1608
1609postfix-expression:
1610 primary-expression
1611 postfix-expression [ unary-expression ]
1612 postfix-expression . identifier
1613 postfix-expressoin -> identifier
1614
1615unary-expression:
1616 postfix-expression
1617 unary-operator postfix-expression
1618
1619unary-operator: one of
1620 + -
1621
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MD
1622assignment-operator:
1623 =
1624
b9606a77
MD
1625type-assignment-operator:
1626 :=
1627
4fa992a5 1628constant-expression-range:
73d61ac3 1629 unary-expression ... unary-expression
4fa992a5
MD
1630
16312.2) Declarations:
1632
1633declaration:
689e04b4 1634 declaration-specifiers declarator-list-opt ;
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MD
1635 ctf-specifier ;
1636
1637declaration-specifiers:
689e04b4 1638 storage-class-specifier declaration-specifiers-opt
4fa992a5
MD
1639 type-specifier declaration-specifiers-opt
1640 type-qualifier declaration-specifiers-opt
1641
1642declarator-list:
1643 declarator
1644 declarator-list , declarator
1645
d285084f
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1646abstract-declarator-list:
1647 abstract-declarator
1648 abstract-declarator-list , abstract-declarator
1649
4fa992a5
MD
1650storage-class-specifier:
1651 typedef
1652
1653type-specifier:
1654 void
1655 char
1656 short
1657 int
1658 long
1659 float
1660 double
1661 signed
1662 unsigned
1663 _Bool
1664 _Complex
cfdd51ec 1665 _Imaginary
9dfcfc0f
MD
1666 struct-specifier
1667 variant-specifier
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MD
1668 enum-specifier
1669 typedef-name
1670 ctf-type-specifier
1671
ec4404a7 1672align-attribute:
73d61ac3 1673 align ( unary-expression )
ec4404a7 1674
4fa992a5 1675struct-specifier:
ec4404a7
MD
1676 struct identifier-opt { struct-or-variant-declaration-list-opt } align-attribute-opt
1677 struct identifier align-attribute-opt
4fa992a5
MD
1678
1679struct-or-variant-declaration-list:
1680 struct-or-variant-declaration
1681 struct-or-variant-declaration-list struct-or-variant-declaration
1682
1683struct-or-variant-declaration:
1684 specifier-qualifier-list struct-or-variant-declarator-list ;
eacb16d1 1685 declaration-specifiers-opt storage-class-specifier declaration-specifiers-opt declarator-list ;
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1686 typealias declaration-specifiers abstract-declarator-list type-assignment-operator declaration-specifiers abstract-declarator-list ;
1687 typealias declaration-specifiers abstract-declarator-list type-assignment-operator declarator-list ;
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1688
1689specifier-qualifier-list:
1690 type-specifier specifier-qualifier-list-opt
1691 type-qualifier specifier-qualifier-list-opt
1692
1693struct-or-variant-declarator-list:
1694 struct-or-variant-declarator
1695 struct-or-variant-declarator-list , struct-or-variant-declarator
1696
1697struct-or-variant-declarator:
1698 declarator
73d61ac3 1699 declarator-opt : unary-expression
4fa992a5
MD
1700
1701variant-specifier:
1702 variant identifier-opt variant-tag-opt { struct-or-variant-declaration-list }
1703 variant identifier variant-tag
1704
1705variant-tag:
37ab95c3 1706 < unary-expression >
4fa992a5
MD
1707
1708enum-specifier:
1709 enum identifier-opt { enumerator-list }
1710 enum identifier-opt { enumerator-list , }
1711 enum identifier
a9b83695
MD
1712 enum identifier-opt : declaration-specifiers { enumerator-list }
1713 enum identifier-opt : declaration-specifiers { enumerator-list , }
4fa992a5
MD
1714
1715enumerator-list:
1716 enumerator
1717 enumerator-list , enumerator
1718
1719enumerator:
1720 enumeration-constant
8d2d41f7
MD
1721 enumeration-constant assignment-operator unary-expression
1722 enumeration-constant assignment-operator constant-expression-range
4fa992a5
MD
1723
1724type-qualifier:
1725 const
1726
1727declarator:
1728 pointer-opt direct-declarator
1729
1730direct-declarator:
1731 identifier
1732 ( declarator )
1ab22b2a 1733 direct-declarator [ unary-expression ]
4fa992a5 1734
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1735abstract-declarator:
1736 pointer-opt direct-abstract-declarator
1737
1738direct-abstract-declarator:
1739 identifier-opt
1740 ( abstract-declarator )
1ab22b2a 1741 direct-abstract-declarator [ unary-expression ]
d285084f
MD
1742 direct-abstract-declarator [ ]
1743
4fa992a5 1744pointer:
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1745 * type-qualifier-list-opt
1746 * type-qualifier-list-opt pointer
4fa992a5
MD
1747
1748type-qualifier-list:
1749 type-qualifier
1750 type-qualifier-list type-qualifier
1751
4fa992a5
MD
1752typedef-name:
1753 identifier
1754
17552.3) CTF-specific declarations
1756
1757ctf-specifier:
662baf84 1758 clock { ctf-assignment-expression-list-opt }
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MD
1759 event { ctf-assignment-expression-list-opt }
1760 stream { ctf-assignment-expression-list-opt }
570ecabe 1761 env { ctf-assignment-expression-list-opt }
4fa992a5 1762 trace { ctf-assignment-expression-list-opt }
b12919a5
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1763 typealias declaration-specifiers abstract-declarator-list type-assignment-operator declaration-specifiers abstract-declarator-list
1764 typealias declaration-specifiers abstract-declarator-list type-assignment-operator declarator-list
4fa992a5
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1765
1766ctf-type-specifier:
1767 floating_point { ctf-assignment-expression-list-opt }
1768 integer { ctf-assignment-expression-list-opt }
1769 string { ctf-assignment-expression-list-opt }
7609d3c7 1770 string
4fa992a5
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1771
1772ctf-assignment-expression-list:
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1773 ctf-assignment-expression ;
1774 ctf-assignment-expression-list ctf-assignment-expression ;
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1775
1776ctf-assignment-expression:
1777 unary-expression assignment-operator unary-expression
1778 unary-expression type-assignment-operator type-specifier
eacb16d1 1779 declaration-specifiers-opt storage-class-specifier declaration-specifiers-opt declarator-list
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1780 typealias declaration-specifiers abstract-declarator-list type-assignment-operator declaration-specifiers abstract-declarator-list
1781 typealias declaration-specifiers abstract-declarator-list type-assignment-operator declarator-list
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