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[ctf.git] / common-trace-format-specification.txt
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87502777 1Common Trace Format (CTF) Specification (v1.8.1)
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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.
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456
457The alignment of the variant is the alignment of the type as selected by the tag
458value for the specific instance of the variant. The alignment of the type
459containing the variant is independent of the variant alignment. The size of the
460variant is the size as selected by the tag value for the specific instance of
461the variant.
462
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463Each variant type selector possess a field name, which is a unique
464identifier within the variant. The identifier is not allowed to use any
465reserved keyword (see Section C.1.2). Replacing reserved keywords with
70375f92 466underscore-prefixed field names is recommended. Fields starting with an
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467underscore should have their leading underscore removed by the CTF trace
468readers.
70375f92 469
4cac83ee 470
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471A named variant declaration followed by its definition within a structure
472declaration:
473
474variant name {
475 field_type sel1;
476 field_type sel2;
477 field_type sel3;
478 ...
479};
480
481struct {
a9b83695 482 enum : integer_type { sel1, sel2, sel3, ... } tag_field;
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483 ...
484 variant name <tag_field> v;
485}
486
487An unnamed variant definition within a structure is expressed by the following
6672e9e1 488TSDL meta-data:
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489
490struct {
a9b83695 491 enum : integer_type { sel1, sel2, sel3, ... } tag_field;
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492 ...
493 variant <tag_field> {
494 field_type sel1;
495 field_type sel2;
496 field_type sel3;
497 ...
498 } v;
499}
500
501Example of a named variant within a sequence that refers to a single tag field:
502
503variant example {
504 uint32_t a;
505 uint64_t b;
506 short c;
507};
508
509struct {
a9b83695 510 enum : uint2_t { a, b, c } choice;
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511 unsigned int seqlen;
512 variant example <choice> v[seqlen];
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513}
514
515Example of an unnamed variant:
516
517struct {
a9b83695 518 enum : uint2_t { a, b, c, d } choice;
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519 /* Unrelated fields can be added between the variant and its tag */
520 int32_t somevalue;
521 variant <choice> {
522 uint32_t a;
523 uint64_t b;
524 short c;
525 struct {
526 unsigned int field1;
527 uint64_t field2;
528 } d;
529 } s;
530}
531
532Example of an unnamed variant within an array:
533
534struct {
a9b83695 535 enum : uint2_t { a, b, c } choice;
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536 variant <choice> {
537 uint32_t a;
538 uint64_t b;
539 short c;
15850440 540 } v[10];
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541}
542
543Example of a variant type definition within a structure, where the defined type
544is then declared within an array of structures. This variant refers to a tag
37ab95c3 545located in an upper static scope. This example clearly shows that a variant
fcba70d4 546type definition referring to the tag "x" uses the closest preceding field from
37ab95c3 547the static scope of the type definition.
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548
549struct {
a9b83695 550 enum : uint2_t { a, b, c, d } x;
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551
552 typedef variant <x> { /*
553 * "x" refers to the preceding "x" enumeration in the
37ab95c3 554 * static scope of the type definition.
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555 */
556 uint32_t a;
557 uint64_t b;
558 short c;
559 } example_variant;
560
561 struct {
a9b83695 562 enum : int { x, y, z } x; /* This enumeration is not used by "v". */
fcba70d4 563 example_variant v; /*
a9b83695 564 * "v" uses the "enum : uint2_t { a, b, c, d }"
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565 * tag.
566 */
567 } a[10];
568}
569
5704.2.3 Arrays
5ba9f198 571
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572Arrays are fixed-length. Their length is declared in the type
573declaration within the meta-data. They contain an array of "inner type"
574elements, which can refer to any type not containing the type of the
575array being declared (no circular dependency). The length is the number
576of elements in an array.
5ba9f198 577
6672e9e1 578TSDL meta-data representation of a named array:
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579
580typedef elem_type name[length];
5ba9f198 581
2152348f 582A nameless array can be declared as a field type within a structure, e.g.:
5ba9f198 583
2152348f 584 uint8_t field_name[10];
80fd2569 585
ec4404a7 586Arrays are always aligned on their element alignment requirement.
5ba9f198 587
fcba70d4 5884.2.4 Sequences
5ba9f198 589
1ab22b2a 590Sequences are dynamically-sized arrays. They refer to a a "length"
37ab95c3 591unsigned integer field, which must appear in either the same static scope,
1ab22b2a 592prior to the sequence field (in field declaration order), in an upper
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593static scope, or in an upper dynamic scope (see Section 7.3.2). This
594length field represents the number of elements in the sequence. The
595sequence per se is an array of "inner type" elements.
5ba9f198 596
1ab22b2a 597TSDL meta-data representation for a sequence type definition:
80fd2569 598
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599struct {
600 unsigned int length_field;
601 typedef elem_type typename[length_field];
602 typename seq_field_name;
603}
604
605A sequence can also be declared as a field type, e.g.:
80fd2569 606
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607struct {
608 unsigned int length_field;
609 long seq_field_name[length_field];
610}
80fd2569 611
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612Multiple sequences can refer to the same length field, and these length
613fields can be in a different upper dynamic scope:
614
615e.g., assuming the stream.event.header defines:
616
617stream {
618 ...
619 id = 1;
620 event.header := struct {
621 uint16_t seq_len;
622 };
623};
624
625event {
626 ...
627 stream_id = 1;
628 fields := struct {
629 long seq_a[stream.event.header.seq_len];
630 char seq_b[stream.event.header.seq_len];
631 };
632};
80fd2569 633
1ab22b2a 634The sequence elements follow the "array" specifications.
5ba9f198 635
fcba70d4 6364.2.5 Strings
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637
638Strings are an array of bytes of variable size and are terminated by a '\0'
6672e9e1
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639"NULL" character. Their encoding is described in the TSDL meta-data. In
640absence of encoding attribute information, the default encoding is
641UTF-8.
5ba9f198 642
6672e9e1 643TSDL meta-data representation of a named string type:
80fd2569 644
359894ac 645typealias string {
5ba9f198 646 encoding = UTF8 OR ASCII;
38b8da21 647} := name;
5ba9f198 648
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649A nameless string type can be declared as a field type:
650
651string field_name; /* Use default UTF8 encoding */
5ba9f198 652
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653Strings are always aligned on byte size.
654
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6555. Event Packet Header
656
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657The event packet header consists of two parts: the "event packet header"
658is the same for all streams of a trace. The second part, the "event
659packet context", is described on a per-stream basis. Both are described
660in the TSDL meta-data. The packets are aligned on architecture-page-sized
661addresses.
3bf79539 662
6672e9e1 663Event packet header (all fields are optional, specified by TSDL meta-data):
3bf79539 664
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665- Magic number (CTF magic number: 0xC1FC1FC1) specifies that this is a
666 CTF packet. This magic number is optional, but when present, it should
667 come at the very beginning of the packet.
668- Trace UUID, used to ensure the event packet match the meta-data used.
669 (note: we cannot use a meta-data checksum in every cases instead of a
670 UUID because meta-data can be appended to while tracing is active)
671 This field is optional.
672- Stream ID, used as reference to stream description in meta-data.
673 This field is optional if there is only one stream description in the
674 meta-data, but becomes required if there are more than one stream in
675 the TSDL meta-data description.
3bf79539 676
6672e9e1 677Event packet context (all fields are optional, specified by TSDL meta-data):
3bf79539 678
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679- Event packet content size (in bits).
680- Event packet size (in bits, includes padding).
cda89682 681- Event packet content checksum. Checksum excludes the event packet
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682 header.
683- Per-stream event packet sequence count (to deal with UDP packet loss). The
684 number of significant sequence counter bits should also be present, so
b11853af 685 wrap-arounds are dealt with correctly.
6672e9e1 686- Time-stamp at the beginning and time-stamp at the end of the event packet.
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687 Both timestamps are written in the packet header, but sampled respectively
688 while (or before) writing the first event and while (or after) writing the
689 last event in the packet. The inclusive range between these timestamps should
690 include all event timestamps assigned to events contained within the packet.
5ba9f198 691- Events discarded count
3bf79539 692 - Snapshot of a per-stream free-running counter, counting the number of
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693 events discarded that were supposed to be written in the stream after
694 the last event in the event packet.
695 * Note: producer-consumer buffer full condition can fill the current
3bf79539 696 event packet with padding so we know exactly where events have been
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697 discarded. However, if the buffer full condition chooses not
698 to fill the current event packet with padding, all we know
699 about the timestamp range in which the events have been
700 discarded is that it is somewhere between the beginning and
701 the end of the packet.
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702- Lossless compression scheme used for the event packet content. Applied
703 directly to raw data. New types of compression can be added in following
704 versions of the format.
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705 0: no compression scheme
706 1: bzip2
707 2: gzip
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708 3: xz
709- Cypher used for the event packet content. Applied after compression.
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710 0: no encryption
711 1: AES
3bf79539 712- Checksum scheme used for the event packet content. Applied after encryption.
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713 0: no checksum
714 1: md5
715 2: sha1
716 3: crc32
717
6672e9e1 7185.1 Event Packet Header Description
3bf79539 719
fc5425db 720The event packet header layout is indicated by the trace packet.header
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721field. Here is a recommended structure type for the packet header with
722the fields typically expected (although these fields are each optional):
fc5425db 723
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724struct event_packet_header {
725 uint32_t magic;
3fde5da1 726 uint8_t uuid[16];
3bf79539 727 uint32_t stream_id;
80fd2569 728};
5ba9f198 729
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730trace {
731 ...
732 packet.header := struct event_packet_header;
733};
734
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735If the magic number is not present, tools such as "file" will have no
736mean to discover the file type.
737
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738If the uuid is not present, no validation that the meta-data actually
739corresponds to the stream is performed.
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740
741If the stream_id packet header field is missing, the trace can only
742contain a single stream. Its "id" field can be left out, and its events
743don't need to declare a "stream_id" field.
744
745
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7465.2 Event Packet Context Description
747
748Event packet context example. These are declared within the stream declaration
6672e9e1 749in the meta-data. All these fields are optional. If the packet size field is
6a7c61df 750missing, the whole stream only contains a single packet. If the content
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751size field is missing, the packet is filled (no padding). The content
752and packet sizes include all headers.
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753
754An example event packet context type:
755
80fd2569 756struct event_packet_context {
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757 uint64_t timestamp_begin;
758 uint64_t timestamp_end;
759 uint32_t checksum;
760 uint32_t stream_packet_count;
761 uint32_t events_discarded;
762 uint32_t cpu_id;
763 uint32_t/uint16_t content_size;
764 uint32_t/uint16_t packet_size;
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765 uint8_t compression_scheme;
766 uint8_t encryption_scheme;
3b0f8e4d 767 uint8_t checksum_scheme;
3bf79539 768};
5ba9f198 769
fcba70d4 770
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7716. Event Structure
772
773The overall structure of an event is:
774
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7751 - Stream Packet Context (as specified by the stream meta-data)
776 2 - Event Header (as specified by the stream meta-data)
777 3 - Stream Event Context (as specified by the stream meta-data)
778 4 - Event Context (as specified by the event meta-data)
779 5 - Event Payload (as specified by the event meta-data)
5ba9f198 780
fdf2bb05 781This structure defines an implicit dynamic scoping, where variants
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782located in inner structures (those with a higher number in the listing
783above) can refer to the fields of outer structures (with lower number in
6c7226e9 784the listing above). See Section 7.3 TSDL Scopes for more detail.
5ba9f198 785
fdf2bb05 7866.1 Event Header
fcba70d4 787
6672e9e1 788Event headers can be described within the meta-data. We hereby propose, as an
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789example, two types of events headers. Type 1 accommodates streams with less than
79031 event IDs. Type 2 accommodates streams with 31 or more event IDs.
5ba9f198 791
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792One major factor can vary between streams: the number of event IDs assigned to
793a stream. Luckily, this information tends to stay relatively constant (modulo
5ba9f198 794event registration while trace is being recorded), so we can specify different
3bf79539 795representations for streams containing few event IDs and streams containing
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MD
796many event IDs, so we end up representing the event ID and time-stamp as
797densely as possible in each case.
5ba9f198 798
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799The header is extended in the rare occasions where the information cannot be
800represented in the ranges available in the standard event header. They are also
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801used in the rare occasions where the data required for a field could not be
802collected: the flag corresponding to the missing field within the missing_fields
803array is then set to 1.
5ba9f198 804
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805Types uintX_t represent an X-bit unsigned integer, as declared with
806either:
5ba9f198 807
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808 typealias integer { size = X; align = X; signed = false } := uintX_t;
809
810 or
811
812 typealias integer { size = X; align = 1; signed = false } := uintX_t;
5ba9f198 813
fdf2bb05 8146.1.1 Type 1 - Few event IDs
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815
816 - Aligned on 32-bit (or 8-bit if byte-packed, depending on the architecture
817 preference).
5ba9f198 818 - Native architecture byte ordering.
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819 - For "compact" selection
820 - Fixed size: 32 bits.
821 - For "extended" selection
822 - Size depends on the architecture and variant alignment.
5ba9f198 823
80fd2569 824struct event_header_1 {
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MD
825 /*
826 * id: range: 0 - 30.
827 * id 31 is reserved to indicate an extended header.
828 */
a9b83695 829 enum : uint5_t { compact = 0 ... 30, extended = 31 } id;
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830 variant <id> {
831 struct {
832 uint27_t timestamp;
833 } compact;
834 struct {
835 uint32_t id; /* 32-bit event IDs */
836 uint64_t timestamp; /* 64-bit timestamps */
837 } extended;
838 } v;
cb108fea 839} align(32); /* or align(8) */
5ba9f198 840
5ba9f198 841
fdf2bb05 8426.1.2 Type 2 - Many event IDs
5ba9f198 843
fcba70d4 844 - Aligned on 16-bit (or 8-bit if byte-packed, depending on the architecture
5ba9f198 845 preference).
5ba9f198 846 - Native architecture byte ordering.
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MD
847 - For "compact" selection
848 - Size depends on the architecture and variant alignment.
849 - For "extended" selection
850 - Size depends on the architecture and variant alignment.
5ba9f198 851
80fd2569 852struct event_header_2 {
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853 /*
854 * id: range: 0 - 65534.
855 * id 65535 is reserved to indicate an extended header.
856 */
a9b83695 857 enum : uint16_t { compact = 0 ... 65534, extended = 65535 } id;
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858 variant <id> {
859 struct {
860 uint32_t timestamp;
861 } compact;
862 struct {
863 uint32_t id; /* 32-bit event IDs */
864 uint64_t timestamp; /* 64-bit timestamps */
865 } extended;
866 } v;
cb108fea 867} align(16); /* or align(8) */
5ba9f198 868
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869
8706.2 Event Context
871
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MD
872The event context contains information relative to the current event.
873The choice and meaning of this information is specified by the TSDL
874stream and event meta-data descriptions. The stream context is applied
875to all events within the stream. The stream context structure follows
876the event header. The event context is applied to specific events. Its
877structure follows the stream context structure.
5ba9f198 878
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879An example of stream-level event context is to save the event payload size with
880each event, or to save the current PID with each event. These are declared
6672e9e1 881within the stream declaration within the meta-data:
5ba9f198 882
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883 stream {
884 ...
6672e9e1 885 event.context := struct {
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MD
886 uint pid;
887 uint16_t payload_size;
6672e9e1 888 };
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MD
889 };
890
891An example of event-specific event context is to declare a bitmap of missing
892fields, only appended after the stream event context if the extended event
893header is selected. NR_FIELDS is the number of fields within the event (a
894numeric value).
5ba9f198 895
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896 event {
897 context = struct {
898 variant <id> {
899 struct { } compact;
900 struct {
901 uint1_t missing_fields[NR_FIELDS]; /* missing event fields bitmap */
902 } extended;
903 } v;
904 };
905 ...
906 }
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MD
907
9086.3 Event Payload
909
910An event payload contains fields specific to a given event type. The fields
6672e9e1 911belonging to an event type are described in the event-specific meta-data
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MD
912within a structure type.
913
9146.3.1 Padding
915
916No padding at the end of the event payload. This differs from the ISO/C standard
917for structures, but follows the CTF standard for structures. In a trace, even
918though it makes sense to align the beginning of a structure, it really makes no
919sense to add padding at the end of the structure, because structures are usually
920not followed by a structure of the same type.
921
922This trick can be done by adding a zero-length "end" field at the end of the C
923structures, and by using the offset of this field rather than using sizeof()
3bf79539 924when calculating the size of a structure (see Appendix "A. Helper macros").
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MD
925
9266.3.2 Alignment
927
928The event payload is aligned on the largest alignment required by types
929contained within the payload. (This follows the ISO/C standard for structures)
930
931
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MD
9327. Trace Stream Description Language (TSDL)
933
934The Trace Stream Description Language (TSDL) allows expression of the
935binary trace streams layout in a C99-like Domain Specific Language
936(DSL).
937
938
6672e9e1 9397.1 Meta-data
6c7226e9
MD
940
941The trace stream layout description is located in the trace meta-data.
942The meta-data is itself located in a stream identified by its name:
943"metadata".
5ba9f198 944
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MD
945The meta-data description can be expressed in two different formats:
946text-only and packet-based. The text-only description facilitates
947generation of meta-data and provides a convenient way to enter the
948meta-data information by hand. The packet-based meta-data provides the
949CTF stream packet facilities (checksumming, compression, encryption,
950network-readiness) for meta-data stream generated and transported by a
951tracer.
952
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953The text-only meta-data file is a plain-text TSDL description. This file
954must begin with the following characters to identify the file as a CTF
9486a18c 955TSDL text-based metadata file (without the double-quotes) :
1b4d35eb 956
ec2b4db8 957"/* CTF"
1b4d35eb 958
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MD
959It must be followed by a space, and the version of the specification
960followed by the CTF trace, e.g.:
961
962" 1.8"
963
964These characters allow automated discovery of file type and CTF
965specification version. They are interpreted as a the beginning of a
966comment by the TSDL metadata parser. The comment can be continued to
967contain extra commented characters before it is closed.
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MD
968
969The packet-based meta-data is made of "meta-data packets", which each
970start with a meta-data packet header. The packet-based meta-data
971description is detected by reading the magic number "0x75D11D57" at the
972beginning of the file. This magic number is also used to detect the
973endianness of the architecture by trying to read the CTF magic number
974and its counterpart in reversed endianness. The events within the
975meta-data stream have no event header nor event context. Each event only
5ae2352d 976contains a "sequence" payload, which is a sequence of bits using the
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MD
977"trace.packet.header.content_size" field as a placeholder for its length
978(the packet header size should be substracted). The formatting of this
979sequence of bits is a plain-text representation of the TSDL description.
980Each meta-data packet start with a special packet header, specific to
981the meta-data stream, which contains, exactly:
6672e9e1
MD
982
983struct metadata_packet_header {
2daeaa3a 984 uint32_t magic; /* 0x75D11D57 */
3fde5da1 985 uint8_t uuid[16]; /* Unique Universal Identifier */
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986 uint32_t checksum; /* 0 if unused */
987 uint32_t content_size; /* in bits */
988 uint32_t packet_size; /* in bits */
989 uint8_t compression_scheme; /* 0 if unused */
990 uint8_t encryption_scheme; /* 0 if unused */
991 uint8_t checksum_scheme; /* 0 if unused */
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992 uint8_t major; /* CTF spec version major number */
993 uint8_t minor; /* CTF spec version minor number */
6672e9e1
MD
994};
995
996The packet-based meta-data can be converted to a text-only meta-data by
3568031f 997concatenating all the strings it contains.
4fafe1ad 998
6672e9e1
MD
999In the textual representation of the meta-data, the text contained
1000within "/*" and "*/", as well as within "//" and end of line, are
1001treated as comments. Boolean values can be represented as true, TRUE,
1002or 1 for true, and false, FALSE, or 0 for false. Within the string-based
1003meta-data description, the trace UUID is represented as a string of
1004hexadecimal digits and dashes "-". In the event packet header, the trace
1005UUID is represented as an array of bytes.
fcba70d4 1006
fdf2bb05 1007
6c7226e9 10087.2 Declaration vs Definition
fdf2bb05
MD
1009
1010A declaration associates a layout to a type, without specifying where
1011this type is located in the event structure hierarchy (see Section 6).
1012This therefore includes typedef, typealias, as well as all type
1013specifiers. In certain circumstances (typedef, structure field and
1014variant field), a declaration is followed by a declarator, which specify
1015the newly defined type name (for typedef), or the field name (for
1016declarations located within structure and variants). Array and sequence,
1017declared with square brackets ("[" "]"), are part of the declarator,
a9b83695 1018similarly to C99. The enumeration base type is specified by
6c7226e9 1019": enum_base", which is part of the type specifier. The variant tag
a9b83695 1020name, specified between "<" ">", is also part of the type specifier.
fdf2bb05
MD
1021
1022A definition associates a type to a location in the event structure
b9606a77
MD
1023hierarchy (see Section 6). This association is denoted by ":=", as shown
1024in Section 7.3.
fdf2bb05
MD
1025
1026
6c7226e9 10277.3 TSDL Scopes
fdf2bb05 1028
37ab95c3
MD
1029TSDL uses three different types of scoping: a lexical scope is used for
1030declarations and type definitions, and static and dynamic scopes are
1031used for variants references to tag fields (with relative and absolute
1032path lookups) and for sequence references to length fields.
fdf2bb05 1033
6c7226e9 10347.3.1 Lexical Scope
fdf2bb05 1035
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1036Each of "trace", "env", "stream", "event", "struct" and "variant" have
1037their own nestable declaration scope, within which types can be declared
1038using "typedef" and "typealias". A root declaration scope also contains
1039all declarations located outside of any of the aforementioned
1040declarations. An inner declaration scope can refer to type declared
1041within its container lexical scope prior to the inner declaration scope.
1042Redefinition of a typedef or typealias is not valid, although hiding an
1043upper scope typedef or typealias is allowed within a sub-scope.
fdf2bb05 1044
37ab95c3 10457.3.2 Static and Dynamic Scopes
fdf2bb05 1046
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MD
1047A local static scope consists in the scope generated by the declaration
1048of fields within a compound type. A static scope is a local static scope
1049augmented with the nested sub-static-scopes it contains.
1050
1051A dynamic scope consists in the static scope augmented with the
7d9d7e92 1052implicit event structure definition hierarchy presented at Section 6.
fdf2bb05 1053
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MD
1054Multiple declarations of the same field name within a local static scope
1055is not valid. It is however valid to re-use the same field name in
1056different local scopes.
1057
1058Nested static and dynamic scopes form lookup paths. These are used for
1059variant tag and sequence length references. They are used at the variant
1060and sequence definition site to look up the location of the tag field
1061associated with a variant, and to lookup up the location of the length
1062field associated with a sequence.
1063
1064Variants and sequences can refer to a tag field either using a relative
4cac83ee
MD
1065path or an absolute path. The relative path is relative to the scope in
1066which the variant or sequence performing the lookup is located.
37ab95c3
MD
1067Relative paths are only allowed to lookup within the same static scope,
1068which includes its nested static scopes. Lookups targeting parent static
1069scopes need to be performed with an absolute path.
1070
1071Absolute path lookups use the full path including the dynamic scope
1072followed by a "." and then the static scope. Therefore, variants (or
1073sequences) in lower levels in the dynamic scope (e.g. event context) can
1074refer to a tag (or length) field located in upper levels (e.g. in the
1075event header) by specifying, in this case, the associated tag with
1076<stream.event.header.field_name>. This allows, for instance, the event
1077context to define a variant referring to the "id" field of the event
1078header as selector.
1079
284724ae 1080The dynamic scope prefixes are thus:
fdf2bb05 1081
570ecabe 1082 - Trace Environment: <env. >,
e0d9e2c7 1083 - Trace Packet Header: <trace.packet.header. >,
7d9d7e92
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1084 - Stream Packet Context: <stream.packet.context. >,
1085 - Event Header: <stream.event.header. >,
1086 - Stream Event Context: <stream.event.context. >,
1087 - Event Context: <event.context. >,
1088 - Event Payload: <event.fields. >.
fdf2bb05 1089
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MD
1090
1091The target dynamic scope must be specified explicitly when referring to
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MD
1092a field outside of the static scope (absolute scope reference). No
1093conflict can occur between relative and dynamic paths, because the
1094keywords "trace", "stream", and "event" are reserved, and thus
1095not permitted as field names. It is recommended that field names
1096clashing with CTF and C99 reserved keywords use an underscore prefix to
1097eliminate the risk of generating a description containing an invalid
70375f92 1098field name. Consequently, fields starting with an underscore should have
92250c71 1099their leading underscore removed by the CTF trace readers.
70375f92 1100
fdf2bb05 1101
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MD
1102The information available in the dynamic scopes can be thought of as the
1103current tracing context. At trace production, information about the
1104current context is saved into the specified scope field levels. At trace
1105consumption, for each event, the current trace context is therefore
1106readable by accessing the upper dynamic scopes.
1107
fdf2bb05 1108
6c7226e9 11097.4 TSDL Examples
d285084f 1110
6672e9e1 1111The grammar representing the TSDL meta-data is presented in Appendix C.
7df6b93a 1112TSDL Grammar. This section presents a rather lighter reading that
6672e9e1 1113consists in examples of TSDL meta-data, with template values.
969f30c0 1114
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MD
1115The stream "id" can be left out if there is only one stream in the
1116trace. The event "id" field can be left out if there is only one event
1117in a stream.
1118
5ba9f198 1119trace {
1e9de2d1
MD
1120 major = value; /* CTF spec version major number */
1121 minor = value; /* CTF spec version minor number */
fdf2bb05 1122 uuid = "aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa"; /* Trace UUID */
58997e9e 1123 byte_order = be OR le; /* Endianness (required) */
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1124 packet.header := struct {
1125 uint32_t magic;
3fde5da1 1126 uint8_t uuid[16];
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MD
1127 uint32_t stream_id;
1128 };
3bf79539 1129};
5ba9f198 1130
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MD
1131/*
1132 * The "env" (environment) scope contains assignment expressions. The
1133 * field names and content are implementation-defined.
1134 */
1135env {
1136 pid = value; /* example */
1137 proc_name = "name"; /* example */
1138 ...
1139};
1140
3bf79539
MD
1141stream {
1142 id = stream_id;
fdf2bb05 1143 /* Type 1 - Few event IDs; Type 2 - Many event IDs. See section 6.1. */
4fa992a5
MD
1144 event.header := event_header_1 OR event_header_2;
1145 event.context := struct {
77a98c82 1146 ...
3bf79539 1147 };
4fa992a5 1148 packet.context := struct {
77a98c82 1149 ...
3bf79539
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1150 };
1151};
5ba9f198
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1152
1153event {
980015f9 1154 name = "event_name";
3bf79539 1155 id = value; /* Numeric identifier within the stream */
67f02e24 1156 stream_id = stream_id;
dc56f167 1157 loglevel = value;
4fa992a5 1158 context := struct {
fcba70d4
MD
1159 ...
1160 };
4fa992a5 1161 fields := struct {
80fd2569
MD
1162 ...
1163 };
3bf79539 1164};
5ba9f198
MD
1165
1166/* More detail on types in section 4. Types */
1167
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1168/*
1169 * Named types:
1170 *
4fa992a5 1171 * Type declarations behave similarly to the C standard.
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1172 */
1173
80af8ac6 1174typedef aliased_type_specifiers new_type_declarators;
2152348f 1175
3d13ef1a 1176/* e.g.: typedef struct example new_type_name[10]; */
80fd2569 1177
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1178/*
1179 * typealias
1180 *
1181 * The "typealias" declaration can be used to give a name (including
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MD
1182 * pointer declarator specifier) to a type. It should also be used to
1183 * map basic C types (float, int, unsigned long, ...) to a CTF type.
1184 * Typealias is a superset of "typedef": it also allows assignment of a
38b8da21 1185 * simple variable identifier to a type.
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1186 */
1187
1188typealias type_class {
80fd2569 1189 ...
38b8da21 1190} := type_specifiers type_declarator;
2152348f 1191
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1192/*
1193 * e.g.:
4fa992a5 1194 * typealias integer {
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1195 * size = 32;
1196 * align = 32;
1197 * signed = false;
38b8da21 1198 * } := struct page *;
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1199 *
1200 * typealias integer {
1201 * size = 32;
1202 * align = 32;
1203 * signed = true;
38b8da21 1204 * } := int;
3d13ef1a 1205 */
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1206
1207struct name {
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1208 ...
1209};
5ba9f198 1210
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1211variant name {
1212 ...
1213};
1214
a9b83695 1215enum name : integer_type {
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1216 ...
1217};
1218
2152348f 1219
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1220/*
1221 * Unnamed types, contained within compound type fields, typedef or typealias.
1222 */
2152348f 1223
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1224struct {
1225 ...
2152348f 1226}
5ba9f198 1227
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1228struct {
1229 ...
1230} align(value)
1231
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1232variant {
1233 ...
1234}
1235
a9b83695 1236enum : integer_type {
80fd2569 1237 ...
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1238}
1239
1240typedef type new_type[length];
3bf79539 1241
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1242struct {
1243 type field_name[length];
1244}
1245
1246typedef type new_type[length_type];
1247
1248struct {
1249 type field_name[length_type];
1250}
1251
1252integer {
80fd2569 1253 ...
2152348f 1254}
3bf79539 1255
2152348f 1256floating_point {
80fd2569 1257 ...
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1258}
1259
1260struct {
1261 integer_type field_name:size; /* GNU/C bitfield */
1262}
1263
1264struct {
1265 string field_name;
1266}
3bf79539 1267
fcba70d4 1268
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12698. Clocks
1270
1271Clock metadata allows to describe the clock topology of the system, as
1272well as to detail each clock parameter. In absence of clock description,
1273it is assumed that all fields named "timestamp" use the same clock
aed18b5e 1274source, which increments once per nanosecond.
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1275
1276Describing a clock and how it is used by streams is threefold: first,
1277the clock and clock topology should be described in a "clock"
1278description block, e.g.:
1279
d803bfcb 1280clock {
58262d97 1281 name = cycle_counter_sync;
2fa70eba 1282 uuid = "62189bee-96dc-11e0-91a8-cfa3d89f3923";
58262d97 1283 description = "Cycle counter synchronized across CPUs";
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1284 freq = 1000000000; /* frequency, in Hz */
1285 /* precision in seconds is: 1000 * (1/freq) */
1286 precision = 1000;
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1287 /*
1288 * clock value offset from Epoch is:
1289 * offset_s + (offset * (1/freq))
1290 */
1291 offset_s = 1326476837;
1292 offset = 897235420;
ce0fadbd 1293 absolute = FALSE;
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1294};
1295
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1296The mandatory "name" field specifies the name of the clock identifier,
1297which can later be used as a reference. The optional field "uuid" is the
1298unique identifier of the clock. It can be used to correlate different
1299traces that use the same clock. An optional textual description string
1300can be added with the "description" field. The "freq" field is the
1301initial frequency of the clock, in Hz. If the "freq" field is not
1302present, the frequency is assumed to be 1000000000 (providing clock
1303increment of 1 ns). The optional "precision" field details the
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1304uncertainty on the clock measurements, in (1/freq) units. The "offset_s"
1305and "offset" fields indicate the offset from POSIX.1 Epoch, 1970-01-01
130600:00:00 +0000 (UTC), to the zero of value of the clock. The "offset_s"
1307field is in seconds. The "offset" field is in (1/freq) units. If any of
1308the "offset_s" or "offset" field is not present, it is assigned the 0
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1309value. The field "absolute" is TRUE if the clock is a global reference
1310across different clock uuid (e.g. NTP time). Otherwise, "absolute" is
1311FALSE, and the clock can be considered as synchronized only with other
1312clocks that have the same uuid.
1313
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1314
1315Secondly, a reference to this clock should be added within an integer
1316type:
1317
1318typealias integer {
1319 size = 64; align = 1; signed = false;
58262d97 1320 map = clock.cycle_counter_sync.value;
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1321} := uint64_ccnt_t;
1322
1323Thirdly, stream declarations can reference the clock they use as a
1324time-stamp source:
1325
1326struct packet_context {
1327 uint64_ccnt_t ccnt_begin;
1328 uint64_ccnt_t ccnt_end;
1329 /* ... */
1330};
1331
1332stream {
1333 /* ... */
1334 event.header := struct {
1335 uint64_ccnt_t timestamp;
1336 /* ... */
1337 }
1338 packet.context := struct packet_context;
1339};
1340
1341For a N-bit integer type referring to a clock, if the integer overflows
1342compared to the N low order bits of the clock prior value, then it is
1343assumed that one, and only one, overflow occurred. It is therefore
1344important that events encoding time on a small number of bits happen
1345frequently enough to detect when more than one N-bit overflow occurs.
1346
1347In a packet context, clock field names ending with "_begin" and "_end"
1348have a special meaning: this refers to the time-stamps at, respectively,
1349the beginning and the end of each packet.
1350
1351
3bf79539 1352A. Helper macros
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1353
1354The two following macros keep track of the size of a GNU/C structure without
1355padding at the end by placing HEADER_END as the last field. A one byte end field
1356is used for C90 compatibility (C99 flexible arrays could be used here). Note
1357that this does not affect the effective structure size, which should always be
1358calculated with the header_sizeof() helper.
1359
1360#define HEADER_END char end_field
1361#define header_sizeof(type) offsetof(typeof(type), end_field)
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1362
1363
1364B. Stream Header Rationale
1365
1366An event stream is divided in contiguous event packets of variable size. These
1367subdivisions allow the trace analyzer to perform a fast binary search by time
1368within the stream (typically requiring to index only the event packet headers)
1369without reading the whole stream. These subdivisions have a variable size to
1370eliminate the need to transfer the event packet padding when partially filled
1371event packets must be sent when streaming a trace for live viewing/analysis.
1372An event packet can contain a certain amount of padding at the end. Dividing
1373streams into event packets is also useful for network streaming over UDP and
1374flight recorder mode tracing (a whole event packet can be swapped out of the
1375buffer atomically for reading).
1376
1377The stream header is repeated at the beginning of each event packet to allow
1378flexibility in terms of:
1379
1380 - streaming support,
1381 - allowing arbitrary buffers to be discarded without making the trace
1382 unreadable,
1383 - allow UDP packet loss handling by either dealing with missing event packet
1384 or asking for re-transmission.
1385 - transparently support flight recorder mode,
1386 - transparently support crash dump.
1387
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1388
1389C. TSDL Grammar
fcba70d4 1390
4fa992a5 1391/*
6c7226e9 1392 * Common Trace Format (CTF) Trace Stream Description Language (TSDL) Grammar.
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1393 *
1394 * Inspired from the C99 grammar:
1395 * http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1124.pdf (Annex A)
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1396 * and c++1x grammar (draft)
1397 * http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2011/n3291.pdf (Annex A)
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1398 *
1399 * Specialized for CTF needs by including only constant and declarations from
1400 * C99 (excluding function declarations), and by adding support for variants,
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1401 * sequences and CTF-specific specifiers. Enumeration container types
1402 * semantic is inspired from c++1x enum-base.
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1403 */
1404
14051) Lexical grammar
1406
14071.1) Lexical elements
1408
1409token:
1410 keyword
1411 identifier
1412 constant
1413 string-literal
1414 punctuator
1415
14161.2) Keywords
1417
1418keyword: is one of
1419
ec4404a7 1420align
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1421const
1422char
2fa70eba 1423clock
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1424double
1425enum
570ecabe 1426env
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1427event
1428floating_point
1429float
1430integer
1431int
1432long
1433short
1434signed
1435stream
1436string
1437struct
1438trace
3e1e1a78 1439typealias
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MD
1440typedef
1441unsigned
1442variant
1443void
1444_Bool
1445_Complex
1446_Imaginary
1447
1448
14491.3) Identifiers
1450
1451identifier:
1452 identifier-nondigit
1453 identifier identifier-nondigit
1454 identifier digit
1455
1456identifier-nondigit:
1457 nondigit
1458 universal-character-name
1459 any other implementation-defined characters
1460
1461nondigit:
1462 _
1463 [a-zA-Z] /* regular expression */
1464
1465digit:
1466 [0-9] /* regular expression */
1467
14681.4) Universal character names
1469
1470universal-character-name:
1471 \u hex-quad
1472 \U hex-quad hex-quad
1473
1474hex-quad:
1475 hexadecimal-digit hexadecimal-digit hexadecimal-digit hexadecimal-digit
1476
14771.5) Constants
1478
1479constant:
1480 integer-constant
1481 enumeration-constant
1482 character-constant
1483
1484integer-constant:
1485 decimal-constant integer-suffix-opt
1486 octal-constant integer-suffix-opt
1487 hexadecimal-constant integer-suffix-opt
1488
1489decimal-constant:
1490 nonzero-digit
1491 decimal-constant digit
1492
1493octal-constant:
1494 0
1495 octal-constant octal-digit
1496
1497hexadecimal-constant:
1498 hexadecimal-prefix hexadecimal-digit
1499 hexadecimal-constant hexadecimal-digit
1500
1501hexadecimal-prefix:
1502 0x
1503 0X
1504
1505nonzero-digit:
1506 [1-9]
1507
1508integer-suffix:
1509 unsigned-suffix long-suffix-opt
1510 unsigned-suffix long-long-suffix
1511 long-suffix unsigned-suffix-opt
1512 long-long-suffix unsigned-suffix-opt
1513
1514unsigned-suffix:
1515 u
1516 U
1517
1518long-suffix:
1519 l
1520 L
1521
1522long-long-suffix:
1523 ll
1524 LL
1525
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1526enumeration-constant:
1527 identifier
1528 string-literal
1529
1530character-constant:
1531 ' c-char-sequence '
1532 L' c-char-sequence '
1533
1534c-char-sequence:
1535 c-char
1536 c-char-sequence c-char
1537
1538c-char:
1539 any member of source charset except single-quote ('), backslash
1540 (\), or new-line character.
1541 escape-sequence
1542
1543escape-sequence:
1544 simple-escape-sequence
1545 octal-escape-sequence
1546 hexadecimal-escape-sequence
1547 universal-character-name
1548
1549simple-escape-sequence: one of
1550 \' \" \? \\ \a \b \f \n \r \t \v
1551
1552octal-escape-sequence:
1553 \ octal-digit
1554 \ octal-digit octal-digit
1555 \ octal-digit octal-digit octal-digit
1556
1557hexadecimal-escape-sequence:
1558 \x hexadecimal-digit
1559 hexadecimal-escape-sequence hexadecimal-digit
1560
15611.6) String literals
1562
1563string-literal:
1564 " s-char-sequence-opt "
1565 L" s-char-sequence-opt "
1566
1567s-char-sequence:
1568 s-char
1569 s-char-sequence s-char
1570
1571s-char:
1572 any member of source charset except double-quote ("), backslash
1573 (\), or new-line character.
1574 escape-sequence
1575
15761.7) Punctuators
1577
1578punctuator: one of
1579 [ ] ( ) { } . -> * + - < > : ; ... = ,
1580
1581
15822) Phrase structure grammar
1583
1584primary-expression:
1585 identifier
1586 constant
1587 string-literal
1588 ( unary-expression )
1589
1590postfix-expression:
1591 primary-expression
1592 postfix-expression [ unary-expression ]
1593 postfix-expression . identifier
1594 postfix-expressoin -> identifier
1595
1596unary-expression:
1597 postfix-expression
1598 unary-operator postfix-expression
1599
1600unary-operator: one of
1601 + -
1602
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1603assignment-operator:
1604 =
1605
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1606type-assignment-operator:
1607 :=
1608
4fa992a5 1609constant-expression-range:
73d61ac3 1610 unary-expression ... unary-expression
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1611
16122.2) Declarations:
1613
1614declaration:
689e04b4 1615 declaration-specifiers declarator-list-opt ;
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1616 ctf-specifier ;
1617
1618declaration-specifiers:
689e04b4 1619 storage-class-specifier declaration-specifiers-opt
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1620 type-specifier declaration-specifiers-opt
1621 type-qualifier declaration-specifiers-opt
1622
1623declarator-list:
1624 declarator
1625 declarator-list , declarator
1626
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1627abstract-declarator-list:
1628 abstract-declarator
1629 abstract-declarator-list , abstract-declarator
1630
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1631storage-class-specifier:
1632 typedef
1633
1634type-specifier:
1635 void
1636 char
1637 short
1638 int
1639 long
1640 float
1641 double
1642 signed
1643 unsigned
1644 _Bool
1645 _Complex
cfdd51ec 1646 _Imaginary
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1647 struct-specifier
1648 variant-specifier
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1649 enum-specifier
1650 typedef-name
1651 ctf-type-specifier
1652
ec4404a7 1653align-attribute:
73d61ac3 1654 align ( unary-expression )
ec4404a7 1655
4fa992a5 1656struct-specifier:
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MD
1657 struct identifier-opt { struct-or-variant-declaration-list-opt } align-attribute-opt
1658 struct identifier align-attribute-opt
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1659
1660struct-or-variant-declaration-list:
1661 struct-or-variant-declaration
1662 struct-or-variant-declaration-list struct-or-variant-declaration
1663
1664struct-or-variant-declaration:
1665 specifier-qualifier-list struct-or-variant-declarator-list ;
eacb16d1 1666 declaration-specifiers-opt storage-class-specifier declaration-specifiers-opt declarator-list ;
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1667 typealias declaration-specifiers abstract-declarator-list type-assignment-operator declaration-specifiers abstract-declarator-list ;
1668 typealias declaration-specifiers abstract-declarator-list type-assignment-operator declarator-list ;
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1669
1670specifier-qualifier-list:
1671 type-specifier specifier-qualifier-list-opt
1672 type-qualifier specifier-qualifier-list-opt
1673
1674struct-or-variant-declarator-list:
1675 struct-or-variant-declarator
1676 struct-or-variant-declarator-list , struct-or-variant-declarator
1677
1678struct-or-variant-declarator:
1679 declarator
73d61ac3 1680 declarator-opt : unary-expression
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1681
1682variant-specifier:
1683 variant identifier-opt variant-tag-opt { struct-or-variant-declaration-list }
1684 variant identifier variant-tag
1685
1686variant-tag:
37ab95c3 1687 < unary-expression >
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1688
1689enum-specifier:
1690 enum identifier-opt { enumerator-list }
1691 enum identifier-opt { enumerator-list , }
1692 enum identifier
a9b83695
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1693 enum identifier-opt : declaration-specifiers { enumerator-list }
1694 enum identifier-opt : declaration-specifiers { enumerator-list , }
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1695
1696enumerator-list:
1697 enumerator
1698 enumerator-list , enumerator
1699
1700enumerator:
1701 enumeration-constant
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1702 enumeration-constant assignment-operator unary-expression
1703 enumeration-constant assignment-operator constant-expression-range
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1704
1705type-qualifier:
1706 const
1707
1708declarator:
1709 pointer-opt direct-declarator
1710
1711direct-declarator:
1712 identifier
1713 ( declarator )
1ab22b2a 1714 direct-declarator [ unary-expression ]
4fa992a5 1715
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1716abstract-declarator:
1717 pointer-opt direct-abstract-declarator
1718
1719direct-abstract-declarator:
1720 identifier-opt
1721 ( abstract-declarator )
1ab22b2a 1722 direct-abstract-declarator [ unary-expression ]
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1723 direct-abstract-declarator [ ]
1724
4fa992a5 1725pointer:
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1726 * type-qualifier-list-opt
1727 * type-qualifier-list-opt pointer
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1728
1729type-qualifier-list:
1730 type-qualifier
1731 type-qualifier-list type-qualifier
1732
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1733typedef-name:
1734 identifier
1735
17362.3) CTF-specific declarations
1737
1738ctf-specifier:
662baf84 1739 clock { ctf-assignment-expression-list-opt }
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1740 event { ctf-assignment-expression-list-opt }
1741 stream { ctf-assignment-expression-list-opt }
570ecabe 1742 env { ctf-assignment-expression-list-opt }
4fa992a5 1743 trace { ctf-assignment-expression-list-opt }
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1744 typealias declaration-specifiers abstract-declarator-list type-assignment-operator declaration-specifiers abstract-declarator-list
1745 typealias declaration-specifiers abstract-declarator-list type-assignment-operator declarator-list
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1746
1747ctf-type-specifier:
1748 floating_point { ctf-assignment-expression-list-opt }
1749 integer { ctf-assignment-expression-list-opt }
1750 string { ctf-assignment-expression-list-opt }
7609d3c7 1751 string
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1752
1753ctf-assignment-expression-list:
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1754 ctf-assignment-expression ;
1755 ctf-assignment-expression-list ctf-assignment-expression ;
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1756
1757ctf-assignment-expression:
1758 unary-expression assignment-operator unary-expression
1759 unary-expression type-assignment-operator type-specifier
eacb16d1 1760 declaration-specifiers-opt storage-class-specifier declaration-specifiers-opt declarator-list
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1761 typealias declaration-specifiers abstract-declarator-list type-assignment-operator declaration-specifiers abstract-declarator-list
1762 typealias declaration-specifiers abstract-declarator-list type-assignment-operator declarator-list
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