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4dfca05b 1Common Trace Format (CTF) Specification (pre-v1.8)
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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
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120An event stream can be divided into contiguous event packets of variable
121size. These subdivisions have a variable size. An event packet can
122contain a certain amount of padding at the end. The stream header is
123repeated at the beginning of each event packet. The rationale for the
124event stream design choices is explained in Appendix B. Stream Header
125Rationale.
5ba9f198 126
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127The event stream header will therefore be referred to as the "event packet
128header" throughout the rest of this document.
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129
130
1314. Types
132
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133Types are organized as type classes. Each type class belong to either of two
134kind of types: basic types or compound types.
135
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1364.1 Basic types
137
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138A basic type is a scalar type, as described in this section. It includes
139integers, GNU/C bitfields, enumerations, and floating point values.
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140
1414.1.1 Type inheritance
142
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143Type specifications can be inherited to allow deriving types from a
144type class. For example, see the uint32_t named type derived from the "integer"
145type class below ("Integers" section). Types have a precise binary
146representation in the trace. A type class has methods to read and write these
147types, but must be derived into a type to be usable in an event field.
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148
1494.1.2 Alignment
150
151We define "byte-packed" types as aligned on the byte size, namely 8-bit.
152We define "bit-packed" types as following on the next bit, as defined by the
370eae99 153"Integers" section.
5ba9f198 154
6672e9e1 155Each basic type must specify its alignment, in bits. Examples of
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156possible alignments are: bit-packed (align = 1), byte-packed (align =
1578), or word-aligned (e.g. align = 32 or align = 64). The choice depends
158on the architecture preference and compactness vs performance trade-offs
159of the implementation. Architectures providing fast unaligned write
160byte-packed basic types to save space, aligning each type on byte
161boundaries (8-bit). Architectures with slow unaligned writes align types
162on specific alignment values. If no specific alignment is declared for a
163type, it is assumed to be bit-packed for integers with size not multiple
164of 8 bits and for gcc bitfields. All other basic types are byte-packed
165by default. It is however recommended to always specify the alignment
166explicitly. Alignment values must be power of two. Compound types are
167aligned as specified in their individual specification.
5ba9f198 168
6672e9e1 169TSDL meta-data attribute representation of a specific alignment:
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170
171 align = value; /* value in bits */
172
1734.1.3 Byte order
174
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175By default, the native endianness of the source architecture the trace is used.
176Byte order can be overridden for a basic type by specifying a "byte_order"
177attribute. Typical use-case is to specify the network byte order (big endian:
178"be") to save data captured from the network into the trace without conversion.
179If not specified, the byte order is native.
5ba9f198 180
6672e9e1 181TSDL meta-data representation:
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182
183 byte_order = native OR network OR be OR le; /* network and be are aliases */
184
1854.1.4 Size
186
187Type size, in bits, for integers and floats is that returned by "sizeof()" in C
188multiplied by CHAR_BIT.
189We require the size of "char" and "unsigned char" types (CHAR_BIT) to be fixed
190to 8 bits for cross-endianness compatibility.
191
6672e9e1 192TSDL meta-data representation:
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193
194 size = value; (value is in bits)
195
1964.1.5 Integers
197
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198Signed integers are represented in two-complement. Integer alignment,
199size, signedness and byte ordering are defined in the TSDL meta-data.
200Integers aligned on byte size (8-bit) and with length multiple of byte
201size (8-bit) correspond to the C99 standard integers. In addition,
202integers with alignment and/or size that are _not_ a multiple of the
203byte size are permitted; these correspond to the C99 standard bitfields,
204with the added specification that the CTF integer bitfields have a fixed
205binary representation. A MIT-licensed reference implementation of the
206CTF portable bitfields is available at:
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207
208 http://git.efficios.com/?p=babeltrace.git;a=blob;f=include/babeltrace/bitfield.h
209
210Binary representation of integers:
211
212- On little and big endian:
213 - Within a byte, high bits correspond to an integer high bits, and low bits
214 correspond to low bits.
215- On little endian:
216 - Integer across multiple bytes are placed from the less significant to the
217 most significant.
218 - Consecutive integers are placed from lower bits to higher bits (even within
219 a byte).
220- On big endian:
221 - Integer across multiple bytes are placed from the most significant to the
222 less significant.
223 - Consecutive integers are placed from higher bits to lower bits (even within
224 a byte).
225
226This binary representation is derived from the bitfield implementation in GCC
227for little and big endian. However, contrary to what GCC does, integers can
6672e9e1 228cross units boundaries (no padding is required). Padding can be explicitly
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229added (see 4.1.6 GNU/C bitfields) to follow the GCC layout if needed.
230
6672e9e1 231TSDL meta-data representation:
5ba9f198 232
80fd2569 233 integer {
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234 signed = true OR false; /* default false */
235 byte_order = native OR network OR be OR le; /* default native */
236 size = value; /* value in bits, no default */
237 align = value; /* value in bits */
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238 /* based used for pretty-printing output, default: decimal. */
239 base = decimal OR dec OR OR d OR i OR u OR 10 OR hexadecimal OR hex OR x OR X OR p OR 16
240 OR octal OR oct OR o OR 8 OR binary OR b OR 2;
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241 /* character encoding, default: none */
242 encoding = none or UTF8 or ASCII;
2152348f 243 }
5ba9f198 244
80fd2569 245Example of type inheritance (creation of a uint32_t named type):
5ba9f198 246
359894ac 247typealias integer {
9e4e34e9 248 size = 32;
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249 signed = false;
250 align = 32;
38b8da21 251} := uint32_t;
5ba9f198 252
80fd2569 253Definition of a named 5-bit signed bitfield:
5ba9f198 254
359894ac 255typealias integer {
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256 size = 5;
257 signed = true;
258 align = 1;
38b8da21 259} := int5_t;
5ba9f198 260
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261The character encoding field can be used to specify that the integer
262must be printed as a text character when read. e.g.:
263
264typealias integer {
265 size = 8;
266 align = 8;
267 signed = false;
268 encoding = UTF8;
269} := utf_char;
270
271
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2724.1.6 GNU/C bitfields
273
274The GNU/C bitfields follow closely the integer representation, with a
275particularity on alignment: if a bitfield cannot fit in the current unit, the
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276unit is padded and the bitfield starts at the following unit. The unit size is
277defined by the size of the type "unit_type".
5ba9f198 278
6672e9e1 279TSDL meta-data representation:
80fd2569 280
d674f4b8 281 unit_type name:size;
80fd2569 282
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283As an example, the following structure declared in C compiled by GCC:
284
285struct example {
286 short a:12;
287 short b:5;
288};
289
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290The example structure is aligned on the largest element (short). The second
291bitfield would be aligned on the next unit boundary, because it would not fit in
292the current unit.
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293
2944.1.7 Floating point
295
6672e9e1 296The floating point values byte ordering is defined in the TSDL meta-data.
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297
298Floating point values follow the IEEE 754-2008 standard interchange formats.
299Description of the floating point values include the exponent and mantissa size
300in bits. Some requirements are imposed on the floating point values:
301
302- FLT_RADIX must be 2.
303- mant_dig is the number of digits represented in the mantissa. It is specified
304 by the ISO C99 standard, section 5.2.4, as FLT_MANT_DIG, DBL_MANT_DIG and
305 LDBL_MANT_DIG as defined by <float.h>.
306- exp_dig is the number of digits represented in the exponent. Given that
307 mant_dig is one bit more than its actual size in bits (leading 1 is not
308 needed) and also given that the sign bit always takes one bit, exp_dig can be
309 specified as:
310
311 - sizeof(float) * CHAR_BIT - FLT_MANT_DIG
312 - sizeof(double) * CHAR_BIT - DBL_MANT_DIG
313 - sizeof(long double) * CHAR_BIT - LDBL_MANT_DIG
314
6672e9e1 315TSDL meta-data representation:
5ba9f198 316
80fd2569 317floating_point {
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318 exp_dig = value;
319 mant_dig = value;
320 byte_order = native OR network OR be OR le;
321 align = value;
2152348f 322}
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323
324Example of type inheritance:
325
359894ac 326typealias floating_point {
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327 exp_dig = 8; /* sizeof(float) * CHAR_BIT - FLT_MANT_DIG */
328 mant_dig = 24; /* FLT_MANT_DIG */
329 byte_order = native;
ec4404a7 330 align = 32;
38b8da21 331} := float;
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332
333TODO: define NaN, +inf, -inf behavior.
334
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335Bit-packed, byte-packed or larger alignments can be used for floating
336point values, similarly to integers.
337
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3384.1.8 Enumerations
339
340Enumerations are a mapping between an integer type and a table of strings. The
341numerical representation of the enumeration follows the integer type specified
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342by the meta-data. The enumeration mapping table is detailed in the enumeration
343description within the meta-data. The mapping table maps inclusive value
344ranges (or single values) to strings. Instead of being limited to simple
3bf79539 345"value -> string" mappings, these enumerations map
80fd2569 346"[ start_value ... end_value ] -> string", which map inclusive ranges of
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347values to strings. An enumeration from the C language can be represented in
348this format by having the same start_value and end_value for each element, which
349is in fact a range of size 1. This single-value range is supported without
4767a9e7 350repeating the start and end values with the value = string declaration.
80fd2569 351
a9b83695 352enum name : integer_type {
359894ac 353 somestring = start_value1 ... end_value1,
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354 "other string" = start_value2 ... end_value2,
355 yet_another_string, /* will be assigned to end_value2 + 1 */
356 "some other string" = value,
357 ...
358};
359
360If the values are omitted, the enumeration starts at 0 and increment of 1 for
361each entry:
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'
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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
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692 - Snapshot of a per-stream free-running counter, counting the number of
693 events discarded that were supposed to be written in the stream prior to
694 the first event in the event packet.
5ba9f198 695 * Note: producer-consumer buffer full condition should fill the current
3bf79539 696 event packet with padding so we know exactly where events have been
5ba9f198 697 discarded.
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698- Lossless compression scheme used for the event packet content. Applied
699 directly to raw data. New types of compression can be added in following
700 versions of the format.
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701 0: no compression scheme
702 1: bzip2
703 2: gzip
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704 3: xz
705- Cypher used for the event packet content. Applied after compression.
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706 0: no encryption
707 1: AES
3bf79539 708- Checksum scheme used for the event packet content. Applied after encryption.
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709 0: no checksum
710 1: md5
711 2: sha1
712 3: crc32
713
6672e9e1 7145.1 Event Packet Header Description
3bf79539 715
fc5425db 716The event packet header layout is indicated by the trace packet.header
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717field. Here is a recommended structure type for the packet header with
718the fields typically expected (although these fields are each optional):
fc5425db 719
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720struct event_packet_header {
721 uint32_t magic;
3fde5da1 722 uint8_t uuid[16];
3bf79539 723 uint32_t stream_id;
80fd2569 724};
5ba9f198 725
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726trace {
727 ...
728 packet.header := struct event_packet_header;
729};
730
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731If the magic number is not present, tools such as "file" will have no
732mean to discover the file type.
733
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734If the uuid is not present, no validation that the meta-data actually
735corresponds to the stream is performed.
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736
737If the stream_id packet header field is missing, the trace can only
738contain a single stream. Its "id" field can be left out, and its events
739don't need to declare a "stream_id" field.
740
741
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7425.2 Event Packet Context Description
743
744Event packet context example. These are declared within the stream declaration
6672e9e1 745in the meta-data. All these fields are optional. If the packet size field is
6a7c61df 746missing, the whole stream only contains a single packet. If the content
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747size field is missing, the packet is filled (no padding). The content
748and packet sizes include all headers.
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749
750An example event packet context type:
751
80fd2569 752struct event_packet_context {
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753 uint64_t timestamp_begin;
754 uint64_t timestamp_end;
755 uint32_t checksum;
756 uint32_t stream_packet_count;
757 uint32_t events_discarded;
758 uint32_t cpu_id;
759 uint32_t/uint16_t content_size;
760 uint32_t/uint16_t packet_size;
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761 uint8_t compression_scheme;
762 uint8_t encryption_scheme;
3b0f8e4d 763 uint8_t checksum_scheme;
3bf79539 764};
5ba9f198 765
fcba70d4 766
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7676. Event Structure
768
769The overall structure of an event is:
770
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7711 - Stream Packet Context (as specified by the stream meta-data)
772 2 - Event Header (as specified by the stream meta-data)
773 3 - Stream Event Context (as specified by the stream meta-data)
774 4 - Event Context (as specified by the event meta-data)
775 5 - Event Payload (as specified by the event meta-data)
5ba9f198 776
fdf2bb05 777This structure defines an implicit dynamic scoping, where variants
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778located in inner structures (those with a higher number in the listing
779above) can refer to the fields of outer structures (with lower number in
6c7226e9 780the listing above). See Section 7.3 TSDL Scopes for more detail.
5ba9f198 781
fdf2bb05 7826.1 Event Header
fcba70d4 783
6672e9e1 784Event headers can be described within the meta-data. We hereby propose, as an
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785example, two types of events headers. Type 1 accommodates streams with less than
78631 event IDs. Type 2 accommodates streams with 31 or more event IDs.
5ba9f198 787
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788One major factor can vary between streams: the number of event IDs assigned to
789a stream. Luckily, this information tends to stay relatively constant (modulo
5ba9f198 790event registration while trace is being recorded), so we can specify different
3bf79539 791representations for streams containing few event IDs and streams containing
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792many event IDs, so we end up representing the event ID and time-stamp as
793densely as possible in each case.
5ba9f198 794
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795The header is extended in the rare occasions where the information cannot be
796represented in the ranges available in the standard event header. They are also
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797used in the rare occasions where the data required for a field could not be
798collected: the flag corresponding to the missing field within the missing_fields
799array is then set to 1.
5ba9f198 800
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801Types uintX_t represent an X-bit unsigned integer, as declared with
802either:
5ba9f198 803
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804 typealias integer { size = X; align = X; signed = false } := uintX_t;
805
806 or
807
808 typealias integer { size = X; align = 1; signed = false } := uintX_t;
5ba9f198 809
fdf2bb05 8106.1.1 Type 1 - Few event IDs
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811
812 - Aligned on 32-bit (or 8-bit if byte-packed, depending on the architecture
813 preference).
5ba9f198 814 - Native architecture byte ordering.
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815 - For "compact" selection
816 - Fixed size: 32 bits.
817 - For "extended" selection
818 - Size depends on the architecture and variant alignment.
5ba9f198 819
80fd2569 820struct event_header_1 {
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821 /*
822 * id: range: 0 - 30.
823 * id 31 is reserved to indicate an extended header.
824 */
a9b83695 825 enum : uint5_t { compact = 0 ... 30, extended = 31 } id;
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826 variant <id> {
827 struct {
828 uint27_t timestamp;
829 } compact;
830 struct {
831 uint32_t id; /* 32-bit event IDs */
832 uint64_t timestamp; /* 64-bit timestamps */
833 } extended;
834 } v;
cb108fea 835} align(32); /* or align(8) */
5ba9f198 836
5ba9f198 837
fdf2bb05 8386.1.2 Type 2 - Many event IDs
5ba9f198 839
fcba70d4 840 - Aligned on 16-bit (or 8-bit if byte-packed, depending on the architecture
5ba9f198 841 preference).
5ba9f198 842 - Native architecture byte ordering.
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843 - For "compact" selection
844 - Size depends on the architecture and variant alignment.
845 - For "extended" selection
846 - Size depends on the architecture and variant alignment.
5ba9f198 847
80fd2569 848struct event_header_2 {
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849 /*
850 * id: range: 0 - 65534.
851 * id 65535 is reserved to indicate an extended header.
852 */
a9b83695 853 enum : uint16_t { compact = 0 ... 65534, extended = 65535 } id;
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854 variant <id> {
855 struct {
856 uint32_t timestamp;
857 } compact;
858 struct {
859 uint32_t id; /* 32-bit event IDs */
860 uint64_t timestamp; /* 64-bit timestamps */
861 } extended;
862 } v;
cb108fea 863} align(16); /* or align(8) */
5ba9f198 864
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865
8666.2 Event Context
867
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868The event context contains information relative to the current event.
869The choice and meaning of this information is specified by the TSDL
870stream and event meta-data descriptions. The stream context is applied
871to all events within the stream. The stream context structure follows
872the event header. The event context is applied to specific events. Its
873structure follows the stream context structure.
5ba9f198 874
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875An example of stream-level event context is to save the event payload size with
876each event, or to save the current PID with each event. These are declared
6672e9e1 877within the stream declaration within the meta-data:
5ba9f198 878
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879 stream {
880 ...
6672e9e1 881 event.context := struct {
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MD
882 uint pid;
883 uint16_t payload_size;
6672e9e1 884 };
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MD
885 };
886
887An example of event-specific event context is to declare a bitmap of missing
888fields, only appended after the stream event context if the extended event
889header is selected. NR_FIELDS is the number of fields within the event (a
890numeric value).
5ba9f198 891
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MD
892 event {
893 context = struct {
894 variant <id> {
895 struct { } compact;
896 struct {
897 uint1_t missing_fields[NR_FIELDS]; /* missing event fields bitmap */
898 } extended;
899 } v;
900 };
901 ...
902 }
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903
9046.3 Event Payload
905
906An event payload contains fields specific to a given event type. The fields
6672e9e1 907belonging to an event type are described in the event-specific meta-data
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MD
908within a structure type.
909
9106.3.1 Padding
911
912No padding at the end of the event payload. This differs from the ISO/C standard
913for structures, but follows the CTF standard for structures. In a trace, even
914though it makes sense to align the beginning of a structure, it really makes no
915sense to add padding at the end of the structure, because structures are usually
916not followed by a structure of the same type.
917
918This trick can be done by adding a zero-length "end" field at the end of the C
919structures, and by using the offset of this field rather than using sizeof()
3bf79539 920when calculating the size of a structure (see Appendix "A. Helper macros").
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MD
921
9226.3.2 Alignment
923
924The event payload is aligned on the largest alignment required by types
925contained within the payload. (This follows the ISO/C standard for structures)
926
927
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MD
9287. Trace Stream Description Language (TSDL)
929
930The Trace Stream Description Language (TSDL) allows expression of the
931binary trace streams layout in a C99-like Domain Specific Language
932(DSL).
933
934
6672e9e1 9357.1 Meta-data
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MD
936
937The trace stream layout description is located in the trace meta-data.
938The meta-data is itself located in a stream identified by its name:
939"metadata".
5ba9f198 940
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MD
941The meta-data description can be expressed in two different formats:
942text-only and packet-based. The text-only description facilitates
943generation of meta-data and provides a convenient way to enter the
944meta-data information by hand. The packet-based meta-data provides the
945CTF stream packet facilities (checksumming, compression, encryption,
946network-readiness) for meta-data stream generated and transported by a
947tracer.
948
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949The text-only meta-data file is a plain-text TSDL description. This file
950must begin with the following characters to identify the file as a CTF
9486a18c 951TSDL text-based metadata file (without the double-quotes) :
1b4d35eb 952
ec2b4db8 953"/* CTF"
1b4d35eb 954
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MD
955It must be followed by a space, and the version of the specification
956followed by the CTF trace, e.g.:
957
958" 1.8"
959
960These characters allow automated discovery of file type and CTF
961specification version. They are interpreted as a the beginning of a
962comment by the TSDL metadata parser. The comment can be continued to
963contain extra commented characters before it is closed.
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964
965The packet-based meta-data is made of "meta-data packets", which each
966start with a meta-data packet header. The packet-based meta-data
967description is detected by reading the magic number "0x75D11D57" at the
968beginning of the file. This magic number is also used to detect the
969endianness of the architecture by trying to read the CTF magic number
970and its counterpart in reversed endianness. The events within the
971meta-data stream have no event header nor event context. Each event only
5ae2352d 972contains a "sequence" payload, which is a sequence of bits using the
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MD
973"trace.packet.header.content_size" field as a placeholder for its length
974(the packet header size should be substracted). The formatting of this
975sequence of bits is a plain-text representation of the TSDL description.
976Each meta-data packet start with a special packet header, specific to
977the meta-data stream, which contains, exactly:
6672e9e1
MD
978
979struct metadata_packet_header {
2daeaa3a 980 uint32_t magic; /* 0x75D11D57 */
3fde5da1 981 uint8_t uuid[16]; /* Unique Universal Identifier */
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982 uint32_t checksum; /* 0 if unused */
983 uint32_t content_size; /* in bits */
984 uint32_t packet_size; /* in bits */
985 uint8_t compression_scheme; /* 0 if unused */
986 uint8_t encryption_scheme; /* 0 if unused */
987 uint8_t checksum_scheme; /* 0 if unused */
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988 uint8_t major; /* CTF spec version major number */
989 uint8_t minor; /* CTF spec version minor number */
6672e9e1
MD
990};
991
992The packet-based meta-data can be converted to a text-only meta-data by
993concatenating all the strings in contains.
4fafe1ad 994
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MD
995In the textual representation of the meta-data, the text contained
996within "/*" and "*/", as well as within "//" and end of line, are
997treated as comments. Boolean values can be represented as true, TRUE,
998or 1 for true, and false, FALSE, or 0 for false. Within the string-based
999meta-data description, the trace UUID is represented as a string of
1000hexadecimal digits and dashes "-". In the event packet header, the trace
1001UUID is represented as an array of bytes.
fcba70d4 1002
fdf2bb05 1003
6c7226e9 10047.2 Declaration vs Definition
fdf2bb05
MD
1005
1006A declaration associates a layout to a type, without specifying where
1007this type is located in the event structure hierarchy (see Section 6).
1008This therefore includes typedef, typealias, as well as all type
1009specifiers. In certain circumstances (typedef, structure field and
1010variant field), a declaration is followed by a declarator, which specify
1011the newly defined type name (for typedef), or the field name (for
1012declarations located within structure and variants). Array and sequence,
1013declared with square brackets ("[" "]"), are part of the declarator,
a9b83695 1014similarly to C99. The enumeration base type is specified by
6c7226e9 1015": enum_base", which is part of the type specifier. The variant tag
a9b83695 1016name, specified between "<" ">", is also part of the type specifier.
fdf2bb05
MD
1017
1018A definition associates a type to a location in the event structure
b9606a77
MD
1019hierarchy (see Section 6). This association is denoted by ":=", as shown
1020in Section 7.3.
fdf2bb05
MD
1021
1022
6c7226e9 10237.3 TSDL Scopes
fdf2bb05 1024
37ab95c3
MD
1025TSDL uses three different types of scoping: a lexical scope is used for
1026declarations and type definitions, and static and dynamic scopes are
1027used for variants references to tag fields (with relative and absolute
1028path lookups) and for sequence references to length fields.
fdf2bb05 1029
6c7226e9 10307.3.1 Lexical Scope
fdf2bb05 1031
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MD
1032Each of "trace", "env", "stream", "event", "struct" and "variant" have
1033their own nestable declaration scope, within which types can be declared
1034using "typedef" and "typealias". A root declaration scope also contains
1035all declarations located outside of any of the aforementioned
1036declarations. An inner declaration scope can refer to type declared
1037within its container lexical scope prior to the inner declaration scope.
1038Redefinition of a typedef or typealias is not valid, although hiding an
1039upper scope typedef or typealias is allowed within a sub-scope.
fdf2bb05 1040
37ab95c3 10417.3.2 Static and Dynamic Scopes
fdf2bb05 1042
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1043A local static scope consists in the scope generated by the declaration
1044of fields within a compound type. A static scope is a local static scope
1045augmented with the nested sub-static-scopes it contains.
1046
1047A dynamic scope consists in the static scope augmented with the
7d9d7e92 1048implicit event structure definition hierarchy presented at Section 6.
fdf2bb05 1049
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MD
1050Multiple declarations of the same field name within a local static scope
1051is not valid. It is however valid to re-use the same field name in
1052different local scopes.
1053
1054Nested static and dynamic scopes form lookup paths. These are used for
1055variant tag and sequence length references. They are used at the variant
1056and sequence definition site to look up the location of the tag field
1057associated with a variant, and to lookup up the location of the length
1058field associated with a sequence.
1059
1060Variants and sequences can refer to a tag field either using a relative
4cac83ee
MD
1061path or an absolute path. The relative path is relative to the scope in
1062which the variant or sequence performing the lookup is located.
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MD
1063Relative paths are only allowed to lookup within the same static scope,
1064which includes its nested static scopes. Lookups targeting parent static
1065scopes need to be performed with an absolute path.
1066
1067Absolute path lookups use the full path including the dynamic scope
1068followed by a "." and then the static scope. Therefore, variants (or
1069sequences) in lower levels in the dynamic scope (e.g. event context) can
1070refer to a tag (or length) field located in upper levels (e.g. in the
1071event header) by specifying, in this case, the associated tag with
1072<stream.event.header.field_name>. This allows, for instance, the event
1073context to define a variant referring to the "id" field of the event
1074header as selector.
1075
284724ae 1076The dynamic scope prefixes are thus:
fdf2bb05 1077
570ecabe 1078 - Trace Environment: <env. >,
e0d9e2c7 1079 - Trace Packet Header: <trace.packet.header. >,
7d9d7e92
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1080 - Stream Packet Context: <stream.packet.context. >,
1081 - Event Header: <stream.event.header. >,
1082 - Stream Event Context: <stream.event.context. >,
1083 - Event Context: <event.context. >,
1084 - Event Payload: <event.fields. >.
fdf2bb05 1085
37ab95c3
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1086
1087The target dynamic scope must be specified explicitly when referring to
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1088a field outside of the static scope (absolute scope reference). No
1089conflict can occur between relative and dynamic paths, because the
1090keywords "trace", "stream", and "event" are reserved, and thus
1091not permitted as field names. It is recommended that field names
1092clashing with CTF and C99 reserved keywords use an underscore prefix to
1093eliminate the risk of generating a description containing an invalid
70375f92 1094field name. Consequently, fields starting with an underscore should have
92250c71 1095their leading underscore removed by the CTF trace readers.
70375f92 1096
fdf2bb05 1097
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1098The information available in the dynamic scopes can be thought of as the
1099current tracing context. At trace production, information about the
1100current context is saved into the specified scope field levels. At trace
1101consumption, for each event, the current trace context is therefore
1102readable by accessing the upper dynamic scopes.
1103
fdf2bb05 1104
6c7226e9 11057.4 TSDL Examples
d285084f 1106
6672e9e1 1107The grammar representing the TSDL meta-data is presented in Appendix C.
7df6b93a 1108TSDL Grammar. This section presents a rather lighter reading that
6672e9e1 1109consists in examples of TSDL meta-data, with template values.
969f30c0 1110
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1111The stream "id" can be left out if there is only one stream in the
1112trace. The event "id" field can be left out if there is only one event
1113in a stream.
1114
5ba9f198 1115trace {
fdf2bb05 1116 major = value; /* Trace format version */
5ba9f198 1117 minor = value;
fdf2bb05 1118 uuid = "aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa"; /* Trace UUID */
58997e9e 1119 byte_order = be OR le; /* Endianness (required) */
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1120 packet.header := struct {
1121 uint32_t magic;
3fde5da1 1122 uint8_t uuid[16];
fc5425db
MD
1123 uint32_t stream_id;
1124 };
3bf79539 1125};
5ba9f198 1126
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1127/*
1128 * The "env" (environment) scope contains assignment expressions. The
1129 * field names and content are implementation-defined.
1130 */
1131env {
1132 pid = value; /* example */
1133 proc_name = "name"; /* example */
1134 ...
1135};
1136
3bf79539
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1137stream {
1138 id = stream_id;
fdf2bb05 1139 /* Type 1 - Few event IDs; Type 2 - Many event IDs. See section 6.1. */
4fa992a5
MD
1140 event.header := event_header_1 OR event_header_2;
1141 event.context := struct {
77a98c82 1142 ...
3bf79539 1143 };
4fa992a5 1144 packet.context := struct {
77a98c82 1145 ...
3bf79539
MD
1146 };
1147};
5ba9f198
MD
1148
1149event {
980015f9 1150 name = "event_name";
3bf79539 1151 id = value; /* Numeric identifier within the stream */
67f02e24 1152 stream_id = stream_id;
dc56f167 1153 loglevel = value;
4fa992a5 1154 context := struct {
fcba70d4
MD
1155 ...
1156 };
4fa992a5 1157 fields := struct {
80fd2569
MD
1158 ...
1159 };
3bf79539 1160};
5ba9f198
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1161
1162/* More detail on types in section 4. Types */
1163
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MD
1164/*
1165 * Named types:
1166 *
4fa992a5 1167 * Type declarations behave similarly to the C standard.
3d13ef1a
MD
1168 */
1169
80af8ac6 1170typedef aliased_type_specifiers new_type_declarators;
2152348f 1171
3d13ef1a 1172/* e.g.: typedef struct example new_type_name[10]; */
80fd2569 1173
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1174/*
1175 * typealias
1176 *
1177 * The "typealias" declaration can be used to give a name (including
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1178 * pointer declarator specifier) to a type. It should also be used to
1179 * map basic C types (float, int, unsigned long, ...) to a CTF type.
1180 * Typealias is a superset of "typedef": it also allows assignment of a
38b8da21 1181 * simple variable identifier to a type.
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1182 */
1183
1184typealias type_class {
80fd2569 1185 ...
38b8da21 1186} := type_specifiers type_declarator;
2152348f 1187
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1188/*
1189 * e.g.:
4fa992a5 1190 * typealias integer {
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1191 * size = 32;
1192 * align = 32;
1193 * signed = false;
38b8da21 1194 * } := struct page *;
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1195 *
1196 * typealias integer {
1197 * size = 32;
1198 * align = 32;
1199 * signed = true;
38b8da21 1200 * } := int;
3d13ef1a 1201 */
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1202
1203struct name {
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1204 ...
1205};
5ba9f198 1206
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1207variant name {
1208 ...
1209};
1210
a9b83695 1211enum name : integer_type {
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1212 ...
1213};
1214
2152348f 1215
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1216/*
1217 * Unnamed types, contained within compound type fields, typedef or typealias.
1218 */
2152348f 1219
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1220struct {
1221 ...
2152348f 1222}
5ba9f198 1223
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1224struct {
1225 ...
1226} align(value)
1227
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1228variant {
1229 ...
1230}
1231
a9b83695 1232enum : integer_type {
80fd2569 1233 ...
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1234}
1235
1236typedef type new_type[length];
3bf79539 1237
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1238struct {
1239 type field_name[length];
1240}
1241
1242typedef type new_type[length_type];
1243
1244struct {
1245 type field_name[length_type];
1246}
1247
1248integer {
80fd2569 1249 ...
2152348f 1250}
3bf79539 1251
2152348f 1252floating_point {
80fd2569 1253 ...
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1254}
1255
1256struct {
1257 integer_type field_name:size; /* GNU/C bitfield */
1258}
1259
1260struct {
1261 string field_name;
1262}
3bf79539 1263
fcba70d4 1264
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12658. Clocks
1266
1267Clock metadata allows to describe the clock topology of the system, as
1268well as to detail each clock parameter. In absence of clock description,
1269it is assumed that all fields named "timestamp" use the same clock
aed18b5e 1270source, which increments once per nanosecond.
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1271
1272Describing a clock and how it is used by streams is threefold: first,
1273the clock and clock topology should be described in a "clock"
1274description block, e.g.:
1275
d803bfcb 1276clock {
58262d97 1277 name = cycle_counter_sync;
2fa70eba 1278 uuid = "62189bee-96dc-11e0-91a8-cfa3d89f3923";
58262d97 1279 description = "Cycle counter synchronized across CPUs";
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1280 freq = 1000000000; /* frequency, in Hz */
1281 /* precision in seconds is: 1000 * (1/freq) */
1282 precision = 1000;
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1283 /*
1284 * clock value offset from Epoch is:
1285 * offset_s + (offset * (1/freq))
1286 */
1287 offset_s = 1326476837;
1288 offset = 897235420;
ce0fadbd 1289 absolute = FALSE;
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1290};
1291
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1292The mandatory "name" field specifies the name of the clock identifier,
1293which can later be used as a reference. The optional field "uuid" is the
1294unique identifier of the clock. It can be used to correlate different
1295traces that use the same clock. An optional textual description string
1296can be added with the "description" field. The "freq" field is the
1297initial frequency of the clock, in Hz. If the "freq" field is not
1298present, the frequency is assumed to be 1000000000 (providing clock
1299increment of 1 ns). The optional "precision" field details the
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1300uncertainty on the clock measurements, in (1/freq) units. The "offset_s"
1301and "offset" fields indicate the offset from POSIX.1 Epoch, 1970-01-01
130200:00:00 +0000 (UTC), to the zero of value of the clock. The "offset_s"
1303field is in seconds. The "offset" field is in (1/freq) units. If any of
1304the "offset_s" or "offset" field is not present, it is assigned the 0
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1305value. The field "absolute" is TRUE if the clock is a global reference
1306across different clock uuid (e.g. NTP time). Otherwise, "absolute" is
1307FALSE, and the clock can be considered as synchronized only with other
1308clocks that have the same uuid.
1309
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1310
1311Secondly, a reference to this clock should be added within an integer
1312type:
1313
1314typealias integer {
1315 size = 64; align = 1; signed = false;
58262d97 1316 map = clock.cycle_counter_sync.value;
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1317} := uint64_ccnt_t;
1318
1319Thirdly, stream declarations can reference the clock they use as a
1320time-stamp source:
1321
1322struct packet_context {
1323 uint64_ccnt_t ccnt_begin;
1324 uint64_ccnt_t ccnt_end;
1325 /* ... */
1326};
1327
1328stream {
1329 /* ... */
1330 event.header := struct {
1331 uint64_ccnt_t timestamp;
1332 /* ... */
1333 }
1334 packet.context := struct packet_context;
1335};
1336
1337For a N-bit integer type referring to a clock, if the integer overflows
1338compared to the N low order bits of the clock prior value, then it is
1339assumed that one, and only one, overflow occurred. It is therefore
1340important that events encoding time on a small number of bits happen
1341frequently enough to detect when more than one N-bit overflow occurs.
1342
1343In a packet context, clock field names ending with "_begin" and "_end"
1344have a special meaning: this refers to the time-stamps at, respectively,
1345the beginning and the end of each packet.
1346
1347
3bf79539 1348A. Helper macros
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1349
1350The two following macros keep track of the size of a GNU/C structure without
1351padding at the end by placing HEADER_END as the last field. A one byte end field
1352is used for C90 compatibility (C99 flexible arrays could be used here). Note
1353that this does not affect the effective structure size, which should always be
1354calculated with the header_sizeof() helper.
1355
1356#define HEADER_END char end_field
1357#define header_sizeof(type) offsetof(typeof(type), end_field)
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1358
1359
1360B. Stream Header Rationale
1361
1362An event stream is divided in contiguous event packets of variable size. These
1363subdivisions allow the trace analyzer to perform a fast binary search by time
1364within the stream (typically requiring to index only the event packet headers)
1365without reading the whole stream. These subdivisions have a variable size to
1366eliminate the need to transfer the event packet padding when partially filled
1367event packets must be sent when streaming a trace for live viewing/analysis.
1368An event packet can contain a certain amount of padding at the end. Dividing
1369streams into event packets is also useful for network streaming over UDP and
1370flight recorder mode tracing (a whole event packet can be swapped out of the
1371buffer atomically for reading).
1372
1373The stream header is repeated at the beginning of each event packet to allow
1374flexibility in terms of:
1375
1376 - streaming support,
1377 - allowing arbitrary buffers to be discarded without making the trace
1378 unreadable,
1379 - allow UDP packet loss handling by either dealing with missing event packet
1380 or asking for re-transmission.
1381 - transparently support flight recorder mode,
1382 - transparently support crash dump.
1383
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1384
1385C. TSDL Grammar
fcba70d4 1386
4fa992a5 1387/*
6c7226e9 1388 * Common Trace Format (CTF) Trace Stream Description Language (TSDL) Grammar.
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1389 *
1390 * Inspired from the C99 grammar:
1391 * http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1124.pdf (Annex A)
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1392 * and c++1x grammar (draft)
1393 * http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2011/n3291.pdf (Annex A)
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1394 *
1395 * Specialized for CTF needs by including only constant and declarations from
1396 * C99 (excluding function declarations), and by adding support for variants,
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1397 * sequences and CTF-specific specifiers. Enumeration container types
1398 * semantic is inspired from c++1x enum-base.
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1399 */
1400
14011) Lexical grammar
1402
14031.1) Lexical elements
1404
1405token:
1406 keyword
1407 identifier
1408 constant
1409 string-literal
1410 punctuator
1411
14121.2) Keywords
1413
1414keyword: is one of
1415
ec4404a7 1416align
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1417const
1418char
2fa70eba 1419clock
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1420double
1421enum
570ecabe 1422env
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1423event
1424floating_point
1425float
1426integer
1427int
1428long
1429short
1430signed
1431stream
1432string
1433struct
1434trace
3e1e1a78 1435typealias
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1436typedef
1437unsigned
1438variant
1439void
1440_Bool
1441_Complex
1442_Imaginary
1443
1444
14451.3) Identifiers
1446
1447identifier:
1448 identifier-nondigit
1449 identifier identifier-nondigit
1450 identifier digit
1451
1452identifier-nondigit:
1453 nondigit
1454 universal-character-name
1455 any other implementation-defined characters
1456
1457nondigit:
1458 _
1459 [a-zA-Z] /* regular expression */
1460
1461digit:
1462 [0-9] /* regular expression */
1463
14641.4) Universal character names
1465
1466universal-character-name:
1467 \u hex-quad
1468 \U hex-quad hex-quad
1469
1470hex-quad:
1471 hexadecimal-digit hexadecimal-digit hexadecimal-digit hexadecimal-digit
1472
14731.5) Constants
1474
1475constant:
1476 integer-constant
1477 enumeration-constant
1478 character-constant
1479
1480integer-constant:
1481 decimal-constant integer-suffix-opt
1482 octal-constant integer-suffix-opt
1483 hexadecimal-constant integer-suffix-opt
1484
1485decimal-constant:
1486 nonzero-digit
1487 decimal-constant digit
1488
1489octal-constant:
1490 0
1491 octal-constant octal-digit
1492
1493hexadecimal-constant:
1494 hexadecimal-prefix hexadecimal-digit
1495 hexadecimal-constant hexadecimal-digit
1496
1497hexadecimal-prefix:
1498 0x
1499 0X
1500
1501nonzero-digit:
1502 [1-9]
1503
1504integer-suffix:
1505 unsigned-suffix long-suffix-opt
1506 unsigned-suffix long-long-suffix
1507 long-suffix unsigned-suffix-opt
1508 long-long-suffix unsigned-suffix-opt
1509
1510unsigned-suffix:
1511 u
1512 U
1513
1514long-suffix:
1515 l
1516 L
1517
1518long-long-suffix:
1519 ll
1520 LL
1521
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MD
1522enumeration-constant:
1523 identifier
1524 string-literal
1525
1526character-constant:
1527 ' c-char-sequence '
1528 L' c-char-sequence '
1529
1530c-char-sequence:
1531 c-char
1532 c-char-sequence c-char
1533
1534c-char:
1535 any member of source charset except single-quote ('), backslash
1536 (\), or new-line character.
1537 escape-sequence
1538
1539escape-sequence:
1540 simple-escape-sequence
1541 octal-escape-sequence
1542 hexadecimal-escape-sequence
1543 universal-character-name
1544
1545simple-escape-sequence: one of
1546 \' \" \? \\ \a \b \f \n \r \t \v
1547
1548octal-escape-sequence:
1549 \ octal-digit
1550 \ octal-digit octal-digit
1551 \ octal-digit octal-digit octal-digit
1552
1553hexadecimal-escape-sequence:
1554 \x hexadecimal-digit
1555 hexadecimal-escape-sequence hexadecimal-digit
1556
15571.6) String literals
1558
1559string-literal:
1560 " s-char-sequence-opt "
1561 L" s-char-sequence-opt "
1562
1563s-char-sequence:
1564 s-char
1565 s-char-sequence s-char
1566
1567s-char:
1568 any member of source charset except double-quote ("), backslash
1569 (\), or new-line character.
1570 escape-sequence
1571
15721.7) Punctuators
1573
1574punctuator: one of
1575 [ ] ( ) { } . -> * + - < > : ; ... = ,
1576
1577
15782) Phrase structure grammar
1579
1580primary-expression:
1581 identifier
1582 constant
1583 string-literal
1584 ( unary-expression )
1585
1586postfix-expression:
1587 primary-expression
1588 postfix-expression [ unary-expression ]
1589 postfix-expression . identifier
1590 postfix-expressoin -> identifier
1591
1592unary-expression:
1593 postfix-expression
1594 unary-operator postfix-expression
1595
1596unary-operator: one of
1597 + -
1598
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1599assignment-operator:
1600 =
1601
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1602type-assignment-operator:
1603 :=
1604
4fa992a5 1605constant-expression-range:
73d61ac3 1606 unary-expression ... unary-expression
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1607
16082.2) Declarations:
1609
1610declaration:
689e04b4 1611 declaration-specifiers declarator-list-opt ;
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1612 ctf-specifier ;
1613
1614declaration-specifiers:
689e04b4 1615 storage-class-specifier declaration-specifiers-opt
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1616 type-specifier declaration-specifiers-opt
1617 type-qualifier declaration-specifiers-opt
1618
1619declarator-list:
1620 declarator
1621 declarator-list , declarator
1622
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1623abstract-declarator-list:
1624 abstract-declarator
1625 abstract-declarator-list , abstract-declarator
1626
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1627storage-class-specifier:
1628 typedef
1629
1630type-specifier:
1631 void
1632 char
1633 short
1634 int
1635 long
1636 float
1637 double
1638 signed
1639 unsigned
1640 _Bool
1641 _Complex
cfdd51ec 1642 _Imaginary
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1643 struct-specifier
1644 variant-specifier
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1645 enum-specifier
1646 typedef-name
1647 ctf-type-specifier
1648
ec4404a7 1649align-attribute:
73d61ac3 1650 align ( unary-expression )
ec4404a7 1651
4fa992a5 1652struct-specifier:
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MD
1653 struct identifier-opt { struct-or-variant-declaration-list-opt } align-attribute-opt
1654 struct identifier align-attribute-opt
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MD
1655
1656struct-or-variant-declaration-list:
1657 struct-or-variant-declaration
1658 struct-or-variant-declaration-list struct-or-variant-declaration
1659
1660struct-or-variant-declaration:
1661 specifier-qualifier-list struct-or-variant-declarator-list ;
eacb16d1 1662 declaration-specifiers-opt storage-class-specifier declaration-specifiers-opt declarator-list ;
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1663 typealias declaration-specifiers abstract-declarator-list type-assignment-operator declaration-specifiers abstract-declarator-list ;
1664 typealias declaration-specifiers abstract-declarator-list type-assignment-operator declarator-list ;
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1665
1666specifier-qualifier-list:
1667 type-specifier specifier-qualifier-list-opt
1668 type-qualifier specifier-qualifier-list-opt
1669
1670struct-or-variant-declarator-list:
1671 struct-or-variant-declarator
1672 struct-or-variant-declarator-list , struct-or-variant-declarator
1673
1674struct-or-variant-declarator:
1675 declarator
73d61ac3 1676 declarator-opt : unary-expression
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1677
1678variant-specifier:
1679 variant identifier-opt variant-tag-opt { struct-or-variant-declaration-list }
1680 variant identifier variant-tag
1681
1682variant-tag:
37ab95c3 1683 < unary-expression >
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1684
1685enum-specifier:
1686 enum identifier-opt { enumerator-list }
1687 enum identifier-opt { enumerator-list , }
1688 enum identifier
a9b83695
MD
1689 enum identifier-opt : declaration-specifiers { enumerator-list }
1690 enum identifier-opt : declaration-specifiers { enumerator-list , }
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MD
1691
1692enumerator-list:
1693 enumerator
1694 enumerator-list , enumerator
1695
1696enumerator:
1697 enumeration-constant
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MD
1698 enumeration-constant assignment-operator unary-expression
1699 enumeration-constant assignment-operator constant-expression-range
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MD
1700
1701type-qualifier:
1702 const
1703
1704declarator:
1705 pointer-opt direct-declarator
1706
1707direct-declarator:
1708 identifier
1709 ( declarator )
1ab22b2a 1710 direct-declarator [ unary-expression ]
4fa992a5 1711
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1712abstract-declarator:
1713 pointer-opt direct-abstract-declarator
1714
1715direct-abstract-declarator:
1716 identifier-opt
1717 ( abstract-declarator )
1ab22b2a 1718 direct-abstract-declarator [ unary-expression ]
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1719 direct-abstract-declarator [ ]
1720
4fa992a5 1721pointer:
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1722 * type-qualifier-list-opt
1723 * type-qualifier-list-opt pointer
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MD
1724
1725type-qualifier-list:
1726 type-qualifier
1727 type-qualifier-list type-qualifier
1728
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1729typedef-name:
1730 identifier
1731
17322.3) CTF-specific declarations
1733
1734ctf-specifier:
1735 event { ctf-assignment-expression-list-opt }
1736 stream { ctf-assignment-expression-list-opt }
570ecabe 1737 env { ctf-assignment-expression-list-opt }
4fa992a5 1738 trace { ctf-assignment-expression-list-opt }
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1739 typealias declaration-specifiers abstract-declarator-list type-assignment-operator declaration-specifiers abstract-declarator-list
1740 typealias declaration-specifiers abstract-declarator-list type-assignment-operator declarator-list
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1741
1742ctf-type-specifier:
1743 floating_point { ctf-assignment-expression-list-opt }
1744 integer { ctf-assignment-expression-list-opt }
1745 string { ctf-assignment-expression-list-opt }
7609d3c7 1746 string
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1747
1748ctf-assignment-expression-list:
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1749 ctf-assignment-expression ;
1750 ctf-assignment-expression-list ctf-assignment-expression ;
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1751
1752ctf-assignment-expression:
1753 unary-expression assignment-operator unary-expression
1754 unary-expression type-assignment-operator type-specifier
eacb16d1 1755 declaration-specifiers-opt storage-class-specifier declaration-specifiers-opt declarator-list
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1756 typealias declaration-specifiers abstract-declarator-list type-assignment-operator declaration-specifiers abstract-declarator-list
1757 typealias declaration-specifiers abstract-declarator-list type-assignment-operator declarator-list
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