...
}
-4.2.2 Variants (Discriminated Unions)
+4.2.2 Variants (Discriminated/Tagged Unions)
A CTF variant is a selection between different types. A CTF variant must always
be defined within the scope of a structure or within fields contained within a
struct {
enum <uint2_t> { a, b, c } choice;
- variant example <choice> u[unsigned int];
+ variant example <choice> v[unsigned int];
}
Example of an unnamed variant:
uint32_t a;
uint64_t b;
short c;
- } u[10];
+ } v[10];
}
Example of a variant type definition within a structure, where the defined type
...
event {
...
- context = struct {
+ context := struct {
uint pid;
uint16_t payload_size;
};
The metadata can be parsed by reading through the metadata strings, skipping
newlines and null-characters. Type names are made of a single identifier, and
can be surrounded by prefix/postfix. Text contained within "/*" and "*/", as
-well as within "//" and end of line, are treated as comments.
+well as within "//" and end of line, are treated as comments. Boolean values can
+be represented as true, TRUE, or 1 for true, and false, FALSE, or 0 for false.
The grammar representing the CTF metadata is presented in
Appendix C. CTF Metadata Grammar.
stream {
id = stream_id;
- event {
- header_alignment = value;
- /* Type 1 - Few event IDs; Type 2 - Many event IDs. See section 6.2. */
- header = event_header_1 OR event_header_2;
- context = struct {
- ...
- };
+ /* Type 1 - Few event IDs; Type 2 - Many event IDs. See section 6.2. */
+ event.header := event_header_1 OR event_header_2;
+ event.context := struct {
+ ...
};
- packet {
- context = struct {
- ...
- };
+ packet.context := struct {
+ ...
};
};
name = event_name;
id = value; /* Numeric identifier within the stream */
stream = stream_id;
- context = struct {
+ context := struct {
...
};
- fields = struct {
+ fields := struct {
...
};
};
/*
* Named types:
*
- * Type declarations behave similarly to the C standard, with the following
- * added feature: new_type can be preceded by a colon to allow creation of a
- * type name with prefix/postfix.
+ * Type declarations behave similarly to the C standard.
*/
typedef aliased_type_prefix aliased_type new_type aliased_type_postfix;
/* e.g.: typedef struct example new_type_name[10]; */
-typedef type_class {
+/*
+ * typealias
+ *
+ * The "typealias" declaration can be used to give a name (including
+ * prefix/postfix) to a type.
+ */
+
+typealias type_class {
...
} : new_type_prefix new_type new_type_postfix;
/*
* e.g.:
- * typedef integer {
+ * typealias integer {
* size = 32;
* align = 32;
* signed = false;
};
-/* Unnamed types, contained within compound type fields or typedef. */
+/*
+ * Unnamed types, contained within compound type fields, typedef or typealias.
+ */
struct {
...
C. CTF Metadata Grammar
-TODO
+/*
+ * Common Trace Format (CTF) Metadata Grammar.
+ *
+ * Inspired from the C99 grammar:
+ * http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1124.pdf (Annex A)
+ *
+ * Specialized for CTF needs by including only constant and declarations from
+ * C99 (excluding function declarations), and by adding support for variants,
+ * sequences and CTF-specific specifiers.
+ */
+
+1) Lexical grammar
+
+1.1) Lexical elements
+
+token:
+ keyword
+ identifier
+ constant
+ string-literal
+ punctuator
+
+1.2) Keywords
+
+keyword: is one of
+
+const
+char
+double
+enum
+event
+floating_point
+float
+integer
+int
+long
+short
+signed
+stream
+string
+struct
+trace
+typealias
+typedef
+unsigned
+variant
+void
+_Bool
+_Complex
+_Imaginary
+
+
+1.3) Identifiers
+
+identifier:
+ identifier-nondigit
+ identifier identifier-nondigit
+ identifier digit
+
+identifier-nondigit:
+ nondigit
+ universal-character-name
+ any other implementation-defined characters
+
+nondigit:
+ _
+ [a-zA-Z] /* regular expression */
+
+digit:
+ [0-9] /* regular expression */
+
+1.4) Universal character names
+
+universal-character-name:
+ \u hex-quad
+ \U hex-quad hex-quad
+
+hex-quad:
+ hexadecimal-digit hexadecimal-digit hexadecimal-digit hexadecimal-digit
+
+1.5) Constants
+
+constant:
+ integer-constant
+ enumeration-constant
+ character-constant
+
+integer-constant:
+ decimal-constant integer-suffix-opt
+ octal-constant integer-suffix-opt
+ hexadecimal-constant integer-suffix-opt
+
+decimal-constant:
+ nonzero-digit
+ decimal-constant digit
+
+octal-constant:
+ 0
+ octal-constant octal-digit
+
+hexadecimal-constant:
+ hexadecimal-prefix hexadecimal-digit
+ hexadecimal-constant hexadecimal-digit
+
+hexadecimal-prefix:
+ 0x
+ 0X
+
+nonzero-digit:
+ [1-9]
+
+integer-suffix:
+ unsigned-suffix long-suffix-opt
+ unsigned-suffix long-long-suffix
+ long-suffix unsigned-suffix-opt
+ long-long-suffix unsigned-suffix-opt
+
+unsigned-suffix:
+ u
+ U
+
+long-suffix:
+ l
+ L
+
+long-long-suffix:
+ ll
+ LL
+
+digit-sequence:
+ digit
+ digit-sequence digit
+
+hexadecimal-digit-sequence:
+ hexadecimal-digit
+ hexadecimal-digit-sequence hexadecimal-digit
+
+enumeration-constant:
+ identifier
+ string-literal
+
+character-constant:
+ ' c-char-sequence '
+ L' c-char-sequence '
+
+c-char-sequence:
+ c-char
+ c-char-sequence c-char
+
+c-char:
+ any member of source charset except single-quote ('), backslash
+ (\), or new-line character.
+ escape-sequence
+
+escape-sequence:
+ simple-escape-sequence
+ octal-escape-sequence
+ hexadecimal-escape-sequence
+ universal-character-name
+
+simple-escape-sequence: one of
+ \' \" \? \\ \a \b \f \n \r \t \v
+
+octal-escape-sequence:
+ \ octal-digit
+ \ octal-digit octal-digit
+ \ octal-digit octal-digit octal-digit
+
+hexadecimal-escape-sequence:
+ \x hexadecimal-digit
+ hexadecimal-escape-sequence hexadecimal-digit
+
+1.6) String literals
+
+string-literal:
+ " s-char-sequence-opt "
+ L" s-char-sequence-opt "
+
+s-char-sequence:
+ s-char
+ s-char-sequence s-char
+
+s-char:
+ any member of source charset except double-quote ("), backslash
+ (\), or new-line character.
+ escape-sequence
+
+1.7) Punctuators
+
+punctuator: one of
+ [ ] ( ) { } . -> * + - < > : ; ... = ,
+
+
+2) Phrase structure grammar
+
+primary-expression:
+ identifier
+ constant
+ string-literal
+ ( unary-expression )
+
+postfix-expression:
+ primary-expression
+ postfix-expression [ unary-expression ]
+ postfix-expression . identifier
+ postfix-expressoin -> identifier
+
+unary-expression:
+ postfix-expression
+ unary-operator postfix-expression
+
+unary-operator: one of
+ + -
+
+assignment-operator:
+ =
+
+constant-expression:
+ unary-expression
+
+constant-expression-range:
+ constant-expression ... constant-expression
+
+2.2) Declarations:
+
+declaration:
+ declaration-specifiers declarator-list-opt ;
+ ctf-specifier ;
+
+declaration-specifiers:
+ storage-class-specifier declaration-specifiers-opt
+ type-specifier declaration-specifiers-opt
+ type-qualifier declaration-specifiers-opt
+
+declarator-list:
+ declarator
+ declarator-list , declarator
+
+storage-class-specifier:
+ typedef
+
+type-specifier:
+ void
+ char
+ short
+ int
+ long
+ float
+ double
+ signed
+ unsigned
+ _Bool
+ _Complex
+ struct-specifier
+ variant-specifier
+ enum-specifier
+ typedef-name
+ ctf-type-specifier
+
+struct-specifier:
+ struct identifier-opt { struct-or-variant-declaration-list }
+ struct identifier
+
+struct-or-variant-declaration-list:
+ struct-or-variant-declaration
+ struct-or-variant-declaration-list struct-or-variant-declaration
+
+struct-or-variant-declaration:
+ specifier-qualifier-list struct-or-variant-declarator-list ;
+
+specifier-qualifier-list:
+ type-specifier specifier-qualifier-list-opt
+ type-qualifier specifier-qualifier-list-opt
+
+struct-or-variant-declarator-list:
+ struct-or-variant-declarator
+ struct-or-variant-declarator-list , struct-or-variant-declarator
+
+struct-or-variant-declarator:
+ declarator
+ declarator-opt : constant-expression
+
+variant-specifier:
+ variant identifier-opt variant-tag-opt { struct-or-variant-declaration-list }
+ variant identifier variant-tag
+
+variant-tag:
+ < identifier >
+
+enum-specifier:
+ enum identifier-opt { enumerator-list }
+ enum identifier-opt { enumerator-list , }
+ enum identifier
+ enum identifier-opt < type-specifier > { enumerator-list }
+ enum identifier-opt < type-specifier > { enumerator-list , }
+ enum identifier < type-specifier >
+ enum identifier-opt < integer-constant > { enumerator-list }
+ enum identifier-opt < integer-constant > { enumerator-list , }
+ enum identifier < integer-constant >
+
+enumerator-list:
+ enumerator
+ enumerator-list , enumerator
+
+enumerator:
+ enumeration-constant
+ enumeration-constant = constant-expression
+ enumeration-constant = constant-expression-range
+
+type-qualifier:
+ const
+
+declarator:
+ pointer-opt direct-declarator
+
+direct-declarator:
+ identifier
+ ( declarator )
+ direct-declarator [ type-specifier ]
+ direct-declarator [ constant-expression ]
+
+pointer:
+ type-qualifier-list-opt
+ type-qualifier-list-opt pointer
+
+type-qualifier-list:
+ type-qualifier
+ type-qualifier-list type-qualifier
+
+typedef-name:
+ identifier
+
+2.3) CTF-specific declarations
+
+ctf-specifier:
+ event { ctf-assignment-expression-list-opt }
+ stream { ctf-assignment-expression-list-opt }
+ trace { ctf-assignment-expression-list-opt }
+
+ctf-type-specifier:
+ floating_point { ctf-assignment-expression-list-opt }
+ integer { ctf-assignment-expression-list-opt }
+ string { ctf-assignment-expression-list-opt }
+
+ctf-assignment-expression-list:
+ ctf-assignment-expression
+ ctf-assignment-expression-list ; ctf-assignment-expression
+
+ctf-assignment-expression:
+ unary-expression assignment-operator unary-expression
+ unary-expression type-assignment-operator type-specifier
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