Update proposal type class description

[ctf.git] / common-trace-format-proposal.txt

diff --git a/common-trace-format-proposal.txt b/common-trace-format-proposal.txt
index 8d8fb7ca04d2582fdf7522c0e54e8f07ff7143fc..458b0977787edbad699d18590dacb10db95de165 100644 (file)
--- a/common-trace-format-proposal.txt
+++ b/common-trace-format-proposal.txt
@@ -83,9 +83,13 @@ header" throughout the rest of this document.
 
 4. Types
 
+Types are organized as type classes. Each type class belong to either of two
+kind of types: basic types or compound types.
+
 4.1 Basic types
 
-A basic type is a scalar type, as described in this section.
+A basic type is a scalar type, as described in this section. It includes
+integers, GNU/C bitfields, enumerations, and floating point values.
 
 4.1.1 Type inheritance
 
@@ -181,19 +185,19 @@ Metadata representation:
 
 Example of type inheritance (creation of a uint32_t named type):
 
-typedef integer {
+typealias integer {
   size = 32;
   signed = false;
   align = 32;
-} uint32_t;
+} : uint32_t;
 
 Definition of a named 5-bit signed bitfield:
 
-typedef integer {
+typealias integer {
   size = 5;
   signed = true;
   align = 1;
-} int5_t;
+} : int5_t;
 
 4.1.6 GNU/C bitfields
 
@@ -248,11 +252,11 @@ floating_point {
 
 Example of type inheritance:
 
-typedef floating_point {
+typealias floating_point {
   exp_dig = 8;         /* sizeof(float) * CHAR_BIT - FLT_MANT_DIG */
   mant_dig = 24;       /* FLT_MANT_DIG */
   byte_order = native;
-} float;
+} : float;
 
 TODO: define NaN, +inf, -inf behavior.
 
@@ -273,8 +277,8 @@ repeating the start and end values with the value = string declaration.
 If a numeric value is encountered between < >, it represents the integer type
 size used to hold the enumeration, in bits.
 
-enum <integer_type OR size> name {
-  string              = start_value1 ... end_value1,
+enum name <integer_type OR size> {
+  somestring          = start_value1 ... end_value1,
   "other string"      = start_value2 ... end_value2,
   yet_another_string,  /* will be assigned to end_value2 + 1 */
   "some other string" = value,
@@ -284,7 +288,7 @@ enum <integer_type OR size> name {
 If the values are omitted, the enumeration starts at 0 and increment of 1 for
 each entry:
 
-enum <32> name {
+enum name <32> {
   ZERO,
   ONE,
   TWO,
@@ -300,8 +304,12 @@ enum <integer_type> {
   ...
 }
 
+
 4.2 Compound types
 
+Compound are aggregation of type declarations. Compound types include
+structures, variant, arrays, sequences, and strings.
+
 4.2.1 Structures
 
 Structures are aligned on the largest alignment required by basic types
@@ -492,9 +500,9 @@ encoding attribute information, the default encoding is UTF-8.
 
 Metadata representation of a named string type:
 
-typedef string {
+typealias string {
   encoding = UTF8 OR ASCII;
-} name;
+} : name;
 
 A nameless string type can be declared as a field type:
 
@@ -591,7 +599,7 @@ struct event_packet_context {
   uint8_t  stream_packet_count_bits;   /* Significant counter bits */
   uint8_t  compression_scheme;
   uint8_t  encryption_scheme;
-  uint8_t  checksum;
+  uint8_t  checksum_scheme;
 };
 
 
@@ -607,10 +615,11 @@ The overall structure of an event is:
 
 6.1 Lexical Scope
 
-The lexical scope of each structure (stream packet context, header, stream event
-context, event context and payload) is extended in the following way: lower
-levels (e.g. 3) can refer to fields defined in prior levels (e.g. 2 and 1). The
-field in the closest level has priority in case of field name conflict.
+For variant tag definition only, the lexical scope of each structure (stream
+packet context, header, stream event context, event context and payload) is
+extended in the following way: lower levels (e.g. 3) can refer to fields defined
+in prior levels (e.g. 2 and 1). The field in the closest level has priority in
+case of field name conflict.
 
 This allows, for instance, the event context to define a variant refering to the
 "id" field of the event header as selector.
@@ -774,6 +783,13 @@ can be surrounded by prefix/postfix. Text contained within "/*" and "*/", as
 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.
 
+Each of "trace", "stream", "event", "struct" and "variant" have their own
+nestable declaration scope, within which types can be declared using "typedef"
+and "typealias". An innermost declaration scope can refer to type declared
+within its container lexical scope prior to the innermost declaration scope.
+Redefinition of a typedef or typealias, or hiding an uppermost definition, is
+not valid.
+
 The grammar representing the CTF metadata is presented in
 Appendix C. CTF Metadata Grammar.
 
@@ -824,7 +840,10 @@ typedef aliased_type_prefix aliased_type new_type aliased_type_postfix;
  * typealias
  *
  * The "typealias" declaration can be used to give a name (including
- * prefix/postfix) to a type.
+ * prefix/postfix) to a type. It should also be used to map basic C types
+ * (float, int, unsigned long, ...) to a CTF type. Typealias is a superset of
+ * "typedef": it also allows assignment of a simple variable identifier to a
+ * type.
  */
 
 typealias type_class {
@@ -838,6 +857,12 @@ typealias type_class {
  *   align = 32;
  *   signed = false;
  * } : struct page *;
+ *
+ * typealias integer {
+ *  size = 32;
+ *  align = 32;
+ *  signed = true;
+ * } : int;
  */
 
 struct name {
@@ -848,7 +873,7 @@ variant name {
   ...
 };
 
-enum <integer_type or size> name {
+enum name <integer_type or size> {
   ...
 };
 
@@ -981,6 +1006,7 @@ stream
 string
 struct
 trace
+typealias
 typedef
 unsigned
 variant
@@ -1152,9 +1178,6 @@ unary-expression:
 unary-operator: one of
        + -
 
-assignment-expression:
-       unary-expression assignment-operator unary-expression
-
 assignment-operator:
        =
 
@@ -1167,11 +1190,11 @@ constant-expression-range:
 2.2) Declarations:
 
 declaration:
-       declaration-specifiers declarator-list-opt ;
+       declaration-specifiers ;
+       declaration-specifiers storage-class-specifier declaration-specifiers declarator-list ;
        ctf-specifier ;
 
 declaration-specifiers:
-       storage-class-specifier declaration-specifiers-opt
        type-specifier declaration-specifiers-opt
        type-qualifier declaration-specifiers-opt
 
@@ -1179,6 +1202,10 @@ declarator-list:
        declarator
        declarator-list , declarator
 
+abstract-declarator-list:
+       abstract-declarator
+       abstract-declarator-list , abstract-declarator
+
 storage-class-specifier:
        typedef
 
@@ -1194,13 +1221,14 @@ type-specifier:
        unsigned
        _Bool
        _Complex
-       struct-or-variant-specifier
+       struct-specifier
+       variant-specifier
        enum-specifier
        typedef-name
        ctf-type-specifier
 
 struct-specifier:
-       struct identifier-opt { struct-or-variant-declaration-list }
+       struct identifier-opt { struct-or-variant-declaration-list-opt }
        struct identifier
 
 struct-or-variant-declaration-list:
@@ -1209,6 +1237,9 @@ struct-or-variant-declaration-list:
 
 struct-or-variant-declaration:
        specifier-qualifier-list struct-or-variant-declarator-list ;
+       declaration-specifiers storage-class-specifier declaration-specifiers declarator-list ;
+       typealias declaration-specifiers abstract-declarator-list : declaration-specifiers abstract-declarator-list ;
+       typealias declaration-specifiers abstract-declarator-list : declarator-list ;
 
 specifier-qualifier-list:
        type-specifier specifier-qualifier-list-opt
@@ -1233,9 +1264,9 @@ 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 < declaration-specifiers > { enumerator-list }
+       enum identifier-opt < declaration-specifiers > { enumerator-list , }
+       enum identifier < declaration-specifiers >
        enum identifier-opt < integer-constant > { enumerator-list }
        enum identifier-opt < integer-constant > { enumerator-list , }
        enum identifier < integer-constant >
@@ -1261,18 +1292,24 @@ direct-declarator:
        direct-declarator [ type-specifier ]
        direct-declarator [ constant-expression ]
 
+abstract-declarator:
+       pointer-opt direct-abstract-declarator
+
+direct-abstract-declarator:
+       identifier-opt
+       ( abstract-declarator )
+       direct-abstract-declarator [ type-specifier ]
+       direct-abstract-declarator [ constant-expression ]
+       direct-abstract-declarator [ ]
+
 pointer:
-       type-qualifier-list-opt
-       type-qualifier-list-opt pointer
+       * type-qualifier-list-opt
+       * type-qualifier-list-opt pointer
 
 type-qualifier-list:
        type-qualifier
        type-qualifier-list type-qualifier
 
-identifier-list:
-       identifier
-       identifier-list , identifier
-
 typedef-name:
        identifier
 
@@ -1282,6 +1319,8 @@ ctf-specifier:
        event { ctf-assignment-expression-list-opt }
        stream { ctf-assignment-expression-list-opt }
        trace { ctf-assignment-expression-list-opt }
+       typealias declaration-specifiers abstract-declarator-list : declaration-specifiers abstract-declarator-list ;
+       typealias declaration-specifiers abstract-declarator-list : declarator-list ;
 
 ctf-type-specifier:
        floating_point { ctf-assignment-expression-list-opt }
@@ -1295,3 +1334,6 @@ ctf-assignment-expression-list:
 ctf-assignment-expression:
        unary-expression assignment-operator unary-expression
        unary-expression type-assignment-operator type-specifier
+       declaration-specifiers storage-class-specifier declaration-specifiers declarator-list
+       typealias declaration-specifiers abstract-declarator-list : declaration-specifiers abstract-declarator-list
+       typealias declaration-specifiers abstract-declarator-list : declarator-list