Change typealias delimiter from : to typename

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

diff --git a/common-trace-format-proposal.txt b/common-trace-format-proposal.txt
index a036b30625c7c3db484e879254146ae424ff2af9..ef6739ff114375135fb65eb57bd2eccbd36b97b1 100644 (file)
--- a/common-trace-format-proposal.txt
+++ b/common-trace-format-proposal.txt
@@ -68,14 +68,10 @@ A metadata event stream contains information on trace event types. It describes:
 3. Event stream
 
 An event stream is divided in contiguous event packets of variable size. These
 3. Event stream
 
 An event stream is divided in contiguous event packets of variable size. These

-subdivisions have a variable size. An event packet can contain a certain amount
-of padding at the end. The rationale for the event stream design choices is
-explained in Appendix B. Stream Header Rationale.
-
-An event stream is divided in contiguous event packets of variable size. These
-subdivisions have a variable size. An event packet can contain a certain amount
-of padding at the end.  The stream header is repeated at the beginning of each
-event packet.
+subdivisions have a variable size. An event packet can contain a certain
+amount of padding at the end. The stream header is repeated at the
+beginning of each event packet. The rationale for the event stream
+design choices is explained in Appendix B. Stream Header Rationale.

 
 The event stream header will therefore be referred to as the "event packet
 header" throughout the rest of this document.
 
 The event stream header will therefore be referred to as the "event packet
 header" throughout the rest of this document.


@@ -103,15 +99,16 @@ types, but must be derived into a type to be usable in an event field.
 
 We define "byte-packed" types as aligned on the byte size, namely 8-bit.
 We define "bit-packed" types as following on the next bit, as defined by the
 
 We define "byte-packed" types as aligned on the byte size, namely 8-bit.
 We define "bit-packed" types as following on the next bit, as defined by the

-"bitfields" section.
+"Integers" section.

 
 All basic types, except bitfields, are either aligned on an architecture-defined
 specific alignment or byte-packed, depending on the architecture preference.
 Architectures providing fast unaligned write byte-packed basic types to save
 space, aligning each type on byte boundaries (8-bit). Architectures with slow
 unaligned writes align types on specific alignment values. If no specific
 
 All basic types, except bitfields, are either aligned on an architecture-defined
 specific alignment or byte-packed, depending on the architecture preference.
 Architectures providing fast unaligned write byte-packed basic types to save
 space, aligning each type on byte boundaries (8-bit). Architectures with slow
 unaligned writes align types on specific alignment values. If no specific

-alignment is declared for a type nor its parents, it is assumed to be bit-packed
-for bitfields and byte-packed for other types.
+alignment is declared for a type, it is assumed to be bit-packed for
+integers with size not multiple of 8 bits and for gcc bitfields. All
+other types are byte-packed.

 
 Metadata attribute representation of a specific alignment:
 
 
 Metadata attribute representation of a specific alignment:
 


@@ -189,7 +186,7 @@ typealias integer {
   size = 32;
   signed = false;
   align = 32;
   size = 32;
   signed = false;
   align = 32;

-} : uint32_t;
+} typename uint32_t;

 
 Definition of a named 5-bit signed bitfield:
 
 
 Definition of a named 5-bit signed bitfield:
 


@@ -197,7 +194,7 @@ typealias integer {
   size = 5;
   signed = true;
   align = 1;
   size = 5;
   signed = true;
   align = 1;

-} : int5_t;
+} typename int5_t;

 
 4.1.6 GNU/C bitfields
 
 
 4.1.6 GNU/C bitfields
 


@@ -256,7 +253,7 @@ typealias floating_point {
   exp_dig = 8;         /* sizeof(float) * CHAR_BIT - FLT_MANT_DIG */
   mant_dig = 24;       /* FLT_MANT_DIG */
   byte_order = native;
   exp_dig = 8;         /* sizeof(float) * CHAR_BIT - FLT_MANT_DIG */
   mant_dig = 24;       /* FLT_MANT_DIG */
   byte_order = native;

-} : float;
+} typename float;

 
 TODO: define NaN, +inf, -inf behavior.
 
 
 TODO: define NaN, +inf, -inf behavior.
 


@@ -274,10 +271,7 @@ this format by having the same start_value and end_value for each element, which
 is in fact a range of size 1. This single-value range is supported without
 repeating the start and end values with the value = string declaration.
 
 is in fact a range of size 1. This single-value range is supported without
 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 name <integer_type OR size> {
+enum name <integer_type> {

   somestring          = start_value1 ... end_value1,
   "other string"      = start_value2 ... end_value2,
   yet_another_string,  /* will be assigned to end_value2 + 1 */
   somestring          = start_value1 ... end_value1,
   "other string"      = start_value2 ... end_value2,
   yet_another_string,  /* will be assigned to end_value2 + 1 */


@@ -288,7 +282,7 @@ enum name <integer_type OR size> {
 If the values are omitted, the enumeration starts at 0 and increment of 1 for
 each entry:
 
 If the values are omitted, the enumeration starts at 0 and increment of 1 for
 each entry:
 

-enum name <32> {
+enum name <unsigned int> {

   ZERO,
   ONE,
   TWO,
   ZERO,
   ONE,
   TWO,


@@ -374,7 +368,7 @@ variant name {
 };
 
 struct {
 };
 
 struct {

-  enum <integer_type or size> { sel1, sel2, sel3, ... } tag_field;
+  enum <integer_type> { sel1, sel2, sel3, ... } tag_field;

   ...
   variant name <tag_field> v;
 }
   ...
   variant name <tag_field> v;
 }


@@ -383,7 +377,7 @@ An unnamed variant definition within a structure is expressed by the following
 metadata:
 
 struct {
 metadata:
 
 struct {

-  enum <integer_type or size> { sel1, sel2, sel3, ... } tag_field;
+  enum <integer_type> { sel1, sel2, sel3, ... } tag_field;

   ...
   variant <tag_field> {
     field_type sel1;
   ...
   variant <tag_field> {
     field_type sel1;


@@ -504,7 +498,7 @@ Metadata representation of a named string type:
 
 typealias string {
   encoding = UTF8 OR ASCII;
 
 typealias string {
   encoding = UTF8 OR ASCII;

-} : name;
+} typename name;

 
 A nameless string type can be declared as a field type:
 
 
 A nameless string type can be declared as a field type:
 


@@ -616,9 +610,9 @@ The overall structure of an event is:
     5 - Event Payload (as specified by the event metadata)
 
 This structure defines an implicit dynamic scoping, where variants
     5 - Event Payload (as specified by the event metadata)
 
 This structure defines an implicit dynamic scoping, where variants

-located in structures with higher number can refer to the fields of
-structures with lower number. See Section 7.2 Metadata Scopes for more
-detail.
+located in inner structures (those with a higher number in the listing
+above) can refer to the fields of outer structures (with lower number in
+the listing above). See Section 7.2 Metadata Scopes for more detail.

 
 6.1 Event Header
 
 
 6.1 Event Header
 


@@ -765,20 +759,23 @@ contained within the payload. (This follows the ISO/C standard for structures)
 
 7. Metadata
 
 
 7. Metadata
 

-The meta-data is located in a stream named "metadata". It is made of "event
-packets", which each start with an event packet header. The event type within
-the metadata stream have no event header nor event context. Each event only
-contains a null-terminated "string" payload, which is a metadata description
-entry. The events are packed one next to another. Each event packet start with
-an event packet header, which contains, amongst other fields, the magic number
-and trace UUID. The trace UUID is represented as a string of hexadecimal digits
-and dashes "-".
-
-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. Boolean values can
-be represented as true, TRUE, or 1 for true, and false, FALSE, or 0 for false.
+The meta-data is located in a stream identified by its name: "metadata".
+It is made of "event packets", which each start with an event packet
+header. The event type within the metadata stream have no event header
+nor event context. Each event only contains a null-terminated "string"
+payload, which is a metadata description entry. The events are packed
+one next to another. Each event packet start with an event packet
+header, which contains, amongst other fields, the magic number and trace
+UUID. In the event packet header, the trace UUID is represented as an
+array of bytes. Within the string-based metadata description, the trace
+UUID is represented as a string of hexadecimal digits and dashes "-".
+
+The metadata can be parsed by reading through the metadata strings,
+skipping 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.
+Boolean values can be represented as true, TRUE, or 1 for true, and
+false, FALSE, or 0 for false.

 
 
 7.1 Declaration vs Definition
 
 
 7.1 Declaration vs Definition


@@ -791,10 +788,12 @@ variant field), a declaration is followed by a declarator, which specify
 the newly defined type name (for typedef), or the field name (for
 declarations located within structure and variants). Array and sequence,
 declared with square brackets ("[" "]"), are part of the declarator,
 the newly defined type name (for typedef), or the field name (for
 declarations located within structure and variants). Array and sequence,
 declared with square brackets ("[" "]"), are part of the declarator,

-similarly to C99.
+similarly to C99. The enumeration type specifier and variant tag name
+(both specified with "<" ">") are part of the type specifier.

 
 A definition associates a type to a location in the event structure
 
 A definition associates a type to a location in the event structure

-hierarchy (see Section 6).
+hierarchy (see Section 6). This association is denoted by ":=", as shown
+in Section 7.3.

 
 
 7.2 Metadata Scopes
 
 
 7.2 Metadata Scopes


@@ -808,34 +807,36 @@ for variants references to tag fields.
 Each of "trace", "stream", "event", "struct" and "variant" have their own
 nestable declaration scope, within which types can be declared using "typedef"
 and "typealias". A root declaration scope also contains all declarations
 Each of "trace", "stream", "event", "struct" and "variant" have their own
 nestable declaration scope, within which types can be declared using "typedef"
 and "typealias". A root declaration scope also contains all declarations

-located outside of any of the aforementioned declarations. An innermost
+located outside of any of the aforementioned declarations. An inner

 declaration scope can refer to type declared within its container
 declaration scope can refer to type declared within its container

-lexical scope prior to the innermost declaration scope. Redefinition of
-a typedef or typealias is not valid, although hiding an uppermost scope
+lexical scope prior to the inner declaration scope. Redefinition of a
+typedef or typealias is not valid, although hiding an upper scope

 typedef or typealias is allowed within a sub-scope.
 
 7.2.2 Dynamic Scope
 
 typedef or typealias is allowed within a sub-scope.
 
 7.2.2 Dynamic Scope
 

-For variant tag definition only, the dynamic scope used to look up the
-location of the associated tag field consists in the lexical scope of
-the structures where the variant is declared, extended with the implicit
-dynamic scope specified by the event structure hierarchy presented at
-the beginning of Section 6. Therefore, lower levels in the dynamic scope
-(e.g. event context) can refer to a tag field located in upper levels
-(e.g. in the event header) by specifying, in this case,
-"header.field_name" as tag identifier.  This allows, for instance, the
-event context to define a variant referring to the "id" field of the
-event header as selector.
+A dynamic scope consists in the lexical scope augmented with the
+implicit event structure definition hierarchy presented at Section 6.
+The dynamic scope is only used for variant tag definitions. It is used
+at definition time to look up the location of the tag field associated
+with a variant.
+
+Therefore, variants in lower levels in the dynamic scope (e.g. event
+context) can refer to a tag field located in upper levels (e.g. in the
+event header) by specifying, in this case, the associated tag with
+<header.field_name>. This allows, for instance, the event context to
+define a variant referring to the "id" field of the event header as
+selector.

 
 The target dynamic scope must be specified explicitly when referring to
 a field outside of the local static scope. The dynamic scope prefixes
 are thus:
 
 
 The target dynamic scope must be specified explicitly when referring to
 a field outside of the local static scope. The dynamic scope prefixes
 are thus:
 

- - Stream Packet Context: "stream.packet.context.",
- - Event Header: "stream.event.header.",
- - Stream Event Context: "stream.event.context.",
- - Event Context: "event.context.",
- - Event Payload: "event.fields.".
+ - Stream Packet Context: <stream.packet.context. >,
+ - Event Header: <stream.event.header. >,
+ - Stream Event Context: <stream.event.context. >,
+ - Event Context: <event.context. >,
+ - Event Payload: <event.fields. >.

 
 Multiple declarations of the same field name within a single scope is
 not valid. It is however valid to re-use the same field name in
 
 Multiple declarations of the same field name within a single scope is
 not valid. It is however valid to re-use the same field name in


@@ -843,8 +844,14 @@ different scopes. There is no possible conflict, because the dynamic
 scope must be specified when a variant refers to a tag field located in
 a different dynamic scope.
 
 scope must be specified when a variant refers to a tag field located in
 a different dynamic scope.
 

+The information available in the dynamic scopes can be thought of as the
+current tracing context. At trace production, information about the
+current context is saved into the specified scope field levels. At trace
+consumption, for each event, the current trace context is therefore
+readable by accessing the upper dynamic scopes.

 
 

-7.2 Metadata Examples
+
+7.3 Metadata Examples

 
 The grammar representing the CTF metadata is presented in
 Appendix C. CTF Metadata Grammar. This section presents a rather ligher
 
 The grammar representing the CTF metadata is presented in
 Appendix C. CTF Metadata Grammar. This section presents a rather ligher


@@ -889,7 +896,7 @@ event {
  * Type declarations behave similarly to the C standard.
  */
 
  * Type declarations behave similarly to the C standard.
  */
 

-typedef aliased_type_prefix aliased_type new_type aliased_type_postfix;
+typedef aliased_type_specifiers new_type_declarators;

 
 /* e.g.: typedef struct example new_type_name[10]; */
 
 
 /* e.g.: typedef struct example new_type_name[10]; */
 


@@ -897,15 +904,17 @@ typedef aliased_type_prefix aliased_type new_type aliased_type_postfix;
  * typealias
  *
  * The "typealias" declaration can be used to give a name (including
  * typealias
  *
  * The "typealias" declaration can be used to give a name (including

- * 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.
+ * pointer declarator specifier) 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. The keyword "typename" is
+ * reserved to separate the aliased type from the newly declared alias
+ * name.

  */
 
 typealias type_class {
   ...
  */
 
 typealias type_class {
   ...

-} : new_type_prefix new_type new_type_postfix;
+} typename type_specifiers type_declarator;

 
 /*
  * e.g.: 
 
 /*
  * e.g.: 


@@ -913,13 +922,13 @@ typealias type_class {
  *   size = 32;
  *   align = 32;
  *   signed = false;
  *   size = 32;
  *   align = 32;
  *   signed = false;

- * } : struct page *;
+ * } typename struct page *;

  *
  * typealias integer {
  *  size = 32;
  *  align = 32;
  *  signed = true;
  *
  * typealias integer {
  *  size = 32;
  *  align = 32;
  *  signed = true;

- * } : int;
+ * } typename int;

  */
 
 struct name {
  */
 
 struct name {


@@ -930,7 +939,7 @@ variant name {
   ...
 };
 
   ...
 };
 

-enum name <integer_type or size> {
+enum name <integer_type> {

   ...
 };
 
   ...
 };
 


@@ -947,7 +956,7 @@ variant {
   ...
 }
 
   ...
 }
 

-enum <integer_type or size> {
+enum <integer_type> {

   ...
 }
 
   ...
 }
 


@@ -1065,6 +1074,7 @@ struct
 trace
 typealias
 typedef
 trace
 typealias
 typedef

+typename

 unsigned
 variant
 void
 unsigned
 variant
 void


@@ -1238,6 +1248,9 @@ unary-operator: one of
 assignment-operator:
        =
 
 assignment-operator:
        =
 

+type-assignment-operator:
+       :=
+

 constant-expression:
        unary-expression
 
 constant-expression:
        unary-expression
 


@@ -1247,11 +1260,11 @@ constant-expression-range:
 2.2) Declarations:
 
 declaration:
 2.2) Declarations:
 
 declaration:

-       declaration-specifiers ;
-       declaration-specifiers storage-class-specifier declaration-specifiers declarator-list ;
+       declaration-specifiers declarator-list-opt ;

        ctf-specifier ;
 
 declaration-specifiers:
        ctf-specifier ;
 
 declaration-specifiers:

+       storage-class-specifier declaration-specifiers-opt

        type-specifier declaration-specifiers-opt
        type-qualifier declaration-specifiers-opt
 
        type-specifier declaration-specifiers-opt
        type-qualifier declaration-specifiers-opt
 


@@ -1278,6 +1291,7 @@ type-specifier:
        unsigned
        _Bool
        _Complex
        unsigned
        _Bool
        _Complex

+       _Imaginary

        struct-specifier
        variant-specifier
        enum-specifier
        struct-specifier
        variant-specifier
        enum-specifier


@@ -1295,8 +1309,8 @@ 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 ;
 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 ;
+       typealias declaration-specifiers abstract-declarator-list typename declaration-specifiers abstract-declarator-list ;
+       typealias declaration-specifiers abstract-declarator-list typename declarator-list ;

 
 specifier-qualifier-list:
        type-specifier specifier-qualifier-list-opt
 
 specifier-qualifier-list:
        type-specifier specifier-qualifier-list-opt


@@ -1324,9 +1338,6 @@ enum-specifier:
        enum identifier-opt < declaration-specifiers > { enumerator-list }
        enum identifier-opt < declaration-specifiers > { enumerator-list , }
        enum identifier < declaration-specifiers >
        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 >

 
 enumerator-list:
        enumerator
 
 enumerator-list:
        enumerator


@@ -1376,8 +1387,8 @@ ctf-specifier:
        event { ctf-assignment-expression-list-opt }
        stream { ctf-assignment-expression-list-opt }
        trace { ctf-assignment-expression-list-opt }
        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 ;
+       typealias declaration-specifiers abstract-declarator-list typename declaration-specifiers abstract-declarator-list ;
+       typealias declaration-specifiers abstract-declarator-list typename declarator-list ;

 
 ctf-type-specifier:
        floating_point { ctf-assignment-expression-list-opt }
 
 ctf-type-specifier:
        floating_point { ctf-assignment-expression-list-opt }


@@ -1392,5 +1403,5 @@ 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
        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
+       typealias declaration-specifiers abstract-declarator-list typename declaration-specifiers abstract-declarator-list
+       typealias declaration-specifiers abstract-declarator-list typename declarator-list