X-Git-Url: http://git.efficios.com/?p=ctf.git;a=blobdiff_plain;f=common-trace-format-proposal.txt;h=ab77a268fd1542145ba6d260b606d58880448afb;hp=361c2ec39c21f35ceb06363b218b0c683113d284;hb=370eae99914830dc4148063c4a5928b3599f60fe;hpb=7d9d7e926e1b628d97b5fbdf4470a0ed26db24c6 diff --git a/common-trace-format-proposal.txt b/common-trace-format-proposal.txt index 361c2ec..ab77a26 100644 --- 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 -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. @@ -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 -"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 -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: @@ -765,20 +762,23 @@ contained within the payload. (This follows the ISO/C standard for structures) 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 @@ -791,10 +791,12 @@ 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, -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 -hierarchy (see Section 6). +hierarchy (see Section 6). This association is denoted by ":=", as shown +in Section 7.3. 7.2 Metadata Scopes @@ -845,8 +847,14 @@ 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. +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 @@ -1240,6 +1248,9 @@ unary-operator: one of assignment-operator: = +type-assignment-operator: + := + constant-expression: unary-expression @@ -1249,11 +1260,11 @@ constant-expression-range: 2.2) Declarations: declaration: - declaration-specifiers ; - declaration-specifiers storage-class-specifier declaration-specifiers declarator-list ; + 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 @@ -1280,6 +1291,7 @@ type-specifier: unsigned _Bool _Complex + _Imaginary struct-specifier variant-specifier enum-specifier