- file : int32:magic int32:version record*
-
- The magic ident is different for the bbg and the counter files.
- The version is the same for both files and is derived from gcc's
- version number. Although the ident and version are formally 32 bit
- numbers, they are derived from 4 character ASCII strings. The
- version number consists of the single character major version
- number, a two character minor version number (leading zero for
- versions less than 10), and a single character indicating the
- status of the release. That will be 'e' experimental, 'p'
- prerelease and 'r' for release. Because, by good fortune, these are
- in alphabetical order, string collating can be used to compare
- version strings, and because numbers are stored big endian, numeric
- comparison can be used when it is read as a 32 bit value. Be aware
- that the 'e' designation will (naturally) be unstable and might be
+ file : int32:magic int32:version int32:stamp record*
+
+ The magic ident is different for the notes and the data files. The
+ magic ident is used to determine the endianness of the file, when
+ reading. The version is the same for both files and is derived
+ from gcc's version number. The stamp value is used to synchronize
+ note and data files and to synchronize merging within a data
+ file. It need not be an absolute time stamp, merely a ticker that
+ increments fast enough and cycles slow enough to distinguish
+ different compile/run/compile cycles.
+
+ Although the ident and version are formally 32 bit numbers, they
+ are derived from 4 character ASCII strings. The version number
+ consists of the single character major version number, a two
+ character minor version number (leading zero for versions less than
+ 10), and a single character indicating the status of the release.
+ That will be 'e' experimental, 'p' prerelease and 'r' for release.
+ Because, by good fortune, these are in alphabetical order, string
+ collating can be used to compare version strings. Be aware that
+ the 'e' designation will (naturally) be unstable and might be