"Michael Kerrisk (man-pages)" <mtk.manpages@xxxxxxxxx> writes:
> A question (which you may or may not be interested in ;-)):
> How feasible do you think it would be to write a script that
> tells me the FTM requirements for a given API?
Parsing the glibc headers is probably out of the question, also because of:
> (Note that the answer will very across glibc versions, so such a
> script would need as input both header files and and some
> glibc-version-specific table mapping the __USE internal macros back to
> FTM settings.
So I would probably let gcc do the work, using a sort of "binary-search"
over the possible combinations of FTMs (complicated by the various FTMs
not providing a linearly increasing set of features, but rather a weird
tree of mutual implications). Something like
(1) create foo.c file containing nothing but #include of the header(s) we
think are necessary
(2) compile with gcc -D_GNU_SOURCE -aux-info foo.aux -o /dev/null -c
foo.c
(3) check that the function we want is actually listed in the .aux file
(these are very easy to parse). If not, we (a) need more/other
headers, (b) have a too old glibc installed and/or (c) need more FTMs,
such as _ISOC11_SOURCE.
If the function is exposed using _GNU_SOURCE, one can then repeat step
(2) with -D_GNU_SOURCE replaced by various combinations of the other
FTMs; at each step recording whether the function is exposed or
not. This should be scriptable, so one gets lots of yes/no data points.
But how one goes from these data points to something like (taken from
valloc(3))
_BSD_SOURCE ||
(_XOPEN_SOURCE >= 500 ||
_XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED) &&
!(_POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE >= 600)
I have no idea.
Rasmus
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