Re: ac_cv_sizeof_X, et al.

[Eric Blake]

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According to Philip Prindeville on 7/14/2008 5:27 PM:

| I'm looking at sox-12.17.9 and seeing in their "configure" file (which
|  claims to be generated via Autoconf 2.59)

Newer autoconf versions are able to accurately determine type sizes when
cross-compiling, making life much easier for porting to a
cross-compilation platform.  You may want to consider putting pressure on
the sox maintainers to use a newer autoconf version for their next release.

|
| I'm also not sure why there's "ac_cv_sizeof_long" and
| "ac_cv_sizeof_long_int", etc. except perhaps to make the cross-compiling
| distro-manager's life hellish.  :-)

Unfortunately, the C standard specifies several alternative spellings for
the same intrinsic type, so you have to worry about all of the possibilities.

|
| Likewise with the "ac_cv_sizeof_charp" versus "ac_cv_sizeof_char_p",

That may (although I haven't checked) stem from a difference in 'char*'
vs. 'char *', where the space is being converted to _.

| and
| "ac_cv_sizeof_char" versus "ac_cv_sizeof_unsigned_char" (are these
| *ever* different???).

C requires sizeof(char), sizeof(signed char), and sizeof(unsigned char) to
all be equal to 1.  Any compiler where this is not true is broken.  Thus,
any package that has a configure test for this is wasting time.  A recent
thread was posted proposing adding a warning if the user does
AC_CHECK_SIZEOF([char]), but no one has implemented something that works
on all the variant spellings.

- --
Don't work too hard, make some time for fun as well!

Eric Blake             address@hidden
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