Re: regex.m4: how do I know that the included regex is used?

[Paolo Bonzini]

On 07/28/2011 04:16 PM, Sam Steingold wrote:
> If course, you can claim that, if gnulib regex.h were incompatible with
> the system one, then configure would have detected that and included
> gnulib regex in libgnu.a.

The gnulib regex.h is always a superset of the system one.  ABI-wise, 
the only difference should be that the system one will never support 
_REGEX_LARGE_OFFSETS.  The gnulib regex should be compatible always with 
the glibc regex; on non-glibc systems the gnulib regex will always be used.

Actually, a few of the syntaxes are also defined differently for some 
reason.  This makes it preferrable to always use the same regex.h, 
independent of which implementation is in use.

> In that case, why the file fnmatch.in.h not called fnmatch.h?
> At any rate, if gnulib regex is included in libgnu.a, then regex.h
> should be copied (or linked) to $(builddir) or $(builddir)/gllib.
> The current situation is clearly wrong: regex is the only gnulib package
> which requires prepending -I$(srcdir)/gllib to CPPFLAGS!

The current situation is ugly---apart from the inconsistency in syntax 
definitions, there is no reason indeed why regex shouldn't use 
regex.in.h too, and no reason why it should require prepending 
-I$(srcdir)/gllib to CPPFLAGS.  But it is not true that regex requires 
different CPPFLAGS depending on whether the included regex is used.

Paolo