[PATCH v3] binutils, gdb: support zstd compressed debug sections

[Simon Marchi]

>>  But what about the other configure.ac files, don't
>> they need PKG_PROG_PKG_CONFIG too?  gdb/configure.ac, for instance, uses
>> pkg-config for debuginfod.  So if the user passes --without-debuginfod
>> --with-zstd, I expect things to fail, as the pkg-config will be skipped.
> 
> No, that will be fine, I think  The reason being that
> PKG_CHECK_MODULES AC_REQUIREs PKG_PROG_PKG_CONFIG.  So the expansion
> of AC_DEBUGINFOD will emit an expansion of PKG_PROG_PKG_CONFIG if that
> has not already occurred, before the entire AC_DEBUGINFOD expansion.

Ah, makes sense.  Thanks for the explanation Alan.

> 
>> binutils/configure.ac probably has the same problem, since it uses
>> PKG_CHECK_MODULES for msgpack.
> 
> I'll fix this one even though it isn't a problem now because
> AC_DEBUGINFOD and AM_ZSTD preceed it.  We should use AS_IF more often,
> particularly when autoconf macros are invoked.

Silly question but... AM_ZSTD was clearly named after AM_ZLIB.  But why
does AM_ZLIB have the "AM" (automake, I suppose) prefix?  It doesn't
seem to have anything to do with automake.

Ack about AS_IF, I will try to remember this for top-level configure
code.

Simon