On 02/21/2014 03:01 PM, Carsten Heinrici wrote: > Hi Julie > > > >>>> I have been working on a changes whereby an autoconf >>>> user can invoke a macro like >>>> >>>> AC_WARN_ADD([-Wextra]) > > The point is the portability. Your flags (-Wextra) depend on the actual compiler. This js against the philosophy behind autoconf, which tries to abstract from it. No, this is totally in line with autoconf philosophy - the point is to call AC_WARN_ADD for a large set of flags that have been shown to work in at least one compiler, and then for each flag in that set, only enable the flags that the current compiler actually honors (or at least silently ignores). The proposal is not to blindly add the gcc-specific -Wextra flag to all $CC runs, but rather to test if $CC supports -Wextra, and if so, THEN add -Wextra to a variable (we probably also want the user to be able to control whether it is added directly to CFLAGS or to some other variable, the way the gnulib module 'manywarnings' already does). > > If wanted, a developper always can add additional specific compiler flags during runtime by specifying them via CFLAGS on command line. This will still remain true. And the developer's choice of CFLAGS should always take precedence over any default flags that autoconf probes for in the absence of a developer preference. > > What would be required is a general macro AC_EXTRA_WARNINGS without arguments which could resolve to the actually current arguments of the tool. Yes, AC_EXTRA_WARNINGS (or whatever spelling gets agreed on) would be the wrapper that has a huge list of known warning flags that various compilers honor, and calls AC_WARN_ADD on each of them, so that for your given $CC, you have then set a variable with the subset of warning flags that made sense for your compiler. -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
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