[Bug 28275] New: -Wall and -fno-strict-aliasing not applied to .cross.o files

http://bugs.winehq.org/show_bug.cgi?id=28275

Summary: -Wall and -fno-strict-aliasing not applied to .cross.o
                    files
           Product: Wine
           Version: 1.3.27
          Platform: x86
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: build-env
        AssignedTo: [e-mail]
        ReportedBy: [e-mail]

If you force -Wall -Werror into CFLAGS (not EXTRACFLAGS), you observe
build errors like

i586-mingw32msvc-gcc -c -I. -I. -I../../include -I../../include  -D__WINESRC__ 
-DWINE_CROSSTEST  -g -O2 -Wall -Werror -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=0 -o
dllfunc.cross.o dllfunc.c
cc1: warnings being treated as errors
dllfunc.c: In function ‘AMovieDllRegisterServer2’:
dllfunc.c:180: warning: dereferencing type-punned pointer will break
strict-aliasing rules

There is some chance that -O2 on the files with those warnings will
generate bad code without -fno-strict-aliasing.
(See e.g. http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42907 for an
explanation.)

In Make.rules.in, the .c.cross.o rule wants $(EXTRACFLAGS), but lacks it
because some of the options in it are not safe for the cross-compiler,
because WINE_TRY_CFLAGS in aclocal.m4 only tests the main compiler.
So cross-compiled source doesn't get compiled with -fno-strict-aliasing
(and in maintainer mode, they don't get compiled with -Wall or -Werror).

A plausible fix would be to extend WINE_TRY_CFLAGS to also try with
the cross-compiler, append the options that work there to
a new variable CROSS_EXTRACFLAGS, and use that in the .c.cross.o rule.