If more than one -fno-builtin-* flag is specified, the first one is ignored.

I've seen other reports of this on Wine the mailing lists.  We use -fno-builtin
to supress the gcc builtins that are incompatible with msvcrt's string
functions.

mike@black:~/wine$ cat b.c
int iswalpha(unsigned short);
mike@black:~/wine$ gcc -fno-builtin-iswalpha -c b.c
mike@black:~/wine$ gcc -fno-builtin-iswalpha -fno-builtin-iswalnum -c b.c
b.c:1: warning: conflicting types for built-in function ‘iswalpha’

mike@black:~/wine$ gcc -v
Using built-in specs.
Target: x86_64-linux-gnu
Configured with: ../src/configure -v
--enable-languages=c,c++,fortran,objc,obj-c++,ada,treelang --prefix=/usr
--enable-shared --with-system-zlib --libexecdir=/usr/lib
--without-included-gettext --enable-threads=posix --enable-nls
--program-suffix=-4.1 --enable-__cxa_atexit --enable-clocale=gnu
--enable-libstdcxx-debug --enable-mpfr --enable-checking=release
x86_64-linux-gnu
Thread model: posix
gcc version 4.1.2 20060715 (prerelease) (Debian 4.1.1-9)
mike@black:~/wine$ uname -a
Linux black 2.6.16.11 #1 Mon May 1 16:44:30 KST 2006 x86_64 GNU/Linux


-- 
           Summary: multiple fno-builtin-* flags broken
           Product: gcc
           Version: 4.1.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: mike at codeweavers dot com
 GCC build triplet: x86_64-linux-gnu
  GCC host triplet: x86_64-linux-gnu
GCC target triplet: x86_64-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28437