Attempting to pass a pointer to a va_list variable to a function expecting such a pointer causes a warning about passing a pointer of incompatible type.

markg@home ~/work/ffdev $ gcc -v -save-temps -ansi -pedantic -Wall -W -O -c t.c
Reading specs from /usr/lib/gcc/powerpc-unknown-linux-gnu/3.4.5/specs
Configured with: /var/tmp/portage/gcc-3.4.5-r1/work/gcc-3.4.5/configure --prefix=/usr --bindir=/usr/powerpc-unknown-linux-gnu/gcc-bin/3.4.5 --includedir=/usr/lib/gcc/powerpc-unknown-linux
-gnu/3.4.5/include --datadir=/usr/share/gcc-data/powerpc-unknown-linux-gnu/3.4.5 --mandir=/usr/share/gcc-data/powerpc-unknown-linux-gnu/3.4.5/man --infodir=/usr/share/gcc-data/powerpc-unk
nown-linux-gnu/3.4.5/info --with-gxx-include-dir=/usr/lib/gcc/powerpc-unknown-linux-gnu/3.4.5/include/g++-v3 --host=powerpc-unknown-linux-gnu --build=powerpc-unknown-linux-gnu --disable-a
ltivec --enable-nls --without-included-gettext --with-system-zlib --disable-checking --disable-werror --disable-libunwind-exceptions --disable-multilib --enable-languages=c,c++,java,f77 -
-enable-shared --enable-threads=posix --enable-__cxa_atexit --enable-clocale=gnu
Thread model: posix
gcc version 3.4.5 (Gentoo 3.4.5-r1, ssp-3.4.5-1.0, pie-8.7.9)
 /usr/libexec/gcc/powerpc-unknown-linux-gnu/3.4.5/cc1 -E -quiet -v -D__unix__ -D__gnu_linux__ -D__linux__ -Asystem=linux -Asystem=unix -Asystem=posix t.c -ansi -pedantic -Wall -W -O -o t.
i
ignoring nonexistent directory "/usr/local/include"
ignoring nonexistent directory "/usr/lib/gcc/powerpc-unknown-linux-gnu/3.4.5/../../../../powerpc-unknown-linux-gnu/include"
#include "..." search starts here:
#include <...> search starts here:
 /usr/lib/gcc/powerpc-unknown-linux-gnu/3.4.5/include
 /usr/include
End of search list.
 /usr/libexec/gcc/powerpc-unknown-linux-gnu/3.4.5/cc1 -fpreprocessed t.i -quiet -dumpbase t.c -ansi -auxbase t -O -pedantic -Wall -W -ansi -version -o t.s
GNU C version 3.4.5 (Gentoo 3.4.5-r1, ssp-3.4.5-1.0, pie-8.7.9) (powerpc-unknown-linux-gnu)
        compiled by GNU C version 3.4.4 (Gentoo 3.4.4-r1, ssp-3.4.4-1.0, pie-8.7.8).
GGC heuristics: --param ggc-min-expand=64 --param ggc-min-heapsize=64407
t.c:3: warning: unused parameter 'arg'
t.c: In function `bar':
t.c:9: warning: passing arg 1 of `foo' from incompatible pointer type
 /usr/lib/gcc/powerpc-unknown-linux-gnu/3.4.5/../../../../powerpc-unknown-linux-gnu/bin/as -mppc -many -V -Qy -o t.o t.s
GNU assembler version 2.16.1 (powerpc-unknown-linux-gnu) using BFD version 2.16.1
markg@home ~/work/ffdev $ cat t.i
# 1 "t.c"
# 1 "<built-in>"
# 1 "<command line>"
# 1 "t.c"
# 1 "/usr/lib/gcc/powerpc-unknown-linux-gnu/3.4.5/include/stdarg.h" 1 3 4
# 43 "/usr/lib/gcc/powerpc-unknown-linux-gnu/3.4.5/include/stdarg.h" 3 4
typedef __builtin_va_list __gnuc_va_list;
# 105 "/usr/lib/gcc/powerpc-unknown-linux-gnu/3.4.5/include/stdarg.h" 3 4
typedef __gnuc_va_list va_list;
# 2 "t.c" 2

void foo(va_list *arg)
{
}

void bar(va_list arg)
{
  foo(&arg);
}
markg@home ~/work/ffdev $ gcc -v
Reading specs from /usr/lib/gcc/powerpc-unknown-linux-gnu/3.4.5/specs
Configured with: /var/tmp/portage/gcc-3.4.5-r1/work/gcc-3.4.5/configure --prefix=/usr --bindir=/usr/powerpc-unknown-linux-gnu/gcc-bin/3.4.5 --includedir=/usr/lib/gcc/powerpc-unknown-linux-gnu/3.4.5/include --datadir=/usr/share/gcc-data/powerpc-unknown-linux-gnu/3.4.5 --mandir=/usr/share/gcc-data/powerpc-unknown-linux-gnu/3.4.5/man --infodir=/usr/share/gcc-data/powerpc-unknown-linux-gnu/3.4.5/info --with-gxx-include-dir=/usr/lib/gcc/powerpc-unknown-linux-gnu/3.4.5/include/g++-v3 --host=powerpc-unknown-linux-gnu --build=powerpc-unknown-linux-gnu --disable-altivec --enable-nls --without-included-gettext --with-system-zlib --disable-checking --disable-werror --disable-libunwind-exceptions --disable-multilib --enable-languages=c,c++,java,f77 --enable-shared --enable-threads=posix --enable-__cxa_atexit --enable-clocale=gnu
Thread model: posix
gcc version 3.4.5 (Gentoo 3.4.5-r1, ssp-3.4.5-1.0, pie-8.7.9)
markg@home ~/work/ffdev $

The warning about the unused variable is expected. The real code (much more complex) from which this was cut down used the variable and still generated the warning about incompatible pointer type.

The standard says that vl_list should be an object type, and others on the news group comp.lang.c agree that my code is valid. See thread http://groups.google.com/group/comp.lang.c/browse_frm/thread/e64d6ffd19ab7ae3/faf78d3f5fb3acfe?lnk=st&q=group%3Acomp.lang.c+insubject%3Ava_list&rnum=1&hl=en#faf78d3f5fb3acfe