https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81980
--- Comment #4 from David Malcolm <dmalcolm at gcc dot gnu.org> ---
With -m32 on ix86 we hit:
9282 static tree
9283 ix86_build_builtin_va_list (void)
9284 {
9285 if (TARGET_64BIT)
....
9318 else
9319 {
9320 /* For i386 we use plain pointer to argument area. */
9321 return build_pointer_type (char_type_node);
and so __builtin_va_list and thus va_list is "char *".
Then, in c-format.c:check_function_format
1147 /* Check if the current function has a parameter to
which
1148 the format attribute could be attached; if not, it
1149 can't be a candidate for a format attribute,
despite
1150 the vprintf-like or vscanf-like call. */
1151 tree args;
1152 for (args = DECL_ARGUMENTS (current_function_decl);
1153 args != 0;
1154 args = DECL_CHAIN (args))
1155 {
1156 if (TREE_CODE (TREE_TYPE (args)) == POINTER_TYPE
1157 && (TYPE_MAIN_VARIANT (TREE_TYPE (TREE_TYPE
(args)))
1158 == char_type_node))
1159 break;
1160 }
1161 if (args != 0)
with -m32, the "va_list ap" is "char *" and thus matches the test at lines
1156-1158;
without -m32 it doesn't.
