This warning is supposed to detect cases like
void
bar (char *d, unsigned n, const char *f, va_list va)
{
vsnprintf (d, n, f, va);
}
where the enclosing function is a candidate for the "format" attribute. The
code assumed that current_function_decl is never null -- a reasonable
assumption since you can't have file-scope function calls in C, but as shown
below, this assumption can be fooled using typeof.
Bootstrapped/regtested on x86_64-linux, ok for trunk?
2018-01-29 Marek Polacek <pola...@redhat.com>
PR c/83966
* c-format.c (check_function_format): Check current_function_decl.
* gcc.dg/format/Wsuggest-attribute-1.c: New test.
diff --git gcc/c-family/c-format.c gcc/c-family/c-format.c
index 7a69d5a295c..3f4f83af219 100644
--- gcc/c-family/c-format.c
+++ gcc/c-family/c-format.c
@@ -1110,7 +1110,9 @@ check_function_format (tree attrs, int nargs, tree
*argarray,
from the format attribute if the called function is decorated
with it. Avoid using calls with string literal formats for
guidance since those are unlikely to be viable candidates. */
- if (warn_suggest_attribute_format && info.first_arg_num == 0
+ if (warn_suggest_attribute_format
+ && current_function_decl != NULL_TREE
+ && info.first_arg_num == 0
&& (format_types[info.format_type].flags
& (int) FMT_FLAG_ARG_CONVERT)
/* c_strlen will fail for a function parameter but succeed
diff --git gcc/testsuite/gcc.dg/format/Wsuggest-attribute-1.c
gcc/testsuite/gcc.dg/format/Wsuggest-attribute-1.c
index e69de29bb2d..5b6fb051e72 100644
--- gcc/testsuite/gcc.dg/format/Wsuggest-attribute-1.c
+++ gcc/testsuite/gcc.dg/format/Wsuggest-attribute-1.c
@@ -0,0 +1,9 @@
+/* PR c/83966 */
+/* { dg-do compile } */
+/* { dg-options "-Wsuggest-attribute=format" } */
+
+#include "format.h"
+
+va_list va;
+const char *f;
+__typeof (vsnprintf ("foo", 0U, f, va)) T;
Marek
