[gcc r12-8993] c-family: Fix ICE with -Wsuggest-attribute [PR98487]

[Marek Polacek <mpolacek@gcc.gnu.org>]

https://gcc.gnu.org/g:0e345504ec9349d9a3bf826c3e16b7e973739485

commit r12-8993-g0e345504ec9349d9a3bf826c3e16b7e973739485
Author: Marek Polacek <polacek@redhat.com>
Date:   Fri Dec 16 12:28:43 2022 -0500

    c-family: Fix ICE with -Wsuggest-attribute [PR98487]
    
    Here we crash because check_function_format was using TREE_PURPOSE
    directly rather than using get_attribute_name.
    
            PR c/98487
    
    gcc/c-family/ChangeLog:
    
            * c-format.cc (check_function_format): Use get_attribute_name.
    
    gcc/testsuite/ChangeLog:
    
            * c-c++-common/Wsuggest-attribute-1.c: New test.
    
    (cherry picked from commit 68e51bd0a85794cd437d3e740357dfef84dc560d)

Diff:
---
 gcc/c-family/c-format.cc                          |  2 +-
 gcc/testsuite/c-c++-common/Wsuggest-attribute-1.c | 36 +++++++++++++++++++++++
 2 files changed, 37 insertions(+), 1 deletion(-)

diff --git a/gcc/c-family/c-format.cc b/gcc/c-family/c-format.cc
index d05e5acd063..fe5ed48b86b 100644
--- a/gcc/c-family/c-format.cc
+++ b/gcc/c-family/c-format.cc
@@ -1205,7 +1205,7 @@ check_function_format (const_tree fntype, tree attrs, int nargs,
 	      for (c = TYPE_ATTRIBUTES (TREE_TYPE (current_function_decl));
 		   c;
 		   c = TREE_CHAIN (c))
-		if (is_attribute_p ("format", TREE_PURPOSE (c))
+		if (is_attribute_p ("format", get_attribute_name (c))
 		    && (decode_format_type (IDENTIFIER_POINTER
 					    (TREE_VALUE (TREE_VALUE (c))))
 			== info.format_type))
diff --git a/gcc/testsuite/c-c++-common/Wsuggest-attribute-1.c b/gcc/testsuite/c-c++-common/Wsuggest-attribute-1.c
new file mode 100644
index 00000000000..8b5b398fb78
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/Wsuggest-attribute-1.c
@@ -0,0 +1,36 @@
+/* PR c/98487 */
+/* { dg-do compile { target { c || c++11 } } } */
+/* { dg-options "-Wsuggest-attribute=format" } */
+
+#include <stdarg.h>
+
+[[gnu::__format__(__printf__, 1, 2)]]
+void
+do_printf(const char * const a0, ...)
+{
+  va_list ap;
+  va_start(ap, a0);
+  __builtin_vprintf(a0, ap);
+  va_end(ap);
+}
+
+[[gnu::__format__(__scanf__, 1, 2)]]
+void
+do_scanf(const char * const a0, ...)
+{
+  va_list ap;
+  va_start(ap, a0);
+  __builtin_vscanf(a0, ap);
+  va_end(ap);
+}
+
+struct tm;
+
+[[gnu::__format__(__strftime__, 1, 0)]]
+void
+do_strftime(const char * const a0, struct tm * a1)
+{
+  char buff[256];
+  __builtin_strftime(buff, sizeof(buff), a0, a1);
+  __builtin_puts(buff);
+}