c++: format attribute redeclaration [PR116954]

Here when merging the two decls, remove_contract_attributes loses
ATTR_IS_DEPENDENT on the format attribute, so apply_late_template_attributes
just returns, so the attribute doesn't get propagated to the type where the
warning looks for it.

Fixed by using copy_node instead of tree_cons to preserve flags.

	PR c++/116954

gcc/cp/ChangeLog:

	* contracts.cc (remove_contract_attributes): Preserve flags
	on the attribute list.

gcc/testsuite/ChangeLog:

	* g++.dg/warn/Wformat-3.C: New test.

(cherry picked from commit b0d7d644f3c25af9bf60c948ab26aa7b09a68787)

diff --git a/gcc/cp/contracts.cc b/gcc/cp/contracts.cc
index 634e3cf4fa9a9243721cf116dfc0bdcea45dd6f3..ff82ad772d0655c855be0df286d02407843a8d4b 100644 (file)
--- a/gcc/cp/contracts.cc
+++ b/gcc/cp/contracts.cc
@@ -870,10 +870,17 @@ cp_contract_assertion_p (const_tree attr)
 void
 remove_contract_attributes (tree fndecl)
 {
+  if (!flag_contracts)
+    return;
+
   tree list = NULL_TREE;
   for (tree p = DECL_ATTRIBUTES (fndecl); p; p = TREE_CHAIN (p))
     if (!cxx_contract_attribute_p (p))
-      list = tree_cons (TREE_PURPOSE (p), TREE_VALUE (p), list);
+      {
+       tree nl = copy_node (p);
+       TREE_CHAIN (nl) = list;
+       list = nl;
+      }
   DECL_ATTRIBUTES (fndecl) = nreverse (list);
 }
 

diff --git a/gcc/testsuite/g++.dg/warn/Wformat-3.C b/gcc/testsuite/g++.dg/warn/Wformat-3.C
new file mode 100644 (file)
index 0000000..e308530
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wformat-3.C
@@ -0,0 +1,19 @@
+// PR c++/116954
+// { dg-additional-options -Wformat }
+
+#ifndef WORKS
+template<int N>
+int fn(char (&buf)[N], const char fmt[], ...)
+  __attribute__ ((__format__ (__printf__, 2, 3)));
+#endif
+
+template<int  N>
+__attribute__ ((__format__ (__printf__, 2, 3)))
+int fn(char (&)[N], const char [], ...)
+{ return 0; }
+
+int main()
+{
+  char buf[20];
+  return fn(buf, "%s", 42); /* { dg-warning "Wformat" } */
+}