https://bugs.gentoo.org/668044
https://gcc.gnu.org/PR87099

From e24ceb4802f0cc1bb9e498af6f5bdd29e556c34b Mon Sep 17 00:00:00 2001
From: jakub <jakub@138bc75d-0d04-0410-961f-82ee72b054a4>
Date: Tue, 28 Aug 2018 11:43:22 +0000
Subject: [PATCH] 	PR middle-end/87099 	* calls.c
 (maybe_warn_nonstring_arg): Punt early if 	warn_stringop_overflow is
 zero.  Don't call get_range_strlen 	on 3rd argument, keep iterating until
 lenrng[1] is INTEGER_CST. 	Only use lenrng[1] if non-NULL and
 INTEGER_CST.  Don't uselessly 	increment lenrng[0].

	* gcc.dg/pr87099.c: New test.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/branches/gcc-8-branch@263917 138bc75d-0d04-0410-961f-82ee72b054a4
---
 gcc/calls.c                    | 12 ++++++++----
 gcc/testsuite/gcc.dg/pr87099.c | 21 +++++++++++++++++++++
 4 files changed, 43 insertions(+), 4 deletions(-)
 create mode 100644 gcc/testsuite/gcc.dg/pr87099.c

--- a/gcc/calls.c
+++ b/gcc/calls.c
@@ -1627,6 +1627,9 @@ maybe_warn_nonstring_arg (tree fndecl, tree exp)
   if (!fndecl || DECL_BUILT_IN_CLASS (fndecl) != BUILT_IN_NORMAL)
     return;
 
+  if (!warn_stringop_overflow)
+    return;
+
   bool with_bounds = CALL_WITH_BOUNDS_P (exp);
 
   unsigned nargs = call_expr_nargs (exp);
@@ -1655,7 +1658,10 @@ maybe_warn_nonstring_arg (tree fndecl, tree exp)
 	   conservatively as the bound for the unbounded function,
 	   and to adjust the range of the bound of the bounded ones.  */
 	unsigned stride = with_bounds ? 2 : 1;
-	for (unsigned argno = 0; argno < nargs && !*lenrng; argno += stride)
+	for (unsigned argno = 0;
+	     argno < MIN (nargs, 2 * stride)
+	     && !(lenrng[1] && TREE_CODE (lenrng[1]) == INTEGER_CST);
+	     argno += stride)
 	  {
 	    tree arg = CALL_EXPR_ARG (exp, argno);
 	    if (!get_attr_nonstring_decl (arg))
@@ -1693,11 +1699,9 @@ maybe_warn_nonstring_arg (tree fndecl, tree exp)
   if (bound)
     get_size_range (bound, bndrng);
 
-  if (*lenrng)
+  if (lenrng[1] && TREE_CODE (lenrng[1]) == INTEGER_CST)
     {
       /* Add one for the nul.  */
-      lenrng[0] = const_binop (PLUS_EXPR, TREE_TYPE (lenrng[0]),
-			       lenrng[0], size_one_node);
       lenrng[1] = const_binop (PLUS_EXPR, TREE_TYPE (lenrng[1]),
 			       lenrng[1], size_one_node);
 
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr87099.c
@@ -0,0 +1,21 @@
+/* PR middle-end/87099 */
+/* { dg-do compile } */
+/* { dg-options "-Wstringop-overflow" } */
+
+void bar (char *);
+
+int
+foo (int n)
+{
+  char v[n];
+  bar (v);
+  return __builtin_strncmp (&v[1], "aaa", 3);
+}
+
+int
+baz (int n, char *s)
+{
+  char v[n];
+  bar (v);
+  return __builtin_strncmp (&v[1], s, 3);
+}
-- 
2.19.1