PR c/85365 - -Wrestrict false positives with -fsanitize=undefined

gcc/ChangeLog:

	PR c/85365
	* gimple-fold.c (gimple_fold_builtin_strcpy): Suppress -Wrestrict
	for null pointers.
	(gimple_fold_builtin_stxcpy_chk): Same.
	* gimple-ssa-warn-restrict.c (check_bounds_or_overlap): Same.

gcc/testsuite/ChangeLog:

	PR c/85365
	* gcc.dg/Wrestrict-15.c: New test.

From-SVN: r259535

5 files changed, 75 insertions, 7 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index b58362d..7509584 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,11 @@
+2018-04-20  Martin Sebor  <msebor@redhat.com>
+
+	PR c/85365
+	* gimple-fold.c (gimple_fold_builtin_strcpy): Suppress -Wrestrict
+	for null pointers.
+	(gimple_fold_builtin_stxcpy_chk): Same.
+	* gimple-ssa-warn-restrict.c (check_bounds_or_overlap): Same.
+
 2018-04-20  Michael Meissner  <meissner@linux.ibm.com>
 
 	PR target/85456
diff --git a/gcc/gimple-fold.c b/gcc/gimple-fold.c
index 7771988..bd8c44a 100644
--- a/gcc/gimple-fold.c
+++ b/gcc/gimple-fold.c
@@ -1612,7 +1612,11 @@ gimple_fold_builtin_strcpy (gimple_stmt_iterator *gsi,
   /* If SRC and DEST are the same (and not volatile), return DEST.  */
   if (operand_equal_p (src, dest, 0))
     {
-      if (!gimple_no_warning_p (stmt))
+      /* Issue -Wrestrict unless the pointers are null (those do
+	 not point to objects and so do not indicate an overlap;
+	 such calls could be the result of sanitization and jump
+	 threading).  */
+      if (!integer_zerop (dest) && !gimple_no_warning_p (stmt))
 	{
 	  tree func = gimple_call_fndecl (stmt);
 
@@ -2593,7 +2597,11 @@ gimple_fold_builtin_stxcpy_chk (gimple_stmt_iterator *gsi,
   /* If SRC and DEST are the same (and not volatile), return DEST.  */
   if (fcode == BUILT_IN_STRCPY_CHK && operand_equal_p (src, dest, 0))
     {
-      if (!gimple_no_warning_p (stmt))
+      /* Issue -Wrestrict unless the pointers are null (those do
+	 not point to objects and so do not indicate an overlap;
+	 such calls could be the result of sanitization and jump
+	 threading).  */
+      if (!integer_zerop (dest) && !gimple_no_warning_p (stmt))
 	{
 	  tree func = gimple_call_fndecl (stmt);
 
diff --git a/gcc/gimple-ssa-warn-restrict.c b/gcc/gimple-ssa-warn-restrict.c
index e7a85fd..3d0664d 100644
--- a/gcc/gimple-ssa-warn-restrict.c
+++ b/gcc/gimple-ssa-warn-restrict.c
@@ -1880,11 +1880,20 @@ check_bounds_or_overlap (gcall *call, tree dst, tree src, tree dstsize,
 
   if (operand_equal_p (dst, src, 0))
     {
-      warning_at (loc, OPT_Wrestrict,
-		  "%G%qD source argument is the same as destination",
-		  call, func);
-      gimple_set_no_warning (call, true);
-      return false;
+      /* Issue -Wrestrict unless the pointers are null (those do
+	 not point to objects and so do not indicate an overlap;
+	 such calls could be the result of sanitization and jump
+	 threading).  */
+      if (!integer_zerop (dst) && !gimple_no_warning_p (call))
+	{
+	  warning_at (loc, OPT_Wrestrict,
+		      "%G%qD source argument is the same as destination",
+		      call, func);
+	  gimple_set_no_warning (call, true);
+	  return false;
+	}
+
+      return true;
     }
 
   /* Return false when overlap has been detected.  */
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 5314d9e..947b974 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2018-04-20  Martin Sebor  <msebor@redhat.com>
+
+	PR c/85365
+	* gcc.dg/Wrestrict-15.c: New test.
+
 2018-04-20  Michael Meissner  <meissner@linux.ibm.com>
 
 	PR target/85456
diff --git a/gcc/testsuite/gcc.dg/Wrestrict-15.c b/gcc/testsuite/gcc.dg/Wrestrict-15.c
new file mode 100644
index 0000000..b0b30a2
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/Wrestrict-15.c
@@ -0,0 +1,38 @@
+/* PR 85365 - -Wrestrict false positives with -fsanitize=undefined
+   { dg-do compile }
+   { dg-options "-O2 -Wrestrict -fsanitize=undefined" } */
+
+typedef __SIZE_TYPE__ size_t;
+
+char *strcpy (char *, const char *);
+char *strcat (char *, const char *);
+
+size_t strlen (char *);
+
+extern char a[], b[], d[];
+
+size_t t1 (char *g, int i)
+{
+  /* The following exercises the handling in gimple-fold.c.  */
+  strcpy (g + 4, i ? b : a);    /* { dg-bogus "\\\[-Wrestrict]" } */
+  return strlen (g + 4);
+}
+
+void t2 (char *g, int i)
+{
+  strcpy (g + 4, i ? b : a);    /* { dg-bogus "\\\[-Wrestrict]" } */
+  strcat (g + 4, d);
+}
+
+void t3 (char *g, int i)
+{
+  /* The following exercises the handling in gimple-ssa-warn-restrict.c.  */
+  strcat (g + 4, i ? b : a);    /* { dg-bogus "\\\[-Wrestrict]" } */
+  strcat (g + 4, d);
+}
+
+void t4 (char *p, char *q)
+{
+  strcpy (p, q);                /* { dg-bogus "\\\[-Wrestrict]" } */
+  strcat (p, q + 32);
+}