PR 85365 is another example of a false positive caused by
the interaction between the instrumentation inserted by
sanitizers, jump threading, and a middle-end warning.
In this case, the warning is easy to avoid by suppressing
-Wrestrict for null pointers. Although undefined, since
they do no point to an object, strictly speaking they do
not indicate an overlap, and so issuing a -Wrestrict
warning is not quite appropriate anyway.
Testing in progress.
Martin
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.
Index: gcc/gimple-fold.c
===================================================================
--- gcc/gimple-fold.c (revision 259298)
+++ gcc/gimple-fold.c (working copy)
@@ -1612,7 +1612,11 @@ gimple_fold_builtin_strcpy (gimple_stmt_iterator *
/* 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_iterat
/* 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);
Index: gcc/gimple-ssa-warn-restrict.c
===================================================================
--- gcc/gimple-ssa-warn-restrict.c (revision 259298)
+++ gcc/gimple-ssa-warn-restrict.c (working copy)
@@ -1880,11 +1880,20 @@ check_bounds_or_overlap (gcall *call, tree dst, tr
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. */
Index: gcc/testsuite/gcc.dg/Wrestrict-15.c
===================================================================
--- gcc/testsuite/gcc.dg/Wrestrict-15.c (nonexistent)
+++ gcc/testsuite/gcc.dg/Wrestrict-15.c (working copy)
@@ -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);
+}
