When -Wstringop-truncation sees a strncpy call where the specified bound
is equal to the size of the destination, it looks at the next statement
to see if it's dst[i] = '\0';, and if it is, it doesn't warn. But it
needs to look at the next nondebug statement, otherwise we can get a
false positive with -g, as this testcase shows.
Bootstrapped/regtested on x86_64-linux, ok for trunk?
2018-02-06 Marek Polacek <pola...@redhat.com>
PR tree-optimization/84228
* tree-ssa-strlen.c (maybe_diag_stxncpy_trunc): Skip debug statements.
* c-c++-common/Wstringop-truncation-3.c: New test.
diff --git gcc/testsuite/c-c++-common/Wstringop-truncation-3.c
gcc/testsuite/c-c++-common/Wstringop-truncation-3.c
index e69de29bb2d..e15e6a42b07 100644
--- gcc/testsuite/c-c++-common/Wstringop-truncation-3.c
+++ gcc/testsuite/c-c++-common/Wstringop-truncation-3.c
@@ -0,0 +1,20 @@
+/* PR tree-optimization/84228 */
+/* { dg-do compile } */
+/* { dg-options "-Wstringop-truncation -O2 -g" } */
+
+char *strncpy (char *, const char *, __SIZE_TYPE__);
+struct S
+{
+ char arr[64];
+};
+
+int
+foo (struct S *p1, const char *a)
+{
+ if (a)
+ goto err;
+ strncpy (p1->arr, a, sizeof p1->arr); /* { dg-bogus "specified bound" } */
+ p1->arr[3] = '\0';
+err:
+ return 0;
+}
diff --git gcc/tree-ssa-strlen.c gcc/tree-ssa-strlen.c
index c3cf432a921..f0f6535017b 100644
--- gcc/tree-ssa-strlen.c
+++ gcc/tree-ssa-strlen.c
@@ -1849,7 +1849,7 @@ maybe_diag_stxncpy_trunc (gimple_stmt_iterator gsi, tree
src, tree cnt)
/* Look for dst[i] = '\0'; after the stxncpy() call and if found
avoid the truncation warning. */
- gsi_next (&gsi);
+ gsi_next_nondebug (&gsi);
gimple *next_stmt = gsi_stmt (gsi);
if (!gsi_end_p (gsi) && is_gimple_assign (next_stmt))
Marek
