Avoid issuing a bogus warning when the source of strncpy is bound by a
constant known to be less than the minimum size of the destination.
Changes from v1:
- Use range-info instead of the MIN_EXPR hack
- Get the minimum size of dst and check for NULL_TREE return
The patch bootstraps successfully and introduces no new regressions in
the testsuite.
gcc/
* tree-ssa-strlen.c (handle_builtin_stxncpy): Check bounds of
source length if available.
gcc/testsuite/
* gcc.dg/builtin-stringop-chk-10.c: New test case.
---
gcc/testsuite/gcc.dg/builtin-stringop-chk-10.c | 17 +++++++++++++++++
gcc/tree-ssa-strlen.c | 15 +++++++++++++++
2 files changed, 32 insertions(+)
create mode 100644 gcc/testsuite/gcc.dg/builtin-stringop-chk-10.c
diff --git a/gcc/testsuite/gcc.dg/builtin-stringop-chk-10.c
b/gcc/testsuite/gcc.dg/builtin-stringop-chk-10.c
new file mode 100644
index 00000000000..13e4bd2f049
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/builtin-stringop-chk-10.c
@@ -0,0 +1,17 @@
+/* Bogus -Wstringop-overflow on strncpy when size is based on strlen but is
+ bound by a constant.
+ { dg-do compile }
+ { dg-options "-O2 -Wstringop-overflow" } */
+
+char dst[1024];
+
+void
+f1 (const char *src)
+{
+ unsigned long limit = 512;
+ unsigned long len = __builtin_strlen (src); /* { dg-bogus "length computed
here" } */
+ if (len > limit)
+ len = limit;
+
+ __builtin_strncpy (dst, src, len); /* { dg-bogus "specified bound depends
on the length of the source argument" } */
+}
diff --git a/gcc/tree-ssa-strlen.c b/gcc/tree-ssa-strlen.c
index 72f6a17cd32..265f351ea85 100644
--- a/gcc/tree-ssa-strlen.c
+++ b/gcc/tree-ssa-strlen.c
@@ -2125,6 +2125,21 @@ handle_builtin_stxncpy (built_in_function,
gimple_stmt_iterator *gsi)
return;
}
+ /* Don't bother about the strlen (SRC) in the LEN computation if the range of
+ values for LEN ends up within dstsize. */
+ if (TREE_CODE (len) == SSA_NAME)
+ {
+ wide_int min, max;
+ enum value_range_type vr = get_range_info (len, &min, &max);
+ tree dstsize = compute_objsize (dst, 3);
+ if (vr == VR_RANGE && dstsize)
+ {
+ tree len_max = wide_int_to_tree (TREE_TYPE (dstsize), max);
+ if (tree_int_cst_lt (len_max, dstsize))
+ return;
+ }
+ }
+
/* Retrieve the strinfo data for the string S that LEN was computed
from as some function F of strlen (S) (i.e., LEN need not be equal
to strlen(S)). */
--
2.14.3
