Avoid issuing a bogus warning when the source of strncpy is bound by a
constant and is known to be less than the size of the destination.
Testsuite run is underway (not complete yet, but no new errors so far)
and a bootstrap is also underway, I'll report status once they're both
done.
gcc/
* 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 | 24 ++++++++++++++++++++++++
2 files changed, 41 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..49a31a551f5 100644
--- a/gcc/tree-ssa-strlen.c
+++ b/gcc/tree-ssa-strlen.c
@@ -2125,6 +2125,30 @@ handle_builtin_stxncpy (built_in_function,
gimple_stmt_iterator *gsi)
return;
}
+ /* When LEN is MIN_EXPR of strlen and a constant, then the copy is bound by
+ that constant. If the destination size is also constant then compare with
+ it to avoid a bogus warning. */
+ if (TREE_CODE (len) == SSA_NAME)
+ {
+ gimple *def_stmt = SSA_NAME_DEF_STMT (len);
+
+ if (is_gimple_assign (def_stmt)
+ && gimple_assign_rhs_code (def_stmt) == MIN_EXPR)
+ {
+ /* RHS1 is the strlen, so check if RHS2 and DSTSIZE are constant. */
+ tree rhs2 = gimple_assign_rhs2 (def_stmt);
+ tree dstsize = compute_objsize (dst, 1);
+
+ if (TREE_CODE (rhs2) == INTEGER_CST
+ && TREE_CODE (dstsize) == INTEGER_CST
+ && int_cst_value (rhs2) < int_cst_value (dstsize))
+ {
+ gimple_set_no_warning (stmt, true);
+ 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
