fortify: rewrite strlen to fold to a constant
This new spelling allows Clang, when parsing C, to fold `strlen("foo")`
into a constant in many more places.
This shouldn't be much of a performance diff, since LLVM is already
fully capable of folding `@__strlen_chk` into `@strlen` or a constant as
appropriate. Mostly it matters for places where constants may be
required, or may result in materially different codegen (e.g., static
initializers, array bounds, ...)
Bug: 139143453
Test: mma
Change-Id: Ib1636402a11338f6e05a731cc5a59c919cca09e8
diff --git a/tests/clang_fortify_c_only_tests.c b/tests/clang_fortify_c_only_tests.c
new file mode 100644
index 0000000..3bec848
--- /dev/null
+++ b/tests/clang_fortify_c_only_tests.c
@@ -0,0 +1,38 @@
+/*
+ * Copyright (C) 2024 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * * Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in
+ * the documentation and/or other materials provided with the
+ * distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <string.h>
+
+// This is a test specifically of bionic's FORTIFY machinery. Other stdlibs need not apply.
+#ifdef __BIONIC__
+
+// Ensure that strlen can be evaluated at compile-time. Clang doesn't support
+// this in C++, but does in C.
+_Static_assert(strlen("foo") == 3, "");
+
+#endif // __BIONIC__