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/libc/include/bits/fortify/string.h b/libc/include/bits/fortify/string.h
index 4d32b04..041967b 100644
--- a/libc/include/bits/fortify/string.h
+++ b/libc/include/bits/fortify/string.h
@@ -220,8 +220,13 @@
}
#if __BIONIC_FORTIFY_RUNTIME_CHECKS_ENABLED
-__BIONIC_FORTIFY_INLINE
-size_t strlen(const char* _Nonnull const s __pass_object_size0) __overloadable {
+/*
+ * Clang, when parsing C, can fold strlen to a constant without LLVM's help.
+ * This doesn't apply to overloads of strlen, so write this differently. We
+ * can't use `__pass_object_size0` here, but that's fine: it doesn't help much
+ * on __always_inline functions.
+ */
+extern __always_inline __inline__ __attribute__((gnu_inline)) size_t strlen(const char* _Nonnull s) {
return __strlen_chk(s, __bos0(s));
}
#endif