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From: Willy Tarreau <[email protected]>
To: "Paul E . McKenney" <[email protected]>
Cc: [email protected], [email protected],
	Ammar Faizi <[email protected]>
Subject: [PATCH 1/2] tools/nolibc/string: do not use __builtin_strlen() at -O0
Date: Wed, 23 Mar 2022 08:18:06 +0100	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

clang wants to use strlen() for __builtin_strlen() at -O0. We don't
really care about -O0 but it at least ought to build, so let's make
sure we don't choke on this, by dropping the optimizationn for
constant strings in this case.

Signed-off-by: Willy Tarreau <[email protected]>
---
 tools/include/nolibc/string.h | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/tools/include/nolibc/string.h b/tools/include/nolibc/string.h
index 0d5e870c7c0b..75a453870498 100644
--- a/tools/include/nolibc/string.h
+++ b/tools/include/nolibc/string.h
@@ -122,7 +122,9 @@ char *strcpy(char *dst, const char *src)
 	return ret;
 }
 
-/* this function is only used with arguments that are not constants */
+/* this function is only used with arguments that are not constants or when
+ * it's not known because optimizations are disabled.
+ */
 static __attribute__((unused))
 size_t nolibc_strlen(const char *str)
 {
@@ -132,11 +134,18 @@ size_t nolibc_strlen(const char *str)
 	return len;
 }
 
+/* do not trust __builtin_constant_p() at -O0, as clang will emit a test and
+ * the two branches, then will rely on an external definition of strlen().
+ */
+#if defined(__OPTIMIZE__)
 #define strlen(str) ({                          \
 	__builtin_constant_p((str)) ?           \
 		__builtin_strlen((str)) :       \
 		nolibc_strlen((str));           \
 })
+#else
+#define strlen(str) nolibc_strlen((str))
+#endif
 
 static __attribute__((unused))
 size_t strlcat(char *dst, const char *src, size_t size)
-- 
2.35.1



  reply	other threads:[~2022-03-23  7:18 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-03-23  7:18 [PATCH 0/2] nolibc: fix two build issues at -O0 Willy Tarreau
2022-03-23  7:18 ` Willy Tarreau [this message]
2022-03-23  7:18 ` [PATCH 2/2] tools/nolibc/stdlib: only reference the external environ when inlined Willy Tarreau
2022-03-23 13:36   ` Ammar Faizi
2022-03-23 23:16 ` [PATCH 0/2] nolibc: fix two build issues at -O0 Paul E. McKenney

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