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Message-Id: <20220419004225.3952530-51-paulmck@kernel.org>
Date: Mon, 18 Apr 2022 17:42:15 -0700
From: "Paul E. McKenney" <paulmck@...nel.org>
To: linux-kernel@...r.kernel.org
Cc: gwml@...r.gnuweeb.org, kernel-team@...com, w@....eu,
Willy Tarreau <w@....eu>,
"Paul E . McKenney" <paulmck@...nel.org>
Subject: [PATCH nolibc 51/61] tools/nolibc/string: do not use __builtin_strlen() at -O0
From: Willy Tarreau <w@....eu>
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 <w@....eu>
Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
---
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)
--
2.31.1.189.g2e36527f23
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