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Subject[PATCH 1/2] tools/nolibc/string: do not use __builtin_strlen() at -O0
Date
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@1wt.eu>
---
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
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