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Subject[tip: perf/core] tools lib: Fix builds when glibc contains strlcpy()
The following commit has been merged into the perf/core branch of tip:

Commit-ID: 6c4798d3f08b81c2c52936b10e0fa872590c96ae
Author: Vitaly Chikunov <>
AuthorDate: Tue, 24 Dec 2019 20:20:29 +03:00
Committer: Arnaldo Carvalho de Melo <>
CommitterDate: Mon, 06 Jan 2020 11:46:10 -03:00

tools lib: Fix builds when glibc contains strlcpy()

Disable a couple of compilation warnings (which are treated as errors)
on strlcpy() definition and declaration, allowing users to compile perf
and kernel (objtool) when:

1. glibc have strlcpy() (such as in ALT Linux since 2004) objtool and
perf build fails with this (in gcc):

In file included from exec-cmd.c:3:
tools/include/linux/string.h:20:15: error: redundant redeclaration of ‘strlcpy’ [-Werror=redundant-decls]
20 | extern size_t strlcpy(char *dest, const char *src, size_t size);

2. clang ignores `-Wredundant-decls', but produces another warning when
building perf:

CC util/string.o
../lib/string.c:99:8: error: attribute declaration must precede definition [-Werror,-Wignored-attributes]
size_t __weak strlcpy(char *dest, const char *src, size_t size)
../../tools/include/linux/compiler.h:66:34: note: expanded from macro '__weak'
# define __weak __attribute__((weak))
/usr/include/bits/string_fortified.h:151:8: note: previous definition is here
__NTH (strlcpy (char *__restrict __dest, const char *__restrict __src,

Committer notes:


#pragma GCC diagnostic

directive was introduced in gcc 4.6, so check for that as well.

Fixes: ce99091 ("perf tools: Move strlcpy() from perf to tools/lib/string.c")
Fixes: 0215d59 ("tools lib: Reinstate strlcpy() header guard with __UCLIBC__")
Signed-off-by: Vitaly Chikunov <>
Reviewed-by: Dmitry Levin <>
Cc: Dmitry Levin <>
Cc: Josh Poimboeuf <>
Cc: kbuild test robot <>
Cc: Peter Zijlstra <>
Cc: Vineet Gupta <>
Signed-off-by: Arnaldo Carvalho de Melo <>
tools/include/linux/string.h | 8 ++++++++
tools/lib/string.c | 7 +++++++
2 files changed, 15 insertions(+)

diff --git a/tools/include/linux/string.h b/tools/include/linux/string.h
index 980cb92..5e9e781 100644
--- a/tools/include/linux/string.h
+++ b/tools/include/linux/string.h
@@ -17,7 +17,15 @@ int strtobool(const char *s, bool *res);
* However uClibc headers also define __GLIBC__ hence the hack below
#if defined(__GLIBC__) && !defined(__UCLIBC__)
+// pragma diagnostic was introduced in gcc 4.6
+#if __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 6)
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wredundant-decls"
extern size_t strlcpy(char *dest, const char *src, size_t size);
+#if __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 6)
+#pragma GCC diagnostic pop

char *str_error_r(int errnum, char *buf, size_t buflen);
diff --git a/tools/lib/string.c b/tools/lib/string.c
index f2ae1b8..f645343 100644
--- a/tools/lib/string.c
+++ b/tools/lib/string.c
@@ -96,6 +96,10 @@ int strtobool(const char *s, bool *res)
* If libc has strlcpy() then that version will override this
* implementation:
+#ifdef __clang__
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wignored-attributes"
size_t __weak strlcpy(char *dest, const char *src, size_t size)
size_t ret = strlen(src);
@@ -107,6 +111,9 @@ size_t __weak strlcpy(char *dest, const char *src, size_t size)
return ret;
+#ifdef __clang__
+#pragma clang diagnostic pop

* skip_spaces - Removes leading whitespace from @str.
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