linux-kernel - [PATCH 4.9 30/68] tools lib: Fix builds when glibc contains strlcpy()

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Message-Id: <20200203161909.959158906@linuxfoundation.org>
Date:   Mon,  3 Feb 2020 16:19:26 +0000
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Vitaly Chikunov <vt@...linux.org>,
        Dmitry Levin <ldv@...linux.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        kbuild test robot <lkp@...el.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Vineet Gupta <vineet.gupta1@...opsys.com>,
        Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: [PATCH 4.9 30/68] tools lib: Fix builds when glibc contains strlcpy()

From: Vitaly Chikunov <vt@...linux.org>

commit 6c4798d3f08b81c2c52936b10e0fa872590c96ae upstream.

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:

The

 #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__")
Resolves: https://bugzilla.kernel.org/show_bug.cgi?id=118481
Signed-off-by: Vitaly Chikunov <vt@...linux.org>
Reviewed-by: Dmitry Levin <ldv@...linux.org>
Cc: Dmitry Levin <ldv@...linux.org>
Cc: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: kbuild test robot <lkp@...el.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: stable@...r.kernel.org
Cc: Vineet Gupta <vineet.gupta1@...opsys.com>
Link: http://lore.kernel.org/lkml/20191224172029.19690-1-vt@altlinux.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 tools/include/linux/string.h |    8 ++++++++
 tools/lib/string.c           |    7 +++++++
 2 files changed, 15 insertions(+)

--- a/tools/include/linux/string.h
+++ b/tools/include/linux/string.h
@@ -13,7 +13,15 @@ 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"
+#endif
 extern size_t strlcpy(char *dest, const char *src, size_t size);
+#if __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 6)
+#pragma GCC diagnostic pop
+#endif
 #endif
 
 char *str_error_r(int errnum, char *buf, size_t buflen);
--- a/tools/lib/string.c
+++ b/tools/lib/string.c
@@ -76,6 +76,10 @@ 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"
+#endif
 size_t __weak strlcpy(char *dest, const char *src, size_t size)
 {
 	size_t ret = strlen(src);
@@ -87,3 +91,6 @@ size_t __weak strlcpy(char *dest, const
 	}
 	return ret;
 }
+#ifdef __clang__
+#pragma clang diagnostic pop
+#endif