During porting libbpf to bcc, I got some warnings like below:
...
[ 2%] Building C object
src/cc/CMakeFiles/bpf-shared.dir/libbpf/src/libbpf.c.o
/home/yhs/work/bcc2/src/cc/libbpf/src/libbpf.c:12:0:
warning: "_GNU_SOURCE" redefined [enabled by default]
#define _GNU_SOURCE
...
[ 3%] Building C object
src/cc/CMakeFiles/bpf-shared.dir/libbpf/src/libbpf_errno.c.o
/home/yhs/work/bcc2/src/cc/libbpf/src/libbpf_errno.c: In function
‘libbpf_strerror’:
/home/yhs/work/bcc2/src/cc/libbpf/src/libbpf_errno.c:45:7:
warning: assignment makes integer from pointer without a cast [enabled by
default]
ret = strerror_r(err, buf, size);
...
bcc is built with _GNU_SOURCE defined and this caused the above warning.
This patch intends to make libpf _GNU_SOURCE friendly by
. define _GNU_SOURCE unless it is not defined
. gnu version strerror_r has different return value than non-gnu version,
so strerror_r return value is handled differently if _GNU_SOURCE is defined.
Signed-off-by: Yonghong Song <y...@fb.com>
---
tools/lib/bpf/libbpf.c | 2 ++
tools/lib/bpf/libbpf_errno.c | 10 ++++++++++
2 files changed, 12 insertions(+)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index ed4212a4c5f9..59b748ebd15f 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -9,7 +9,9 @@
* Copyright (C) 2017 Nicira, Inc.
*/
+#ifndef _GNU_SOURCE
#define _GNU_SOURCE
+#endif
#include <stdlib.h>
#include <stdio.h>
#include <stdarg.h>
diff --git a/tools/lib/bpf/libbpf_errno.c b/tools/lib/bpf/libbpf_errno.c
index d83b17f8435c..286e497c50ec 100644
--- a/tools/lib/bpf/libbpf_errno.c
+++ b/tools/lib/bpf/libbpf_errno.c
@@ -40,9 +40,19 @@ int libbpf_strerror(int err, char *buf, size_t size)
err = err > 0 ? err : -err;
if (err < __LIBBPF_ERRNO__START) {
+#ifdef _GNU_SOURCE
+ const char *ret_buf;
+#endif
int ret;
+#ifdef _GNU_SOURCE
+ ret_buf = strerror_r(err, buf, size);
+ if (ret_buf != buf)
+ snprintf(buf, size, "%s", ret_buf);
+ ret = 0;
+#else
ret = strerror_r(err, buf, size);
+#endif
buf[size - 1] = '\0';
return ret;
}
--
2.17.1
