[PATCH v2] libbpf: Add namespace for errstr making it libbpf_errstr

[Ian Rogers <irogers@google.com>]

When statically linking symbols can be replaced with those from other
statically linked libraries depending on the link order and the hoped
for "multiple definition" error may not appear. To avoid conflicts it
is good practice to namespace symbols, this change renames errstr to
libbpf_errstr. To avoid churn a #define is used to turn use of
errstr(err) to libbpf_errstr(err).

Fixes: 1633a83bf993 ("libbpf: Introduce errstr() for stringifying errno")
Signed-off-by: Ian Rogers <irogers@google.com>
---
v2: Use #define to avoid churn renaming errstr as suggested by Andrii
    Nakryiko <andrii@kernel.org>.

v1: I feel like this patch shouldn't be strictly necessary, it turned
    out for a use-case it was and people who know better than me say
    the linker is working as intended. The conflicting errstr was
    from: https://sourceforge.net/projects/linuxquota/ The fixes tag
    may not be strictly necessary.
---
 tools/lib/bpf/str_error.c | 2 +-
 tools/lib/bpf/str_error.h | 7 +++++--
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/tools/lib/bpf/str_error.c b/tools/lib/bpf/str_error.c
index 8743049e32b7..9a541762f54c 100644
--- a/tools/lib/bpf/str_error.c
+++ b/tools/lib/bpf/str_error.c
@@ -36,7 +36,7 @@ char *libbpf_strerror_r(int err, char *dst, int len)
 	return dst;
 }
 
-const char *errstr(int err)
+const char *libbpf_errstr(int err)
 {
 	static __thread char buf[12];
 
diff --git a/tools/lib/bpf/str_error.h b/tools/lib/bpf/str_error.h
index 66ffebde0684..53e7fbffc13e 100644
--- a/tools/lib/bpf/str_error.h
+++ b/tools/lib/bpf/str_error.h
@@ -7,10 +7,13 @@
 char *libbpf_strerror_r(int err, char *dst, int len);
 
 /**
- * @brief **errstr()** returns string corresponding to numeric errno
+ * @brief **libbpf_errstr()** returns string corresponding to numeric errno
  * @param err negative numeric errno
  * @return pointer to string representation of the errno, that is invalidated
  * upon the next call.
  */
-const char *errstr(int err);
+const char *libbpf_errstr(int err);
+
+#define errstr(err) libbpf_errstr(err)
+
 #endif /* __LIBBPF_STR_ERROR_H */
-- 
2.49.0.395.g12beb8f557-goog