Do not call strerror()

...because everything is terrible.

strerror() is not documented as having to be thread-safe by POSIX and
C11. (Which is pretty much bullshit, because both mandate threads and
some form of thread-local storage - so there's no excuse why
implementation couldn't implement this in a thread-safe way. Especially
with C11 this is ridiculous, because there is no way to use threads and
convert error numbers to strings at the same time!)

Since we heavily use threads now, we should avoid unsafe functions like
strerror().

strerror_r() is in POSIX, but GNU/glibc deliberately fucks it up and
gives the function different semantics than the POSIX one. It's a bit of
work to convince this piece of shit to expose the POSIX standard
function, and not the messed up GNU one.

strerror_l() is also in POSIX, but only since the 2008 standard, and
thus is not widespread.

The solution is using avlibc (libavutil, by its official name), which
handles the unportable details for us, mostly. We avoid some pain.

2 files changed, 12 insertions, 0 deletions

diff --git a/common/common.c b/common/common.c
index 449c95be26..4c1f9f327a 100644
--- a/common/common.c
+++ b/common/common.c
@@ -20,6 +20,7 @@
 #include <assert.h>
 
 #include <libavutil/common.h>
+#include <libavutil/error.h>
 
 #include "talloc.h"
 #include "misc/bstr.h"
@@ -243,3 +244,11 @@ bool mp_append_escaped_string(void *talloc_ctx, bstr *dst, bstr *src)
     }
     return false;
 }
+
+// Behaves like strerror()/strerror_r(), but is thread- and GNU-safe.
+char *mp_strerror_buf(char *buf, size_t buf_size, int errnum)
+{
+    // This handles the nasty details of calling the right function for us.
+    av_strerror(AVERROR(errnum), buf, buf_size);
+    return buf;
+}
diff --git a/common/common.h b/common/common.h
index 3e5ee1190f..e3411427a5 100644
--- a/common/common.h
+++ b/common/common.h
@@ -89,4 +89,7 @@ bool mp_append_escaped_string_noalloc(void *talloc_ctx, struct bstr *dst,
 bool mp_append_escaped_string(void *talloc_ctx, struct bstr *dst,
                               struct bstr *src);
 
+char *mp_strerror_buf(char *buf, size_t buf_size, int errnum);
+#define mp_strerror(e) mp_strerror_buf((char[80]){0}, 80, e)
+
 #endif /* MPLAYER_MPCOMMON_H */