osdep: add a pthread debugging wrapper

Because pthread failures are virtually undebuggable (which sure is
pretty strange, given all these heavy instrumentation tools these days).

Of course it affects only files which include osdep/threads.h.

I'm departing from the usual way to add symbols with config.h and using
"#if", and defining it on the compiler command line + "#ifdef" because I
don't want to include config.h from a header (which would be necessary
in this case) to keep things slightly cleaner. Maybe this is misguided,
but still.

This would have been easier if mpv defined its own wrappers for all
thread functions. But we don't (which to be honest is probably better
than e.g. going crazy like VLC and essentially reimplementing
everything). This seems to be a good compromise. Since it's off by
default and basically a developer tool, the minor undefined behavior
(redefining reserved symbols) isn't much of an issue.

1 files changed, 9 insertions, 0 deletions

diff --git a/wscript b/wscript
index a2451e8009..1dda323f67 100644
--- a/wscript
+++ b/wscript
@@ -206,6 +206,15 @@ main_dependencies = [
         'req': True,
         'fmsg': 'Unable to find pthreads support.'
     }, {
+        # NB: this works only if a source file includes osdep/threads.h
+        #     also, technically, triggers undefined behavior (reserved names)
+        'name': '--pthread-debug',
+        'desc': 'pthread runtime debugging wrappers',
+        'default': 'disable',
+        'func': check_cc(cflags='-DMP_PTHREAD_DEBUG'),
+        # The win32 wrapper defines pthreads symbols as macros only.
+        'deps_neg': 'win32-internal-pthreads',
+    }, {
         'name': '--stdatomic',
         'desc': 'C11 stdatomic.h',
         'func': check_libs(['atomic'],