Why does glibc disagree with the eventfd manpage?

man 2 eventfd says:

SYNOPSIS

   #include <sys/eventfd.h>

   int eventfd(unsigned int initval, int flags);

but in /usr/include/sys/eventfd.h I see:

extern int eventfd (int __count, int __flags) __THROW;

I hit this because I needed to pass eventfd as a function pointer and I got a warning when it had the signature described in the manpage. Is this signature non-portable? Do I need to be aware of this in code I write?

Solution

The signature in glibc was changed in 2014 with this commit to the glibc tree:

diff --git a/sysdeps/unix/sysv/linux/hppa/sys/eventfd.h b/sysdeps/unix/sysv/linux/hppa/sys/eventfd.h
index 2d198a8..a3c340e 100644 (file)
--- a/sysdeps/unix/sysv/linux/hppa/sys/eventfd.h
+++ b/sysdeps/unix/sysv/linux/hppa/sys/eventfd.h
@@ -40,7 +40,7 @@ __BEGIN_DECLS

 /* Return file descriptor for generic event channel.  Set initial
    value to COUNT.  */
-extern int eventfd (int __count, int __flags) __THROW;
+extern int eventfd (unsigned int __count, int __flags) __THROW;

 /* Read event counter and possibly wait for events.  */
 extern int eventfd_read (int __fd, eventfd_t *__value);

I suppose in terms of portability, then, if you have an old version of glibc, the best you can do is cast your pointer to eventfd to int (*f)(unsigned int, int).