mkfifoat: Work around a Haiku bug

[Bruno Haible]

On Haiku, I'm seeing this test failure:

  FAIL: test-mkfifoat
  ===================

  ../../gltests/test-mkfifo.h:36: assertion 'result == 0' failed
  Abort
  FAIL test-mkfifoat (exit status: 149)

This patch fixes that failure. The test still later fails, but in a less
important way.

If more platforms are affected, we should consider to adapt the autoconf
test from m4/mknod.m4 to m4/mkfifoat.m4. I haven't done this yet.


2024-08-30  Bruno Haible  <bruno@clisp.org>

        mkfifoat: Work around a Haiku bug.
        * lib/mknodat.c (rpl_mknodat): On Haiku, handle S_IFIFO explicitly.
        * doc/posix-functions/mknodat.texi: Mention the S_IFIFO flag bug.

diff --git a/doc/posix-functions/mknodat.texi b/doc/posix-functions/mknodat.texi
index 53f695db68..a837f89b53 100644
--- a/doc/posix-functions/mknodat.texi
+++ b/doc/posix-functions/mknodat.texi
@@ -16,6 +16,10 @@
 This function does not fail when the file name argument ends in a slash
 and (without the slash) names a nonexistent file, on some platforms:
 AIX 7.2.
+@item
+This function does not handle the @code{S_IFIFO} flag on some platforms:
+@c https://dev.haiku-os.org/ticket/19032
+Haiku.
 @end itemize
 
 Portability problems not fixed by Gnulib:
diff --git a/lib/mknodat.c b/lib/mknodat.c
index 66d5b3566f..a31450abab 100644
--- a/lib/mknodat.c
+++ b/lib/mknodat.c
@@ -54,6 +54,12 @@ rpl_mknodat (int fd, char const *file, mode_t mode, dev_t 
dev)
       return -1;
     }
 
+# if defined __HAIKU__
+  /* POSIX requires mknodat to create fifos for non-privileged processes, but
+     on Haiku it fails with ENOTSUP.  */
+  if (S_ISFIFO (mode) && dev == 0)
+    return mkfifo (file, mode & ~S_IFIFO);
+# endif
   return mknodat (fd, file, mode, dev);
 }