1 files changed, 31 insertions, 1 deletions
diff --git a/lib/fpending.c b/lib/fpending.c
index a503b9f53ae..ce93604e518 100644
--- a/lib/fpending.c
+++ b/lib/fpending.c
@@ -19,12 +19,42 @@
 
 #include <config.h>
 
+/* Specification.  */
 #include "fpending.h"
 
+#include "stdio-impl.h"
+
 /* Return the number of pending (aka buffered, unflushed)
    bytes on the stream, FP, that is open for writing.  */
 size_t
 __fpending (FILE *fp)
 {
-  return PENDING_OUTPUT_N_BYTES;
+  /* Most systems provide FILE as a struct and the necessary bitmask in
+     <stdio.h>, because they need it for implementing getc() and putc() as
+     fast macros.  */
+#if defined _IO_ftrylockfile || __GNU_LIBRARY__ == 1 /* GNU libc, BeOS, Haiku, Linux libc5 */
+  return fp->_IO_write_ptr - fp->_IO_write_base;
+#elif defined __sferror || defined __DragonFly__ || defined __ANDROID__
+  /* FreeBSD, NetBSD, OpenBSD, DragonFly, Mac OS X, Cygwin, Android */
+  return fp->_p - fp->_bf._base;
+#elif defined __EMX__                /* emx+gcc */
+  return fp->_ptr - fp->_buffer;
+#elif defined __minix                /* Minix */
+  return fp_->_ptr - fp_->_buf;
+#elif defined _IOERR                 /* AIX, HP-UX, IRIX, OSF/1, Solaris, OpenServer, mingw, MSVC, NonStop Kernel */
+  return (fp_->_ptr ? fp_->_ptr - fp_->_base : 0);
+#elif defined __UCLIBC__             /* uClibc */
+  return (fp->__modeflags & __FLAG_WRITING ? fp->__bufpos - fp->__bufstart : 0);
+#elif defined __QNX__                /* QNX */
+  return (fp->_Mode & 0x2000 /*_MWRITE*/ ? fp->_Next - fp->_Buf : 0);
+#elif defined __MINT__               /* Atari FreeMiNT */
+  return fp->__bufp - fp->__buffer;
+#elif defined EPLAN9                 /* Plan9 */
+  return fp->wp - fp->buf;
+#elif defined __VMS                  /* VMS */
+  return (*fp)->_ptr - (*fp)->_base;
+#else
+# error "Please port gnulib fpending.c to your platform!"
+  return 1;
+#endif
 }