Work around fpurge bug on BSD systems.

1 files changed, 44 insertions, 10 deletions

diff --git a/lib/fpurge.c b/lib/fpurge.c
index 863f8536ba..e5d673ae96 100644
--- a/lib/fpurge.c
+++ b/lib/fpurge.c
@@ -20,15 +20,47 @@
 /* Specification.  */
 #include "fpurge.h"
 
+#if HAVE___FPURGE                   /* glibc >= 2.2, Solaris >= 7 */
+# include <stdio_ext.h>
+#endif
 #include <stdlib.h>
 
 int
 fpurge (FILE *fp)
 {
+#if HAVE___FPURGE                   /* glibc >= 2.2, Solaris >= 7 */
+
+  __fpurge (fp);
+  /* The __fpurge function does not have a return value.  */
+  return 0;
+
+#elif HAVE_FPURGE                   /* FreeBSD, NetBSD, OpenBSD, MacOS X */
+
+  /* Call the system's fpurge function.  */
+# undef fpurge
+# if !HAVE_DECL_FPURGE
+  extern int fpurge (FILE *);
+# endif
+  int result = fpurge (fp);
+# if defined __sferror              /* FreeBSD, NetBSD, OpenBSD, MacOS X, Cygwin */
+  if (result == 0)
+    /* Correct the invariants that fpurge broke.
+       <stdio.h> on BSD systems says:
+         "The following always hold: if _flags & __SRD, _w is 0."
+       If this invariant is not fulfilled and the stream is read-write but
+       currently writing, subsequent putc or fputc calls will write directly
+       into the buffer, although they shouldn't be allowed to.  */
+    if ((fp->_flags & __SRD) != 0)
+      fp->_w = 0;
+# endif
+  return result;
+
+#else
+
   /* 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_ferror_unlocked     /* GNU libc, BeOS */
+# if defined _IO_ferror_unlocked    /* GNU libc, BeOS */
   fp->_IO_read_end = fp->_IO_read_ptr;
   fp->_IO_write_ptr = fp->_IO_write_base;
   /* Avoid memory leak when there is an active ungetc buffer.  */
@@ -38,20 +70,20 @@ fpurge (FILE *fp)
       fp->_IO_save_base = NULL;
     }
   return 0;
-#elif defined __sferror             /* FreeBSD, NetBSD, OpenBSD, MacOS X, Cygwin */
+# elif defined __sferror            /* FreeBSD, NetBSD, OpenBSD, MacOS X, Cygwin */
   fp->_p = fp->_bf._base;
   fp->_r = 0;
-  fp->_w = ((fp->_flags & (__SLBF | __SNBF)) == 0 /* fully buffered? */
+  fp->_w = ((fp->_flags & (__SLBF | __SNBF | __SRD)) == 0 /* fully buffered and not currently reading? */
 	    ? fp->_bf._size
 	    : 0);
   /* Avoid memory leak when there is an active ungetc buffer.  */
-# if defined __NetBSD__ || defined __OpenBSD__ /* NetBSD, OpenBSD */
+#  if defined __NetBSD__ || defined __OpenBSD__ /* NetBSD, OpenBSD */
    /* See <http://cvsweb.netbsd.org/bsdweb.cgi/src/lib/libc/stdio/fileext.h?rev=HEAD&content-type=text/x-cvsweb-markup>
       and <http://www.openbsd.org/cgi-bin/cvsweb/src/lib/libc/stdio/fileext.h?rev=HEAD&content-type=text/x-cvsweb-markup> */
-#  define fp_ub ((struct { struct __sbuf _ub; } *) fp->_ext._base)->_ub
-# else                                         /* FreeBSD, MacOS X, Cygwin */
-#  define fp_ub fp->_ub
-# endif
+#   define fp_ub ((struct { struct __sbuf _ub; } *) fp->_ext._base)->_ub
+#  else                                         /* FreeBSD, MacOS X, Cygwin */
+#   define fp_ub fp->_ub
+#  endif
   if (fp_ub._base != NULL)
     {
       if (fp_ub._base != fp->_ubuf)
@@ -59,12 +91,14 @@ fpurge (FILE *fp)
       fp_ub._base = NULL;
     }
   return 0;
-#elif defined _IOERR                /* AIX, HP-UX, IRIX, OSF/1, Solaris, mingw */
+# elif defined _IOERR               /* AIX, HP-UX, IRIX, OSF/1, Solaris, mingw */
   fp->_ptr = fp->_base;
   if (fp->_ptr != NULL)
     fp->_cnt = 0;
   return 0;
-#else
+# else
  #error "Please port gnulib fpurge.c to your platform! Look at the definitions of fflush, setvbuf and ungetc on your system, then report this to bug-gnulib."
+# endif
+
 #endif
 }