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[gnulib.git] / m4 / fflush.m4

diff --git a/m4/fflush.m4 b/m4/fflush.m4
old mode 100755 (executable)
new mode 100644 (file)
index a9889d4..97f1284
--- a/m4/fflush.m4
+++ b/m4/fflush.m4
@@ -1,6 +1,6 @@
-#serial 1
+# fflush.m4 serial 6
 
-# Copyright (C) 2007 Free Software Foundation, Inc.
+# Copyright (C) 2007-2008 Free Software Foundation, Inc.
 # This file is free software; the Free Software Foundation
 # gives unlimited permission to copy and/or distribute it,
 # with or without modifications, as long as this notice is preserved.
@@ -8,8 +8,7 @@
 dnl From Eric Blake
 
 dnl Find out how to obey POSIX semantics of fflush(stdin) discarding
-dnl unread input, rather than C99 undefined semantics.  fpurge is not
-dnl standardized, but has the desired properties.
+dnl unread input on seekable streams, rather than C99 undefined semantics.
 
 AC_DEFUN([gl_FUNC_FFLUSH],
 [
@@ -21,9 +20,12 @@ AC_DEFUN([gl_FUNC_FFLUSH],
 #include <stdio.h>
 #include <unistd.h>
        ]], [[FILE *f = fopen ("conftest.txt", "r");
-         char buffer[10];
-        int fd = fileno (f);
-         if (!f || 0 > fd || fread (buffer, 1, 5, f) != 5)
+        char buffer[10];
+        int fd;
+        if (f == NULL)
+          return 1;
+        fd = fileno (f);
+        if (fd < 0 || fread (buffer, 1, 5, f) != 5)
           return 2;
         /* For deterministic results, ensure f read a bigger buffer.  */
         if (lseek (fd, 0, SEEK_CUR) == 5)
@@ -31,7 +33,11 @@ AC_DEFUN([gl_FUNC_FFLUSH],
         /* POSIX requires fflush-fseek to set file offset of fd.  */
         if (fflush (f) != 0 || fseek (f, 0, SEEK_CUR) != 0)
           return 4;
-        return !(lseek (fd, 0, SEEK_CUR) == 5);
+        if (lseek (fd, 0, SEEK_CUR) != 5)
+          return 5;
+        /* TODO: Verify behaviour of fflush after ungetc, see
+           <http://lists.gnu.org/archive/html/bug-gnulib/2008-03/msg00131.html>.  */
+        return 0;
        ]])], [gl_cv_func_fflush_stdin=yes], [gl_cv_func_fflush_stdin=no],
      [dnl Pessimistically assume fflush is broken.  This is wrong for
       dnl at least glibc and cygwin; but lib/fflush.c takes this into account.
@@ -45,16 +51,17 @@ AC_DEFUN([gl_FUNC_FFLUSH],
 
 AC_DEFUN([gl_REPLACE_FFLUSH],
 [
-  AC_CHECK_HEADERS_ONCE([stdio_ext.h])
-  AC_CHECK_FUNCS_ONCE([fpurge __fpurge])
-dnl Linux documents int fpurge(), but only declares void __fpurge().
-  AC_CHECK_DECLS([fpurge], [], [], [[
-#include <stdio.h>
-#if HAVE_STDIO_EXT_H
-# include <stdio_ext.h>
-#endif
-]])
   AC_LIBOBJ([fflush])
+  AC_LIBOBJ([fseeko])
   AC_REQUIRE([gl_STDIO_H_DEFAULTS])
   REPLACE_FFLUSH=1
+  REPLACE_FSEEKO=1
+  gl_PREREQ_FFLUSH
+])
+
+# Prerequisites of lib/fflush.c.
+AC_DEFUN([gl_PREREQ_FFLUSH],
+[
+  AC_REQUIRE([AC_C_INLINE])
+  :
 ])