document mingw linker fix and close associated bug

[debian/gzip] / m4 / fflush.m4

diff --git a/m4/fflush.m4 b/m4/fflush.m4
index 56c0aedc8920ecd012c5266aa7acb3c438ce6825..9098b100a5121fec831a5bd504b9199fd2b73064 100644 (file)
--- a/m4/fflush.m4
+++ b/m4/fflush.m4
@@ -1,6 +1,6 @@
-# fflush.m4 serial 7
+# fflush.m4 serial 17
 
-# Copyright (C) 2007-2010 Free Software Foundation, Inc.
+# Copyright (C) 2007-2018 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.
@@ -12,13 +12,32 @@ dnl unread input on seekable streams, rather than C99 undefined semantics.
 
 AC_DEFUN([gl_FUNC_FFLUSH],
 [
+  AC_REQUIRE([gl_STDIO_H_DEFAULTS])
+  gl_FUNC_FFLUSH_STDIN
+  case "$gl_cv_func_fflush_stdin" in
+    *yes) ;;
+    *) REPLACE_FFLUSH=1 ;;
+  esac
+])
+
+dnl Determine whether fflush works on input streams.
+dnl Sets gl_cv_func_fflush_stdin.
+
+AC_DEFUN([gl_FUNC_FFLUSH_STDIN],
+[
+  AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
+  AC_CHECK_HEADERS_ONCE([unistd.h])
   AC_CACHE_CHECK([whether fflush works on input streams],
     [gl_cv_func_fflush_stdin],
     [echo hello world > conftest.txt
      AC_RUN_IFELSE([AC_LANG_PROGRAM(
        [[
 #include <stdio.h>
-#include <unistd.h>
+#if HAVE_UNISTD_H
+# include <unistd.h>
+#else /* on Windows with MSVC */
+# include <io.h>
+#endif
        ]], [[FILE *f = fopen ("conftest.txt", "r");
          char buffer[10];
          int fd;
@@ -27,16 +46,16 @@ AC_DEFUN([gl_FUNC_FFLUSH],
            return 1;
          fd = fileno (f);
          if (fd < 0 || fread (buffer, 1, 5, f) != 5)
-           return 2;
+           { fclose (f); return 2; }
          /* For deterministic results, ensure f read a bigger buffer.  */
          if (lseek (fd, 0, SEEK_CUR) == 5)
-           return 3;
+           { fclose (f); return 3; }
          /* POSIX requires fflush-fseek to set file offset of fd.  This fails
             on BSD systems and on mingw.  */
          if (fflush (f) != 0 || fseek (f, 0, SEEK_CUR) != 0)
-           return 4;
+           { fclose (f); return 4; }
          if (lseek (fd, 0, SEEK_CUR) != 5)
-           return 5;
+           { fclose (f); return 5; }
          /* Verify behaviour of fflush after ungetc. See
             <http://www.opengroup.org/austin/aardvark/latest/xshbug3.txt>  */
          /* Verify behaviour of fflush after a backup ungetc.  This fails on
@@ -45,38 +64,36 @@ AC_DEFUN([gl_FUNC_FFLUSH],
          ungetc (c, f);
          fflush (f);
          if (fgetc (f) != c)
-           return 6;
+           { fclose (f); return 6; }
          /* Verify behaviour of fflush after a non-backup ungetc.  This fails
             on glibc 2.8 and on BSD systems.  */
          c = fgetc (f);
          ungetc ('@', f);
          fflush (f);
          if (fgetc (f) != c)
-           return 7;
+           { fclose (f); return 7; }
+         fclose (f);
          return 0;
-       ]])], [gl_cv_func_fflush_stdin=yes], [gl_cv_func_fflush_stdin=no],
-     [dnl Pessimistically assume fflush is broken.
-      gl_cv_func_fflush_stdin=no])
+       ]])],
+       [gl_cv_func_fflush_stdin=yes],
+       [gl_cv_func_fflush_stdin=no],
+       [case "$host_os" in
+                  # Guess no on native Windows.
+          mingw*) gl_cv_func_fflush_stdin="guessing no" ;;
+          *)      gl_cv_func_fflush_stdin=cross ;;
+        esac
+       ])
      rm conftest.txt
     ])
-  if test $gl_cv_func_fflush_stdin = no; then
-    gl_REPLACE_FFLUSH
-  fi
-])
-
-AC_DEFUN([gl_REPLACE_FFLUSH],
-[
-  AC_LIBOBJ([fflush])
-  AC_LIBOBJ([fseeko])
-  AC_REQUIRE([gl_STDIO_H_DEFAULTS])
-  REPLACE_FFLUSH=1
-  REPLACE_FSEEKO=1
-  gl_PREREQ_FFLUSH
+  case "$gl_cv_func_fflush_stdin" in
+    *yes) gl_func_fflush_stdin=1 ;;
+    *no)  gl_func_fflush_stdin=0 ;;
+    *)    gl_func_fflush_stdin='(-1)' ;;
+  esac
+  AC_DEFINE_UNQUOTED([FUNC_FFLUSH_STDIN], [$gl_func_fflush_stdin],
+    [Define to 1 if fflush is known to work on stdin as per POSIX.1-2008,
+     0 if fflush is known to not work, -1 if unknown.])
 ])
 
 # Prerequisites of lib/fflush.c.
-AC_DEFUN([gl_PREREQ_FFLUSH],
-[
-  AC_REQUIRE([AC_C_INLINE])
-  :
-])
+AC_DEFUN([gl_PREREQ_FFLUSH], [:])