closein: correct comments

[gnulib.git] / m4 / ftruncate.m4

diff --git a/m4/ftruncate.m4 b/m4/ftruncate.m4
index 473fde2..c3c3342 100644 (file)
--- a/m4/ftruncate.m4
+++ b/m4/ftruncate.m4
@@ -1,27 +1,46 @@
-#serial 2
+# serial 16
 
-# See if we need to emulate a missing ftruncate function using fcntl.
+# See if we need to emulate a missing ftruncate function using fcntl or chsize.
 
-AC_DEFUN(jm_FUNC_FTRUNCATE,
-[
-  AC_CHECK_FUNCS(ftruncate, , [ftruncate_missing=yes])
+# Copyright (C) 2000-2001, 2003-2007, 2009-2011 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.
+
+# FIXME: remove this macro, along with all uses of HAVE_FTRUNCATE in 2012,
+# if the check below provokes no more reports.  So far, the only report
+# arose from a test build of this gnulib module, cross-compiling to mingw:
+# <http://thread.gmane.org/gmane.comp.lib.gnulib.bugs/9203>
+# Now (in 2010), MSVC has been raised as a possible target:
+# <http://thread.gmane.org/gmane.comp.lib.gnulib.bugs/21394/focus=21396>
 
-  if test "$ftruncate_missing" = yes; then
-    AC_CHECK_HEADERS(unistd.h)
-    AC_MSG_CHECKING([fcntl emulation of ftruncate])
-    AC_CACHE_VAL(fu_cv_sys_ftruncate_emulation,
-    [AC_TRY_LINK([
-#include <sys/types.h>
-#include <fcntl.h>], [
-#if !defined(F_CHSIZE) && !defined(F_FREESP)
-  chsize();
-#endif
-  ],
-      fu_cv_sys_ftruncate_emulation=yes,
-      fu_cv_sys_ftruncate_emulation=no)])
-    AC_MSG_RESULT($fu_cv_sys_ftruncate_emulation)
-    if test $fu_cv_sys_ftruncate_emulation = yes; then
-      AC_LIBOBJ([ftruncate])
-    fi
+AC_DEFUN([gl_FUNC_FTRUNCATE],
+[
+  AC_REQUIRE([gl_UNISTD_H_DEFAULTS])
+  AC_REQUIRE([AC_CANONICAL_HOST])
+  AC_CHECK_FUNCS_ONCE([ftruncate])
+  if test $ac_cv_func_ftruncate = no; then
+    HAVE_FTRUNCATE=0
+    case "$host_os" in
+      mingw*)
+        # Yes, we know mingw lacks ftruncate.
+        ;;
+      *)
+        # If someone lacks ftruncate, make configure fail, and request
+        # a bug report to inform us about it.
+        if test x"$SKIP_FTRUNCATE_CHECK" != xyes; then
+          AC_MSG_FAILURE([Your system lacks the ftruncate function.
+              Please report this, along with the output of "uname -a", to the
+              bug-coreutils@gnu.org mailing list.  To continue past this point,
+              rerun configure with SKIP_FTRUNCATE_CHECK=yes.
+              E.g., ./configure SKIP_FTRUNCATE_CHECK=yes])
+        fi
+    esac
   fi
 ])
+
+# Prerequisites of lib/ftruncate.c.
+AC_DEFUN([gl_PREREQ_FTRUNCATE],
+[
+  AC_CHECK_FUNCS([chsize])
+])