fflush, fseeko: port to musl cross-compiles

* lib/fseeko.c (fseeko): Assume that fflushing stdin works if
on some implementation that (1) is not known to be buggy,
(2) claims conformance to POSIX.1-2008 or later, and (3) is being
cross-compiled to so we can't easily check for lack of
conformance.  This is for cross-compiling to musl.
Reported by Rich Felker in
<http://lists.gnu.org/archive/html/bug-gnulib/2013-06/msg00043.html>.
* m4/fclose.m4 (gl_FUNC_FCLOSE):
* m4/fflush.m4 (gl_FUNC_FFLUSH):
* m4/fseeko.m4 (gl_FUNC_FSEEKO):
Adjust to above change.
* m4/fflush.m4 (gl_FUNC_FFLUSH_STDIN): Set gl_cv_func_fflush_stdin
to 'cross', not to 'no', when cross-compiling.  AC_DEFINE
FUNC_FFLUSH_STDIN to 1, 0, -1 if fflushing stdin is known to work,
known not to work, or unknown.

5 files changed, 42 insertions, 10 deletions

diff --git a/ChangeLog b/ChangeLog
index 3c3794fb2f..09e36b0e1e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,22 @@
+2013-06-18  Paul Eggert  <eggert@cs.ucla.edu>
+
+	fflush, fseeko: port to musl cross-compiles
+	* lib/fseeko.c (fseeko): Assume that fflushing stdin works if
+	on some implementation that (1) is not known to be buggy,
+	(2) claims conformance to POSIX.1-2008 or later, and (3) is being
+	cross-compiled to so we can't easily check for lack of
+	conformance.  This is for cross-compiling to musl.
+	Reported by Rich Felker in
+	<http://lists.gnu.org/archive/html/bug-gnulib/2013-06/msg00043.html>.
+	* m4/fclose.m4 (gl_FUNC_FCLOSE):
+	* m4/fflush.m4 (gl_FUNC_FFLUSH):
+	* m4/fseeko.m4 (gl_FUNC_FSEEKO):
+	Adjust to above change.
+	* m4/fflush.m4 (gl_FUNC_FFLUSH_STDIN): Set gl_cv_func_fflush_stdin
+	to 'cross', not to 'no', when cross-compiling.  AC_DEFINE
+	FUNC_FFLUSH_STDIN to 1, 0, -1 if fflushing stdin is known to work,
+	known not to work, or unknown.
+
 2013-06-15  Paul Eggert  <eggert@cs.ucla.edu>
 
 	msvc-inval: port to mingw-w64
diff --git a/lib/fseeko.c b/lib/fseeko.c
index a625803b95..ec5a6aacdd 100644
--- a/lib/fseeko.c
+++ b/lib/fseeko.c
@@ -19,7 +19,7 @@
 /* Specification.  */
 #include <stdio.h>
 
-/* Get off_t and lseek.  */
+/* Get off_t, lseek, _POSIX_VERSION.  */
 #include <unistd.h>
 
 #include "stdio-impl.h"
@@ -99,8 +99,14 @@ fseeko (FILE *fp, off_t offset, int whence)
 #elif defined EPLAN9                /* Plan9 */
   if (fp->rp == fp->buf
       && fp->wp == fp->buf)
+#elif FUNC_FFLUSH_STDIN < 0 && 200809 <= _POSIX_VERSION
+  /* Cross-compiling to some other system advertising conformance to
+     POSIX.1-2008 or later.  Assume fseeko and fflush work as advertised.
+     If this assumption is incorrect, please report the bug to
+     bug-gnulib.  */
+  if (0)
 #else
-  #error "Please port gnulib fseeko.c to your platform! Look at the code in fpurge.c, then report this to bug-gnulib."
+  #error "Please port gnulib fseeko.c to your platform! Look at the code in fseeko.c, then report this to bug-gnulib."
 #endif
     {
       /* We get here when an fflush() call immediately preceded this one (or
diff --git a/m4/fclose.m4 b/m4/fclose.m4
index 2cc2e12936..b306b6d48a 100644
--- a/m4/fclose.m4
+++ b/m4/fclose.m4
@@ -1,4 +1,4 @@
-# fclose.m4 serial 5
+# fclose.m4 serial 6
 dnl Copyright (C) 2008-2013 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -9,7 +9,7 @@ AC_DEFUN([gl_FUNC_FCLOSE],
   AC_REQUIRE([gl_STDIO_H_DEFAULTS])
 
   gl_FUNC_FFLUSH_STDIN
-  if test $gl_cv_func_fflush_stdin = no; then
+  if test $gl_cv_func_fflush_stdin != yes; then
     REPLACE_FCLOSE=1
   fi
 
diff --git a/m4/fflush.m4 b/m4/fflush.m4
index 6df5173681..c16b314e3c 100644
--- a/m4/fflush.m4
+++ b/m4/fflush.m4
@@ -1,4 +1,4 @@
-# fflush.m4 serial 14
+# fflush.m4 serial 15
 
 # Copyright (C) 2007-2013 Free Software Foundation, Inc.
 # This file is free software; the Free Software Foundation
@@ -14,7 +14,7 @@ AC_DEFUN([gl_FUNC_FFLUSH],
 [
   AC_REQUIRE([gl_STDIO_H_DEFAULTS])
   gl_FUNC_FFLUSH_STDIN
-  if test $gl_cv_func_fflush_stdin = no; then
+  if test $gl_cv_func_fflush_stdin != yes; then
     REPLACE_FFLUSH=1
   fi
 ])
@@ -72,10 +72,17 @@ AC_DEFUN([gl_FUNC_FFLUSH_STDIN],
            return 7;
          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=cross])
      rm conftest.txt
     ])
+  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.
diff --git a/m4/fseeko.m4 b/m4/fseeko.m4
index e0f2dfbe1f..ca9da2835d 100644
--- a/m4/fseeko.m4
+++ b/m4/fseeko.m4
@@ -1,4 +1,4 @@
-# fseeko.m4 serial 16
+# fseeko.m4 serial 17
 dnl Copyright (C) 2007-2013 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -37,7 +37,7 @@ AC_DEFUN([gl_FUNC_FSEEKO],
     fi
     m4_ifdef([gl_FUNC_FFLUSH_STDIN], [
       gl_FUNC_FFLUSH_STDIN
-      if test $gl_cv_func_fflush_stdin = no; then
+      if test $gl_cv_func_fflush_stdin != yes; then
         REPLACE_FSEEKO=1
       fi
     ])