On AIX 7.2, I see this test failure:
FAIL: test-fclose
=================
../../gltests/test-fclose.c:74: assertion 'lseek (fd, 0, SEEK_CUR) == 3' failed
FAIL test-fclose (exit status: 134)
The cause is that while POSIX specify a certain behaviour regarding the
position of the underlying file descriptor for fflush() and fclose(),
most systems
- either do it right for both — like musl libc —
- or wrong for both — like glibc (at least up to version 2.32) —,
whereas AIX gets it right for fflush() but wrong for fclose().
This patch fixes it.
2021-01-05 Bruno Haible <br...@clisp.org>
fclose: Fix test failure on AIX 7.2.
* m4/fclose.m4 (gl_FUNC_FCLOSE_STDIN): New macro.
(gl_FUNC_FCLOSE): Invoke it. Set REPLACE_FCLOSE accordingly.
* doc/posix-functions/fclose.texi: Update platform information.
* doc/posix-functions/fflush.texi: Likewise.
diff --git a/doc/posix-functions/fclose.texi b/doc/posix-functions/fclose.texi
index d3606b4..fb83f6a 100644
--- a/doc/posix-functions/fclose.texi
+++ b/doc/posix-functions/fclose.texi
@@ -11,7 +11,7 @@ Portability problems fixed by Gnulib:
@item
On some platforms, this function fails to set the file position of a
seekable input stream to the byte after the last one actually read:
-glibc 2.13, FreeBSD.
+glibc 2.32, FreeBSD, AIX 7.2.
@item
This function crashes if the stream's file descriptor has already been
closed on some platforms:
diff --git a/doc/posix-functions/fflush.texi b/doc/posix-functions/fflush.texi
index 1964da4..665951d 100644
--- a/doc/posix-functions/fflush.texi
+++ b/doc/posix-functions/fflush.texi
@@ -11,7 +11,8 @@ Portability problems fixed by Gnulib:
@item
@code{fflush} followed by @code{fseek} or @code{fseeko}, applied to an input
stream, should have the effect of positioning the underlying file descriptor.
-It doesn't do this on some platforms.
+It doesn't do this on some platforms:
+glibc 2.32 and others.
@item
@code{fflush} on an input stream changes the position of the stream to the
end of the previous buffer, on some platforms: mingw, MSVC 14.
diff --git a/m4/fclose.m4 b/m4/fclose.m4
index 13e1799..74a04e1 100644
--- a/m4/fclose.m4
+++ b/m4/fclose.m4
@@ -1,4 +1,4 @@
-# fclose.m4 serial 8
+# fclose.m4 serial 9
dnl Copyright (C) 2008-2021 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
@@ -23,4 +23,76 @@ AC_DEFUN([gl_FUNC_FCLOSE],
case "$host_os" in
openedition) REPLACE_FCLOSE=1 ;;
esac
+
+ if test $REPLACE_FCLOSE = 0; then
+ gl_FUNC_FCLOSE_STDIN
+ case "$gl_cv_func_fclose_stdin" in
+ *yes) ;;
+ *) REPLACE_FCLOSE=1 ;;
+ esac
+ fi
+])
+
+dnl Determine whether fclose works on input streams.
+dnl Sets gl_cv_func_fclose_stdin.
+
+AC_DEFUN([gl_FUNC_FCLOSE_STDIN],
+[
+ AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
+ AC_CHECK_HEADERS_ONCE([unistd.h])
+ AC_CACHE_CHECK([whether fclose works on input streams],
+ [gl_cv_func_fclose_stdin],
+ [echo hello world > conftest.txt
+ AC_RUN_IFELSE(
+ [AC_LANG_PROGRAM(
+ [[#include <fcntl.h>
+ #include <stdio.h>
+ #if HAVE_UNISTD_H
+ # include <unistd.h>
+ #else /* on Windows with MSVC */
+ # include <io.h>
+ #endif
+ ]GL_MDA_DEFINES],
+ [[int fd;
+ int fd2;
+ FILE *fp;
+ fd = open ("conftest.txt", O_RDONLY);
+ if (fd < 0)
+ return 1;
+ if (lseek (fd, 1, SEEK_SET) != 1)
+ return 2;
+ fd2 = dup (fd);
+ if (fd2 < 0)
+ return 3;
+ fp = fdopen (fd2, "r");
+ if (fp == NULL)
+ return 4;
+ if (fgetc (fp) != 'e')
+ { fclose (fp); return 5; }
+ /* This fclose() call should reposition the underlying file
+ descriptor. */
+ if (fclose (fp) != 0)
+ return 6;
+ if (lseek (fd2, 0, SEEK_CUR) != -1) /* should fail with EBADF */
+ return 7;
+ /* Verify the file position. */
+ if (lseek (fd, 0, SEEK_CUR) != 2)
+ return 8;
+ return 0;
+ ]])],
+ [gl_cv_func_fclose_stdin=yes],
+ [gl_cv_func_fclose_stdin=no],
+ [case "$host_os" in
+ # Guess no on glibc systems.
+ *-gnu* | gnu*) gl_cv_func_fclose_stdin="guessing no" ;;
+ # Guess yes on musl systems.
+ *-musl*) gl_cv_func_fclose_stdin="guessing yes" ;;
+ # Guess no on native Windows.
+ mingw*) gl_cv_func_fclose_stdin="guessing no" ;;
+ # If we don't know, obey --enable-cross-guesses.
+ *) gl_cv_func_fclose_stdin="$gl_cross_guess_normal" ;;
+ esac
+ ])
+ rm conftest.txt
+ ])
])
