pread: Work around HP-UX 11 bugs.

* m4/pread.m4 (gl_FUNC_PREAD): When pread exists, test whether it works
and set REPLACE_PREAD if not.
* doc/posix-functions/pread.texi: Document the HP-UX 11 bugs.

diff --git a/ChangeLog b/ChangeLog
index 3cb5bbee24fd9c7b649d8e58ddc3047344b27d2d..6c7d4530044f97fd39115c3db8ece4dd933ddce1 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2010-12-31  Bruno Haible  <bruno@clisp.org>
+
+       pread: Work around HP-UX 11 bugs.
+       * m4/pread.m4 (gl_FUNC_PREAD): When pread exists, test whether it works
+       and set REPLACE_PREAD if not.
+       * doc/posix-functions/pread.texi: Document the HP-UX 11 bugs.
+
 2010-12-31  Eric Blake  <eblake@redhat.com>
 
        nl_langinfo: fix YESEXPR on Irix 6.5

diff --git a/doc/posix-functions/pread.texi b/doc/posix-functions/pread.texi
index 743253b6f67db914a902d8ef6c6ee92c81d26706..0a4fc7c1caed75df2a8d52f465c3ca2503877dd1 100644 (file)
--- a/doc/posix-functions/pread.texi
+++ b/doc/posix-functions/pread.texi
@@ -11,6 +11,13 @@ Portability problems fixed by Gnulib:
 @item
 This function is missing on some platforms:
 HP-UX 10, mingw, BeOS.
+@item
+This function returns zero instead of positive values when large file support
+is enabled on some platforms:
+HP-UX 11.11.
+@item
+This function does not fail on pipes on some platforms:
+HP-UX 11.31.
 @end itemize
 
 Portability problems not fixed by Gnulib:

diff --git a/m4/pread.m4 b/m4/pread.m4
index f1425a6b1de25b30e9c2f598f0a041da416714a8..15a92d77a442aef3db48439de5730d38d6f4cbaf 100644 (file)
--- a/m4/pread.m4
+++ b/m4/pread.m4
@@ -1,4 +1,4 @@
-# pread.m4 serial 2
+# pread.m4 serial 3
 dnl Copyright (C) 2009-2010 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -7,12 +7,82 @@ dnl with or without modifications, as long as this notice is preserved.
 AC_DEFUN([gl_FUNC_PREAD],
 [
   AC_REQUIRE([gl_UNISTD_H_DEFAULTS])
+  AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
+
   dnl Persuade glibc <unistd.h> to declare pread().
   AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])
 
   AC_CHECK_FUNCS_ONCE([pread])
-  if test $ac_cv_func_pread = no; then
+  if test $ac_cv_func_pread = yes; then
+    dnl On HP-UX 11.11 with _FILE_OFFSET_BITS=64, pread() on a file returns 0
+    dnl instead of a positive value.
+    dnl On HP-UX 11.31, pread() on a pipe does not fail.
+    AC_CACHE_CHECK([whether pread works],
+      [gl_cv_func_pread_works],
+      [
+        dnl Initial guess, used when cross-compiling.
+changequote(,)dnl
+        case "$host_os" in
+                 # Guess no on HP-UX.
+          hpux*) gl_cv_func_pread_works="guessing no" ;;
+                 # Guess yes otherwise.
+          *)     gl_cv_func_pread_works="guessing yes" ;;
+        esac
+changequote([,])dnl
+        gl_save_CPPFLAGS="$CPPFLAGS"
+        CPPFLAGS="$CPPFLAGS -D_FILE_OFFSET_BITS=64"
+        AC_RUN_IFELSE(
+          [AC_LANG_SOURCE([[
+#include <sys/types.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <stdio.h>
+             ]],
+             [[
+{
+  int result = 0;
+  /* This test fails on HP-UX 11.00..11.11.  */
+  {
+    int fd = open ("conftest.c", O_RDONLY);
+    if (fd < 0)
+      result |= 1;
+    else
+      {
+        char byte_buf;
+        if (pread (fd, &byte_buf, 1, (off_t) 0) != 1)
+          result |= 2;
+        close (fd);
+      }
+  }
+  /* This test fails on HP-UX 11.00..11.31.  */
+  {
+    FILE *fp = popen ("echo", "r");
+    if (fp == NULL)
+      result |= 1;
+    else
+      {
+        int fd = fileno (fp);
+        char byte_buf;
+        if (pread (fd, &byte_buf, 1, (off_t) 0) >= 0)
+          result |= 4;
+        pclose (fp);
+      }
+  }
+  return result;
+}]])],
+          [gl_cv_func_pread_works=yes],
+          [gl_cv_func_pread_works=no],
+          [:])
+        CPPFLAGS="$gl_save_CPPFLAGS"
+      ])
+    case "$gl_cv_func_pread_works" in
+      *yes) ;;
+      *) REPLACE_PREAD=1 ;;
+    esac
+  else
     HAVE_PREAD=0
+  fi
+  if test $HAVE_PREAD = 0 || test $REPLACE_PREAD = 1; then
     AC_LIBOBJ([pread])
   fi
 ])