pread on HP-UX 11

[Bruno Haible]

On HP-UX 11.11 and 11.31 I'm observing two different failures of the 'pread'
test:

  test-pread.c:61: assertion failed
  ./test-pread.sh[5]: 26534 Abort(coredump)
  FAIL: test-pread.sh

  test-pread.c:80: assertion failed
  ./test-pread.sh[5]: 13130 Abort(coredump)
  FAIL: test-pread.sh

This patch adds workarounds to gnulib:


2010-12-31  Bruno Haible  <address@hidden>

        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.

--- doc/posix-functions/pread.texi.orig Sat Jan  1 01:47:49 2011
+++ doc/posix-functions/pread.texi      Fri Dec 31 23:28:30 2010
@@ -11,6 +11,13 @@
 @item
 This function is missing on some platforms:
 HP-UX 10, mingw, BeOS.
address@hidden
+This function returns zero instead of positive values when large file support
+is enabled on some platforms:
+HP-UX 11.11.
address@hidden
+This function does not fail on pipes on some platforms:
+HP-UX 11.31.
 @end itemize
 
 Portability problems not fixed by Gnulib:
--- m4/pread.m4.orig    Sat Jan  1 01:47:49 2011
+++ m4/pread.m4 Fri Dec 31 23:51:22 2010
@@ -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 @@
 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
 ])