Re: [PATCH] perror: test for output mismatch

[Bruno Haible]

Eric Blake wrote on 2011-06-21:
> diff --git a/ChangeLog b/ChangeLog
> index 07f3819..36d72ae 100644
> --- a/ChangeLog
> +++ b/ChangeLog
> @@ -1,5 +1,9 @@
>  2011-06-21  Eric Blake  <address@hidden>
> 
> +     perror: test for output mismatch
> +     * m4/perror.m4 (gl_FUNC_PERROR): Add test, in order to replace
> +     perror on IRIX.
> +
>       strerror_r: fix OpenBSD behavior on out-of-range
>       * lib/strerror_r.c (strerror_r): Always use maximal string.
>       * doc/posix-functions/strerror_r.texi (strerror_r): Document it.
> diff --git a/m4/perror.m4 b/m4/perror.m4
> index d08f365..86e2020 100644
> --- a/m4/perror.m4
> +++ b/m4/perror.m4
> @@ -1,4 +1,4 @@
> -# perror.m4 serial 2
> +# perror.m4 serial 3
>  dnl Copyright (C) 2008-2011 Free Software Foundation, Inc.
>  dnl This file is free software; the Free Software Foundation
>  dnl gives unlimited permission to copy and/or distribute it,
> @@ -9,13 +9,45 @@ AC_DEFUN([gl_FUNC_PERROR],
>    AC_REQUIRE([gl_STDIO_H_DEFAULTS])
>    AC_REQUIRE([gl_HEADER_ERRNO_H])
>    AC_REQUIRE([gl_FUNC_STRERROR_R])
> -  if test -n "$ERRNO_H"; then
> +  AC_REQUIRE([gl_FUNC_STRERROR_0])
> +  dnl We intentionally do not check for the broader REPLACE_STRERROR_R,
> +  dnl since on glibc systems, strerror_r is replaced only for signature
> +  dnl issues, and perror is just fine.  Rather, we only want to
> +  dnl replace perror if strerror_r was replaced for a content fix.
> +  if test "$ERRNO_H:$REPLACE_STRERROR_0" != :0; then
>      dnl The system's perror() cannot know about the new errno values we add
> -    dnl to <errno.h>. Replace it.
> +    dnl to <errno.h>, or any fix for strerror(0). Replace it.
>      REPLACE_PERROR=1
>    fi
>    case ${gl_cv_func_strerror_r_works-unset} in
> -    unset|*yes) ;;
> +    unset|*yes)
> +      AC_CACHE_CHECK([whether perror matches strerror],
> +        [gl_cv_func_perror_works],
> +        [AC_RUN_IFELSE(
> +           [AC_LANG_PROGRAM(
> +              [[#include <errno.h>
> +                #include <stdio.h>
> +              ]],
> +              [[char *str = strerror (-1);
> +                if (!getenv("CONFTEST_OUTPUT")) return 0;
> +                if (!str) str = "";
> +                puts (str);
> +                errno = -1;
> +                perror ("");
> +              ]])],
> +           [CONFTEST_OUTPUT=1 ./conftest$EXEEXT >conftest.txt1 
> 2>conftest.txt2
> +            if cmp conftest.txt1 conftest.txt2 >/dev/null; then
> +              gl_cv_func_perror_works=yes
> +            else
> +              gl_cv_func_perror_works=no
> +            fi
> +            rm -rf conftest.txt1 conftest.txt2],
> +           [gl_cv_func_perror_works=no],
> +           [dnl Guess no when cross-compiling.
> +            gl_cv_func_perror_works="guessing no"])])
> +       if test "$gl_cv_func_perror_works" != yes; then
> +         REPLACE_PERROR=1
> +       fi ;;
>      *) dnl The system's perror() probably inherits the bugs in the
>         dnl system's strerror_r(). Replace it.
>        REPLACE_PERROR=1 ;;

Sorry, but the indentation in this patch is not consistent: 2 vs. 3 spaces
in the same case alternative. I'm fixing it like this.

Probably the tendency to put all closing ])])]) parentheses and brackets
on the end of the same line contributed to this mistake. I'm in favour
of aligning corresponding brackets vertically if it can avoid misindentation
or - worse - confusion about which is the corresponding opening bracket.

2011-10-22  Bruno Haible  <address@hidden>

        perror: Fix indentation.
        * m4/perror.m4 (gl_FUNC_PERROR): Fix indentation.

*** m4/perror.m4.orig   Sat Oct 22 14:20:29 2011
--- m4/perror.m4        Sat Oct 22 14:16:55 2011
***************
*** 1,4 ****
! # perror.m4 serial 4
  dnl Copyright (C) 2008-2011 Free Software Foundation, Inc.
  dnl This file is free software; the Free Software Foundation
  dnl gives unlimited permission to copy and/or distribute it,
--- 1,4 ----
! # perror.m4 serial 5
  dnl Copyright (C) 2008-2011 Free Software Foundation, Inc.
  dnl This file is free software; the Free Software Foundation
  dnl gives unlimited permission to copy and/or distribute it,
***************
*** 46,57 ****
              rm -rf conftest.txt1 conftest.txt2],
             [gl_cv_func_perror_works=no],
             [dnl Guess no when cross-compiling.
!             gl_cv_func_perror_works="guessing no"])])
!        if test "$gl_cv_func_perror_works" != yes; then
!          REPLACE_PERROR=1
!        fi ;;
!     *) dnl The system's perror() probably inherits the bugs in the
!        dnl system's strerror_r(). Replace it.
!       REPLACE_PERROR=1 ;;
    esac
  ])
--- 46,62 ----
              rm -rf conftest.txt1 conftest.txt2],
             [gl_cv_func_perror_works=no],
             [dnl Guess no when cross-compiling.
!             gl_cv_func_perror_works="guessing no"
!            ])
!         ])
!       if test "$gl_cv_func_perror_works" != yes; then
!         REPLACE_PERROR=1
!       fi
!       ;;
!     *)
!       dnl The system's perror() probably inherits the bugs in the
!       dnl system's strerror_r(). Replace it.
!       REPLACE_PERROR=1
!       ;;
    esac
  ])
-- 
In memoriam Nunilo and Alodia <http://en.wikipedia.org/wiki/Nunilo_and_Alodia>