Re: [PATCH] tests: factor st_ctime-comparison out of two headers

[Ben Pfaff]

Simon Josefsson <address@hidden> writes:

> Ben Pfaff <address@hidden> writes:
>
>> Simon Josefsson <address@hidden> writes:
>>
>>> Bruno Haible <address@hidden> writes:
>>>
>>>> Jim Meyering wrote:
>>>>> -W
>>> ...
>>>>> -Wwrite-strings
>>>>> -fdiagnostics-show-option
>>>>
>>>> Thanks. I've updated my build script to include these for glibc/x86 builds
>>>> (except -Werror, which causes a configuration error already in
>>>> "checking whether the compiler works...").
>>>
>>> I recommend putting warning flags in a separate variable,
>>> e.g. WARN_CFLAGS, which is not used during ./configure checks but only
>>> when building (parts of) the project code.  That way, -Werror can be
>>> used, which I find helpful since I can mentally ignore the compilation
>>> output since I know I will be interrupted if there is anything real to
>>> pay attention to.
>>
>> Another approach is to add -Werror last (this is what Eric Blake
>> suggested on the autoconf mailing list a long time ago), e.g.:
>>
>> AC_DEFUN([OVS_ENABLE_WERROR],
>>   [AC_ARG_ENABLE(
>>      [Werror],
>>      [AC_HELP_STRING([--enable-Werror], [Add -Werror to CFLAGS])],
>>      [], [enable_Werror=no])
>>    AC_CONFIG_COMMANDS_PRE(
>>      [if test "X$enable_Werror" = Xyes; then
>>         CFLAGS="$CFLAGS -Werror"
>>       fi])])
>
> But does that really work?  Don't you risk affecting ./configure checks
> that often are written in a way that triggers warnings, and with the
> -Werror flag, leads to compilation errors.   [...]

The argument to AC_CONFIG_COMMANDS_PRE is run just before
creating config.status, regardless of when the
AC_CONFIG_COMMANDS_PRE command itself runs, so it doesn't risk
affecting any configure checks.

Here's the documentation for AC_CONFIG_COMMANDS_PRE from the
Autoconf manual.

 -- Macro: AC_CONFIG_COMMANDS_PRE (CMDS)
     Execute the CMDS right before creating `config.status'.

     This macro presents the last opportunity to call `AC_SUBST',
     `AC_DEFINE', or `AC_CONFIG_ITEMS' macros.

-- 
Ben Pfaff 
http://benpfaff.org