Re: Improved AC_LANG_WERROR

[Andrey Simonenko]

On Fri, Apr 13, 2007 at 11:21:10AM +0300, Andrey Simonenko wrote:
> 
> What is the better place for:
> 
> 1. initialization of ac_X_werror_flag variables for all languages
>    (which say how to treat warnings).
> 2. initialization of m4 _AC_LANG_X_WERROR_FLAG macro variables for
>    all languages (which are used for building stacks of settings).

> All these variables should be initialized only once and for each
> language.  Right now this is not implemented, so single two calls:

I decided to implement this in the following way:

lang.m4:

# AC_LANG_WERROR([VALUE])
# -----------------------
# How to treat warnings from the current language's preprocessor, compiler,
# and linker (works in a stack-like fashion):
# 1. No arguments:
#       Similarly to AC_LANG_WERROR([on])
# 2. One argument:
#       on  -- treat warnings as fatal errors + remember previous value;
#       off -- do not treat warnings as fatal errors + remember previous value;
#       pop -- restore previous value.
AC_DEFUN([AC_LANG_WERROR],
[
m4_ifdef(_AC_LANG_[]_AC_LANG_ABBREV[]_WERROR_FLAG, [], [
    m4_divert_text([DEFAULTS], [
        m4_define(_AC_LANG_[]_AC_LANG_ABBREV[]_WERROR_FLAG, [off])
        ac_[]_AC_LANG_ABBREV[]_werror_flag=])])
m4_if(
    $#, 1, [m4_if(
        [$1], [on], [
            m4_pushdef(_AC_LANG_[]_AC_LANG_ABBREV[]_WERROR_FLAG, [on])
            ac_[]_AC_LANG_ABBREV[]_werror_flag=yes],
        [$1], [off], [
            m4_pushdef(_AC_LANG_[]_AC_LANG_ABBREV[]_WERROR_FLAG, [off])
            ac_[]_AC_LANG_ABBREV[]_werror_flag=],
        [$1], [pop], [
            m4_popdef(_AC_LANG_[]_AC_LANG_ABBREV[]_WERROR_FLAG)
            m4_ifdef(_AC_LANG_[]_AC_LANG_ABBREV[]_WERROR_FLAG, [],
                [m4_fatal([$0: unbalanced number of `on/off' and `pop' calls 
for] _AC_LANG)])
            m4_if(
                m4_defn(_AC_LANG_[]_AC_LANG_ABBREV[]_WERROR_FLAG), [on],
                    [ac_[]_AC_LANG_ABBREV[]_werror_flag=yes],
                m4_defn(_AC_LANG_[]_AC_LANG_ABBREV[]_WERROR_FLAG), [off],
                    [ac_[]_AC_LANG_ABBREV[]_werror_flag=],
                [m4_fatal([$0: stack of values is damaged])])],
        [m4_fatal([$0: wrong argument: `$1'])])],
    $#, 0, [AC_LANG_WERROR([on])],
    [m4_fatal([$0: incorrect number of arguments: $#])])
])# AC_LANG_WERROR

Also I have a question.  To remove all new line characters and extra
white-space characters, which are produced by this macro, from the
configure script, it is necessary to insert many dnl and make code of
this macro unintended.  Is this correct, or I misunderstand something?