Re: Autoheader should ignore m4 "dnl" comments

[Kang-Che Sung]

Allow me to re-describe the bug in a clearer way:

In the configure.ac in Flex (lexer) project, I used a quoted argument with
"dnl" comments in within AC_CHECK_FUNCS like this:

    AC_CHECK_FUNCS([dnl
    pow dnl Used only by "examples/manual/expr"
    setlocale dnl Needed only if NLS is enabled
    reallocarr dnl NetBSD function. Use reallocarray if not available.
    reallocarray dnl OpenBSD function. We have replacement if not available.
    ])

After running autoreconf, the generated 'configure' script is correct:

    for ac_func in dup2 memset pow regcomp setlocale strchr strdup strtol
    do :
      as_ac_var=`$as_echo "ac_cv_func_$ac_func" | $as_tr_sh`
    ac_fn_c_check_func "$LINENO" "$ac_func" "$as_ac_var"
    if eval test \"x\$"$as_ac_var"\" = x"yes"; then :
      cat >>confdefs.h <<_ACEOF
    #define `$as_echo "HAVE_$ac_func" | $as_tr_cpp` 1
    _ACEOF

    fi
    done

But config.h.in comes with unneeded HAVE_ macros such as:

    /* Define to 1 if you have the `available.' function. */
    #undef HAVE_AVAILABLE_

    /* Define to 1 if you have the `by' function. */
    #undef HAVE_BY

    /* Define to 1 if you have the `dnl' function. */
    #undef HAVE_DNL

The result I would expect is either:

(a.) Both 'configure' and 'config.h.in' generated correctly, without redundant
macros in the latter file.

(b.) Both files generated consistently, with 'dnl', 'by' and others
treated as function tokens in the former file. That is, the 'configure' script
"broken" like this.

    for ac_func in dnl pow dnl Used only by "examples/manual/expr"
setlocale dnl Needed only if NLS is enabled
    do :
    #...
    done

So that I would know I mustn't quote the argument if I had comments
within the AC_CHECK_FUNCS syntax.

> Note: Tested this with Autoconf 2.69 and Automake 1.15.1. Detailed
> steps to reproduce:
>
> $ git clone --depth 1 --branch v2.6.4 https://github.com/westes/flex flex
> $ cd flex
> $ autoheader
> $ cat src/config.h.in
>
> See the useless HAVE_ macros in the header.

That's it.