Boost C++ Libraries: Ticket #3909: parse_command_line has bad declaration

anonymous — Mon, 08 Feb 2010 11:28:09 GMT

Also there is a problem with constness in charT.

This causes problem:

int main(int argc, char const* const argv[])
{
  parse_command_line(argc, argv);
}

parse_command_line cannot receive char const* const
charT = char const , there is no specialization for basic_parsed_options<char const> So there is a need to remove_cv<charT> and only then specialize basic_parsed_options.

template<class charT>
basic_parsed_options<typename remove_cv<charT>::type>
parse_command_line(int argc, charT* const argv[],
                   ....)

vladimir — Mon, 08 Feb 2010 12:42:34 GMT

Could you clarify? The type of argv you use in your example is in violation of the C++ standard, I believe.

anonymous — Mon, 08 Feb 2010 15:05:02 GMT

I am not sure about violation because adding const does not destroy anything. But the Standard says about int main(int argc, char* argv[]), so from this point of view you are right.

Anyway I don't know if there is a compiler which rejects main function with char const* const argv[]. Event Comeau compiler accepts it.

I suggest you to add remove_cv anyway, it will make code more correct. Thank you.

ilyasokol@… — Mon, 24 May 2010 12:16:10 GMT

See these use cases:

http://lists.boost.org/boost-users/2006/01/16620.php http://lists.boost.org/boost-users/2009/08/50968.php

The signature can be changed as follows:

template<class charT>
basic_parsed_options<typename remove_cv<charT>::type>
parse_command_line(int argc, const charT* const argv[],
                   ....)
or
template<class charT>
basic_parsed_options<typename remove_cv<charT>::type>
parse_command_line(int argc, const charT* const* argv,
                   ....)

(The second is a bit more readable for me)

There is no need to remove_cv<charT> and the change is fully backward compatible.

Marshall Clow — Wed, 01 Dec 2010 18:54:44 GMT

(In [66959]) Take argv as const; refs #3909

Marshall Clow — Sat, 04 Dec 2010 17:39:27 GMT

(In [67006]) patch tests for Sun; refs #3909

status changed; resolution set

Vladimir Prus — Sat, 25 Dec 2010 11:33:12 GMT

status new → closed
resolution → fixed

I assume this is fixed by earlier commits. Thanks Marshall!