Re: [Boost-users] Boost program_options

Subject: Re: [Boost-users] Boost program_options
From: Asif Lodhi (asif.lodhi_at_[hidden])
Date: 2009-08-24 19:15:54

Hi Steve,

Though I am not at all familiar with program_options but may be your
situation has something to do with the fact that the type of a string
literal in standard C++ is  "array of the appropriate number of const
characters" - "The C++ Programming Language, 3rd Ed." by Bjarne
Stroustrup says so.

It also says that you can assign a string literal to a char* but you
cannot modify a string literal through such a pointer. The book says
"If we want a string that we are guaranteed to be able to modify, we
must copy the characters into an array.

void f()
{
    char p[] = "Zero";
    p[0] = 'R';
} "

Best regards.

-Asif

On 8/22/09, Steve Nolen <drnuke_at_[hidden]> wrote:
> in program_options::parse_command_line - why can't the the argument
> "argv" be of type 'const charT*' rather than 'charT*'?
>
> i ask because our unit tests were giving a bunch of errors because they
> were written like this..
>
> vector< char* > cmdLine;
> cmdLine.push_back( "someExec" );
> cmdLine.push_back( "--optflag1" );
> cmdLine.push_back( "value1" );
> etc.
>
> then...
> char ** argv = &cmdLine[ 0 ];
>
> then passing this to parse_command_line.  when we compile under g++ 4.x
> we get warnings that assigning string literals to char* is a deprecated
> conversion.  Actually I agree with the rationale, but this leaves me
> with a problem calling parse_command_line.  Is it going to change any of
> these values?
>
> I know the c standard calls for the argv in main's prototype to be
> non-const, but why can't parse_command_line be more restrictive?