const string in the header file - solutions?

[C. Jayachandran]

I've inherited some code which has const std::string values defined in
a header file, like

const std::string str = "foo";

This causes a large amount of bloat, as all the compilation units
including this header file will have a copy of the string, as well as
code to construct and destruct the string, even if the string is not
used within the CPP file.

I cannot use the straight-forward solution of converting the 'const' to
'extern const' because this would involve adding a new library, which
is not possible at this point.

The only solution I can think of which will avoid most of the bloat is
to change the definition to:

inline const std::string &get_const_str( ) { static const std::string s
= "foo"; return s; }

But this would mean turning the const variable to a function. I would
really appreciate any suggestions on how to get a similar effect
without converting the constants to functions, any GCC specific trick
will do too...

Thanks,
JC.

[Alf P. Steinbach]

Re: const string in the header file - solutions?

* C. Jayachandran:[color=blue]
> I've inherited some code which has const std::string values defined in
> a header file, like
>
> const std::string str = "foo";
>
> This causes a large amount of bloat, as all the compilation units
> including this header file will have a copy of the string, as well as
> code to construct and destruct the string, even if the string is not
> used within the CPP file.
>
> I cannot use the straight-forward solution of converting the 'const' to
> 'extern const' because this would involve adding a new library, which
> is not possible at this point.
>
> The only solution I can think of which will avoid most of the bloat is
> to change the definition to:
>
> inline const std::string &get_const_str( ) { static const std::string s
> = "foo"; return s; }
>
> But this would mean turning the const variable to a function. I would
> really appreciate any suggestions on how to get a similar effect
> without converting the constants to functions, any GCC specific trick
> will do too...[/color]

The first you should do is _measure_ whether it actually makes a
difference.

If it really really matters, then you can use the template constant
trick (patent pending... ;-) ),

template< typename T >
struct Strings_{ static const std::string str; };

template< typename T >
std::string const Strings_<T>::st r = "foo";

typedef Strings_<void> Strings;

int main()
{
std::cout << Strings::str << std::endl;
}

Hth.

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