Why is Marshal::StringToHGlobalAnsi argument not const?

[Kenneth Porter]

I try to be const correct everywhere and found that I can't pass a const
String to this API. Is it going to change the value? Or is the signature
not the best it could be?

I want to write this:

// based on http://msdn.microsoft.com/en-us/magazine/bb985936.aspx

std::string MarshalString (const System::String^ s)
{
using namespace System::Runtime ::InteropServic es;
const char* chars =
(const char*)(Marshal: :StringToHGloba lAnsi
(s)).ToPointer( );
os = chars;
Marshal::FreeHG lobal(IntPtr((v oid*)chars));
return os;
}

Should I copy the argument and convert the copy?

[Kenneth Porter]

Re: Why is Marshal::String ToHGlobalAnsi argument not const?

Kenneth Porter <shiva.blacklis t@sewingwitch.c omwrote in
news:Xns9A92C01 0EA61Cshivawell com@207.46.248. 16:

I try to be const correct everywhere and found that I can't pass a const
String to this API. Is it going to change the value? Or is the signature
not the best it could be?

I've discovered the answer to my question. The CLR threw const-correctness
on the scrap heap to be compatible with VB's lack of const, and that
decision infected C# and C++/CLI:

http://blogs.msdn.com/oldnewthing/ar...27/121049.aspx

So I guess I'll be copying my const Strings to non-const Strings before
passing them to system libraries.

[Ben Voigt [C++ MVP]]

Re: Why is Marshal::String ToHGlobalAnsi argument not const?


"Kenneth Porter" <shiva.blacklis t@sewingwitch.c omwrote in message
news:Xns9A92C42 7F1EFBshivawell com@207.46.248. 16...

Kenneth Porter <shiva.blacklis t@sewingwitch.c omwrote in
news:Xns9A92C01 0EA61Cshivawell com@207.46.248. 16:
>

>I try to be const correct everywhere and found that I can't pass a const
>String to this API. Is it going to change the value? Or is the signature
>not the best it could be?

>
I've discovered the answer to my question. The CLR threw const-correctness
on the scrap heap to be compatible with VB's lack of const, and that
decision infected C# and C++/CLI:

Yup, and you can't do *anything* with a const managed type, because there
aren't any const member functions, so even reading properties isn't
possible. There's no syntax for defining const member functions in your own
types either, although it would have been easy for the C++ compiler to
implement this using attributes.

>
http://blogs.msdn.com/oldnewthing/ar...27/121049.aspx
>
So I guess I'll be copying my const Strings to non-const Strings before
passing them to system libraries.