[Mono-dev] String comparison failing between C# and C

[Robert Jordan]

Dan Osawa wrote:
> Hello,
> 
> I'm currently testing Mono's interoperability between C# and C code, and
> have run into an interesting scenario.
> 
> 
> 
> In my test case I have a C shared object that implements two functions:
> setString and getString.  The first function, setString, simply copies the
> string into a local buffer.  The second function, getString, returns a
> pointer to the internal buffer holding the string.
> 
> 
> 
> What's interesting is that the first case (in the below C# code) fails when
> it tries to compare "hello" against the return value of getString.  Is this
> a problem with trying to compare a unicode string with an ansi string?  This
> test case passes when running under Windows via CLR...fails in Linux via
> Mono.

The error is most likely in your C code you didn't post.
You're probably returning a const ptr to a string:

char *
getString ()
{
	return "hello";
}

This is wrong. The interop rules demand that that string was
allocated from the heap:

char *
getString ()
{
	return strdup ("hello");
}


Robert