[Mono-devel-list] Problem with P/Invoke

[Jonathan Pryor]

Below...

On Sun, 2004-02-01 at 10:07, Martin Baulig wrote:
> On Sat, 2004-01-31 at 23:27, Jonathan Pryor wrote:
> > Thus, your DllImport should be:
> > 
> > 	[DllImport ("libc.so")]
> > 	private static extern IntPtr strncpy (StringBuilder dest,
> > 		string src, uint len);
> > 
> > Now, the bad news begins.  When I try this under Mono 0.29, the code
> > doesn't work correctly.  Nothing appears to be copied.
> 
> You forgot a more serious issue:
> 
> The first argument or strncpy is a `char *' and you can't just overwrite
> the managed `StringBuilder' instance.

The runtime is supposed to handle this transparently, so that
StringBuilder can be used with fixed-with buffers.

See (beware line wraps):

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpguide/html/cpcondefaultmarshalingforstrings.asp?frame=true&hidetoc=true

 - Jon