Problem Passing Struct to C

[Steven Schveighoffer]

On Fri, 06 May 2011 09:16:02 -0400, Jacob Carlborg <doob at me.com> wrote:

> On 2011-05-06 11:56, Mike Parker wrote:
>> Testing out a new binding I knocked up for a C library. One of the
>> functions takes a struct by value. It looks somewhat like this:
>>
>> struct S {}
>> struct Color
>> {
>> float r,g,b,a;
>> }
>>
>> extern C void function(S* s, Color color, int x, int y, in char*)
>> draw_text;
>>
>> Now, there is another function that adjusts color values when making a
>> color. In C, it is sometimes used like so:
>>
>> draw_text(s, map_color(255, 0, 0, 0), 0, 0, "Blarg");
>>
>> When I'm calling draw_text like this on the D side, my text output is
>> corrupt. I keep getting weird things like ^^P^, but in the appropriate
>> color. It's consistent, no matter what string I pass, but is different
>> for each color value. If I call draw_text like this:
>>
>> auto color = map_color(...);
>> draw_text(s, color, 0, 0, "Blarg");
>>
>> It works as expected. Has anyone else seen this, or know of a
>> workaround? I'm going to dig through bugzilla later on and see if it's
>> been reported already, but I'm curious if anyone knows of the cause off
>> hand.
>
> You need to convert the string into a C string;
>
> import std.string;
> auto color = map_color(...);
> draw_text(s, color, 0, 0, "Blarg".toStringz);
>

No, D implicitly casts string literals to zero-terminated const(char)*.   
That part is fine.

-Steve