On Saturday, September 10, 2011 13:00:02 Joel Christensen wrote: > Hi, > > In the std.string document at toStringz it has this note: > > Important Note: When passing a char* to a C function, and the C function > keeps it around for any reason, make sure that you keep a reference to > it in your D code. Otherwise, it may go away during a garbage collection > cycle and cause a nasty bug when the C code tries to use it. > > What does it mean, and what is an example of how to do it? > > It's not done like this is it? > > char* a = cast(char*)toStringz( "test" ); > char* b = cast(char*)toStringz( "word" ); > hold ~= a; > hold ~= b; > > char* cstr2 = al_get_config_value( cfg, a, b ); > > My programs using a C library do crash when exiting some times.
It means that you need to keep a pointer to the result of toStringz around if the C function that you pass it to keeps a pointer to it. As long as your D code still has a copy of the pointer, the GC won't collect it. But if your D code doesn't have a copy of the pointer, then the GC may choose to collect it at some point. And once it collects it, the C code which kept the pointer has a pointer to freed memory and will have memory corruption problems (which could result in crash among other things). If the C code doesn't keep a pointer to the data that you pass to it, then it's not an issue. It's just a problem if the C code retains a pointer to it. > Also, how do I go the other way round, some thing like toDString. I've > made my own version. I can't seem to find fromStringz. If you want to convert from a pointer to a string, use std.conv.to. It should do it. If it doesn't, it's a bug. - Jonathan M Davis
