Bug 8054 – assert(0) doesn't fire when called by C code, but triggers in debugger

I don't have a test case for this yet (the code is huge, and I'd have to trim a lot of Win32 window code to get this), but basically how it goes is this: If you subclass a window by changing its WNDPROC in Windows, and then assert(0) inside the WNDPROC, it doesn't always get propagated back; however, if a debugger is attached, it is always detected. Funny thing is, *sometimes* it /does/ get propagated back -- it happened when I used SendMessage() /before/ my assertion. But when I omitted it, I didn't get any errors. The same exact issue happens when I say asm { int 3; } -- it just jumps out of the method, but the code continues fine outside of the C callback (SendMessage). And yet if the debugger is attached, it fires. (I don't have any catch() blocks in my code.) I'll try to produce a test case for it when I get the chance (hopefully I'll remember by then...) but that's the issue right now.

I think I found the cause: http://blog.paulbetts.org/index.php/2010/07/20/the-case-of-the-disappearing-onload-exception-user-mode-callback-exceptions-in-x64/ Doesn't seem like it's a D problem. :\