When execvp() failed to replace the stack, the forked process would return to Blender's WM_main(..) loop then hang when attempting to draw the window. Resolve by calling _exit() when execvp fails.
When execvp() failed to replace the stack, the forked process would return to Blender's WM_main(..) loop then hang when attempting to draw the window. Resolve by calling _exit() when execvp fails.