asm
int3
end;
IIRC "int3" without space (but may need to double check.
Also may depend on the debug backend.
Using FpDebug, you need to adjust the setting. In the Tools option > Debug backend => in the property grid: "HandleDebugBreakInstruction": disable the setting "dboIgnoreAll"
On Windows you also have on OS function for that. But then you do stop in that function, instead of the caller. (one day that may get changed... one day...)