step-over, step-out and run-until plant a one-shot breakpoint at the address
they want execution to return to. Keeping it in breakPoints_ alongside the
user's own meant the two kept colliding:
- Adding a log-only user breakpoint at the same address hijacked the temporary
one. AddBreakPoint() didn't match across temp-ness so both existed, and then
ChangeBreakPoint() looked up "the first enabled breakpoint at this address" -
a log-only breakpoint isn't enabled, so the temporary one won and had its
action overwritten to log-only. It lost PAUSE and the step never came back.
- RemoveBreakPoint() erased up to two entries per address to catch an
overlapping temporary one, so deleting either deleted both - including the
interpreter's cleanup path in CheckExecBreakpoints() taking the user's
breakpoint with it.
- ExecBreakPoint() handled one breakpoint per address, so with both at the same
address only one of them did anything: the step completed but the user's log
line never printed.
- Nothing dropped it when something *else* stopped us first, so an interrupted
step left a breakpoint armed at an address nobody was waiting for anymore,
which later fired as a phantom stop.
It's a single TempBreakPoint member now, invisible to the breakpoint lists and
untouched by user edits. One is enough: step over/out and cross-thread step into
all require the CPU to already be stepping and resume it immediately, so only
one can be in flight, and run-until now replaces rather than stacking (two
pending run-untils had no coherent meaning, and the loser stayed armed).
Behavior follows what other debuggers do. Both breakpoints at an address are
evaluated independently and their actions combine, so a log-only breakpoint
logs without stopping and still lets the step finish. Core_Break() drops the
temporary breakpoint on any stop, whatever the reason - the same way gdb deletes
its step-resume breakpoint and lldb discards the thread plan.
Two things to be careful of, both covered by the new TempBreakpoints test:
HasBreakPoints() has to account for it, or the interpreter's checked run loop
and the JIT skip breakpoint checking entirely and a step with no user
breakpoints set never returns; and IsAddressBreakPoint() (user-facing, for the
lists and disassembly markers) is now separate from NeedsBreakCheckAt() (what
the JIT frontends and interpreter ask), since only the latter should see it.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GZq8ZtJmFY7bkX5FVkr3P9
Henrik Rydgård