1096736 - The frontend shouldn't do any code-deleting optimizations because it makes the debugger unable to set breakpoints on that code

Status: NEW

(Core :: JavaScript Engine, defect, P3)

Description

[Nick Fitzgerald [:fitzgen] [⏰PST; UTC-8]]

No breakpoints because no offsets.

Things like "if (true) \n..." get optimized, resulting in not being able to break on the conditional.

Comment 1

[Jason Orendorff [:jorendorff]]

Quickest fix: In js/src/frontend/FoldConstants.cpp, in the second switch statement, try deleting
the code in "case PNK_IF:" and "case PNK_CONDITIONAL:".

Comment 2

[Jason Orendorff [:jorendorff]]

Er, in the function Fold().

Comment 3

[Jason Laster [:jlast]]

Brian, is this still a concern?

Comment 4

[Brian Hackett [Laid off!]]

Yeah, it is. If I open the page below in the debugger, breakpoints can only be set on the bar() call, and not the 'if (true)' or the baz() call.

<script>
if (true) {
bar();
} else {
baz();
}
</script>