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Poison generators when any terminator unwinds

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This didn't cause issues before since generator types were always
considered to "need drop", leading to unwind paths
(including a `Resume` block) always getting generated.
This commit is contained in:
Jonas Schievink 2020-03-08 00:55:29 +01:00
parent 5ac41a1a8d
commit 46aeef6e65
1 changed files with 31 additions and 5 deletions
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36
src/librustc_mir/transform/generator.rs
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@ -1055,11 +1055,37 @@ fn create_generator_resume_function<'tcx>(
body: &mut BodyAndCache<'tcx>,
can_return: bool,
) {
let can_unwind = can_unwind(tcx, body);
// Poison the generator when it unwinds
for block in body.basic_blocks_mut() {
let source_info = block.terminator().source_info;
if let &TerminatorKind::Resume = &block.terminator().kind {
block.statements.push(transform.set_discr(VariantIdx::new(POISONED), source_info));
if can_unwind {
let poison_block = BasicBlock::new(body.basic_blocks().len());
let source_info = source_info(body);
body.basic_blocks_mut().push(BasicBlockData {
statements: vec![transform.set_discr(VariantIdx::new(POISONED), source_info)],
terminator: Some(Terminator { source_info, kind: TerminatorKind::Resume }),
is_cleanup: true,
});
for (idx, block) in body.basic_blocks_mut().iter_enumerated_mut() {
let source_info = block.terminator().source_info;
if let TerminatorKind::Resume = block.terminator().kind {
// An existing `Resume` terminator is redirected to jump to our dedicated
// "poisoning block" above.
if idx != poison_block {
*block.terminator_mut() = Terminator {
source_info,
kind: TerminatorKind::Goto { target: poison_block },
};
}
} else if !block.is_cleanup {
// Any terminators that *can* unwind but don't have an unwind target set are also
// pointed at our poisoning block (unless they're part of the cleanup path).
if let Some(unwind @ None) = block.terminator_mut().unwind_mut() {
*unwind = Some(poison_block);
}
}
}
}
@ -1080,7 +1106,7 @@ fn create_generator_resume_function<'tcx>(
);
}
if can_unwind(tcx, body) {
if can_unwind {
cases.insert(
2,
(POISONED, insert_panic_block(tcx, body, ResumedAfterPanic(generator_kind))),