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Prevent .eh_frame
from being emitted for -C panic=abort
#112403
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Original file line number | Diff line number | Diff line change |
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@@ -0,0 +1,10 @@ | ||
# only-linux | ||
# | ||
# This test ensures that `panic=abort` code (without `C-unwind`, that is) should not have any | ||
# unwinding related `.eh_frame` sections emitted. | ||
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include ../tools.mk | ||
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all: | ||
$(RUSTC) foo.rs --crate-type=lib --emit=obj=$(TMPDIR)/foo.o -Cpanic=abort | ||
objdump --dwarf=frames $(TMPDIR)/foo.o | $(CGREP) -v 'DW_CFA' |
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Original file line number | Diff line number | Diff line change |
---|---|---|
@@ -0,0 +1,10 @@ | ||
#![no_std] | ||
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#[panic_handler] | ||
fn handler(_: &core::panic::PanicInfo<'_>) -> ! { | ||
loop {} | ||
} | ||
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pub unsafe fn oops(x: *const u32) -> u32 { | ||
*x | ||
} |
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This feels like something we're going to regress on with the next similar check in MIR -- can we introduce another run of AbortUnwindingCalls or otherwise make this more general?
(I'm not super familiar with mir opts so not sure if that pass is very expensive).
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Currently this pass is the only pass that can add a new call, and given that this pass is only enabled with debug assertions, re-running
AbortUnwindingCalls
feels a bit unnecessary?There was a problem hiding this comment.
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can we run
AbortUnwindingCalls
after it (or rather, run the alignment checks before it)There was a problem hiding this comment.
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alternatively, MIR validation could check that no normal unwind actions are present on panic=abort
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UnwindAction::Terminate may be present in
-Cpanic=abort
whenC-unwind
is used so we couldn't just do it in validation.Lifting the
CheckAlignment
pass might make sense.There was a problem hiding this comment.
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terminate existing with panic=unwind could happen, but other unwind actions with panic=abort shouldn't, right? that could be validated
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That's entirely orthogonal to this PR though.
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I just checked we couldn't lift
CheckAlignment
, because alignment checks are not doable for CTFE, so it must stay as an optimization pass. We also couldn't delayAbortUnwindingCalls
, because it needs to be run before generator lowering.There was a problem hiding this comment.
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If I understood @saethlin correctly, this could be
Unreachable
always?Either way there should be a comment explaining why this is unreachable. "Because we use the non-unwinding panic machinery" seems like a good answer to me; it is explicitly intended to not unwind so I have no issue with this non-local dependency.
EDIT: Ah, #112599 already did this. :)