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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 | 
|---|---|---|
| @@ -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 {} | ||
| } | ||
| 
     | 
||
| 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
AbortUnwindingCallsfeels a bit unnecessary?There was a problem hiding this comment.
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can we run
AbortUnwindingCallsafter 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=abortwhenC-unwindis used so we couldn't just do it in validation.Lifting the
CheckAlignmentpass 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.Uh oh!
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If I understood @saethlin correctly, this could be
Unreachablealways?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. :)