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[DWARF] Make -g with empty assembler source work better.
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Authored by probinson on Feb 27 2019, 5:23 PM.

Details

Summary

This was sometimes causing clang or llvm-mc to crash, and in other
cases could emit a bogus DWARF line-table header. This should be a
cleaner and more complete fix than r352541.

Addresses PR40538.

Diff Detail

Repository
rL LLVM

Event Timeline

probinson created this revision.Feb 27 2019, 5:23 PM
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probinson edited the summary of this revision. (Show Details)Feb 27 2019, 5:24 PM
aprantl added inline comments.Feb 27 2019, 5:37 PM
clang/tools/driver/cc1as_main.cpp
336 ↗(On Diff #188652)

Why not move this to line 411?

llvm/lib/MC/MCDwarf.cpp
1018 ↗(On Diff #188652)

Are there guaranteed to be >1 MCDwarfFiles?

probinson marked 2 inline comments as done.Feb 28 2019, 7:37 AM
probinson added inline comments.
clang/tools/driver/cc1as_main.cpp
336 ↗(On Diff #188652)

Because on line 341, we std::move(*Buffer) into SrcMgr. I could try to figure out how to extract it from SrcMgr afterward, I guess.

llvm/lib/MC/MCDwarf.cpp
1018 ↗(On Diff #188652)

Yes, because MCDwarfFiles[0] is never used. If it's non-empty, size will be at least 2. I could expand on the comment to say so; there's another place where I have a comment like that.

probinson updated this revision to Diff 188792.Feb 28 2019, 2:32 PM

Address review comments & rebase.

probinson marked 2 inline comments as done.Feb 28 2019, 2:32 PM
aprantl accepted this revision.Feb 28 2019, 2:35 PM
This revision is now accepted and ready to land.Feb 28 2019, 2:35 PM
dblaikie added inline comments.Feb 28 2019, 3:56 PM
llvm/lib/MC/MCContext.cpp
586 ↗(On Diff #188792)

No need for the "(void)" here - this function isn't marked NO_DISCARD or anything liek that, by the looks of it?

probinson marked 2 inline comments as done.Feb 28 2019, 4:04 PM
probinson added inline comments.
llvm/lib/MC/MCContext.cpp
586 ↗(On Diff #188792)

No, it's not. Wasn't entirely sure what the criteria were. I'll remove this.

This revision was automatically updated to reflect the committed changes.
probinson marked an inline comment as done.