[Lldb-commits] [PATCH] D72158: [DebugInfo] Make most debug line prologue errors non-fatal to parsing

Fri Feb 14 08:05:13 PST 2020

jhenderson marked an inline comment as done.
jhenderson added inline comments.

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Comment at: llvm/lib/DebugInfo/DWARF/DWARFDebugLine.cpp:323-325
+    // Treat this error as unrecoverable - we cannot be sure what any of
+    // the data represents including the length field, so cannot skip it or make
+    // any reasonable assumptions.
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labath wrote:
> BTW, I think this error should be recoverable too. I believe the reason why the length field comes *before* the version number is specifically so that one can skip over contributions with unsupported (future) version numbers.
> 
> While it's hard to say what the future versions of dwarf will look like, I would expect that the committee will try very hard to avoid  making changes in the length field. I think they'd use one of the DW_LENGTH_lo_reserved..DW_LENGTH_hi_reserved-1 constants for severely incompatible changes.
"Unrecoverable" here means don't try to parse this table, but do allow parsing the next. I think the comment might be slightly misleading in this regard. FWIW, a version of 0 or 1 probably doesn't have a leading length, so it is definitely unrecoverable. For versions > 5, which are now checked, we don't know what the structure of the header is, so although we could take a guess, we'd almost certainly get it wrong and produce invalid (possibly very invalid) output. I don't have a strong opinion as to whether that should be an unrecoverable error or not (currently it is).

Repository:
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  https://reviews.llvm.org/D72158/new/

https://reviews.llvm.org/D72158