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Fix .debug_aranges parsing. #2019

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jasonmolenda
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Fix .debug_aranges parsing.

Code was added that used llvm error checking to parse .debug_aranges, but the error check after parsing the DWARFDebugArangesSet was reversed and was causing no error to be returned with no valid address ranges being actually used. This meant we always would fall back onto creating out own address ranges by parsing the compile unit's ranges. This was causing problems for cases where the DW_TAG_compile_unit had a single address range by using a DW_AT_low_pc and DW_AT_high_pc attribute pair (not using a DW_AT_ranges attribute), but the .debug_aranges had correct split ranges. In this case we would end up using the single range for the compile unit that encompassed all of the ranges from the .debug_aranges section and would cause address resolving issues in LLDB where address lookups would fail for certain addresses.

Differential Revision: https://reviews.llvm.org/D87626

(cherry picked from commit 79f22b1)

Code was added that used llvm error checking to parse .debug_aranges, but the error check after parsing the DWARFDebugArangesSet was reversed and was causing no error to be returned with no valid address ranges being actually used. This meant we always would fall back onto creating out own address ranges by parsing the compile unit's ranges. This was causing problems for cases where the DW_TAG_compile_unit had a single address range by using a DW_AT_low_pc and DW_AT_high_pc attribute pair (not using a DW_AT_ranges attribute), but the .debug_aranges had correct split ranges. In this case we would end up using the single range for the compile unit that encompassed all of the ranges from the .debug_aranges section and would cause address resolving issues in LLDB where address lookups would fail for certain addresses.

Differential Revision: https://reviews.llvm.org/D87626

(cherry picked from commit 79f22b1)
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@swift-ci please test

@jasonmolenda jasonmolenda merged commit 639d0aa into swiftlang:apple/stable/20200714 Oct 22, 2020
@jasonmolenda jasonmolenda deleted the eng/r70541925-fix-aranges-parsing branch October 22, 2020 02:57
JDevlieghere added a commit that referenced this pull request Nov 7, 2020
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