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[llvm-dwarfdump] - Simplify the test case.
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Authored by grimar on Dec 4 2018, 3:16 AM.

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Summary

This was requested during the post-commit review for D55113.

I added/updated the comment and removed excessive things.

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rL LLVM

Event Timeline

grimar created this revision.Dec 4 2018, 3:16 AM
dblaikie added inline comments.Dec 4 2018, 8:45 AM
test/tools/llvm-dwarfdump/X86/no_debug_addr.s
5–6 ↗(On Diff #176589)

Not sure I understand this comment - but I think I get where you're going with it, might just be some grammar improvement to make it more clear?

Oh, actually, here's a thought - did this bug pop-up when using rnglists in .dwo files? They certainly won't have a debug_addr & would then be a fully realistic scenario rather than one where a section of debug info would have to be dropped to demonstrate the failure?

So maybe a comment like this:

  1. Ensure bogus empty section names are not printed when dumping rnglists that reference debug_addr when it is not present (such as in .dwo files).

Yep, looks like it does, so here's a really short example I worked up:

      .section        .debug_info.dwo,"e",@progbits
      .long   .Ldebug_info_dwo_end1-.Ldebug_info_dwo_start1   # Length of Unit
.Ldebug_info_dwo_start1:
      .short  5                       # DWARF version number
      .byte   5                       # DWARF Unit Type
      .byte   8                       # Address Size (in bytes)
      .long   0                       # Offset Into Abbrev. Section
      .quad   -6809755978868859807
      .byte   1                       # Abbrev [1] 0x14:0x32 DW_TAG_compile_unit
      .byte   0                       # DW_AT_ranges
.Ldebug_info_dwo_end1:
      .section        .debug_abbrev.dwo,"e",@progbits
      .byte   1                       # Abbreviation Code
      .byte   17                      # DW_TAG_compile_unit
      .byte   0                       # DW_CHILDREN_no
      .byte   85                      # DW_AT_ranges
      .byte   35                      # DW_FORM_rnglistx
      .byte   0                       # EOM(1)
      .byte   0                       # EOM(2)
      .section        .debug_rnglists.dwo,"e",@progbits
      .long   .Ldebug_rnglist_table_end1-.Ldebug_rnglist_table_start1 # Length
.Ldebug_rnglist_table_start1:
      .short  5                       # Version
      .byte   8                       # Address size
      .byte   0                       # Segment selector size
      .long   1                       # Offset entry count
.Lrnglists_dwo_table_base0:
      .long   .Ldebug_ranges0-.Lrnglists_dwo_table_base0
.Ldebug_ranges0:
      .byte   1                       # DW_RLE_base_addressx
      .byte   0                       #   base address index
      .byte   4                       # DW_RLE_offset_pair
      .byte   0                       #   starting offset
      .byte   1                       #   ending offset
      .byte   3                       # DW_RLE_startx_length
      .byte   1                       #   start index
      .byte   2                       #   length
      .byte   0                       # DW_RLE_end_of_list
.Ldebug_rnglist_table_end1:
grimar marked an inline comment as done.Dec 4 2018, 9:03 AM
grimar added inline comments.
test/tools/llvm-dwarfdump/X86/no_debug_addr.s
5–6 ↗(On Diff #176589)

Idea about using the .dwo is interesting, thanks! I'll check it and probably update this patch tomorrow.

Oh, actually, here's a thought - did this bug pop-up when using rnglists in .dwo files?

I faced this in LLD actually. Its implementation of the llvm::DWARFObject did not override the getRnglistsSection
and the effect from returning the empty section by default implementation was the same as rnglists section is absent.

dblaikie added inline comments.Dec 4 2018, 9:05 AM
test/tools/llvm-dwarfdump/X86/no_debug_addr.s
5–6 ↗(On Diff #176589)

Guess you meant "getAddrSection"/addr section is absent - yeah, could totally believe that - great find! & the same bug totally shows up in other places, like the dwo dumping - so handy to fix all around :)

grimar marked an inline comment as done.Dec 4 2018, 9:09 AM
grimar added inline comments.
test/tools/llvm-dwarfdump/X86/no_debug_addr.s
5–6 ↗(On Diff #176589)

Yeah, it was getAddrSection, I looked at the wrong place.
(Had to add both getRnglistsSection and getAddrSection in that patch: https://reviews.llvm.org/D55109)

grimar updated this revision to Diff 176790.Dec 5 2018, 4:10 AM
  • Used the code and comment suggested.
dblaikie accepted this revision.Dec 5 2018, 8:23 AM

Great, thanks!

This revision is now accepted and ready to land.Dec 5 2018, 8:23 AM

Thanks for the review and ideas, David!

This revision was automatically updated to reflect the committed changes.