[Lldb-commits] [lldb] r268110 - Watch out for compilers that generate bad bitfield info. If the bit size of a bitfield member doesn't lie within the bit bounds of the type itself, just leave it out so we don't get clang asserting and killing our IDE when it gets unhappy with the information.

[Zachary Turner via lldb-commits]

If clang is generating bad debug info, do you think you should file a bug
against clang for that?

On Fri, Apr 29, 2016 at 2:32 PM Greg Clayton via lldb-commits <
lldb-commits at lists.llvm.org> wrote:

> Author: gclayton
> Date: Fri Apr 29 16:26:46 2016
> New Revision: 268110
>
> URL: http://llvm.org/viewvc/llvm-project?rev=268110&view=rev
> Log:
> Watch out for compilers that generate bad bitfield info. If the bit size
> of a bitfield member doesn't lie within the bit bounds of the type itself,
> just leave it out so we don't get clang asserting and killing our IDE when
> it gets unhappy with the information.
>
> https://llvm.org/bugs/show_bug.cgi?id=27515
> <rdar://problem/21082998>
>
>
> Modified:
>
> lldb/trunk/packages/Python/lldbsuite/test/lang/c/bitfields/TestBitfields.py
>     lldb/trunk/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp
>
> Modified:
> lldb/trunk/packages/Python/lldbsuite/test/lang/c/bitfields/TestBitfields.py
> URL:
> http://llvm.org/viewvc/llvm-project/lldb/trunk/packages/Python/lldbsuite/test/lang/c/bitfields/TestBitfields.py?rev=268110&r1=268109&r2=268110&view=diff
>
> ==============================================================================
> ---
> lldb/trunk/packages/Python/lldbsuite/test/lang/c/bitfields/TestBitfields.py
> (original)
> +++
> lldb/trunk/packages/Python/lldbsuite/test/lang/c/bitfields/TestBitfields.py
> Fri Apr 29 16:26:46 2016
> @@ -22,7 +22,6 @@ class BitfieldsTestCase(TestBase):
>
>      @skipIfWindows # BitFields exhibit crashes in record layout on
> Windows (http://llvm.org/pr21800)
>      @skipIf("llvm.org/pr27510", oslist=["linux"], compiler="clang",
> compiler_version=[">=", "3.9"]) # expectedFailure, skip to avoid crash
> -    @skipIf("llvm.org/pr27515", oslist=["macosx"]) # Assertion failed:
> (Offset >= Size), function insertPadding CGRecordLayoutBuilder.cpp
>      def test_and_run_command(self):
>          """Test 'frame variable ...' on a variable with bitfields."""
>          self.build()
>
> Modified:
> lldb/trunk/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/lldb/trunk/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp?rev=268110&r1=268109&r2=268110&view=diff
>
> ==============================================================================
> --- lldb/trunk/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp
> (original)
> +++ lldb/trunk/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp Fri
> Apr 29 16:26:46 2016
> @@ -2645,6 +2645,10 @@ DWARFASTParserClang::ParseChildMembers(c
>      if (!parent_die)
>          return 0;
>
> +    // Get the parent byte size so we can verify any members will fit
> +    const uint64_t parent_byte_size =
> parent_die.GetAttributeValueAsUnsigned(DW_AT_byte_size, UINT64_MAX) * 8;
> +    const uint64_t parent_bit_size = parent_byte_size == UINT64_MAX ?
> UINT64_MAX : parent_byte_size * 8;
> +
>      uint32_t member_idx = 0;
>      BitfieldInfo last_field_info;
>
> @@ -2890,10 +2894,23 @@ DWARFASTParserClang::ParseChildMembers(c
>                                      if (byte_size == 0)
>                                          byte_size =
> member_type->GetByteSize();
>
> -                                    if
> (die.GetDWARF()->GetObjectFile()->GetByteOrder() == eByteOrderLittle)
> +                                    ObjectFile *objfile =
> die.GetDWARF()->GetObjectFile();
> +                                    if (objfile->GetByteOrder() ==
> eByteOrderLittle)
>                                      {
>                                          this_field_info.bit_offset +=
> byte_size * 8;
>                                          this_field_info.bit_offset -=
> (bit_offset + bit_size);
> +
> +                                        if (this_field_info.bit_offset >=
> parent_bit_size)
> +                                        {
> +
> objfile->GetModule()->ReportWarning("0x%8.8" PRIx64 ": %s bitfield named
> \"%s\" has invalid bit offset (0x%8.8" PRIx64 ") member will be ignored.
> Please file a bug against the compiler and include the preprocessed output
> for %s\n",
> +
>       die.GetID(),
> +
>       DW_TAG_value_to_name(tag),
> +
>       name,
> +
>       this_field_info.bit_offset,
> +
>       sc.comp_unit ? sc.comp_unit->GetPath().c_str() : "the source file");
> +                                            this_field_info.Clear();
> +                                            continue;
> +                                        }
>                                      }
>                                      else
>                                      {
>
>
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