[lldb-dev] Questions about DWARFDebugInfoEntry::Extract and DWARFDebugInfoEntry::FastExtract

[Warren.Paul at nokia.com]

Hi Greg,

Attached is patch that fixes a few issues:

1) The infinite loop in FastExtract.  I fixed it by doing what Extract
does which uses a goto.  I'm not a fan of goto's but the alternative of
setting "form_is_indirect = false" for everything other cases didn't seem
like a good solution either.  Now Extract and FastExtract are almost
identical, so at some point we should probably consolidate the common code
into a shared function, or just make them one and deviate the differences
based on a parameter.

2) Fixed a crasher in SymbolFileDWARF.  Where it was crashing would
probably never get executed with unix-style paths in the Dwarf, but does
with Windows-style paths.  This is just a bandaid for now.  The code
checks for absolute paths by checking if it starts with '/'.  We'll need
to fix that up for Windows builds.  I'd prefer not to have #ifdef's for
Windows in places like this  so perhaps we can add a static function to
FileSpec or something that checks for absolute paths?  I know there's been
some changes to FileSpec in the last couple of days but I haven't looked
closely at them yet.  Another minor change is to fix the build when
ENABLE_DEBUG_PRINTF is defined.

3) Added some more Dwarf->Clang type mappings in ClangASTContext.


I've ran several of our sym files through the parser and it's working well
for compile units and function scopes.  I'm still getting a lot of
crashers though when trying to parse types and variables.  I'll send you a
couple in a separate email if you're interested in having a look.

Thanks,
Warren




On 2/3/11 8:19 PM, "ext Greg Clayton" <gclayton at apple.com> wrote:

>The fast path currently ignores checking if offsets are valid while
>parsing a single DIE which can be bad if we have bad DWARF. So both
>should stay.
>
>Send a patch to the list for one and I can fix it in both!
>
>If you have an example file that contains DWARF with this issue, I
>wouldn't mind getting my hands on a few more external DWARF files so I
>can test my DWARF tools with them. I am not sure if you can spare any
>sample DWARF files if they don't contain anything proprietary, but if you
>can, please email me some directly.
>
>Greg Clayton
>
>
>On Feb 3, 2011, at 12:34 PM, Warren.Paul at nokia.com wrote:
>
>> I hit an infinite loop in DWARFDebugInfoEntry::FastExtract when
>>consuming some of our sym files containing DW_FORM_indirect attribute
>>forms.  In fixing the problem, I saw DWARFDebugInfoEntry::Extract which
>>does pretty much the same thing (and did not have the bug).  But looking
>>at the call graph, it doesn't look like Extract is called, at least not
>>by any functions that are called themselves (see call graph at the
>>bottom).  It's basically used by Dump and Verify and helpers for those
>>methods.
>> 
>> So the question is, should I get rid of Extract and change everything
>>to use FastExtract, or just fix the problem in FastExtract and leave
>>everything else be?
>> 
>> Thanks,
>> Warren
>> 
>> 
>> 
>> DWARFDebugInfoEntry::Extract(SymbolFileDWARF *, const DWARFCompileUnit
>>*, dw_offset_t *)
>>     DWARFDebugInfo::Parse(SymbolFileDWARF *, Callback, void *)
>>         DWARFDebugInfo::Dump(lldb_private::Stream *, SymbolFileDWARF *,
>>unsigned int, unsigned int)
>>         DWARFDebugInfo::Find(const char *, bool, std::vector<unsigned
>>int,std::allocator<unsigned int>> &)
>>         DWARFDebugInfo::Find(lldb_private::RegularExpression &,
>>std::vector<unsigned int,std::allocator<unsigned int>> &)
>>         DWARFDebugInfo::Verify(lldb_private::Stream *, SymbolFileDWARF
>>*)
>>     DWARFDebugInfoEntry::AppendTypeName(SymbolFileDWARF *, const
>>DWARFCompileUnit *, unsigned int, lldb_private::Stream *)
>>         DWARFDebugInfoEntry::AppendTypeName(SymbolFileDWARF *, const
>>DWARFCompileUnit *, unsigned int, lldb_private::Stream *)
>>         DWARFDebugInfoEntry::DumpAttribute(SymbolFileDWARF *, const
>>DWARFCompileUnit *, const lldb_private::DataExtractor &, uint32_t *,
>>lldb_private::Stream *, dw_attr_t, dw_form_t)
>>             DWARFDebugInfoEntry::Dump(SymbolFileDWARF *, const
>>DWARFCompileUnit *, lldb_private::Stream *, uint32_t)
>>                 DumpCallback(SymbolFileDWARF *, DWARFCompileUnitSP &,
>>DWARFDebugInfoEntry *, unsigned int, unsigned int, void *) (4 matches)
>>                     DWARFDebugInfo::Dump(lldb_private::Stream *,
>>SymbolFileDWARF *, unsigned int, unsigned int)
>>                     DWARFDebugInfo::Dump(lldb_private::Stream *,
>>unsigned int, unsigned int)
>>                 DWARFDebugInfo::Dump(lldb_private::Stream *, unsigned
>>int, unsigned int)
>>                 DWARFDebugInfoEntry::Dump(SymbolFileDWARF *, const
>>DWARFCompileUnit *, lldb_private::Stream *, uint32_t)
>>                 DWARFDebugInfoEntry::DumpAncestry(SymbolFileDWARF *,
>>const DWARFCompileUnit *, const DWARFDebugInfoEntry *,
>>lldb_private::Stream *, uint32_t)
>>                     DWARFDebugInfoEntry::DumpAncestry(SymbolFileDWARF
>>*, const DWARFCompileUnit *, const DWARFDebugInfoEntry *,
>>lldb_private::Stream *, uint32_t)
>>     DWARFDebugInfoEntry::GetName(SymbolFileDWARF *, const
>>DWARFCompileUnit *, unsigned int, lldb_private::Stream *)
>>         DWARFDebugInfoEntry::DumpAttribute(SymbolFileDWARF *, const
>>DWARFCompileUnit *, const lldb_private::DataExtractor &, uint32_t *,
>>lldb_private::Stream *, dw_attr_t, dw_form_t)
>>             DWARFDebugInfoEntry::Dump(SymbolFileDWARF *, const
>>DWARFCompileUnit *, lldb_private::Stream *, uint32_t)
>>                 DumpCallback(SymbolFileDWARF *, DWARFCompileUnitSP &,
>>DWARFDebugInfoEntry *, unsigned int, unsigned int, void *) (4 matches)
>>                     DWARFDebugInfo::Dump(lldb_private::Stream *,
>>SymbolFileDWARF *, unsigned int, unsigned int)
>>                     DWARFDebugInfo::Dump(lldb_private::Stream *,
>>unsigned int, unsigned int)
>>                 DWARFDebugInfo::Dump(lldb_private::Stream *, unsigned
>>int, unsigned int)
>>                 DWARFDebugInfoEntry::Dump(SymbolFileDWARF *, const
>>DWARFCompileUnit *, lldb_private::Stream *, uint32_t)
>>                 DWARFDebugInfoEntry::DumpAncestry(SymbolFileDWARF *,
>>const DWARFCompileUnit *, const DWARFDebugInfoEntry *,
>>lldb_private::Stream *, uint32_t)
>>                     DWARFDebugInfoEntry::DumpAncestry(SymbolFileDWARF
>>*, const DWARFCompileUnit *, const DWARFDebugInfoEntry *,
>>lldb_private::Stream *, uint32_t)
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