[Lldb-commits] [PATCH] D40211: Add comments to DWARFCompileUnit length fields/methods

[Greg Clayton via lldb-commits]

sizeof(struct) tends to include system level padding for the current host. But to answer your question, no there isn't a structure defined like this and we wouldn't use them anyway as we want to fill out one compile unit struct that works for both. 

> On Nov 20, 2017, at 8:01 AM, Zachary Turner <zturner at google.com> wrote:
> 
> Right but isn’t there a DWARF64_HEADER and DEARF32_HEADER struct somewhere? This way you could just say 
> 
> return m_isdwarf64 ? sizeof(DWARF64_HEADER) : sizeof(DWARF32_HEADER);
> On Mon, Nov 20, 2017 at 7:50 AM Greg Clayton <clayborg at gmail.com <mailto:clayborg at gmail.com>> wrote:
> 
>> On Nov 19, 2017, at 4:56 PM, Zachary Turner <zturner at google.com <mailto:zturner at google.com>> wrote:
>> 
>> 
>> 
>> On Sun, Nov 19, 2017 at 6:35 AM Jan Kratochvil via Phabricator via lldb-commits <lldb-commits at lists.llvm.org <mailto:lldb-commits at lists.llvm.org>> wrote:
>> This revision was automatically updated to reflect the committed changes.
>> Closed by commit rL318626: Add comments to DWARFCompileUnit length fields/methods (authored by jankratochvil).
>> 
>> Changed prior to commit:
>>   https://reviews.llvm.org/D40211?vs=123472&id=123498#toc <https://reviews.llvm.org/D40211?vs=123472&id=123498#toc>
>> 
>> Repository:
>>   rL LLVM
>> 
>> https://reviews.llvm.org/D40211 <https://reviews.llvm.org/D40211>
>> 
>> Files:
>>   lldb/trunk/source/Plugins/SymbolFile/DWARF/DWARFCompileUnit.h
>> 
>> 
>> Index: lldb/trunk/source/Plugins/SymbolFile/DWARF/DWARFCompileUnit.h
>> ===================================================================
>> --- lldb/trunk/source/Plugins/SymbolFile/DWARF/DWARFCompileUnit.h
>> +++ lldb/trunk/source/Plugins/SymbolFile/DWARF/DWARFCompileUnit.h
>> @@ -41,26 +41,24 @@
>>    void Clear();
>>    bool Verify(lldb_private::Stream *s) const;
>>    void Dump(lldb_private::Stream *s) const;
>> +  // Offset of the initial length field.
>>    dw_offset_t GetOffset() const { return m_offset; }
>>    lldb::user_id_t GetID() const;
>> -  uint32_t Size() const {
>> -    return m_is_dwarf64 ? 23
>> -                        : 11; /* Size in bytes of the compile unit header */
>> -  }
>> +  // Size in bytes of the initial length + compile unit header.
>> +  uint32_t Size() const { return m_is_dwarf64 ? 23 : 11; }
>> 
>> This is pretty gross.  Don't we have a structure somewhere that represents a compile unit header?  That we can just call sizeof on?  Same goes for the rest of the patch
> 
> It varies depending on data on how the length unit is represented in the data stream. If the length starts with UINT32_MAX, it is followed by a 64 bit length. If the length isn't UINT32_MAX it is just a 32 bit length. 

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