[LLVMdev] Win32 COFF Support

[Michael Spencer]

On Tue, Sep 28, 2010 at 7:39 PM, Michael Spencer <bigcheesegs at gmail.com> wrote:
> On Sun, Sep 26, 2010 at 5:27 PM, Nathan Jeffords
> <blunted2night at gmail.com> wrote:
>> Hi guys,
>> While trying to get dwarf debugging information to work with Win32 COFF
>> targets, I came across a couple of issues with the current implementation
>> of WinCOFFObjectWriter. Emitting empty section causes debug information to
>> invalid, as the presence of certain debug section implies available
>> information, and emission of labels as symbols confused gdb about the
>> structure of the program.
>> The attached patch allows the WinCOFFObjectWriter to drop empty sections,
>> and label symbols. It converts relocations targeted at symbols into
>> relocations relative to the containing section.
>> I have not run the tests in the '/test/MC/COFF', but have run through the
>> unit-test framework for my compiler and generated some text executables with
>> clang and everything looks to be in order. It may change the output of
>> the  '/test/MC/COFF' if the string references are emitted as temporaries.
>> -Nathan
>
> http://llvm.org/bugs/show_bug.cgi?id=8248
>
> It seems that there actually is a bug. I thought it was due to
> something else, but reverting this patch fixes it. Why/when exactly
> does gdb expect IMAGE_SYM_CLASS_LABEL?
>
> - Michael Spencer
>

I've attached a patch that fixes the above problem while keeping the
LABEL storage class on labels. Can you verify that it keeps the
behavior you wanted?

- Michael Spencer
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