[LLVMdev] [LLD] support for dlltool generated libs in COFF/PECOFF

[Martell Malone]

Hi again rui, :)

I've got all the patches into llvm and clang for supporting mingw-w64 via
compiler-rt and now we are able to build a full mingw-w64 toolchain without
gcc :)
With great help from yaron and rnk.

I've CC'd them as they might have interest in seeing this target through
with me to the end :)

So I have again turned my attention to LLD so that we can also remove ld as
a depend for this target

Previously I raised the issue that while lld would infact link exe's for me
the issue was the sections were malformed and thus crashed on launch.

I've done some debugging reguarding this and discovered it is due to
differences between what MSVC's lib.exe and binutils dlltool produces

I have attached a very simple .def file and generated libs via dlltool
along with an objdump -s log of the lib.exe version

I don't know too much about the internals of lld to be able to tell the
exact cause of the problem but there are 3 specific differences I noted.

1. With dlltool each object has the name of a compiled .o file this is the
one it generates when building the code section
With lib each object has the dll name

2. With dlltool section 7 is used for the dll name and the function names
with lib section 6 is used

3. Other differences are that there is no debug section with dlltool and
the text section comes first rather than last with lib (that probably
doesn't matter much though)

Please see attached notes.txt with objdump's of both libs

Can could you give me your thoughts on this and how best we support both
layouts in COFF/PECOFF ?

What source files should I be looking at to patch this or is this something
you can support with very little effort ?

I don't know if you would be opposed to supporting this or not being honest
dlltool should generate libs using the same section number as lib.exe but
we can't exactly change that now because existing toolchains and libs have
already been built with this and changing that would break them.

If you are opposed I would like you to still tell me what I have to change
to get it working after I do that I can narrow the scope for getting a
patch up streamed into binutils to fix this :)

Kind Regards
Martell
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