[LLVMdev] [lld] need to figure out if file is an archive member and record more information...

[shankarke]

Thanks Rui for the feedback.

I would settle for a derived class and the class would be called LinkerMemoryBuffer. I will send a patch for review soon.

Shankar Easwaran


> On Dec 2, 2014, at 23:40, Rui Ueyama [via LLVM] <ml-node+s1065342n74959h12 at n5.nabble.com> wrote:
> 
> I think another way to do what you want is to add a new parameter to parse() to propagate library file name to the parser, so that the parser can determine if it's reading a library member. In this way you don't have to make a derived class of MemoryBuffer.
> 
> One fault of that approach is the new parameter seems a bit arbitrary. In order to get file name, you would call MemoryBuffer::getIdentifier, but in order to get, you would use the second parameter of parse(). This is not wrong but looks odd.
> 
> The other approach is to parse "filename(libraryname)" string returned from MemoryBuffer::getIdentifier. But this is of course not robust. (What if we have an object file whose file path contains parentheses?)
> 
> So I think making a derived class would be fine.
> 
>> On Tue, Dec 2, 2014 at 9:24 PM, Shankar Easwaran <[hidden email]> wrote:
>>> On 12/2/2014 11:19 PM, Rui Ueyama wrote:
>>> Do you have to know whether a MemoryBuffer was in a library or not during
>>> parsing that MemoryBuffer?
>> Yes, I need to know that while parsing the buffer too.
>> 
>>> 
>>> If not, we could just set a library name to a File in
>>> FileArchive::instantiateMember after we call _registry.parseFile.
>>> 
>>> On Tue, Dec 2, 2014 at 9:08 PM, Shankar Easwaran <[hidden email]>
>>> wrote:
>>> 
>>>> Hi Nick,
>>>> 
>>>> Currently the Reader doesnot have  a way to figure out that a file that is
>>>> being parsed is part of an archive.
>>>> 
>>>> For linker script support this is needed to match a rule that matches only
>>>> if the file is from an archive library (or a member of an archive.
>>>> 
>>>> For example :-
>>>> 
>>>> SECTIONS {
>>>> .myoutputsection : {
>>>>      libc.a : { *(.text) }
>>>>      printf.o : { *(.rodata) }
>>>> }
>>>> }
>>>> 
>>>> The colon is used to denote an archive file or a member of an archive file
>>>> and the rule says pick all text sections from members of libc.a that the
>>>> linker uses for the current link step.
>>>> 
>>>> Current Design
>>>> ------------------------
>>>> In the current design we record the archive file and the member in the
>>>> memory buffer and identify using library(member) which is part of the
>>>> MemoryBuffer.
>>>> 
>>>> Information that needs to be recorded
>>>> ---------------------------------------------------------
>>>> The linker also needs to store the library and the member names separately
>>>> as the linker script syntax allows to to distinguish library names and
>>>> member names.
>>>> 
>>>> Approach we could take is :-
>>>> -------------------------------------------
>>>> a) Rename MemoryBuffer to LinkerMemoryBuffer, which is a container for
>>>> MemoryBuffer but with extra information(that contains the filename and an
>>>> optional member name)
>>>> 
>>>> If the member name is not empty, the Reader could treat this as an archive
>>>> member.
>>>> 
>>>> Comments ??
>>>> 
>>>> Shankar Easwaran
>>>> 
>>>> --
>>>> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted
>>>> by the Linux Foundation
>>>> 
>>>> _______________________________________________
>>>> LLVM Developers mailing list
>>>> [hidden email]         http://llvm.cs.uiuc.edu
>>>> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>> 
>> 
>> -- 
>> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by the Linux Foundation
> 
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