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

[Shankar Easwaran]

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 <shankare at codeaurora.org>
> 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
>>
>> --
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>> by the Linux Foundation
>>
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