[PATCH] [lld][ELF] Add linker script ENTRY command

[Nick Kledzik]

On May 22, 2013, at 3:15 PM, Rui Ueyama <ruiu at google.com> wrote:
>  It seems that TargetInfo and its subclasses are not copyable even after separating LinkerInput. The classes have many fields that are not copyable, such as memory allocators, file readers and writers. I think such fields are implementation details and not part of the API because they are used only in Core Linking. But they make TargetInfo hard to copy.
> 
>  We may want to split TargetInfo into two classes.
> 
>   - New TargetInfo class is a public API and is constructed and modified by Driver.This class has default copy constructor.
>   - A new class have other fields that are not exposed to Driver. It holds a copy of TargetInfo, list of input files, memory allocators, readers, writers, etc. This is not copyable.
> 
>  What do you think?

I do think we need to split up TargetInfo, but not along those boundaries.  For the library case we want to be able to create a TargetInfo that is reused to link different sets of files.  So, it is the list of files that needs to be factored out.  The rest of the TargetInfo can remain const.

Backing up, it is supporting ENTRY in a linker script that is driving this, right?  So, can't we make the entrySymbolName() method in TargetInfo virtual, then have ELFTargetInfo:: entrySymbolName() check the input files to see if there is a linker script and if so check to see if it defines ENTRY, otherwise fallback to whatever command line or default was used when the ELFTargetInfo was created?

-Nick