Re: [gold] "patch" for the incremental link design document

[Ian Lance Taylor <iant at google dot com>]

Rafael Espindola <espindola@google.com> writes:

> --------------------------------
> Change the "For an object file or shared library" section into:
>
> For an object file, shared library or archive
>
> 1. 4 byte count of input sections
>
>    * Always zero for a shared library or archive.
>
> 2. 4 byte count of global symbols. In the case of an archive, this
> will be the count of symbols in the *unused* members.
>
> 3. For each input section:
>
>   1. 4 byte offset to section name in .gnu_incremental_strtab section
>   2. 4 byte output section index
>          * If input section is omitted, this is zero.
>   3. 8 byte offset of input section in output section
>   4. 8 byte input section size
>
> 4. For each global symbol:
>
>   1. 4 byte index into output global symbol table if the symbol if an
> object file or library. 4 byte offset into .gnu_incremental_strtab if
> an archive.
>   2. 4 byte offset to next linked list entry
>          * Linked list starts from global symbol list.
>          * Offset is to entry in input file list.
>   3. 4 byte count of relocations for this file.
>   4. 4 byte offset to relocations in .gnu_incremental_relocs section.
> ---------------------------------
>
> The change is that now t the symbols in unused archive members point
> to the incremental string table. This should give us enough
> information to build the necessary lists for each symbol.
>
> For example, lets say b.o defines foo and is used. c.o defines bar and
> is unused. Executing
>
> ar q a,a b,o c,o
> ld -incremental d.o a.a -o exec
>
> Will produce (among others) the lists
>
> foo -> b.o
> bar -> a.a
>
> now if we change d.o and add an undefined reference to bar we can just
> look up the list for bar, find that a.a is on it and force a relink.


This seems entirely reasonable to me.  You should add a section on how
to look up a symbol which is mentioned in some archive in the earlier
link but is not in the global symbol table.

Ian