From: Alan Modra <amodra@gmail.com>
To: "H.J. Lu" <hjl.tools@gmail.com>
Cc: binutils@sourceware.org
Subject: Re: [PATCH] LTO: Ignore undefined symbols without relocation
Date: Thu, 30 Jul 2020 19:02:14 +0930 [thread overview]
Message-ID: <20200730093214.GT9601@bubble.grove.modra.org> (raw)
In-Reply-To: <20200729222258.3016925-1-hjl.tools@gmail.com>
On Wed, Jul 29, 2020 at 03:22:58PM -0700, H.J. Lu via Binutils wrote:
> Normally an undefined symbol is treated as a reference. Linker will
> try to satisfy the reference. This feature is used to bring a symbol
> definition into output without explicit relocation. If there is no
> definition nor relocation, linker will remove undefined symbol from
> symbol table in output (PR ld/4317). But GCC 10 LTO may generate
> separate debug info files which contain undefined symbols without
> relocations:
Surely this is just a gcc bug? We search libraries again after
loading the LTO output, so one would expect that undefined symbols
satisfied by an archive (or as-needed shared library) would lead to
extra files being linked.
I'd like to better understand just how this problem occurs though. As
it is, I suspect there might be something else going on here, for
example, ranlib being run without a plugin when building the archives.
> (sym_cache): Moved before elf_link_hash_table.
> (elf_link_hash_table): Add sym_cache.
Please commit the above and related backend changes as a separate
patch, preapproved.
> * elflink.c (_bfd_elf_merge_symbol): After all LTO IR symbols
> have been read, skip all undefined symbols without relocation.
> (elf_link_add_object_symbols): Set has_reloc_after_lto_all_symbols_read
> after all LTO IR symbols have been read.
But not this bit just yet.
--
Alan Modra
Australia Development Lab, IBM
next prev parent reply other threads:[~2020-07-30 9:32 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-29 22:22 H.J. Lu
2020-07-30 9:32 ` Alan Modra [this message]
2020-07-30 10:39 ` [PATCH] elf: Add sym_cache to elf_link_hash_table H.J. Lu
2020-07-30 11:51 ` [PATCH] LTO: Ignore undefined symbols without relocation H.J. Lu
2020-07-31 8:12 ` Alan Modra
2020-07-31 9:51 ` Nick Clifton
2020-07-31 10:07 ` Nick Clifton
2020-07-31 11:02 ` Alan Modra
2020-07-31 11:43 ` H.J. Lu
2020-07-31 15:47 ` V2 " H.J. Lu
2020-08-03 7:26 ` Alan Modra
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