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Re: [gold patch] Incremental 15/18: Add --incremental-base option.
- From: Ian Lance Taylor <iant at google dot com>
- To: Cary Coutant <ccoutant at google dot com>
- Cc: Binutils <binutils at sourceware dot org>
- Date: Tue, 24 May 2011 07:58:36 -0700
- Subject: Re: [gold patch] Incremental 15/18: Add --incremental-base option.
- References: <BANLkTimtBoXNSe+ECPp7RQVp6nQ-HcwehQ@mail.gmail.com> <BANLkTi=bPiP_vgh4_x5EMKeGn5jGnD1Y2A@mail.gmail.com>
Cary Coutant <ccoutant@google.com> writes:
> * gold.cc (queue_initial_tasks): Pass incremental base filename
> to Output_file::open_base_file; don't print error message.
> * incremental-dump.cc (main): Adjust call to
> Output_file::open_for_modification.
> * incremental-dump.cc (main): Likewise.
> * incremental.cc (Incremental_inputs::report_command_line):
> Ignore --incremental-base option when comparing command lines.
> * options.h (class General_options): Add --incremental-base.
> * output.cc (Output_file::Output_file):
> (Output_file::open_base_file): Add base_name and writable parameters;
> copy base file to new file; print error message here.
> (Output_file::map_no_anonymous): Add writable parameter; adjust all
> callers.
> * output.h (Output_file::open_for_modification): Rename to...
> (Output_file::open_base_file): ...this; add base_name and
> writable parameters; adjust all callers.
> (Output_file::map_no_anonymous): Add writable parameter; adjust all
> callers.
> * testsuite/Makefile.am (incremental_test_4): Test
> --incremental-base.
> * testsuite/Makefile.in: Regenerate.
> @@ -861,6 +861,7 @@ Incremental_inputs::report_command_line(int argc, const char* const* argv)
> || strcmp(argv[i], "--incremental-changed") == 0
> || strcmp(argv[i], "--incremental-unchanged") == 0
> || strcmp(argv[i], "--incremental-unknown") == 0
> + || is_prefix_of("--incremental-base=", argv[i])
> || is_prefix_of("--debug=", argv[i]))
> continue;
Will this work correctly if the user does
ld --incremental-base old-file
? That is, if they pass the argument as a separate argv entry, rather
than using =? I guess the same question arises for --debug.
> + // If the base file and the output file are different, open a
> + // new output file and copy the contents from the base file.
> + if (use_base_file)
> + {
> + unsigned char* base = this->base_;
> + this->open(s.st_size);
> + memcpy(this->base_, base, s.st_size);
> + ::munmap(base, s.st_size);
> + ::close(o);
> + }
You're going to some mild contortions to map in the base file, and then
you are throwing away the mapping. If you are going to stick with this
copying approach, then I think it would be simpler to just map the
output file as for a non-incremental link, and then open() the base file
and read() the contents into the mapping you just created. That will be
just as efficient--it's a nice sequential read--and will save you from
running out of memory when you in effect map the output file twice.
Ian