LTO output objects have an STT_FILE symbol using the name of the file,
a temporary file. This results in executables that can't be exactly
reproduced, so the file name needs to be dropped. We don't want to
lose all file symbols when linking a mix of lto and non-lto objects as
a file symbol can be used to figure which source file generated a
given local symbol. So lto output objects need to be marked.
I chose to mark lto output objects with a new bfd flag. This flag is
also used to fix a bug in the link-once handling; An object being
loaded after "loading_lto_outputs" is set might be one extracted from
an archive to satisfy new references from lto objects, not an lto
object itself.
The new flag is copied from archive to elements, and the same done
for no_export. This fixes a bug in that --exclude-libs doesn't work
with thin archives. I'm not completely happy with this part of the
patch and may revist this to avoid the hack in
_bfd_look_for_bfd_in_cache.
PR ld/17973
include/
* bfdlink.h (struct bfd_link_info): Delete loading_lto_outputs.
bfd/
* bfd.c (struct bfd): Add lto_output.
* linker.c (_bfd_handle_already_linked): Explicitly test for
objects added by the lto plugin.
* opncls.c (_bfd_new_bfd_contained_in): Copy lto_output and
no_export flags from archive.
* archive.c (open_nested_file): New function, setting lto_output
and no_export, extracted from..
(find_nested_archive): ..here. Flip params. Rename from
_bfd_find_nested_archive.
(_bfd_get_elt_at_filepos): Correct var typo. Use open_nested_file.
(_bfd_look_for_bfd_in_cache): Copy no_export.
* elflink.c (elf_link_add_object_symbols): Remove now unnecessary
my_archive->no_export test.
(elf_link_input_bfd): Drop existing lto_output STT_FILE syms.
Don't use the file name when adding lto_output STT_FILE sym.
* bfd-in2.h: Regenerate.
ld/
* ldlang.h (struct lang_input_statement_flags): Add lto_output.
* ldlang.c (lang_process): Don't set loading_lto_outputs.
* ldfile.c (ldfile_try_open_bfd): Transfer entry flags.lto_output
to bfd.
* plugin.c (add_input_file, add_input_library): Set flags.lto_output.
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README for LD
This is the GNU linker. It is distributed with other "binary
utilities" which should be in ../binutils. See ../binutils/README for
more general notes, including where to send bug reports.
There are many features of the linker:
* The linker uses a Binary File Descriptor library (../bfd)
that it uses to read and write object files. This helps
insulate the linker itself from the format of object files.
* The linker supports a number of different object file
formats. It can even handle multiple formats at once:
Read two input formats and write a third.
* The linker can be configured for cross-linking.
* The linker supports a control language.
* There is a user manual (ld.texinfo), as well as the
beginnings of an internals manual (ldint.texinfo).
Installation
============
See ../binutils/README.
If you want to make a cross-linker, you may want to specify
a different search path of -lfoo libraries than the default.
You can do this by setting the LIB_PATH variable in ./Makefile
or using the --with-lib-path configure switch.
To build just the linker, make the target all-ld from the top level
directory (one directory above this one).
Porting to a new target
=======================
See the ldint.texinfo manual.
Reporting bugs etc
===========================
See ../binutils/README.
Known problems
==============
The Solaris linker normally exports all dynamic symbols from an
executable. The GNU linker does not do this by default. This is
because the GNU linker tries to present the same interface for all
similar targets (in this case, all native ELF targets). This does not
matter for normal programs, but it can make a difference for programs
which try to dlopen an executable, such as PERL or Tcl. You can make
the GNU linker export all dynamic symbols with the -E or
--export-dynamic command line option.
HP/UX 9.01 has a shell bug that causes the linker scripts to be
generated incorrectly. The symptom of this appears to be "fatal error
- scanner input buffer overflow" error messages. There are various
workarounds to this:
* Build and install bash, and build with "make SHELL=bash".
* Update to a version of HP/UX with a working shell (e.g., 9.05).
* Replace "(. ${srcdir}/scripttempl/${SCRIPT_NAME}.sc)" in
genscripts.sh with "sh ${srcdir}..." (no parens) and make sure the
emulparams script used exports any shell variables it sets.
Copyright (C) 2012-2015 Free Software Foundation, Inc.
Copying and distribution of this file, with or without modification,
are permitted in any medium without royalty provided the copyright
notice and this notice are preserved.
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