In <https://sourceware.org/ml/binutils/2015-12/msg00190.html> (commit
4a07dc8135), Kwok fixed a problem with
the template used for a dummy BFD for an IR file for LTO on MinGW,
where the input and output formats are not the same.
A problem, however, remains in the case of linking for
x86_64-w64-mingw32 -m32, where LTO linking reports an ambiguity
between the pe-i386 and pei-i386 formats. An object (pe-i386) with
plugin data is being tested by the linker to see what formats match.
The default format initially set by the linker when
bfd_check_format_matches is called is pei-i386 (as that's the output
format from the linker script), which does not match, so the function
goes on to the loop over possible BFD vectors. The pe-i386 vector
matches, as it should. One other vector matches: the plugin vector.
bfd_check_format_matches tests a vector for matching by temporarily
modifying the BFD object to use that vector then using
_bfd_check_format on it. So the BFD object is temporarily using
plugin_vec. _bfd_check_format ends up using bfd_plugin_object_p which
uses plugin_object_p from ld which uses plugin_get_ir_dummy_bfd which
succeeds, having created a BFD based on link_info.output_bfd (because
srctemplate is the BFD temporarily using plugin_vec, even after Kwok's
patch link_info.output_bfd is all that's available to base the dummy
BFD on). So we end up with a match from the plugin vector which uses
the pei-i386 vector even though the pei-i386 vector itself does not
match the input object. (In the i686-mingw32 case, as opposed to this
multilib case, pe-i386 is the default BFD target, which would
short-circuit that logic.)
There are two cases of the linker handling inputs with a plugin: they
may be inputs that are also accepted by some non-plugin BFD format, as
here, or they may be a format that would not be recognized at all, as
with some tests in the ld testsuite. In the former case, there is no
need for BFD to accept the objects using the plugin vector, as the
linker has its own logic to allow plugins to claim objects accepted by
some other BFD vector. Thus, this patch arranges for the plugin
vector to have the lowest match priority, and for the priority from
that vector to be used in the relevant case (the attempted match to
the plugin vector results in TEMP pointing to the pei-i386 vector).
Tested for GCC and Binutils testsuites for x86_64-pc-linux-gnu, as
well as verifying that it fixes the observed LTO issue for
x86_64-w64-mingw32.
* plugin.c (plugin_vec): Set match priority to 255.
* format.c (bfd_check_format_matches) [BFD_SUPPORTS_PLUGINS]: When
matching against the plugin vector, take priority from there not
from TEMP.
This file contains invisible Unicode characters that are indistinguishable to humans but may be processed differently by a computer. If you think that this is intentional, you can safely ignore this warning. Use the Escape button to reveal them.
BFD is an object file library. It permits applications to use the
same routines to process object files regardless of their format.
BFD is used by the GNU debugger, assembler, linker, and the binary
utilities.
The documentation on using BFD is scanty and may be occasionally
incorrect. Pointers to documentation problems, or an entirely
rewritten manual, would be appreciated.
There is some BFD internals documentation in doc/bfdint.texi which may
help programmers who want to modify BFD.
BFD is normally built as part of another package. See the build
instructions for that package, probably in a README file in the
appropriate directory.
BFD supports the following configure options:
--target=TARGET
The default target for which to build the library. TARGET is
a configuration target triplet, such as sparc-sun-solaris.
--enable-targets=TARGET,TARGET,TARGET...
Additional targets the library should support. To include
support for all known targets, use --enable-targets=all.
--enable-64-bit-bfd
Include support for 64 bit targets. This is automatically
turned on if you explicitly request a 64 bit target, but not
for --enable-targets=all. This requires a compiler with a 64
bit integer type, such as gcc.
--enable-shared
Build BFD as a shared library.
--with-mmap
Use mmap when accessing files. This is faster on some hosts,
but slower on others. It may not work on all hosts.
Report bugs with BFD to bug-binutils@gnu.org.
Patches are encouraged. When sending patches, always send the output
of diff -u or diff -c from the original file to the new file. Do not
send default diff output. Do not make the diff from the new file to
the original file. Remember that any patch must not break other
systems. Remember that BFD must support cross compilation from any
host to any target, so patches which use ``#ifdef HOST'' are not
acceptable. Please also read the ``Reporting Bugs'' section of the
gcc manual.
Bug reports without patches will be remembered, but they may never get
fixed until somebody volunteers to fix them.
Copyright (C) 2012-2016 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.
64bfc2584c