git commit 46434633f9 said
Make undefined symbols in allocate_dynrelocs dynamic
..if they have dynamic relocs. An undefined symbol in a PIC object
that finds no definition ought to become dynamic in order to support
--allow-shlib-undefined, but there is nothing in the generic ELF
linker code to do this if the reference isn't via the GOT or PLT. (An
initialized function pointer is an example.) So it falls to backend
code to ensure the symbol is made dynamic.
The above isn't true. Undefined symbols are indeed made dynamic for
shared libraries. Undefined symbols are not automatically made
dynamic in executables, and it was the PIE case that triggered an
internal consistency assertion on powerpc64. I guess I could have
jumped the other way when fixing PR21988, and not created a dynamic
reloc. Either way, it doesn't matter a great deal. We're going to
get an error on strong undefined symbols in an executable anyway, and
broken binaries if you try to use --unresolved-symbols=ignore-all to
disable the error.
* testsuite/ld-undefined/fundef.s: New test.
* testsuite/ld-undefined/undefined.exp: Test that undefined
symbols in shared libraries are made dynamic.
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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
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* The linker supports a number of different object file
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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.
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