Alan Modra 7ba115508a PR26580, Size and alignment of commons vs as-needed shared lib
Two pieces to this puzzle:
1) Revert HJ's fix for PR13250 so that size and alignment isn't
   sticky, instead attack the real underlying problem that
   _bfd_generic_link_add_one_symbol does the wrong thing in making a
   common section in a shared library bfd.
2) Save and restore common u.c.p fields, which hold the section and
   alignment.

A better fix for (2) would be to throw away all of that horrible code
saving and restoring the hash table when loading as-needed library
symbols, and instead do a scan over as-needed library symbols before
adding anything.

bfd/
	PR 13250
	PR 26580
	* elflink.c (_bfd_elf_merge_symbol): Make "override" a bfd**.
	Return oldbfd in override when old common should override new
	common.
	(_bfd_elf_add_default_symbol): Adjust to suit.
	(elf_link_add_object_symbols): Likewise.  Pass "override" to
	_bfd_generic_link_add_one_symbol.  Save and restore common u.c.p
	field for --as-needed shared libraries.  Revert pr13250 changes.
ld/
	* testsuite/ld-elf/pr26580-a.s,
	* testsuite/ld-elf/pr26580-b.s,
	* testsuite/ld-elf/pr26580-1.sd,
	* testsuite/ld-elf/pr26580-2.sd: New tests
	* testsuite/ld-elf/comm-data.exp: Run new tests.
	* testsuite/ld-elf/pr26580-a.c,
	* testsuite/ld-elf/pr26580-b.c,
	* testsuite/ld-elf/pr26580-3.out,
	* testsuite/ld-elf/pr26580-4.out: New tests.
	* testsuite/ld-elf/shared.exp: Run new tests.
2020-09-08 22:30:38 +09:30
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2020-06-21 22:16:10 +09:30

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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.texi), as well as the
  beginnings of an internals manual (ldint.texi).

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.texi 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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