We can add multiple undefined atoms having the same name to the symbol table.
If such atoms are added, the symbol table compares their canBeNull attributes,
and select one having a stronger constraint. If their canBeNulls are the same,
the choice is arbitrary. Currently it choose the existing one.

This patch changes the preference, so that the symbol table choose the new one
if the new atom has a greater canBeNull or a fallback atom. This shouldn't
change the behavior except the case described below.

A new undefined atom may have a new fallback atom attribute. By choosing the new
atom, we can update the fallback atom during Core Linking. PE/COFF actually need
that. For example, _lseek is an alias for __lseek on Windows. One of an object
file in OLDNAMES.LIB has an undefined atom for _lseek with the fallback to
__lseek. When the linker tries to resolve _read, it supposed to read the file
from OLDNAMES.LIB and use the new fallback from the file. Currently LLD cannot
handle such case because duplicate undefined atoms with the same attributes are
ignored.

Differential Revision: http://llvm-reviews.chandlerc.com/D2161

llvm-svn: 194777

llvm-svn: 194671

llvm-svn: 194641

llvm-svn: 194624

llvm-svn: 194620

llvm-svn: 194619

This reverts commit r194551 because it broke the buildbot.

llvm-svn: 194552

llvm-svn: 194551

llvm-svn: 194177

llvm-svn: 194037

It was never transporting any value in addition to the error_code.

llvm-svn: 194028

Enable this for the following flavors

a) core
b) gnu
c) darwin

Its disabled for the flavor PECOFF. Convenient markers are added with FIXME
comments in the Driver that would be removed and code removed from each flavor.

llvm-svn: 193585

The patch have completely broken COFF port and disabled many tests.
This also reverts r193302 (comment fix).

llvm-svn: 193362

Disable tests to be run with REQUIRES: disable. Note disable is not added to the
config by the test runner Mkaefiles, so essentially disables the test.

Code changes would be required to fix these tests :-

test/darwin/hello-world.objtxt
test/elf/check.test
test/elf/phdr.test
test/elf/ppc.test
test/elf/undef-from-main-dso.test
test/elf/X86_64/note-sections-ro_plus_rw.test
test/pecoff/alignment.test
test/pecoff/base-reloc.test
test/pecoff/bss-section.test
test/pecoff/drectve.test
test/pecoff/dynamic.test
test/pecoff/dynamicbase.test
test/pecoff/entry.test
test/pecoff/hello.test
test/pecoff/imagebase.test
test/pecoff/importlib.test
test/pecoff/lib.test
test/pecoff/multi.test
test/pecoff/reloc.test
test/pecoff/weak-external.test

llvm-svn: 193300

Dead-strip root symbols can be undefined atoms, but should not really be
nonexistent, because dead-strip root symbols should be added to initial
undefined atoms at startup. Whenever you look up its name in the symbol
table, some type of atom will always exist.

llvm-svn: 192831

We want to make the program to exit with non-zero exit code if there's an error
during dead stripping.

llvm-svn: 192771

llvm-svn: 192424

llvm-svn: 192422

llvm-svn: 192416

This patch also handles errors other than no_more_files error. They were silently
ignored.

llvm-svn: 192415

This change removes code in various places which was setting the File Ordinals.
This is because the file ordinals are assigned by the way files are resolved.

There was no other way than making the getNextFileAndOrdinal be set const and
change the _nextOrdinal to mutable.

There are so many places in code, that you would need to cleanup to make
LinkingContext non-const!

llvm-svn: 192280

llvm-svn: 192277

This associates resolveState to FileNodes. The control node derive
their resolution state from the inputElements that are contained in
it.

This makes --start-group/--end-group to work with ELF linking.

llvm-svn: 192269

llvm-svn: 192261

llvm-svn: 192260

llvm-svn: 192183

llvm-svn: 192163

llvm-svn: 192149

Summary:
The original code with enum "_" is intended to emulate scoped enums.
Now we have real scoped enums, so use it.

Reviewers: Bigcheese

CC: llvm-commits

Differential Revision: http://llvm-reviews.chandlerc.com/D1852

llvm-svn: 192148

Changes :-

a) Functionality in InputGraph to insert Input elements at any position
b) Functionality in the Resolver to use nextFile
c) Move the functionality of assigning file ordinals to InputGraph
d) Changes all inputs to MemoryBuffers
e) Remove LinkerInput, InputFiles, ReaderArchive

llvm-svn: 192081

This adds an option --output-filetype that can be set to either
YAML/Native(case insensitive). The linker would create the outputs
associated with the type specified by the user.

Changes all the tests to use the new option.

llvm-svn: 191183

This also makes it support debugging executables built with lld.

Initial patch done by Bigcheese. This is only a revised patch to
have the functionality in the Writer.

llvm-svn: 191032

Used the fallback mechanism to implement COFF weak external symbols.

llvm-svn: 190633

In COFF, an undefined symbol can have up to one alternative name. If a symbol
is resolved by its regular name, then it's linked normally. If a symbol is not
found in any input files, all references to the regular name are resolved using
the alternative name. If the alternative name is not found, it's a link error.
This mechanism is called "weak externals".

To support this mechanism, I added a new member function fallback() to undefined
atom. If an undefined atom has the second name, fallback() returns a new undefined
atom that should be used instead of the original one to resolve undefines. If it
does not have the second name, the function returns nullptr.

Differential Revision: http://llvm-reviews.chandlerc.com/D1550

llvm-svn: 190625

attribute in LinkerInput to isWholeArchive and use that for deciding
whether library archives should be expanded. Implement the -all_load
option of the Darwin linker using this flag and drop the support for it
in GNU mode.

llvm-svn: 190275

reference. Move readFile logic into FileNode::createLinkerInput.

llvm-svn: 190253

It looks like there is a possibility of seeing RO/RW note sections
and we would need to create an appropriate RO/RW segment associated
with them.

Adds a test too.

llvm-svn: 189907

Emit note sections if the input contains a note section.

Also emit a note segment.

llvm-svn: 189896

llvm-svn: 189775

This adds an API to the LinkingContext for flavors to add Internal files
containing atoms that need to appear in the YAML output as well, when -emit-yaml
switch is used.

Flavors can add more internal files for other options that are needed.

llvm-svn: 189718