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

llvm-svn: 190619

llvm-svn: 190612

The first section in the output was not aligned to the alignment of the section.

llvm-svn: 190610

This associates rodata and sections which just have the SHF_ALLOC flag
to be set to typeConstant.

llvm-svn: 190609

We need to order atoms that exist in the same chain. This is to make sure that
the command line order is preserved when we emit the atoms to the output file.

Credits: BigCheese for finding the bug.

Adds a test which otherwise would fail.

llvm-svn: 190608

llvm-svn: 190586

Mangling scheme varies on platform, and prepending an underscore is valid only
on 32-bit x86. Added a method to mangle name to PECOFFLinkingContext and use
it to avoid hard coding mangled names.

llvm-svn: 190585

llvm-svn: 190554

Patch by Joe Ranieri

llvm-svn: 190453

-current_version, -compatibility_version, and -install_name.

Patch by Joe Ranieri

llvm-svn: 190452

and a parsePackedVersion() utility.

Patch by Joe Ranieri

llvm-svn: 190451

Process::GetEnv() uses GetEnvironmentVariableW, which is a Windows API
to get an environment variable and is preferable over getenv().

llvm-svn: 190431

llvm-svn: 190332

llvm-svn: 190329

llvm-svn: 190302

llvm-svn: 190301

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

llvm-svn: 190255

llvm-svn: 190254

reference. Move readFile logic into FileNode::createLinkerInput.

llvm-svn: 190253

Patch by Ron Ofir.

llvm-svn: 190210

Patch by Ron Ofir.

llvm-svn: 190198

llvm-svn: 190121

llvm-svn: 190120

llvm-svn: 190119

llvm-svn: 190117

llvm-svn: 190095

llvm-svn: 190031

Writable note sections if they exist should not appear before text
they belong in the data segment

llvm-svn: 190024

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

The compiler is allowed to add a linker option starting with -?<name> to
.drectve section. If the linker can interpret -<name>, it's processed as if
there's no question mark there. If not, such option is silently ignored.

This is a COFF's feature to allow the compiler to emit new linker options
while keeping compatibility with older linkers.

llvm-svn: 189897

Emit note sections if the input contains a note section.

Also emit a note segment.

llvm-svn: 189896

Before this patch, name of driver implementation is not consistent with its
option table file. Specifically, LDOptions has a different prefix than
GnuLdDriver.

This patch renames option files, so that the option files have the same prefix
as the corresponding driver files.

Differential Revision: http://llvm-reviews.chandlerc.com/D1591

llvm-svn: 189895

llvm-svn: 189891

llvm-svn: 189890

Also add a llvm_unreachable call so that the linker will trip on unhandled
inputElement types.

llvm-svn: 189887

llvm-svn: 189883

llvm-svn: 189881

llvm-svn: 189877