The rules for dllexported symbols are overly complicated due to
x86 name decoration, fuzzy symbol resolution, and the fact that
one symbol can be resolved by so many different names. The rules
are probably intended to be "intuitive", so that users don't have
to understand the name mangling schemes, but it seems that it can
lead to unintended symbol exports.
To make it clear what I'm trying to do with this patch, let me
write how the export rules are subtle and complicated.
- x86 name decoration: If machine type is i386 and export name
is given by a command line option, like /export:foo, the
real symbol name the linker has to search for is _foo because
all symbols are decorated with "_" prefixes. This doesn't happen
on non-x86 machines. This automatic name decoration happens only
when the name is not C++ mangled.
However, the symbol name exported from DLLs are ones without "_"
on all platforms.
Moreover, if the option is given via .drectve section, no
symbol decoration is done (the reason being that the .drectve
section is created by a compiler and the compiler should always
know the exact name of the symbol, I guess).
- Fuzzy symbol resolution: In addition to x86 name decoration,
the linker has to look for cdecl or C++ mangled symbols
for a given /export. For example, it searches for not only
_foo but also _foo@<number> or ??foo@... for /export:foo.
Previous implementation didn't get it right. I'm trying to make
it as compatible with MSVC linker as possible with this patch
however the rules are. The new code looks a bit messy to me, but
I don't think it can be simpler due to the ad-hoc-ness of the rules.
llvm-svn: 246424
It is currently failing with "'__uncaught_exception': identifier not found"
error. I guess it is due to r246219 because after that change, eh.h is
included only when threading is enabled.
llvm-svn: 246416
Now that we print a symbol table and all symbol kinds are at least declared,
we can test all combinations that don't produce an error.
This also includes a few fixes to keep the test passing:
* Keep the strong symbol in a weak X strong pair
* Handle common symbols.
The common X common case will be finished in a followup patch.
llvm-svn: 246401
This is exposed via a new flag /opt:lldltojobs=N, where N is the number of
code generation threads.
Differential Revision: http://reviews.llvm.org/D12309
llvm-svn: 246342
Now it is possible to have mips-linux-gnu-ld executable and link MIPS 64-bit
little-endian binaries providing -melf64ltsmip command line argument.
llvm-svn: 246335
lib.exe has a feature to create import library files (which contain
short import files) from module-definition files. Previously, we were
using that feature, but it turned out that the feature is not complete
for us.
There seems no way to specify "Import Types" in module-definition file.
lib.exe always adds "_" to given symbols and specify IMPORT_NAME_UNDECORATE.
We need more fine-grainded control on that value.
This patch teaches LLD to create short import files itself.
We are still using lib.exe, but the use of the tool is limited to create
empty import library files. We then create short import files and add them
to the empty files as new members.
This patch does not intend to change the functionality. LLD produces
the same import libraries as before. I'll make another change to create
different import libraries in a follow-up patch.
llvm-svn: 246292
InputFiles.h:98:53: error: invalid use of incomplete type ‘class lld::elf2::SymbolBody’
return SymbolBodies[SymbolIndex - FirstNonLocal]->getReplacement();
llvm-svn: 246262
This is a basic implementation that allows lld to emit binaries
consumable by the HSA runtime.
Differential Revision: http://reviews.llvm.org/D11267
llvm-svn: 246155
ICF is a feature to merge sections not by name (which is the regular
COMDAT merging) but by contents. If two or more sections have the
identical contents and relocations, ICF merges them to save space.
Accessors or templated functions tend to have the same contents, and
ICF can hold them.
If we consider sections as vertices and relocations as edges, the
problem is to find as many isomorphic graphs as possile from input
graphs. MSVC linker is smart enough to identify isomorphic graphs
even if they contain circles (GNU gold cannot handle circles
according to http://research.google.com/pubs/pub36912.html, so this
is impressive).
Circular references are not uncommon in COFF object files.
One example is .pdata. .pdata sections contain exception handler info
for functions, so they naturally have relocations for the functions.
The functions in turn have references to the .pdata sections so that
the functions and their .pdata are linked together. As a result, they
form circles.
This is a test case for circular graphs. LLD is not able to handle
this test case yet. I'll add code soon.
llvm-svn: 245827
The old test files were just compiler outputs, so it was hard to
debug if something goes wrong. The new test file is carefully
hand-crafted to trigger ICF to avoid that.
llvm-svn: 245826
__NULL_IMPORT_DESCRIPTOR is a symbol used by MSVC liner to construct
the import descriptor table. We do not use the symbol. Previously,
we had code to skip that symbol. That code does not actually do
anything meaningful because no one is referencing the symbol, the
symbol would naturally be ignored. This patch stops recognizing
the symbol.
llvm-svn: 245280
Previously, weak external symbols could reference only symbols that
appeared before them. Although that covers almost all use cases
of weak externals, there are object files out there which contains
weak externals that have forward references.
This patch supports such weak externals.
llvm-svn: 245258
There are some DLLs whose initializers depends on other DLLs'
initializers. The initialization order matters for them.
MSVC linker uses the order of the libraries from the command line.
LLD used ASCII-betical order. So they were incompatible.
This patch makes LLD compatible with MSVC.
llvm-svn: 245201
With this patch only the name is set. I will set the other fields shortly.
For now the table doesn't include local symbols. This is equivalent to using
--discard-all with gnu ld. This is OK for now since the symbols are not
needed for execution and for testing symbol resolution we only need the
global symbols.
llvm-svn: 245044
This is more convenient than the offset from the start of the file as we
don't have to worry about it changing when we move the output section.
This is a port of r245008 from ELF.
llvm-svn: 245018
With OutputSection being a virtual interface, each concrete OutputSection
handles only one type of chunk and we don't need a base Chunk class.
So for we have a class that handles input sections and one that handles
the string table, but this extends naturally for other outputs (symbol table,
merging of SHF_MERGE sections, etc.).
llvm-svn: 244972
We were creating the string table in a completely ad hoc way. Now the
string table is an output section and gets its output offset set just like
any other section.
This opens the way for other linker created sections like the symbol table.
llvm-svn: 244969
This is a bit more c++ code, but:
* It is less machine code: lld's text is 44688 bytes smaller.
* It should be a bit more efficient in the non native endian case.
* It should be a bit more efficient on architectures with slow unaligned access.
llvm-svn: 244934
Add PT_PHDR segment depending on its availability in linker script's
PHDRS command, fallback if no linker script is given.
Handle FILEHDR, PHDRS and FLAGS attributes of program header.
Differential Revision: http://reviews.llvm.org/D11589
llvm-svn: 244743
Rui Ueyama