This diff adds support for weak definitions, though it doesn't handle weak
symbols in dylibs quite correctly -- we need to emit binding opcodes for them
in the weak binding section rather than the lazy binding section.
What *is* covered in this diff:
1. Reading the weak flag from symbol table / export trie, and writing it to the
export trie
2. Refining the symbol table's rules for choosing one symbol definition over
another. Wrote a few dozen test cases to make sure we were matching ld64's
behavior.
We can now link basic C++ programs.
Reviewed By: #lld-macho, compnerd
Differential Revision: https://reviews.llvm.org/D83532
Summary:
This allows us to link against stripped dylibs. Moreover, it's simply
more correct: The symbol table includes symbols that the dylib uses but
doesn't export.
This temporarily regresses our ability to do lazy symbol binding because
dyld_stub_binder isn't in libSystem's export trie. Rather, it is in one
of the sub-libraries libSystem re-exports. (This doesn't affect our
tests since we are mocking out dyld_stub_binder there.) A follow-up diff
will address this by adding support for sub-libraries.
Depends on D79114.
Reviewers: ruiu, pcc, MaskRay, smeenai, alexshap, gkm, Ktwu, christylee
Subscribers: mgorny, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D79226
Summary: Similar to other formats, input sections in the MachO
implementation are now grouped under output sections. This is primarily
a refactor, although there's some new logic (like resolving the output
section's flags based on its inputs).
Differential Revision: https://reviews.llvm.org/D77893
Currently, getVA() returns a virtual address with the assumption that
the ImageBase is zero. As I understand, this is what lld-ELF is doing.
However, under our current design, it seems like an awkward setup --
I'm finding that I have to add and subtract ImageBase in several places
to make things work out.
As such, I think it's simpler to have getVA() return a non-relative VA,
but I'm not sure if I'm missing something. Would love to hear more from
folks familiar with lld-ELF.
Differential Revision: https://reviews.llvm.org/D78168
Build the trie by performing a three-way radix quicksort: We start by
sorting the strings by their first characters, then sort the strings
with the same first characters by their second characters, and so on
recursively. Each time the prefixes diverge, we add a node to the trie.
Thanks to @ruiu for the idea.
I used llvm-mc's radix quicksort implementation as a starting point. The
trie offset fixpoint code was taken from
MachONormalizedFileBinaryWriter.cpp.
Differential Revision: https://reviews.llvm.org/D76977
Jez Ng