This fixes a bug with string merging with string symbols that contain
NULLs, as is the case in the `merge-string.s` test.
The bug only showed when we run with `--relocatable` and then try read
the resulting object back in. In this case we would end up with string
symbols that extend past the end of the segment in which they live.
The problem comes from the fact that sections which are flagged as
string mergable assume that all strings are NULL terminated. The
merging algorithm will drop trailing chars that follow a NULL since they
are essentially unreachable. However, the "size" attribute (in the
symbol table) of such a truncated symbol is not updated resulting a
symbol size that can overlap the end of the segment.
I verified that this can happen in ELF too given the right conditions
and the its harmless enough. In practice Strings that contain embedded
null should not be part of a mergable section.
Differential Revision: https://reviews.llvm.org/D102281
Don't include the relocation addend when calculating the
virtual address of a symbol. Instead just pass the symbol's
offset and add the addend afterwards.
Without this fix we hit the `offset is outside the section`
error in MergeInputSegment::getSegmentPiece.
This fixes a real world error we were are seeing in emscripten.
Differential Revision: https://reviews.llvm.org/D102271
This change was originally landed in: 5000a1b4b9
It was reverted in: 061e071d8c
This change adds support for a new WASM_SEG_FLAG_STRINGS flag in
the object format which works in a similar fashion to SHF_STRINGS
in the ELF world.
Unlike the ELF linker this support is currently limited:
- No support for SHF_MERGE (non-string merging)
- Always do full tail merging ("lo" can be merged with "hello")
- Only support single byte strings (p2align 0)
Like the ELF linker merging is only performed at `-O1` and above.
This fixes part of https://bugs.llvm.org/show_bug.cgi?id=48828,
although crucially it doesn't not currently support debug sections
because they are not represented by data segments (they are custom
sections)
Differential Revision: https://reviews.llvm.org/D97657
This change adds support for a new WASM_SEG_FLAG_STRINGS flag in
the object format which works in a similar fashion to SHF_STRINGS
in the ELF world.
Unlike the ELF linker this support is currently limited:
- No support for SHF_MERGE (non-string merging)
- Always do full tail merging ("lo" can be merged with "hello")
- Only support single byte strings (p2align 0)
Like the ELF linker merging is only performed at `-O1` and above.
This fixes part of https://bugs.llvm.org/show_bug.cgi?id=48828,
although crucially it doesn't not currently support debug sections
because they are not represented by data segments (they are custom
sections)
Differential Revision: https://reviews.llvm.org/D97657
Sam Clegg