search for: osreadlittleendian

I looked into this further. ld64 has a macho_nlist abstraction over the various underlying nlist structures [1]. On x86-64, the P::getP referenced in n_value will resolve to [2], which in turn goes to [3], which calls OSReadLittleInt64. On a little endian machine, OSReadLittleEndian just calls _OSReadInt64 [4], which in turn does a pointer arithmetic and cast and then dereferences the pointer [5]. As far as I can see, this will invoke UB for an unaligned int64, unless ld64 is built against a different version of OSReadLittleEndian, or unless I’m missing something. [1] https:/...

As part of our work on LLD for Mach-O, we’ve observed that the object files produced by LLVM don’t always have aligned nlist_64 entries. For context, nlist_64 is the 64-bit symbol table entry structure for Mach-O, and the symbol table is an array of nlist_64 entries. nlist_64 has an 8 byte member, so it should be 8-byte aligned, but we’ve seen object files where the symbol table only has a 4-byte