[lld] [ELF] Set sh_entsize of .{init, fini, preinit}_array to the word size (PR #226697)

[dong jianqiang via llvm-commits]

dongjianqiang2 wrote:

> If we want parity with GNU, the change belongs to the LLVM integrated assembler (LLVMMC). See #226875

We found this while migrating from GNU ld to lld: our bare-metal runtime reads sh_entsize of .init_array from the linked ELF to walk the entries, and lld's 0 breaks it (GNU ld always writes the word size).

Agreed the writeHeaderTo approach can't tell the two zero cases apart.

#226875 fixes the common case, thanks. The gap left for us is linker-script sections with no input sections (.init_array (TYPE=SHT_INIT_ARRAY) : { ... }). Would a fallback limited to that case be acceptable? If not, we'll carry it downstream.

https://github.com/llvm/llvm-project/pull/226697