[PATCH] D17733: [ELF] Fix reading of PC values of FDEs

[Rafael Espíndola via llvm-commits]

Small preference for a lambda, but LGTM without it too if Rui prefers
it that way.

Cheers,
Rafael


On 1 March 2016 at 16:30, Simon Atanasyan <simon at atanasyan.com> wrote:
> atanasyan added inline comments.
>
> ================
> Comment at: ELF/OutputSections.cpp:669-670
> @@ -668,16 +668,4 @@
>  typename EhFrameHeader<ELFT>::uintX_t
>  EhFrameHeader<ELFT>::getFdePc(uintX_t EhVA, const FdeData &F) {
> -  const endianness E = ELFT::TargetEndianness;
> -  assert((F.Enc & 0xF0) != DW_EH_PE_datarel);
> -
> -  uintX_t FdeOff = EhVA + F.Off + 8;
> -  switch (F.Enc & 0xF) {
> -  case DW_EH_PE_udata2:
> -  case DW_EH_PE_sdata2:
> -    return FdeOff + read16<E>(F.PCRel);
> -  case DW_EH_PE_udata4:
> -  case DW_EH_PE_sdata4:
> -    return FdeOff + read32<E>(F.PCRel);
> -  case DW_EH_PE_udata8:
> -  case DW_EH_PE_sdata8:
> -    return FdeOff + read64<E>(F.PCRel);
> +  auto Read = [=](uint8_t Size) -> uint64_t {
> +    const endianness E = ELFT::TargetEndianness;
> ----------------
> ruiu wrote:
>> Do you have to use lambda? It seems you can write without it in a more regular way.
>>
>>   const endianness E = ELFT::TargetEndianness;
>>
>>   int Size = F.Enc & 0x7;
>>   if (Size == DW_EH_PE_absptr)
>>     Size = sizeof(uintX_t) == 8 ? DW_EH_PE_udata8 : DW_EH_PE_udata4;
>>
>>   uintX_t V;
>>   switch (Size) {
>>   case DW_EH_PE_udata2:
>>     V = read16<E>(F.PCRel);
>>   case DW_EH_PE_udata4:
>>     V = read32<E>(F.PCRel);
>>   case DW_EH_PE_udata8:
>>     V = read64<E>(F.PCRel);
>>   default:
>>     fatal("unknown FDE size encoding");
>>   }
>>
>>   switch (F.Enc & 0x70) {
>>   case DW_EH_PE_absptr:
>>     return V;
>>   case DW_EH_PE_pcrel:
>>     return V + EhVA + F.Off + 8;
>>   default:
>>     fatal("unknown FDE size relative encoding");
>>   }
>>
>> Do you have to use lambda? It seems you can write without it in a more regular way.
>
> The lambda is not mandatory. But without it the code is a bit longer because we have to add `break` to each case of the `switch (Size)`.
>
>
> Repository:
>   rL LLVM
>
> http://reviews.llvm.org/D17733
>
>
>