[lld] r257753 - [ELF] - implemented --eh-frame-hdr command line option.

[Simon Atanasyan via llvm-commits]

On Thu, Jan 14, 2016 at 8:14 PM, George Rimar <grimar at accesssoftek.com> wrote:
>>
>>crtend.o file has .eh_frame section four byte length filled by zero.
>>If i do not make a mistake after this commit LLD crashes on this
>>section with "corrupted or unsupported CIE information" error.
>>...
>>
>>--
>>Simon Atanasyan
>
> Hello, Simon,
> thanks for info !
>
> The case you're pointing really looks like a special case which we should support.
> I`ll take a look closer on it tomorrow if you dont mind.
>
> As far as I know both bfd and gold just drop the creation of eh_frame_hdr if are not able to parse something in eh_frame.
> We did it in another way. We assume that inputs should be correct and just exit with error.
> I wonder if this is the only such exception we can meet in real life ? Currently lld will error exit on all corrupted/unsupported eh_frames if --eh-frame-hdr is specified.

I think this case is a standard. FDE has multiple 'required' fields
but the first field "Length" has the following description:
[[
A 4 byte unsigned value indicating the length in bytes of the CIE
structure, not including the Length field itself... If Length contains
the value 0, then this CIE shall be considered a terminator and
processing shall end.
]]
https://refspecs.linuxfoundation.org/LSB_3.0.0/LSB-PDA/LSB-PDA/ehframechpt.html

Here is one more reference link. Look at the line 656.
https://github.com/gcc-mirror/gcc/blob/master/libgcc/crtstuff.c#L656

-- 
Simon Atanasyan