Re: [PATCH/RFC] On the use of -funreachable-traps to deal with PR 109627

[Jeff Law <jeffreyalaw@gmail.com>]

On 4/8/24 5:04 PM, Iain Sandoe wrote:
> Hi
> 
> PR 109627 is about functions that have had their bodies completely elided, but still have the wrappers for EH frames (either .cfi_xxx or LFSxx/LFExx).
> 
> These are causing issues for some linkers because such functions result in FDEs with a 0 code extent.
> 
> The simplest representation of this is (from PR109527)
> 
> void foo () { __builtin_unreachable (); }
With the possibility of sounding like a broken record, I think 
__builtin_unreachable is fundamentally flawed.   It generates no code 
and just lets the program continue if ever "reached".  This is a 
security risk and (IMHO) just plain silly.  We're in a situation that is 
never supposed to happen, so continuing to execute code is just asking 
for problems.

If it were up to me, I'd have __builtin_unreachable emit a trap or 
similar construct that should (in general) halt execution.

Jeff