Direct recursion detection possible?

[Cecil Ward]

On Thursday, 25 May 2023 at 02:30:35 UTC, Steven Schveighoffer 
wrote:
> On 5/24/23 7:04 PM, Cecil Ward wrote:
>
>> Is it possible for our compilers to detect direct infinite 
>> recursion ? I’m ignoring the indirect call case, and I’m also 
>> ignoring anything involving function pointers, so given those 
>> restrictions, we will be able to see that the generated code 
>> of a routine is calling its own address, because that address 
>> is a literal and we know what the current function is that 
>> we’re currently in.
>
> Not in the general case. Direct recursion is a common pattern 
> (direct inifite recursion obviously is not desired, but 
> detecting that is the halting problem).
>
> -Steve

Could that one limited case of direct straight loops be detected 
in the backend, just as one limited common pattern, then sending 
a message upwards to throw out an error message for the user in 
the error listing and stop object code generation? It seems 
worthwhile to me having been bitten by it for the first time. 
Spotting "l1: jmp l1" could be almost like a regex but I wouldn’t 
think that’s how it works.