Naked functions

kinke noone at
Fri Jul 27 17:53:51 UTC 2018

On Friday, 27 July 2018 at 10:11:03 UTC, Jack Applegame wrote:
> There is one strange thing.
> Should  the compiler to insert the return command for naked 
> functions?
> I suppose it shouldn't.
> [...]
> Looks like LDC removes the prologue/epilogue, but not 
> completely, leaving the return from function.

In this case I'd think it has to, you're even using an explicit 
return statement. I'm not familiar with the ARM calling 
convention wrt. call/return, but gcc emitting no return seems 
very strange (where is it supposed to continue after the add 
instruction? the next function in the final binary?!). Did you 
test that it actually works as intended?

I updated the PR yesterday, so that LDC's pro-/epilogue is 
excluded too, which allows the usage of params (not just in some 
cases like yours together with -O). [Your sample doesn't work 
anymore now, crashing the compiler, as it now requires __asm() 
and/or inlineIR() to work with params.]

AFAIK, a return is required as we go through LLVM IR and not 
directly to the assembler (which for example allows you to write 
the function body in LLVM IR). Yesterday's variant probably 
crashes if there's no explicit return (e.g., with __asm() and a 
naked function returning void).

I take it this is just a toy example for gcc/LDC comparison, or 
do you really need to omit a return instruction in real-world 

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