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[SOLVED] ProcedureReturn
Posted: Sat May 11, 2024 11:26 pm
by boddhi
Hello,
Can someone explain to me why this code returns 1 instead 0?
(I tried to find some topic about this but too much collected results with keyword ProcedureReturn)
Code: Select all
Procedure.a Test()
Protected.a ReturnValue,Test
If Not Test:ProcedureReturn:EndIf
Debug "Test1"
Debug "Test2"
ProcedureReturn ReturnValue
EndProcedure
ReturnValue.a=test()
Debug ReturnValue
As there is no value after ProcedureReturn, I expected 0 to be returned.
This is the first time I've been faced with this situation in 20 years....
Re: ProcedureReturn
Posted: Sat May 11, 2024 11:31 pm
by Mindphazer
That's weird. On MacOS, your code returns 0 as expected (PB 6.10)
But on Windows, it returns 1 (PB 6.10 too)
Re: ProcedureReturn
Posted: Sat May 11, 2024 11:35 pm
by r-i-v-e-r
From the documentation:
This is an important behaviour meant to ease usage of inline assembly for the ASM backend, where the content of EAX/RAX is used accordingly as return value.
Without this, you'd have to MOV your result from ASM into a PB variable and then return the variable separately, which is inconvenient and a bit wasteful if it's already present in EAX/RAX.
Mindphazer wrote: Sat May 11, 2024 11:31 pm
That's weird. On MacOS, your code returns 0 as expected (PB 6.10)
But on Windows, it returns 1 (PB 6.10 too)
For the C-backend it will return a zero-value instead, so this is indeed a source of variation between backends, but is allowed per the "undefined behaviour" disclaimer.
Re: ProcedureReturn
Posted: Sun May 12, 2024 12:50 am
by juergenkulow
Code: Select all
; If Not Test:ProcedureReturn:EndIf
CMP byte [rsp+48],0
JE No0
XOR rax,rax
JMP Ok0
No0:
MOV rax,1
Ok0:
AND rax,rax
JE _EndIf2
JMP _EndProcedure1
_EndIf2:
Code: Select all
// If Not Test:ProcedureReturn:EndIf
if (!(!(v_test))) { goto no2; }
r=0;
goto end;
no2:;
Re: ProcedureReturn
Posted: Sun May 12, 2024 1:41 am
by boddhi
@r-i-v-e-r
Thanks for your explanation.
And now that you say it, I actually have a vague memory of having read this somewhere a very very long time ago (C-backend didn't exist yet!).
Bad news, I will have to make sure on all my codes that there are no hidden defects in them.
@juergenkulow
Cool, but I don't understand anything in assembler coding!
