[Bug]: AND with a constant-folded first operand emits an orphan pop af → stack corruption (v1.18.7, -O1…-O4)

[Menyiques]

Contact Details

@Menyiques

Compiler version

v1.18.7

What happened?

Compiling:
Dim a as uByte
Dim s as uByte
a = 1
s = 10
If a and s >= 6 Then s = 2
print s

with zxbc -O 2 bug.bas -o bug.asm -A
(O=1,2,3,4)
generates:

.core.MAIN_PROGRAM:
ld a, 1
ld (_a), a
ld a, 10
ld (_s), a
sub 6
ccf
sbc a, a
ld h, a
pop af ; <<< orphan: no matching "push af" anywhere
or a
jr z, .LABEL.__LABEL2
ld a, h
.LABEL.__LABEL2:
or a
jp z, .LABEL.__LABEL1

Error and Warning messages

Code of Conduct

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[Menyiques]

Notes
The bug triggers whenever the optimizer knows the first operand is a compile-time constant, regardless of its value:
a = 1 : If a And expr Then … → orphan pop af (unbalanced)
a = 0 : If a And expr Then … → orphan pop af (unbalanced)
a = 1 : If a Or expr Then … → folded correctly (no push, no pop)
a = 0 : If a Or expr Then … → folded correctly
So the constant-folding path for OR cleans up the merge code, but the one for AND does not.
Workaround: replace If a And b Then … with nested If a Then : If b Then … when the first operand may be constant-foldable.

[boriel]

Please, try this version and let me know:
https://boriel-basic.net/files/zxb/zxbasic-v1.19.0-beta16.tar.gz
https://boriel-basic.net/files/zxb/zxbasic-v1.19.0-beta16.zip
https://boriel-basic.net/files/zxb/zxbasic-v1.19.0-beta16-win32.zip
https://boriel-basic.net/files/zxb/zxbasic-v1.19.0-beta16-linux64.tar.gz
https://boriel-basic.net/files/zxb/zxbasic-v1.19.0-beta16-macos.tar.gz

[Menyiques]

Now is working! Thanks!