Near return does not accept operand size override prefix

[lab-bat]

Using nasm-3.01 on following file (command: nasm -fwin32 -w+error test.asm -o test.obj -l test.lst)

segment .text code use16
test:
BITS 16
        o32     ret
BITS 32
        o16     ret
.end:

I have to turn off -w+error to compile system management mode interrupt service routine function.

[ecm-pushbx]

For the record, this displays the warning shown:

test$ ~/proj/nasmtest/rc/nasm -v
NASM version 3.02rc0 compiled on Oct 13 2025
test$ cat test.asm
segment .text code use16
test:
BITS 16
        o32     ret
BITS 32
        o16     ret
.end:
test$ ~/proj/nasmtest/rc/nasm test.asm -fobj
test.asm:4: warning: invalid operand size prefix o32, must be o16 [-w+prefix-opsize]
test.asm:6: warning: invalid operand size prefix o16, must be o32 [-w+prefix-opsize]
test$ ~/proj/nasmtest/rc/nasm test.asm -felf
test.asm:1: warning: unknown section attribute 'code' ignored on declaration of section `.text' [-w+other]
test.asm:1: warning: unknown section attribute 'use16' ignored on declaration of section `.text' [-w+other]
test.asm:4: warning: invalid operand size prefix o32, must be o16 [-w+prefix-opsize]
test.asm:6: warning: invalid operand size prefix o16, must be o32 [-w+prefix-opsize]
test$ ~/proj/nasmtest/rc/nasm test.asm -fbin
test.asm:1: warning: ignoring unknown section attribute: "code" [-w+other]
test.asm:1: warning: ignoring unknown section attribute: "use16" [-w+other]
test.asm:4: warning: invalid operand size prefix o32, must be o16 [-w+prefix-opsize]
test.asm:6: warning: invalid operand size prefix o16, must be o32 [-w+prefix-opsize]
test$

[lab-bat]

ok, suppress some warning with the generic code snippet.

section .text
test:
BITS 16
        o32     ret
BITS 32
        o16     ret
.end:

[hpax]

Use retw/retd or put the prefix on a separate line.
Still, it's definitely a bug and should be fixed.

[hpax]

This turns out to be a surprisingly complicated problem. Just wanted to let you know that it seems to have uncovered quite the little rats nest.

[hpax]

I think this is solved in the current master branch (and daily snapshots) now. Could you see if it solves your specific use case?

[lab-bat]

Yes, the build from current master branch is solved. hash number 94923e13 via git log --pretty=format:%h -n 1
By the way, daily snapshots is outdated? latest build has hash number e9fac2fa

[hpax]

Looks like there is something broken there, indeed.