Add a warning for unknown cross-mapping references

2026-07-08T19:27:49Z

Some segments, like the 'vectors' one, will reference code that is outside of its mapping. But in some other configurations, segments cannot make these cross-mapping references so happily. Imagine: .segment "SWAPPABLE" .proc foo rts .endproc .segment "FIXED" jsr foo Here the assembler will properly detect the address of 'foo' in the context of the 'SWAPPABLE' segment. But what this assembler doesn't know is that this segment is swappable (e.g. UNROM chip). Hence, if the bank being mapped right now is not the one containing the 'SWAPPABLE' segment, then the address computed for 'foo' and used in that 'jsr' instruction will point to something else entirely. This would be similar to a use-after-free bug. This is something that can only be inspected at runtime, and so the assembler cannot be of much help here. Hence, this commit adds a warning so the programmer can understand the potentially dangerous operation. All of that being said, this commit also adds support for "asan:safe" or "check:safe", which is a magic comment that the programmer can write to re-assure the assembler that this operation is fine (e.g. there is a guarantee that the mapped bank is that one we are expecting). Hence, the code above could now be written like so: jsr foo ; check:safe Signed-off-by: Miquel Sabaté Solà

tools.nes/tests/expected/unrom.nes, branch main

Add a warning for unknown cross-mapping references