From 6f58e4ab8d90166cac4e4da269a77c5134f12f1e Mon Sep 17 00:00:00 2001
From: Miquel Sabaté Solà <mssola@mssola.com>
Date: Thu, 9 Jul 2026 22:07:47 +0200
Subject: Add support for the asan:fixed-segments comment
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Content-Type: text/plain; charset=UTF-8
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This magic comment allows for the definition of segments that are fixed
and for which references are always safe. This goes in tandem with the
asan:safe comment, which can then be used more sporadically.

Signed-off-by: Miquel Sabaté Solà <mssola@mssola.com>
---
 tests/expected/fixed-segments.nes | Bin 0 -> 131088 bytes
 tests/expected/fixed-segments.txt |   1 +
 tests/fixed-segments.s            | 131 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 132 insertions(+)
 create mode 100644 tests/expected/fixed-segments.nes
 create mode 100644 tests/expected/fixed-segments.txt
 create mode 100644 tests/fixed-segments.s

(limited to 'tests')

diff --git a/tests/expected/fixed-segments.nes b/tests/expected/fixed-segments.nes
new file mode 100644
index 0000000..06959e0
Binary files /dev/null and b/tests/expected/fixed-segments.nes differ
diff --git a/tests/expected/fixed-segments.txt b/tests/expected/fixed-segments.txt
new file mode 100644
index 0000000..9a93bf4
--- /dev/null
+++ b/tests/expected/fixed-segments.txt
@@ -0,0 +1 @@
+warning: referencing 'hello_bank1' from 'FIXED', which belongs to the 'BANK1' segment (fixed-segments.s: line 114)
diff --git a/tests/fixed-segments.s b/tests/fixed-segments.s
new file mode 100644
index 0000000..2d502a5
--- /dev/null
+++ b/tests/fixed-segments.s
@@ -0,0 +1,131 @@
+;;; asan:fixed-segments BANK0, FIXED
+
+.segment "HEADER"
+    .byte 'N', 'E', 'S', $1A
+    .byte $08                   ; 128KB  of PRG-ROM (8 x 16KB)
+    .byte $00                   ; No CHR-ROM. Games using this chip used RAM instead.
+
+    ;; On the 6th byte we have to set the lower nibble of the mapper (#%0010 for
+    ;; UNROM).
+    .byte $20
+
+    ;; Forcing iNES 2.0 format, which will help us for the next bytes.
+    .byte $08
+
+    ;; And now iNES 2.0-specific thingies.
+    .byte $00       ; No submapper
+    .byte $00       ; PRG ROM not 4 MiB or larger
+    .byte $00       ; No PRG RAM
+    .byte $07       ; 8192 (64 * 2^7) bytes CHR RAM, no battery
+    .byte $00       ; NTSC; use $01 for PAL
+    .byte $00       ; No special PPU
+
+.segment "VECTORS"
+    .addr nmi, reset, irq
+
+.segment "BANK0"
+
+hello_bank0:
+    lda #2
+    sta $10
+    rts
+
+.segment "BANK1"
+
+hello_bank1:
+    lda #3
+    sta $11
+    rts
+
+.segment "BANK2"
+.byte $00
+
+.segment "BANK3"
+.byte $00
+
+.segment "BANK4"
+.byte $00
+
+.segment "BANK5"
+.byte $00
+
+.segment "BANK6"
+.byte $00
+
+.segment "FIXED"
+
+banktable:
+  .byte $00, $01, $02, $03, $04, $05, $06
+
+zp_current_bank = $00
+
+bankswitch:
+    sty zp_current_bank
+    tya
+    sta banktable, y
+    rts
+
+.proc reset
+    sei
+    cld
+    ldx #$40
+    stx $4017
+
+    ldx #$FF
+    txs
+
+    inx
+    stx $2000
+    stx $2001
+    stx $4010
+
+    bit $2002
+@vblankwait1:
+    bit $2002
+    bpl @vblankwait1
+
+    ldx #0
+    lda #0
+@ram_reset_loop:
+    sta $000, x
+    sta $100, x
+    sta $200, x
+    sta $300, x
+    sta $400, x
+    sta $500, x
+    sta $600, x
+    sta $700, x
+    inx
+    bne @ram_reset_loop
+
+@vblankwait2:
+    bit $2002
+    bpl @vblankwait2
+
+    ;;;
+    ;; NOTE: configuration/reset is done, the code below is our actual program :D
+
+    ldy #0
+    jsr bankswitch
+    jsr hello_bank0
+
+    ldy #1
+    jsr bankswitch
+    jsr hello_bank1
+
+    lda $10
+    clc
+    adc $11
+    sta $12
+
+@loop:
+    jmp @loop
+.endproc
+
+.proc nmi
+    rti
+.endproc
+
+.proc irq
+    rti
+.endproc
-- 
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