code wiki / _hdl_build / nx_arg7_repro.nx
`nx_arg7_repro.nx` source

1// nx_arg7_repro.nx -- minimal repro of the >6-param segfault. p7 takes 7 pointer params and WRITES THROUGH the
2// 7th (g) LATE, after using the first six -- mirroring expand_one's selbox[0]=sel. If the toolchain mishandles
3// param idx 6 (the stack arg), g[0]=99 dereferences garbage -> SIGSEGV. expect: g[0]==99, sum prints, exit 0.
4// license_tier: ORIGINAL
5import "nx_syscalls.nx"
6
7func pw(s: *u8) -> i64 { var n: i64=0; while s[n]!=(0 as u8){n=n+1} sys_write(1,s,n); return 0 }
8func pn(v: i64) -> i64 { if v==0 { sys_write(1,"0" as *u8,1); return 0 } var m: i64=v; if m<0 { sys_write(1,"-" as *u8,1); m=0-m } let t: *u8=sys_mmap(24); var k: i64=0; while m>0 { t[k]=(48+(m%10)) as u8; m=m/10; k=k+1 } let o: *u8=sys_mmap(24); var w: i64=0; var q: i64=k-1; while q>=0 { o[w]=t[q]; w=w+1; q=q-1 } sys_write(1,o,w); return 0 }
9
10func clobber(x: i64) -> i64 { var s: i64=0; var i: i64=0; while i<x { s=s+i; i=i+1 } return s }
11// an 8-param callee (like sf_keep) -- itself uses 2 stack args; called from inside the 7-param p7.
12func p8(a: i64, b: i64, c: i64, d: i64, e: i64, f: i64, g: i64, h: i64) -> i64 { return a+b+c+d+e+f+g+h }
13
14func p7(a: *i64, b: *i64, c: *i64, d: *i64, e: *i64, f: *i64, g: *i64) -> i64 {
15    let s: i64 = a[0]+b[0]+c[0]+d[0]+e[0]+f[0]   // use the 6 register params first
16    // INTERVENING 8-PARAM CALLS (like expand_one calling sf_keep) -- stack-arg calls from a 7-param fn
17    let junk: i64 = p8(1,2,3,4,5,6,7,8) + p8(8,7,6,5,4,3,2,1) + clobber(300)
18    g[0] = 99                                    // WRITE THROUGH the 7th param AFTER the calls -- the real test
19    return s + g[0] + (junk * 0)
20}
21
22func main() -> i64 {
23    pw("=== nx_arg7_repro: 7-param function writing through the 7th param ===\n" as *u8)
24    let a: *i64=sys_mmap(8) as *i64; a[0]=1
25    let b: *i64=sys_mmap(8) as *i64; b[0]=2
26    let c: *i64=sys_mmap(8) as *i64; c[0]=3
27    let d: *i64=sys_mmap(8) as *i64; d[0]=4
28    let e: *i64=sys_mmap(8) as *i64; e[0]=5
29    let f: *i64=sys_mmap(8) as *i64; f[0]=6
30    let g: *i64=sys_mmap(8) as *i64; g[0]=0
31    pw("calling p7 (if the next line prints, the 7th param survived)...\n" as *u8)
32    let r: i64=p7(a,b,c,d,e,f,g)
33    pw("p7 returned=" as *u8); pn(r); pw(" (expect 120: 1+2+3+4+5+6=21, +99) g[0]=" as *u8); pn(g[0]); pw(" (expect 99)\n" as *u8)
34    if r==120 { if g[0]==99 { pw("RESULT: PASS -- 7th param works\n" as *u8); sys_exit(0); return 0 } }
35    pw("RESULT: FAIL -- 7th param mishandled\n" as *u8); sys_exit(1); return 1
36}
nx_arg7_repro.nx source

`nx_arg7_repro.nx` source
