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[interpreter] Fix en/decoding of s33 #2294

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Merged
rossberg merged 2 commits into from
Oct 21, 2026
Merged

[interpreter] Fix en/decoding of s33 #2294

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d5d2701
[interpreter] Fix en/decoding of s33
rossberg Oct 21, 2026
ea9ab61
Another test
rossberg Oct 21, 2026
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13 changes: 7 additions & 6 deletions interpreter/binary/decode.ml
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Original file line number Diff line number Diff line change
Expand Up @@ -105,7 +105,7 @@ let u32 s = I32.of_int_u (I64.to_int_u (uN 32 s))
let u64 s = uN 64 s
let s7 s = I64.to_int_s (sN 7 s)
let s32 s = I32.of_int_s (I64.to_int_s (sN 32 s))
let s33 s = Convert.I32_.wrap_i64 (sN 33 s)
let s33 s = sN 33 s
let s64 s = sN 64 s
let f32 s = F32.of_bits (word32 s)
let f64 s = F64.of_bits (word64 s)
Expand Down Expand Up @@ -149,6 +149,7 @@ open Types

let zero s = expect 0x00 s "zero byte expected"
let idx s = u32 s
let idx32 s = Convert.I64_.extend_i32_u (idx s)
let laneidx s = u8 s

let mutability s =
Expand All @@ -160,7 +161,7 @@ let mutability s =
let typeuse idx s =
let pos = pos s in
match idx s with
| i when i >= 0l -> Idx i
| i when i >= 0L -> Idx (Convert.I32_.wrap_i64 i)
| _ -> error s pos "malformed type index"

let numtype s =
Expand Down Expand Up @@ -262,11 +263,11 @@ let subtype s =
match peek s with
| Some i when i = -0x30 land 0x7f ->
skip 1 s;
let uts = vec (typeuse u32) s in
let uts = vec (typeuse idx32) s in
SubT (NoFinal, uts, comptype s)
| Some i when i = -0x31 land 0x7f ->
skip 1 s;
let uts = vec (typeuse u32) s in
let uts = vec (typeuse idx32) s in
SubT (Final, uts, comptype s)
| _ -> SubT (Final, [], comptype s)

Expand All @@ -287,7 +288,7 @@ let limits uN s =

let tagtype s =
zero s;
TagT (typeuse idx s)
TagT (typeuse idx32 s)

let globaltype s =
let t = valtype s in
Expand All @@ -305,7 +306,7 @@ let tabletype s =

let externtype s =
match byte s with
| 0x00 -> ExternFuncT (typeuse idx s)
| 0x00 -> ExternFuncT (typeuse idx32 s)
| 0x01 -> ExternTableT (tabletype s)
| 0x02 -> ExternMemoryT (memorytype s)
| 0x03 -> ExternGlobalT (globaltype s)
Expand Down
15 changes: 8 additions & 7 deletions interpreter/binary/encode.ml
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Original file line number Diff line number Diff line change
Expand Up @@ -65,7 +65,7 @@ struct
let u32 i = u64 Int64.(logand (of_int32 i) 0xffffffffL)
let s7 i = s64 (Int64.of_int i)
let s32 i = s64 (Int64.of_int32 i)
let s33 i = s64 (Convert.I64_.extend_i32_s i)
let s33 i = s64 i
let f32 x = word32 (F32.to_bits x)
let f64 x = word64 (F64.to_bits x)
let v128 v = String.iter (put s) (V128.to_bits v)
Expand Down Expand Up @@ -100,13 +100,14 @@ struct
open Source

let idx x = u32 x.it
let idx32 x = u32 (Convert.I32_.wrap_i64 x)

let mutability = function
| Cons -> byte 0
| Var -> byte 1

let typeuse idx = function
| Idx x -> idx x
| Idx x -> idx (Convert.I64_.extend_i32_u x)
| Rec _ | Def _ -> assert false

let numtype = function
Expand Down Expand Up @@ -176,8 +177,8 @@ struct

let subtype = function
| SubT (Final, [], ct) -> comptype ct
| SubT (Final, uts, ct) -> s7 (-0x31); vec (typeuse u32) uts; comptype ct
| SubT (NoFinal, uts, ct) -> s7 (-0x30); vec (typeuse u32) uts; comptype ct
| SubT (Final, uts, ct) -> s7 (-0x31); vec (typeuse idx32) uts; comptype ct
| SubT (NoFinal, uts, ct) -> s7 (-0x30); vec (typeuse idx32) uts; comptype ct

let rectype = function
| RecT [st] -> subtype st
Expand All @@ -188,7 +189,7 @@ struct
byte flags; u64 min; opt u64 max

let tagtype = function
| TagT ut -> u32 0x00l; typeuse u32 ut
| TagT ut -> u32 0x00l; typeuse idx32 ut

let globaltype = function
| GlobalT (mut, t) -> valtype t; mutability mut
Expand All @@ -200,7 +201,7 @@ struct
| TableT (at, lim, t) -> reftype t; limits at lim

let externtype = function
| ExternFuncT ut -> byte 0x00; typeuse u32 ut
| ExternFuncT ut -> byte 0x00; typeuse idx32 ut
| ExternTableT tt -> byte 0x01; tabletype tt
| ExternMemoryT mt -> byte 0x02; memorytype mt
| ExternGlobalT gt -> byte 0x03; globaltype gt
Expand Down Expand Up @@ -228,7 +229,7 @@ struct

let blocktype = function
| VarBlockType x -> typeuse s33 (Idx x.it)
| ValBlockType None -> s33 (-0x40l)
| ValBlockType None -> s33 (-0x40L)
| ValBlockType (Some t) -> valtype t

let local (n, loc) =
Expand Down
19 changes: 19 additions & 0 deletions test/core/binary.wast
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@tlively tlively Oct 21, 2026

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Gemini suggests that we could also add an assert_malformed test for a negative s33 (e.g. -0x1_0000_0000 encoded as \80\80\80\80\70), which would previously wrap to 0l.

@rossberg rossberg Oct 21, 2026

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Done.

Original file line number Diff line number Diff line change
Expand Up @@ -1232,3 +1232,22 @@
)
"illegal opcode ff"
)

;; Decoding of s33
(assert_invalid
(module binary
"\00asm" "\01\00\00\00"
"\01\0a\01" ;; type section with 1 entry
"\60\01\63\80\80\80\80\08\00" ;; (func (param (ref null 0x8000_0000)))
)
"unknown type"
)

(assert_malformed
(module binary
"\00asm" "\01\00\00\00"
"\01\0a\01" ;; type section with 1 entry
"\60\01\63\80\80\80\80\70\00" ;; (func (param (ref null -0x1_0000_0000)))
)
"integer representation"
)
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