decode: Fix UB for shift of negative offset

Fixes #12.
aengelke · Dec 13, 2024 · 1c708f1 · 1c708f1
1 parent c9c107e
commit 1c708f1
Showing 1 changed file with 2 additions and 2 deletions.
diff --git a/decode.c b/decode.c
@@ -526,7 +526,7 @@ fd_decode(const uint8_t* buffer, size_t len_sz, int mode_int, uintptr_t address,
                 if (op_byte & 0x40) {
                     if (UNLIKELY((off += 1) > len))
                         return FD_ERR_PARTIAL;
-                    instr->disp = (int8_t) LOAD_LE_1(dispbase) << dispscale;
+                    instr->disp = (int8_t) LOAD_LE_1(dispbase) * (1 << dispscale);
                 } else if (op_byte & 0x80 || (op_byte & 0xc7) == 0x06) {
                     if (UNLIKELY((off += 2) > len))
                         return FD_ERR_PARTIAL;
@@ -578,7 +578,7 @@ fd_decode(const uint8_t* buffer, size_t len_sz, int mode_int, uintptr_t address,
             if (op_byte & 0x40) {
                 if (UNLIKELY((off += 1) > len))
                     return FD_ERR_PARTIAL;
-                instr->disp = (int8_t) LOAD_LE_1(dispbase) << dispscale;
+                instr->disp = (int8_t) LOAD_LE_1(dispbase) * (1 << dispscale);
             } else if (op_byte & 0x80 || (op_byte < 0x40 && base == 5)) {
                 if (UNLIKELY((off += 4) > len))
                     return FD_ERR_PARTIAL;