gbdev/rgbds
1
0
Fork 0
mirror of https://github.com/gbdev/rgbds.git synced 2026-09-23 14:17:06 +00:00
Code Issues Packages Projects Releases Wiki Activity

Avoid signed overflow in RGBLINK's +, -, and * (#2060)

Browse Source 
RGBASM computes these with unsigned arithmetic and casts back, since
signed overflow is UB in C++, but RGBLINK's RPN evaluator used `int32_t`
directly, so `src/link/patch.cpp` tripped UBSan on lines 117, 121, and
124. Share the three operators through `opmath.cpp` so both evaluators
stay in step.
This commit is contained in:
Max Freedom Pollard
2026-09-07 16:15:07 -04:00
committed by GitHub
parent fdd6cece30
commit 631ef003e7
7 changed files with 35 additions and 7 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/opmath.cpp
+17
View File
@@ -8,6 +8,23 @@
#include "helpers.hpp" // assume, clz, ctz
// Signed overflow is UB, so these compute with unsigned arithmetic, which wraps around.
// Casting back is OK because the types implement two's complement behavior.
int32_t op_add(int32_t augend, int32_t addend) {
return static_cast<int32_t>(static_cast<uint32_t>(augend) + static_cast<uint32_t>(addend));
}
int32_t op_sub(int32_t minuend, int32_t subtrahend) {
return static_cast<int32_t>(static_cast<uint32_t>(minuend) - static_cast<uint32_t>(subtrahend));
}
int32_t op_mul(int32_t multiplicand, int32_t multiplier) {
return static_cast<int32_t>(
static_cast<uint32_t>(multiplicand) * static_cast<uint32_t>(multiplier)
);
}
int32_t op_divide(int32_t dividend, int32_t divisor) {
assume(divisor != 0); // Division by 0 is UB
assume(dividend != INT32_MIN || divisor != -1); // INT32_MIN / -1 is UB