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Avoid UB when checking truncation range

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Fixes #1818
This commit is contained in:
Rangi42
2025-09-04 12:04:10 -04:00
parent 5b67dc94b6
commit bdc885bd69
1 changed files with 8 additions and 5 deletions
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11
src/link/patch.cpp
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@@ -505,8 +505,10 @@ void patch_CheckAssertions() {
}
static void checkPatchSize(Patch const &patch, int32_t v, uint8_t n) {
static constexpr unsigned m = CHAR_BIT * sizeof(int);
if (n < m && (v < -(1 << n) || v >= 1 << n)) {
assume(n != 0); // That doesn't make sense
assume(n < CHAR_BIT * sizeof(int)); // Otherwise `1 << n` is UB
if (v < -(1 << n) || v >= 1 << n) {
diagnosticAt(
patch,
WARNING_TRUNCATION_1,
@@ -515,8 +517,7 @@ static void checkPatchSize(Patch const &patch, int32_t v, uint8_t n) {
v < 0 ? " (may be negative?)" : "",
n
);
return;
} else if (n < m + 1 && v < -(1 << (n - 1))) {
} else if (v < -(1 << (n - 1))) {
diagnosticAt(
patch,
WARNING_TRUNCATION_2,
@@ -568,7 +569,9 @@ static void applyFilePatches(Section &section, Section &dataSection) {
dataSection.data[offset] = jumpOffset & 0xFF;
} else {
// Patch a certain number of bytes
if (typeSize < sizeof(int)) {
checkPatchSize(patch, value, typeSize * 8);
}
for (uint8_t i = 0; i < typeSize; ++i) {
dataSection.data[offset + i] = value & 0xFF;
value >>= 8;