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Handle zero-sized literal output buffers #2852

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8 changes: 8 additions & 0 deletions src/literal.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -474,6 +474,10 @@ Result FloatParser<T>::Parse(LiteralType literal_type,
// static
template <typename T>
void FloatWriter<T>::WriteHex(char* out, size_t size, Uint bits) {
if (size == 0) {
return;
}

static constexpr int kNumNybbles = Traits::kBits / 4;
static constexpr int kTopNybbleShift = Traits::kBits - 4;
static constexpr Uint kTopNybble = Uint(0xf) << kTopNybbleShift;
Expand Down Expand Up @@ -811,6 +815,10 @@ void WriteDoubleHex(char* buffer, size_t size, uint64_t bits) {
}

void WriteUint128(char* buffer, size_t size, v128 bits) {
if (size == 0) {
return;
}

uint64_t digits;
uint64_t remainder;
char reversed_buffer[40];
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17 changes: 17 additions & 0 deletions src/test-literal.cc
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Expand Up @@ -29,6 +29,16 @@ using namespace wabt;

namespace {

TEST(WriteHexTest, ZeroSizeDoesNotAccessOutput) {
char output = 'x';

WriteFloatHex(&output, 0, 0);
EXPECT_EQ('x', output);

WriteDoubleHex(&output, 0, 0);
EXPECT_EQ('x', output);
}

enum ParseIntTypeCombo {
UnsignedOnly,
SignedAndUnsigned,
Expand Down Expand Up @@ -853,6 +863,13 @@ TEST(WriteUint128, Basic) {
AssertWriteUint128Equals({0, 0, 1, 0}, "18446744073709551616");
}

TEST(WriteUint128, ZeroSizeDoesNotAccessOutput) {
char output = 'x';

WriteUint128(&output, 0, {0, 0, 0, 0});
EXPECT_EQ('x', output);
}

TEST(WriteUint128, BufferTooSmall) {
{
char buffer[20];
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