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Fix using uninitialized bytes in move constructor #1728

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Fix using uninitialized bytes in move constructor #1728

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Fix using uninitialized bytes in move constructor
rg3igalia Oct 23, 2026
ed3102d
Merge branch 'master' into patch-1
baylesj Oct 26, 2026
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1 change: 1 addition & 0 deletions src/lib_json/json_value.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1035,6 +1035,7 @@ const Value& Value::operator[](int index) const {
void Value::initBasic(ValueType type, bool allocated) {
setType(type);
setIsAllocated(allocated);
value_.uint_ = 0;

@greptile-apps greptile-apps Bot Oct 23, 2026

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P2 Some bytes remain uninitialized

With JSON_NO_INT64, LargestUInt is unsigned int. If that type is four bytes and double is eight, this assignment initializes only half of ValueHolder. The move constructor still swaps the whole union, so it still copies uninitialized bytes in that configuration. Clear the whole value_ storage rather than only value_.uint_.

Knowledge Base Used: Value storage and traversal internals

@rg3igalia rg3igalia Oct 23, 2026

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memset(&value_, 0, sizeof(value_)); also works and prevents the warning.

@greptile-apps greptile-apps Bot Oct 23, 2026

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Agreed—memset(&value_, 0, sizeof(value_)); clears the entire union storage, including the bytes left untouched when LargestUInt is narrower than double. That resolves my concern about value_.uint_ = 0 being insufficient under JSON_NO_INT64.

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