zeromem: Do not call memset when there is nothing to zero - #1750
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yumasansansan wants to merge 1 commit into
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zeromem() passes what it is given straight to memset(), whose declaration forbids a null pointer however many bytes it is asked to fill -- nought included. A buffer of no samples holds no address, so clearing one is a call that UndefinedBehaviorSanitizer stops the program at: modules/juce_core/memory/juce_Memory.h:40:79: runtime error: null pointer passed as argument 1, which is declared to never be null AudioBuffer::clear() is one way there: AudioProcessor::processBlockBypassed() clears the channels it has no input for, and a host that asks a plug-in for no samples at all may hand over a buffer whose channels are nowhere. Nothing is written either way, so only the call goes away. This is the shape of the fix for MemoryBlock::matches(), where memcmp() was given the null pointer of an empty block. A fuzz target of ADLplug-Next found it, one that gives the plug-in the blocks a host asks for, of the sizes and the channel counts a host chooses.
This was referenced Sep 20, 2026
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zeromem()passes what it is given straight tomemset(), whose declaration forbids a null pointer however many bytes it is asked to fill -- nought included. A buffer of no samples holds no address, so clearing one is a call that UndefinedBehaviorSanitizer stops the program at:AudioBuffer::clear()is one way there.AudioProcessor::processBlockBypassed()clears the channels the plug-in has no input for, and a host that asks a plug-in for no samples at all may hand over a buffer whose channels are nowhere;FloatVectorOperations::clear()then reacheszeromem()with that pointer and no bytes. Nothing is written either way, so only the call goes away.This is the shape of #1749's second commit, where
MemoryBlock::matches()was given the null pointer of an empty block formemcmp().A fuzz target of ADLplug-Next found it: it gives an
AudioProcessorthe blocks a host asks for, of the sizes and the channel counts a host chooses, including none of either.It is in 9.0.2 and in
developas it stands, and it is independent of the commits of ours that are already open.