[UE4]追查了两天内存疯狂泄露的原因，竟然是Log没关？？？——UE4如何查内存泄露

各种怀疑，各种debug，最后发现是log窗口没关，因为cache机制所以内存越来越多。然后内存耗尽。。。

好吧，我比较菜。

一天后。。。[更新]

内存耗尽和log窗口的log关系不大，主要是ue4下使用std标准库，因为不同的内存管理机制，会造成内存被cache住无法释放。

在UE4引擎端，会hook所有的内存分配。

`Engine\Source\Runtime\Core\Public\HAL\FMemory.inl`

```c++

FMEMORY_INLINE_FUNCTION_DECORATOR void* FMemory::Malloc(SIZE_T Count, uint32 Alignment)

{

    void* Ptr;

    if (!FMEMORY_INLINE_GMalloc)

    {

        Ptr = MallocExternal(Count, Alignment);

    }

    else

    {

        DoGamethreadHook(0);

        FScopedMallocTimer Timer(0);

        Ptr = FMEMORY_INLINE_GMalloc->Malloc(Count, Alignment);

    }

    // optional tracking of every allocation

    LLM_IF_ENABLED(FLowLevelMemTracker::Get().OnLowLevelAlloc(ELLMTracker::Default, Ptr, Count, ELLMTag::Untagged, ELLMAllocType::FMalloc));

    return Ptr;

}

​

FMEMORY_INLINE_FUNCTION_DECORATOR void* FMemory::Realloc(void* Original, SIZE_T Count, uint32 Alignment)

{

    // optional tracking -- a realloc with an Original pointer of null is equivalent

    // to malloc() so there's nothing to free

    LLM_REALLOC_SCOPE(Original);

    LLM_IF_ENABLED(if (Original != nullptr) FLowLevelMemTracker::Get().OnLowLevelFree(ELLMTracker::Default, Original, ELLMAllocType::FMalloc));

​

    void* Ptr;

    if (!FMEMORY_INLINE_GMalloc)

    {

        Ptr = ReallocExternal(Original, Count, Alignment);

    }

    else

    {

        DoGamethreadHook(1);

        FScopedMallocTimer Timer(1);

        Ptr = FMEMORY_INLINE_GMalloc->Realloc(Original, Count, Alignment);

    }

​

    // optional tracking of every allocation - a realloc with a Count of zero is equivalent to a call 

    // to free() and will return a null pointer which does not require tracking. If realloc returns null

    // for some other reason (like failure to allocate) there's also no reason to track it

    LLM_IF_ENABLED(if (Ptr != nullptr) FLowLevelMemTracker::Get().OnLowLevelAlloc(ELLMTracker::Default, Ptr, Count, ELLMTag::Untagged, ELLMAllocType::FMalloc));

​

    return Ptr;

}

​

FMEMORY_INLINE_FUNCTION_DECORATOR void FMemory::Free(void* Original)

{

    if (!Original)

    {

        FScopedMallocTimer Timer(3);

        return;

    }

​

    // optional tracking of every allocation

    LLM_IF_ENABLED(FLowLevelMemTracker::Get().OnLowLevelFree(ELLMTracker::Default, Original, ELLMAllocType::FMalloc));

​

    if (!FMEMORY_INLINE_GMalloc)

    {

        FreeExternal(Original);

        return;

    }

    DoGamethreadHook(2);

    FScopedMallocTimer Timer(2);

    FMEMORY_INLINE_GMalloc->Free(Original);

}

​

```

所有的内存分配如果是新增内存，走 FMemory::Malloc，如果是已有内存走 FMemory::Realloc。std有自己的一套内存管理机制。会造成内存无法被ue4立即释放。

所以最后是用TArray,TMap,TSet等Ue4容器代替std容器。

然后在FMomory::Malloc和Memory::Realloc设置断点，追查所有的新开内存，然后逐个优化掉，即可。