MallocStomp.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "CoreTypes.h"
#include "HAL/MemoryBase.h"
 
class FOutputDevice;
class UWorld;
 
#if WITH_MALLOC_STOMP
 
#if PLATFORM_WINDOWS
    #include "Windows/WindowsHWrapper.h"
#endif
 
class FMallocStomp final : public FMalloc
{
    struct FAllocationData;
 
    const SIZE_T PageSize;
 
    const bool bUseUnderrunMode;
 
    static constexpr SIZE_T VirtualAddressBlockSize = 1 * 1024 * 1024 * 1024; // 1 GB blocks
 
public:
    // FMalloc interface.
    explicit FMallocStomp(const bool InUseUnderrunMode = false);
 
    virtual void* Malloc(SIZE_T Size, uint32 Alignment) override;
 
    virtual void* TryMalloc(SIZE_T Size, uint32 Alignment) override;
 
    virtual void* Realloc(void* InPtr, SIZE_T NewSize, uint32 Alignment) override;
 
    virtual void* TryRealloc(void* InPtr, SIZE_T NewSize, uint32 Alignment) override;
 
    virtual void Free(void* InPtr) override;
 
    virtual bool GetAllocationSize(void *Original, SIZE_T &SizeOut) override;
 
    virtual void DumpAllocatorStats( FOutputDevice& Ar ) override
    {
        // No meaningful stats to dump.
    }
 
    virtual bool ValidateHeap() override
    {
        // Nothing to do here since validation happens as data is accessed
        // through page protection, and on each free checking the sentinel.
        return true;
    }
 
#if UE_ALLOW_EXEC_COMMANDS
    virtual bool Exec( UWorld* InWorld, const TCHAR* Cmd, FOutputDevice& Ar ) override
    {
        return false;
    }
#endif
 
    virtual const TCHAR* GetDescriptiveName() override
    {
        return TEXT( "Stomp" );
    }
 
    virtual bool IsInternallyThreadSafe() const override
    {
        // Unix and Mac uses mmap which is thread-safe
        // Windows uses virtual alloc which is thread-safe
        // Other platforms using FPlatformMemory::BinnedAllocFromOS are all assumed to have thread-safe implementation already
        // VirtualAddressCursor and VirtualAddressMax are thread-locals so each thread has its virtual reserved block
        return true;
    }
};
 
#endif // WITH_MALLOC_STOMP