基准测试 - g++ 从 MSVC 生成不同的代码

Question

I'm writing a benchmark, that measures speed and memory use of my program. I work in VS19, but my test will be run on a linux machine, so I need to compile it in g++. My problem is, that in VS19 my code produces correct results that I expect, compiled with g++ it produces wrong results.

The issue is in memory measurement. In Functions.cpp I have overloaded new and delete

AllocationMetrics s_allocationMetrics;

void* operator new(size_t size) {
    //cout << "Allocate " << size << " bytes\n";
    s_allocationMetrics.totalMemory += size;
    return malloc(size);
}

void operator delete(void* ptr, size_t size) {
    //cout << "Deallocate " << size << " bytes\n";
    s_allocationMetrics.totalFree += size;
    free(ptr);
}

and in Functions.h I have created this struct, that tracks the memory allocations

struct AllocationMetrics {
    uint64_t totalMemory = 0;
    uint64_t totalFree = 0;
    uint64_t getCurrentUsage() { return totalMemory - totalFree; }
    uint64_t maxMem=0;
    void setMaxMem() {
        uint64_t temp= getCurrentUsage();
        if (temp > maxMem)
            maxMem = temp;
    }
    void resetMaxMem() { maxMem = 0; }
};

In the in functions from Functions.cpp, that I need measured, I call setMaxMem and in my Benchmark.cpp I call resetMaxMem , when appropriate. The struct is declared in Functionc.cpp, and in all other .cpp files it is declared as extern.

For this example, I run my benchmark 6x in a loop and with Visual Studio's MSVC I get the expected memory results, with all possible settings (debug, release, etc).

Params:                 1063 x 24       5       5       255
        Sorting                 0.0084792s              0.36439MB
        Stripes                 0.0179886s              1.64792MB

Params:                 1063 x 24       5       5       255
        Sorting                 0.0080979s              0.364406MB
        Stripes                 0.0165975s              1.64794MB

Params:                 1063 x 24       5       5       255
        Sorting                 0.0080586s              0.364422MB
        Stripes                 0.0163024s              1.64795MB

Params:                 1063 x 24       5       5       255
        Sorting                 0.0081503s              0.364438MB
        Stripes                 0.016274s               1.64797MB

Params:                 1063 x 24       5       5       255
        Sorting                 0.0079747s              0.364454MB
        Stripes                 0.0170647s              1.64799MB

Params:                 1063 x 24       5       5       255
        Sorting                 0.0079046s              0.364486MB
        Stripes                 0.0160469s              1.64801MB

When I compile the same code with g++ compiler g++ Source.cpp Functionc.cpp benchmarking.cpp , I get these wrong results

Params:                 1063 x 24       5       5       255
        Sorting                 0.063828s               1.0806MB
        Stripes                 0.171574s               3.73044MB

Params:                 1063 x 24       5       5       255
        Sorting                 0.061869s               4.32227MB
        Stripes                 0.172318s               6.97212MB

Params:                 1063 x 24       5       5       255
        Sorting                 0.067859s               7.56395MB
        Stripes                 0.170573s               10.2138MB

Params:                 1063 x 24       5       5       255
        Sorting                 0.063863s               10.8057MB
        Stripes                 0.171541s               13.4555MB

Params:                 1063 x 24       5       5       255
        Sorting                 0.062963s               14.0473MB
        Stripes                 0.170528s               16.6972MB

Params:                 1063 x 24       5       5       255
        Sorting                 0.064827s               17.2891MB
        Stripes                 0.171541s               19.9389MB

Everything else is correct in g++ compilation, I tried different optimization levels, this memory bug didn't change. I use g++ (MinGW.org GCC-6.3.0-1) 6.3.0 version. I also tried running this with clang, but same mistake appeared.

It appears as if the delete overload didn't take an effect with g++, or that delete isn't called when freeing variables. I tried compiling on both Windows and Linux (same version of g++), this bug appeared in both versions.

EDIT1 : forgot a line of code with temp definition.

Answer 1

Thanks to Jarod42 for the useful comments.

The issue lies in GCC 6.3.0 choosing a different overload of the delete, namely delete(void*) instead of delete(void*, size_t size) which I have targeted. In order to have GCC behave I upgraded it to a newer 11.2.0 version.