制作自己的malloc函数用C [英] making your own malloc function in C

问题描述

我需要你在此帮助。我对C的平均知识和这里的问题。我将用一些基准来对新的处理器测试一些计算机体系结构的东西（分支未命中，高速缓存未命中）。有关的事情是，基准是C，但我必须不包括任何库的调用。例如，我不能用malloc的，因为我得到的错误

I need your help in this. I have an average knowledge of C and here is the problem. I am about to use some benchmarks to test some computer architecture stuff (branch misses, cache misses) on a new processor. The thing about that is that benchmarks are in C but I must not include any library calls. For example, I cannot used malloc because I am getting the error

"undefined reference to malloc" 

即使我已经包括图书馆。所以，我有写我自己的malloc。我不希望它是超高效的 - 只是做基础。当我想到它，我必须在内存中有一个地址，每次一个malloc发生，我返回一个指针到该地址，并增加了大小BU计数器。 malloc的两次发生在我的计划，所以我甚至都不需要大容量内存。

even if I have included the library. So I have to write my own malloc. I do not want it to be super efficient - just do the basics. As I am thinking it I must have an address in memory and everytime a malloc happens, I return a pointer to that address and increment the counter bu that size. Malloc happens twice in my program so I do not even need large memory.

您能帮我一下吗？我是一个Verilog的设计，没有使用C这么多的经验。

Can you help me on that? I am a verilog designed and do not have so much experience in C.

我见过previous的答案，但都似乎对我来说太复杂了。除此之外，我没有获得K·R的书。

I have seen previous answers but all seem too complicated for me. Besides, I do not have access to K-R book.

干杯！

编辑：也许这可以帮助你更多：
我没有用gcc，但SDE-gcc编译器。这有什么区别？也许这就是为什么我越来越不确定和参考的malloc？

maybe this can help you more: I am not using gcc but sde-gcc compiler. Does it make any difference? Maybe thats why I am getting and undefined reference to malloc?

EDIT2：
我测试MIPS架构：

I am testing a mips architecture:

我已经包括：

#include <stdlib.h>

和错误是：

undefined reference to malloc
relocation truncated to fit: R_MIPS_26 against malloc

和编译器命令ID：

test.o: test.c cap.h
sde-gcc -c -o test.s test.c -EB -march=mips64 -mabi=64 -G -O -ggdb -O2 -S
    sde-as -o test.o test.s EB -march=mips64 -mabi=64 -G -O -ggdb
    as_objects:=test.o init.o

编辑3：
确定我使用的实现上面，它运行没有任何问题。问题是，在做嵌入式编程的时候，你只需要定义您的一切使用，所以我定义我自己的malloc。 SDE-GCC没有认识到malloc函数。

EDIT 3: ok I used implementation above and it run without any problems. The problem is that when doing embedded programming, you just have to define everything you are using so I defined my own malloc. sde-gcc didn't recognized the malloc function.

推荐答案

这是一个非常简单的方法，它可以让你过去的2 mallocs：

This is a very simple approach, which may get you past your 2 mallocs:

static unsigned char our_memory[1024 * 1024]; //reserve 1 MB for malloc
static size_t next_index = 0;

void *malloc(size_t sz)
{
    void *mem;

    if(sizeof our_memory - next_index < sz)
        return NULL;

    mem = &our_memory[next_index];
    next_index += sz;
    return mem;
}

void free(void *mem)
{
   //we cheat, and don't free anything.
}

如果需要，您可能需要将内存块你的手回来，所以如你一直
还给这是对那是无论你需要4个，8个，16个或多个地址的内存地址。

If required, you might need to align the memory piece you hand back, so e.g. you always give back memory addresses that's on an address that's a multiple of 4, 8, 16 or whatever you require.

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