• Linux 下进程的内存空间分配


    这里主要是以 C 语言为例,其他语言开发的程序,每个进程都会有一个类似的空间。下面是一段 C 代码:

    #include    <stdlib.h>
    #include    <stdio.h>
    
    double t[0x02000000];
    
    void segments()
    {
        static int s = 42;
        void *p = malloc(2);
    
        printf("stack	%010p
    brk	%010p
    heap	%010p
    "
                "static	%010p
    static	%010p
    text	%010p
    ",
                &p, sbrk(0),p,t,&s,segments);
    }
    
    void writeFreeSpace()
    {
        char *p = sbrk(0) - 1;
        *p = 1;
        printf("assign to sbrk(0)-1 is succed! 
    ");
    
        p = sbrk(0) + 1;
        *p = 1;
        printf("assign to sbrk(0)+1 is succed! 
    ");
    }
    
    int main(int argc, char *argv[])
    {
        segments();
        writeFreeSpace();
        exit(0);
    }

    这里主要打印了:指针 p 的地址(stack),进程当前的 break 的位置( heap 的边界),指针 p 指向的地址(heap),全局变量 t 的地址,局部 static 变量的地址,还有函数 segments() 的地址。

    使用 gcc 便以后,这段代码的运行结果如下:

    stack    0xbfaa9edc
    brk    0x18856000
    heap    0x18835008
    static    0x0804a060
    static    0x0804a024
    text    0x08048494
    Size of heap: 20ff8 
    assign to sbrk(0)-1 is succed! 
    Segmentation fault

    这很好的证明了下图中的分布关系:

    其中,可能不常见的是 sbrk() 函数。一般情况下,应用编程的时候不推荐使用 sbrk(),所以我们见得少。通过 man 得知,sbrk( int ) 是用来增加 Heap 的大小的,当给它喂参数 0 ,它返回 Heap 的边界( sbrk(0) 返回的地址已经在 heap() 之外了,可以改动 writeFreeSpace() 中的地址尝试;从上面可以看出,这里 heap 的最小值默认是 132k Bytes(20ff8+8=21000),前面8 个 byte 是保留的,具体作用需要再作了解)。

    valgrind

    Valgrind是一套用于内存调试、内存泄漏检测以及性能分析的软件开发工具。下面是来自它官网的介绍:

    The Valgrind tool suite provides a number of debugging and profiling tools that help you make your programs faster and more correct. The most popular of these tools is called Memcheck. It can detect many memory-related errors that are common in C and C++ programs and that can lead to crashes and unpredictable behaviour.

    The Valgrind distribution currently includes six production-quality tools: a memory error detector, two thread error detectors, a cache and branch-prediction profiler, a call-graph generating cache and branch-prediction profiler, and a heap profiler. It also includes three experimental tools: a stack/global array overrun detector, a second heap profiler that examines how heap blocks are used, and a SimPoint basic block vector generator. It runs on the following platforms: X86/Linux, AMD64/Linux, ARM/Linux, ARM64/Linux, PPC32/Linux, PPC64/Linux, PPC64BE/Linux, S390X/Linux, MIPS32/Linux, MIPS64/Linux, ARM/Android (2.3.x and later), X86/Android (4.0 and later), MIPS32/Android, X86/Darwin and AMD64/Darwin (Mac OS X 10.9, with limited support for 10.8).

    快速上手:http://valgrind.org/docs/manual/quick-start.html

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  • 原文地址:https://www.cnblogs.com/pied/p/4613463.html
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