将strcpy(）与动态内存一起使用

Using strcpy() with dynamic memory

本文关键字：内存 一起 动态 strcpy      更新时间：2023-10-16

我的代码运行正常，没有内存泄漏。然而，我得到了valgrind错误：

==6304== 14 errors in context 4 of 4:
==6304== Invalid write of size 1
==6304==    at 0x4A0808F: __GI_strcpy (mc_replace_strmem.c:443)
==6304==    by 0x401453: main (calc.cpp:200)
==6304==  Address 0x4c390f1 is 0 bytes after a block of size 1 alloc'd
==6304==    at 0x4A075BC: operator new(unsigned long) (vg_replace_malloc.c:298)
==6304==    by 0x401431: main (calc.cpp:199)
==6304== 4 errors in context 2 of 4:
==6304== Invalid read of size 1
==6304==    at 0x39ADE3B0C0: ____strtod_l_internal (in /lib64/libc-2.12.so)
==6304==    by 0x401471: main (calc.cpp:203)
==6304==  Address 0x4c390f1 is 0 bytes after a block of size 1 alloc'd
==6304==    at 0x4A075BC: operator new(unsigned long) (vg_replace_malloc.c:298)
==6304==    by 0x401431: main (calc.cpp:199)

除了初始地址之外，错误1和3分别与2和4相同

这些错误意味着什么？我该如何修复它们？

 int main(){
    //Dlist is a double ended list. Each Node has a datum,
    //a pointer to the previous Node and a pointer to the next Node
    Dlist<double> hold;
    Dlist<double>* stack = &hold;
    string* s = new string;
    bool run = true;
    while (run && cin >> *s){
        char* c = new char;
        strcpy(c, s->c_str());   //valgrind errors here
        if (isdigit(c[0]))
            stack->insertFront(atof(c));
        else{
            switch(*c){
                //calculator functions
            }
        delete c;
        c = 0;
  }
delete s;
s = 0;

valgrind将从stdlib函数中抛出许多通常无害的警告，因为它们有点"作弊"。但这是而不是这里的情况：

char* c = new char; // this is bad

只分配一个字符，而不是一个字符缓冲区，try:

char* c = new char[s->size()+1];

然后将删除更改为：

delete [] c;

char*c=new char；c的大小是1，即使要复制1个字符串，也需要两个字符长的缓冲区（第二个字符用于容纳空终止符）

就在这里：

    char* c = new char;

您只分配了一个字符。改为分配阵列：

    char* c = new char[str->length() + 1];

还记得调用delete[]。您分配+1为字符串的null终止腾出空间。

    char* c = new char;

您正在分配一个字符，然后将一个太长而无法容纳的字符串复制到内存中。您需要分配一个足够大的数组。

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