将std :: string数据的深拷贝存储到std :: vector中

我一定要疯了，但我在Convert std::string to const char* or char*的例子之后，我在valgrind中得到了很多Invalid read of size 1。我基本上试图分割空白分隔的字符串，并将它们存储到std::vector<const char*>。我知道，因为从c_str()返回的指针可能随时失效，您必须执行一个副本才能安全地使用数据。但是，自从valgrind抱怨之后，我似乎一定会失去一些东西。在绝对最低，我复制了顶部的答案，这样做：将std :: string数据的深拷贝存储到std :: vector中

#include <iostream> 
#include <sstream> 
#include <vector> 
using namespace std; 

int main() 
{ 
    std::vector<const char*> args; 

    std::string str = "hey"; 

    char * writable = new char[str.size() + 1]; 
    std::copy(str.begin(), str.end(), writable); 
    writable[str.size()] = '\0'; // don't forget the terminating 0 
    args.push_back(writable); 
    delete[] writable; 

    for (size_t i = 0; i < args.size(); ++i) 
     cout << args[i] << "\n"; 

    return 0; 
}

下面的输出，这导致从Valgrind的：

==5297== Invalid read of size 1 
==5297== at 0x4C2BFC2: __GI_strlen (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so) 
==5297== by 0x400CFF: main (in /tmp/1411705143.17426/a.out) 
==5297== Address 0x5c2a0a0 is 0 bytes inside a block of size 4 free'd 
==5297== at 0x4C2A09C: operator delete[](void*) (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so) 
==5297== by 0x400CD9: main (in /tmp/1411705143.17426/a.out) 
==5297== 
==5297== Invalid read of size 1 
==5297== at 0x4C2BFD4: __GI_strlen (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so) 
==5297== by 0x400CFF: main (in /tmp/1411705143.17426/a.out) 
==5297== Address 0x5c2a0a1 is 1 bytes inside a block of size 4 free'd 
==5297== at 0x4C2A09C: operator delete[](void*) (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so) 
==5297== by 0x400CD9: main (in /tmp/1411705143.17426/a.out) 
==5297== 
==5297== Invalid read of size 1 
==5297== at 0x58E6DB8: _IO_default_xsputn (genops.c:480) 
==5297== by 0x58E4D19: [email protected]@GLIBC_2.2.5 (fileops.c:1393) 
==5297== by 0x58DA98C: fwrite (iofwrite.c:45) 
==5297== by 0x4EC8A35: std::basic_ostream<char, std::char_traits<char> >& std::__ostream_insert<char, std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char const*, long) (streambuf:451) 
==5297== by 0x400D0F: main (in /tmp/1411705143.17426/a.out) 
==5297== Address 0x5c2a0a0 is 0 bytes inside a block of size 4 free'd 
==5297== at 0x4C2A09C: operator delete[](void*) (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so) 
==5297== by 0x400CD9: main (in /tmp/1411705143.17426/a.out) 
==5297== 
==5297== Invalid read of size 1 
==5297== at 0x58E6DC7: _IO_default_xsputn (genops.c:479) 
==5297== by 0x58E4D19: [email protected]@GLIBC_2.2.5 (fileops.c:1393) 
==5297== by 0x58DA98C: fwrite (iofwrite.c:45) 
==5297== by 0x4EC8A35: std::basic_ostream<char, std::char_traits<char> >& std::__ostream_insert<char, std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char const*, long) (streambuf:451) 
==5297== by 0x400D0F: main (in /tmp/1411705143.17426/a.out) 
==5297== Address 0x5c2a0a2 is 2 bytes inside a block of size 4 free'd 
==5297== at 0x4C2A09C: operator delete[](void*) (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so) 
==5297== by 0x400CD9: main (in /tmp/1411705143.17426/a.out) 
==5297==

我怀疑，这种解决方案并不因为工作删除后，矢量内的数据指向垃圾。我也试过args.push_back(std::move(writable))。什么是解决方法？

来源

2014-09-26 user4081979

为什么不直接存储'std :: string'？为什么要让自己头疼存储'char'数组副本？ – Brandon 2014-09-26 04:36:58

这个例子说“使用它之后不要忘记释放字符串”“。你是delete - 将地址插入向量后立即进入内存。当您尝试稍后访问相同的地址时，这会导致代码非常糟糕。

没有深入研究整个方法的优点（以及为什么要做自己正在做的事情），解决问题的直接方法是只有在完成地址的使用后才调用delete在向量中。

请注意，您需要遍历向量并在矢量中的每个地址上调用delete。

来源

2014-09-26 04:35:53 Srikanth

我决定让一个智能指针处理我的记忆。

std::vector<std::unique_ptr<char[]>> args; 

std::string str = "hey"; 

char * writable = new char[str.size() + 1]; 
std::copy(str.begin(), str.end(), writable); 
writable[str.size()] = '\0'; // don't forget the terminating 0 
args.push_back(std::unique_ptr<char[]>(writable));

来源

2014-09-26 04:45:16 user4081979

哦，亲爱的。使用'std :: vector args;'后面跟着'args.emplace_back（str）;'或'args.emplace_back（pointer_to_first_character，num_characters）;' - 使用'args.push_back（std :: string（ pointer_to_first_character，num_characters））;'如果仍然在C++ 03上。如果原始字符串/缓冲区处于悬停状态，则可以编写一个'类Const_Text_By_Pointer {const char * p_; size_t n_; ...};'只要原始文件可以使用它，就可以根据需要补偿缺少终止NUL的类 - 这会更快并且使用更少的内存。 – 2014-09-26 05:48:02

你得到的valgrind读的问题，因为 '写' 在线上读 “COUT < < ARGS [I] < < ”之前\ n删除“;”。

您应该在引用它之后删除它。

来源

2014-09-26 04:53:37 user3867376

将std :: string数据的深拷贝存储到std :: vector中

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