const char* and std::string problem with .net (works with 6.0)

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anelma - 31 Aug 2004 06:35 GMT

Following code works fine, when compiled with VS 6.0, but not anymore when compiled in .NET. What's wrong here, I can't see it by myself?
arrString content will be garbage with .net compilation, but when compiled with 6.0 it contains string from Vector (that's how I want it to work).

std::vector<std::string> Vector;
..

void MyClass::DoThis(std::vector<std::string> Vector)
{
const char *arrString[10];

for (int i = 0; i < 10 && i < Vector.size(); i++)
arrString[i] = Vector[i].c_str();

When I debug these, I see that the problem is with my array of const char*. Const char* items seems to change, when std:string changes. For example,
Vector[0].c_str = "dog"
arrString[0]="dog"
Vector[1].c_str = "cat"
arrString[0]="cat" --> this is the problem, why it happens?
This happens only with .net, with 6.0 remains arrString[0] = "dog"

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Ary Sulistyono - 31 Aug 2004 09:05 GMT

Using VS.Net 2003, I don't see the problem you're seeing.

void
MyChass::DoSomething(vector<string> v)
{
    const char *arr[10];
    for (int i = 0; i < 10 && i < v.size(); i++)
    {
        arr[i] = v[i].c_str();
    }

    // this will print "dog" and "cat" correctly
    for (int j=0; j < 10 && j < v.size(); j++)
    {
        cout << "arr[" << j << "] = " << arr[j] << endl;
    }
}

int _tmain(int argc, _TCHAR* argv[])
{
    MyChass m;
    std::string s1 = "dog";
    std::string s2 = "cat";
    std::vector<std::string> v;
    v.push_back(s1);
    v.push_back(s2);
    m.DoSomething(v);
    return 0;
}

Ary Sulistyono

> Following code works fine, when compiled with VS 6.0, but not anymore when compiled in .NET. What's wrong here, I can't see it by myself?
> arrString content will be garbage with .net compilation, but when compiled with 6.0 it contains string from Vector (that's how I want it to work).
[quoted text clipped - 22 lines]
>
> <Id>FCPH9ioddE2faW+WEvjukQ==</Id

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Vladimir Nesterovsky - 31 Aug 2004 09:34 GMT

example,

> Vector[0].c_str = "dog"
> arrString[0]="dog"
> Vector[1].c_str = "cat"
> arrString[0]="cat" --> this is the problem, why it happens?
> This happens only with .net, with 6.0 remains arrString[0] = "dog"

std::string owns memory returned with c_str(). Destiny of this memory is
implementation defined when string is changed.

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Vladimir Nesterovsky
e-mail: vladimir@nesterovsky-bros.com
home: www.nesterovsky-bros.com

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const char* and std::string problem with .net (works with 6.0)

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