MBR IT/.NET 247 : const char* and std::string problem with .net (works with 6.0) on microsoft.public.dotnet.languages.vc

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

Messages

Related Types

This message was discovered on microsoft.public.dotnet.languages.vc.
Responses highlighted in red are from those people who are likely to be able to contribute good, authoratitive information to this discussion. They include Microsoft employees, MVP's and others who IMHO contribute well to these kinds of discussions.

Post a new message to this list...

anelma via .NET 247 (VIP)

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"

--------------------------------
From: anelma

-----------------------
Posted by a user from .NET 247 (http://www.dotnet247.com/)

<Id>FCPH9ioddE2faW+WEvjukQ==</Id>

Reply to this message...

Vladimir Nesterovsky

"anelma via .NET 247" <Click here to reveal e-mail address> wrote in message
news:Click here to reveal e-mail address...
> 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).
[Original message clipped]

example,
[Original message clipped]

std::string owns memory returned with c_str(). Destiny of this memory is
implementation defined when string is changed.
--
Vladimir Nesterovsky
e-mail: Click here to reveal e-mail address
home: www.nesterovsky-bros.com

Reply to this message...

Ary Sulistyono

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

anelma via .NET 247 wrote:
[Original message clipped]

Reply to this message...

MBR BootFX
Best-of-breed application framework for .NET projects, developed by Matthew Baxter-Reynolds and MBR IT

	Copyright © Matthew Baxter-Reynolds 2001-2008. '.NET 247 Software Development Services' is a trading style of MBR IT Solutions Ltd.
	Contact Us - Terms of Use - Privacy Policy - www.dotnet247.com