Segfault with stringstream

This is my function:

string GaugeStr;
void someFunction() {
    float pie = someFloat();
    stringstream ss (stringstream::in | stringstream::out);
    ss << pie;
    GaugeStr = ss.str();
}

When I run the function, it works properly. When I call it however for a second time (someFunction(); someFunction();, then my program crashes with a segmentation fault.

I tried p开发者_如何学Cutting stringstream ss (stringstream::in | stringstream::out); out of the function to make it a global variable, but the contents I want to send to GaugeStr get appended to ss. For example, if we assume that someFloat() always returns 1.2, then the second time I run the function, GaugeStr is set to 1.21.2.

So, I inserted ss.str("") in the function, but the program crashes again with a segfault.

What can I do to put the value of someFloat() is GaugeStr as a string without a segfault?

Exact Function

void CPU_BenchmarkFrame::OnButton1Click(wxCommandEvent& event) {
    float pie = PiAlgo (Gauge2);
    stringstream ss (stringstream::in | stringstream::out);
    ss << pie;
    wxMessageBox(_("Alert"), _("Sample Alert")); //To test where the segfault happens
    string GaugeStr = ss.str();

    wstring GaugeWid;
    std::copy(GaugeStr.begin(), GaugeStr.end(), GaugeWid.begin());

    StaticText2->SetLabel(GaugeWid);
}

Even more edits

The problem is one or more lines here:

    wstring GaugeWid;
    std::copy(GaugeStr.begin(), GaugeStr.end(), GaugeWid.begin());

    StaticText2->SetLabel(GaugeWid);

when I commented them the script worked normally.

---

This doesn't work

std::wstring GaugeWid;
std::copy(GaugeStr.begin(), GaugeStr.end(), GaugeWid.begin());

when GaugeWid doesn't have a size. And it doesn't convert the characters either.

If you want a wide string, use a wstringstream.

---

@Bo spotted a good line (after the question was edited...). I agree.

Here is a suggestion to fix it:

GaugeWid.clear();
std::copy(GaugeStr.begin(), GaugeStr.end(), std::back_inserter(GaugeWid));

---

@kongr45gpen:

I suspect a threading bug:

• you are doing updates of a variable names GaugeStr (sounds like meter monitoring)
• the code breaks on innocuous assignment to ....... a global.

Sounds like a threading bug. Do you use threads, if so, you must appropriately lock GaugeStr or make it a thread local.

Drop me a note if I need to expand on these, because at current I cannot be sure you are using threading.

---

I just tried it:

#include <iostream>
#include <sstream>

using namespace std;

string GaugeStr;

float someFloat() {  
   return (float) 3.41; 
}

void someFunction() {

    float pie = someFloat();
    stringstream ss (stringstream::in | stringstream::out);
    ss << pie;
    GaugeStr = ss.str(); 
}

int main() {    
   someFunction();    
   someFunction();

   return 0; 
}

This compiles with gcc-compiler version 4.4.0 (running on Windows, IDE: CodeBlocks).