C++ CString Format With %f, Double Number Became Very Big Value

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Problem Description:

I am maintaining C++ project but i am not family with C++.

I am facing an issue, we use CString to convert a double value to String by

double Dose;
CString Dose2;
if(Dose>0)
{
    Dose2.Format("%f",Dose);
}else{
    Dose2.Format("0");
}

When I set break point after format %f line of code, the value before and after totally different.

Can you explain why this problem occurred? Some time the string value is correct, sometime not correct.

Before

After

Solution – 1

I tried to write Dose value to file before format string, it also had big value.

FILE *fpversion;
fpversion = fopen("doserate.txt", "a");
fprintf(fpversion, "%f", Dose);
fclose(fpversion);

I take a look at source code set Dose value in another dialog.

if(m_MapDlg.GetSafeHwnd()!=NULL)
{
    m_MapDlg.Dose=Result;
}

I tried to make function to set Dose value as

void CMapDlg::SetDose(double dose) {
    this->Dose = dose;
}

And replace

m_MapDlg.Dose=Result;

m_MapDlg.SetDose(Result);

The Dose value got corrected value.

I shared my solution for whom concerned.

Thank @Jonathan Leffler for your suggestion.

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