vsprintf can not work on mac OS

shangke

On mac OS, the function vsprintf can't print string with parameter %s or %ls ,
but it works well on Windows.
I have tried on Qt5.8 and Qt5.9.

Please help me, thanks.
code:

#include <QCoreApplication>

#include <string>
using namespace std;

wstring FormatStr( const wchar_t* wszFormat, ... )
{
va_list ptr;
va_start(ptr, wszFormat);

int nLen = vwprintf(wszFormat, ptr) + 1;

wchar_t* lpDest = new wchar_t[nLen];

vswprintf(lpDest, nLen, wszFormat, ptr);
va_end(ptr);

wstring strRe = lpDest;

delete lpDest;
return strRe;

}

string FormatStrA( const char* szFormat, ... )
{
va_list ptr;
va_start(ptr, szFormat);
int nLen = vprintf(szFormat, ptr) + 1;

char* lpDest = new char[nLen];

vsprintf( lpDest, szFormat, ptr );
va_end(ptr);

string strRe = lpDest;

delete lpDest;
return strRe;

}

int main(int argc, char *argv[])
{
QCoreApplication a(argc, argv);
wstring str = FormatStr( L"%ls/%d/%d/%ls", L"https://www.google.com", 2, 3, L"asdfasdfasd");
string str1 = FormatStrA( "%s/%d/%d/%s", "https://www.google.com", 2, 3, "asdfasdfasd");

// On windows: str == str1  == "https://www.google.com/2/3/asdfasdfasd"
// On Mac: str == str1 == (null)/2/3/(null)
return a.exec();

}

mpergand

You use vprintf two times for the same valist ...

#include <string>
#include <cwchar>
#include <iostream>
using namespace std;

wstring FormatStr( const wchar_t* wszFormat, ... )
{
va_list ptr;
va_start(ptr, wszFormat);
int nLen = vwprintf(wszFormat, ptr) + 1;
va_end(ptr);

std::cout<<" (1)"<<std::endl;
wchar_t* lpDest = new wchar_t[nLen];

va_start(ptr, wszFormat);
vswprintf(lpDest, nLen, wszFormat, ptr);
va_end(ptr);

wstring strRe = lpDest;

delete lpDest;
return strRe;
}

string FormatStrA( const char* szFormat, ... )
{
va_list ptr;
va_start(ptr, szFormat);
int nLen = vprintf(szFormat, ptr) + 1;
va_end(ptr);

char* lpDest = new char[nLen];
std::cout<<" (2)"<<std::endl;

va_start(ptr, szFormat);
vsprintf( lpDest, szFormat, ptr );
va_end(ptr);

string strRe = lpDest;

delete lpDest;
return strRe;
}




int main(int argc, char *argv[])
{
wstring str = FormatStr( L"%ls/%d/%d/%ls", L"https://www.google.com", 2, 3, L"asdfasdfasd");
string str1 = FormatStrA( "%s/%d/%d/%s", "https://www.google.com", 2, 3, "asdfasdfasd");
std::wcout<<str<<" (3)"<<std::endl;
std::cout<<str1<<" (4)"<<std::endl;

logs:

https://www.google.com/2/3/asdfasdfasd (1)
https://www.google.com/2/3/asdfasdfasd (2)
https://www.google.com/2/3/asdfasdfasd (3)
https://www.google.com/2/3/asdfasdfasd (4)

on Mac OSX 10.9.5

shangke

Thank you very much!
It does work on mac OS.
But,
I found that the function FormatStrA crashed on ubuntu16.
Please help me one more time, thank you.

mpergand

What does the debugger say ?
It can crash in many ways.

Maybe you could use a large static buffer:
char dest[1000];
and use vsnprintf, vswprintf instead.