std::string stringf(const char* format, ...)

std::string stringf(const char* format, ...)
{
va_list arg_list;

va_start(arg_list, format);

// SUSv2 version doesn‘t work for buf NULL/size 0, so try printing
// into a small buffer that avoids the double-rendering and alloca path too...
char short_buf[256];
const size_t needed = vsnprintf(short_buf, sizeof short_buf,
format, arg_list) + 1;
if (needed <= sizeof short_buf)
return short_buf;

// need more space...
char* p = static_cast<char*>(alloca(needed));
vsnprintf(p, needed, format, arg_list);
return p;
}

std::string stringf(const char* format, ...)

原文：http://www.cnblogs.com/ytjjyy/p/4233046.html