How do you call vsnprintf() safely?

Question

I\'m porting some very old (> 10y) C code to modern Linuxes. I\'m getting segmentation faults within a custom-written vsnprintf() wrapper (apparently its task is to detect d

Answer 1

As I understand the code, its purpose is to detect the size needed by sprintf to fully write the output string in the buffer. There is a function that do this for you: asprintf (or vasprintf here).

Prototype:

int vasprintf(char **strp, const char *fmt, va_list ap);

Just use it as follow:

String strVPrintf(const String fmt, va_list ap)
{
    char *ans;
    int n;
    n = vasprintf(&ans, fmt, ap);
    // do the checks
    return ans;
}

With this function, you do not need this wrapper any more, I think.