string vstringf(char const *format, va_list args)
{
// estimate string length
va_list args2;
va_copy(args2, args);
int est = vnprintf(format, args2);
va_end(args2);
// allocate space
Array<char> buf(est+1);
// render the string
int len = vsprintf(buf, format, args);
// check the estimate, and fail *hard* if it was low, to avoid any
// possibility that this might become exploitable in some context
// (do *not* turn this check off in an NDEGUG build)
if (len > est) {
// don't go through fprintf, etc., because the state of memory
// makes that risky
static char const msg[] =
"fatal error: vnprintf failed to provide a conservative estimate,\n"
"memory is most likely corrupted\n";
write(2 /*stderr*/, msg, strlen(msg));
abort();
}
// happy
return string(buf);
}
void printk(const char *format, ...)
{
va_list ap;
va_start(ap, format);
vnprintf(_putc, (char*)format, ap);
};
int nprintf(char const *format, ...)
{
va_list args;
va_start(args, format);
int ret = vnprintf(format, args);
va_end(args);
return ret;
}
void nprintfVector(char const *format, ...)
{
va_list args;
// run vnprintf to obtain estimate
va_start(args, format);
int est = vnprintf(format, args);
va_end(args);
// make that much space
char *buf = new char[est+1 + 50 /*safety margin*/];
// run the real vsprintf
va_start(args, format);
int len = vsprintf(buf, format, args);
va_end(args);
if (len > est) {
printf("nprintf failed to conservatively estimate!\n");
printf(" format: %s\n", format);
printf(" estimate: %d\n", est);
printf(" actual: %d\n", len);
exit(2);
}
if (len != est) {
// print the overestimates; they shouldn't be much noise in the
// common case, but might hint at a problem earlier than I'd
// otherwise notice
printf("nprintf overestimate:\n");
printf(" format: %s\n", format);
printf(" estimate: %d\n", est);
printf(" actual: %d\n", len);
}
delete[] buf;
}
