Re: fix the sscanf usage in etags

[Jan Djärv]

Kevin Ryde skrev:
> Masatake YAMATO <address@hidden> writes:
> > -         if (sscanf (lbp->buffer, "#line %d \"%n", &lno, &start) == 1)
> > +         if (sscanf (lbp->buffer, "#line %d \"%n", &lno, &start) == 2)
>
> I think that's wrong, I believe %n is not included in the return
> count.  Eg. in the current glibc, and in the posix spec (under "n"),
>
>     http://www.opengroup.org/onlinepubs/007904975/functions/scanf.html

The man page on GNU/Linux says:
              The C standard says: "Execution of  a  %n  directive
              does  not increment the assignment count returned at the comple-
              tion of execution" but the Corrigendum seems to contradict this.
              Probably it is wise not to make any assumptions on the effect of
              %n conversions on the return value.

So I guess we safely can test for >= 1 instead for those implementations that 
do return 2.  I've checked in that change.

> It does look like there's a problem with degenerate input having
> "start" used uninitialized though.  Eg. say
>
>         #line 00000000000000000000000000000

We can switch places between \" and %n and check for ":

          if (sscanf (lbp->buffer, "#line %d %n\"", &lno, &start) >= 1
              && lbp->buffer[start] == '"')
            {
              char *endp = lbp->buffer + ++start;

        Jan D.