Re: cpplib startup patch

[Dave Brolley <brolley@cygnus.com>]

I've looked into this a bit more and now I'm confused. It appears as though the C
and C++ front ends use already check_newline to recognize an initial #line
directive (actually any initial directive) and it is done in lang_init whether
cpplib is used or not. Is the problem that this is too late to check this? If so,
then it's not a cpplib specific problem. If not, then I need help understanding
the need for this patch.

Also, it turns out that the code in check_newline will recognize an initial #line
directive which begins with whitespace.

Thanks,
Dave

Jason Merrill wrote:

> This patch fixes a problem with cpplib reading preprocessed input; it makes
> up its mind too soon as to what the main filename is.  If the input has a
> #line directive at the beginning, we should respect it.
>
> Thu Jul  8 18:06:30 1999  Jason Merrill  <jason@yorick.cygnus.com>
>
>         * cpplib.c (cpp_unget): New fn.
>         (output_initial_line_command): New fn.
>         * cppinit.c (cpp_start_read): Use it.
>
> Index: cppinit.c
> ===================================================================
> RCS file: /egcs/carton/cvsfiles/egcs/gcc/cppinit.c,v
> retrieving revision 1.14
> diff -c -p -r1.14 cppinit.c
> *** cppinit.c   1999/05/10 15:24:34     1.14
> --- cppinit.c   1999/07/09 01:09:06
> *************** cpp_start_read (pfile, fname)
> *** 988,994 ****
>     ih_fake->limit = 0;
>     if (!finclude (pfile, f, ih_fake))
>       return 0;
> !   output_line_command (pfile, same_file);
>     pfile->only_seen_white = 2;
>
>     /* The -imacros files can be scanned now, but the -include files
> --- 988,994 ----
>     ih_fake->limit = 0;
>     if (!finclude (pfile, f, ih_fake))
>       return 0;
> !   output_initial_line_command (pfile, same_file);
>     pfile->only_seen_white = 2;
>
>     /* The -imacros files can be scanned now, but the -include files
> Index: cpplib.c
> ===================================================================
> RCS file: /egcs/carton/cvsfiles/egcs/gcc/cpplib.c,v
> retrieving revision 1.82
> diff -c -p -r1.82 cpplib.c
> *** cpplib.c    1999/06/07 10:35:26     1.82
> --- cpplib.c    1999/07/09 01:09:06
> *************** cpp_file_buffer (pfile)
> *** 827,832 ****
> --- 827,862 ----
>     return NULL;
>   }
>
> + /* At the beginning of compilation, we want to feed the frontend a # line
> +    directive so it knows what file we're compiling.  But if the input begins
> +    with a line directive, use that one instead.  */
> +
> + void
> + output_initial_line_command (pfile)
> +      cpp_reader *pfile;
> + {
> +   if (PEEKC() == '#')
> +     {
> +       int c;
> +       unsigned char *save_cur = CPP_BUFFER (pfile)->cur;
> +
> +       FORWARD (1);
> +       cpp_skip_hspace (pfile);
> +       c = PEEKC ();
> +       if (c >= '0' && c <= '9')
> +       {
> +         /* Handle # followed by a line number.  */
> +         if (CPP_PEDANTIC (pfile))
> +           cpp_pedwarn (pfile, "`#' followed by integer");
> +         do_line (pfile, NULL);
> +         return;
> +       }
> +       else
> +       CPP_BUFFER (pfile)->cur = save_cur;
> +     }
> +
> +   output_line_command (pfile, same_file);
> + }
>   /*
>    * write out a #line command, for instance, after an #include file.
>    * FILE_CHANGE says whether we are entering a file, leaving, or neither.