Hello,
On Tue, 29 Nov 2022, James K. Lowden wrote:
> I don't understand how to access in a front end the arguments to the -I
> option on the command line.
>
> Cobol has a feature similar to the C preprecessor, known as the
> Compiler Directing Facility (CDF). The CDF has a COPY statement that
> resembles an #include directive in C, and shares the property that COPY
> names a file that is normally found in a "copybook" which, for our
> purposes, is a directory of such files. The name of that directory is
> defined outside the Cobol program.
>
> I would like to use the -I option to pass the names of copybook
> directories to the cobol front end. A bit of exploration yesterday left
> me with the sense that the -I argument, in C at least, is not passed to
> the compiler, but to the preprocessor. Access to -fmax-errors I think
> I've figured out, but -I is a mystery.
>
> I'm a little puzzled by the status quo as I understand it. Unless I
> missed it, it's not discussed in gccint. ISTM ideally there would be
> some kind of getopt(3) processing, and the whole set of command-line
> options captured in an array of structures accessible to any front
> end.
There is, it's just much more complicated than getopt :)
If you're looking at the C frontends for inspiration, then:
c-family/c.opt defines which options are recognized and several specifics
about them, e.g. for -I it has:
----
I
C ObjC C++ ObjC++ Joined Separate MissingArgError(missing path after %qs)
-I <dir> Add <dir> to the end of the main include path.
----
(look at some other examples therein, also in common.opt to get a feel).
Then code in c-family/c-opts.c:c_common_handle_option actually handles the
option:
case OPT_I:
if (strcmp (arg, "-"))
add_path (xstrdup (arg), INC_BRACKET, 0, true);
else
.,.
That function is made a langhook for option processing so that it's
actually called via c/c-objc-common.h:
#define LANG_HOOKS_HANDLE_OPTION c_common_handle_option
If you're also using the model of a compiler driver (i.e. the gcc program,
source in gcc.cc) that actually calls compiler (cc1), assembler and
linker, then you also need to arrange for that program to pass all -I
options to the compiler proper. That is done with the spec language, by
somewhere having '{I*}' in the specs for invoking the cobol compiler.
E.g. look in gcc.cc for '@c' (matching the file extension) how that entry
uses '%(cpp_unique_options)', and how cpp_unique_options is defined for
the specs language:
INIT_STATIC_SPEC ("cpp_unique_options", &cpp_unique_options),
and
static const char *cpp_unique_options =
"%{!Q:-quiet} %{nostdinc*} %{C} %{CC} %{v} %@{I*&F*} %{P} %I\
(the specs language used here is documented in a lengthy comment early in
gcc.cc, "The Specs Language")
The "%@{I*F*}" is the one that makes gcc pass -Iwhatever to cc1 (and
ensures relative order with -F options is retained and puts all these into
an @file if one is given on the cmdline, otherwise leaves it on cmdline).
If you use the compiler driver then using '-v' when invoking it will
quickly tell you if that options passing worked, as it will show the
concrete command it exec's for the compiler proper.
Hope this helps.
Ciao,
Michael.
