[Bug driver/111014] New: do_spec_1 terminates arguments too eagerly when processing spec function

["pexu@gcc-bugzilla.mail.kapsi.fi" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111014

            Bug ID: 111014
           Summary: do_spec_1 terminates arguments too eagerly when
                    processing spec function
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: driver
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pexu@gcc-bugzilla.mail.kapsi.fi
  Target Milestone: ---

Hi.

do_spec_1 always terminates the current argument (via end_going_arg) if
processing a spec function.

6881      if (processing_spec_function)
6882        end_going_arg ();

If a spec function returns a non-null string it is expanded using do_spec_1.  

7043      funcval = eval_spec_function (func, args, soft_matched_part);
7044      if (funcval != NULL && do_spec_1 (funcval, 0, NULL) < 0)

However, because processing_spec_function is in this case non-zero, there is
always a termination after each nested %-sequence has been processed.

Thus, e.g. "%:version-compare(>= 1.0 -version-compare= %%(do_spec))" and
"%(do_spec)" behave differently if the expanded %-sequences have any trailing
parts:

# cat version_compare_string.spec
*self_spec:
+ --version-compare=1.0 %<-version-compare=*

*do_spec:
-W%{!Werror:no-}error

*cc1_options:
+ %:version-compare(>= 1.0 -version-compare= %%(do_spec)) %(do_spec)

# gcc -c -xc -specs=version_compare_string.spec - < /dev/null
cc1: error: unrecognized command-line option ‘-Wno-’
[...]

In the first case, do_spec is not expanded as "-Wno-error" but as "-Wno-" and
"error".  I wonder if this termination is really necessary; the same effect can
be archieved by simply having a whitespace character to follow the spec
function, if concatenation is not to be desired.