Re: Ada files now checked in

[Zack Weinberg <zack at codesourcery dot com>]

On Thu, Oct 04, 2001 at 02:24:36PM -0400, Richard Kenner wrote:
>     With the appended patch, using the Debian packages of gnat 3.13p, I
>     can get as far as where it trips over the absence of .spt files and/or
>     xsinfo/xnmake/xtreeprs.  I believe this is the problem Laurent is
>     addressing?
> 
> Sort of.  The real problem is that "touch" commands are missing since the
> files are there.

I tend to agree with the people who are saying that these files ought
to be generated in the build directory during the bootstrap.

> I don't even begin to understand your patch, though.

Sorry, I should have explained it the first time.

Ignore the change to aclocal.m4 for the moment.  The remainder of the
patch is straightforward.  It does two things: 

1. Any compilation of an Ada source file (.ads or .adb) might have to
use a different program from the one used to compile C source.  This
program is given the makefile variable ADAC (for "ada compiler"),
which is set by the configure script.  All the rules that formerly
used $(CC) to compile Ada are changed to use $(ADAC) instead.

2. Since gnat 3.13 objects to -W options, compilation command lines
for Ada must not include them.  However, compilation of C in the ada
subdirectory should include -W options.  

They are appearing because the top level Makefile sets submake CFLAGS
to "$(CFLAGS) $(WARN_CFLAGS)" (look for the definition of
ORDINARY_FLAGS_TO_PASS).  This is fine for C, but for Ada we want just
the toplevel CFLAGS (which is where -g and -O switches appear).  In
ada/Make-lang.in, therefore, I cause ADA_CFLAGS to be set to $(CFLAGS)
in the sub-make invocation.  ada/Makefile.in is then changed to use
just ADA_CFLAGS in ALL_ADAFLAGS and MOST_ADAFLAGS.  All $(ADAC)
invocations use one of those two, so we are now safe.

As a side effect ADA_CFLAGS is no longer available for overriding by
target Makefile fragments.  The only ones that do are pa/t-* which all
set -mdisable-indexing.  Does anyone know what that switch means?

Now, the aclocal.m4 gook has the sole purpose of setting ADAC and
GNATBIND correctly.  GNATBIND is easy - just call AC_CHECK_TOOL.
(AC_CHECK_PROG was being used, but that will pick the wrong program in
a cross-compilation.)  ADAC is trickier.  The core is this loop:

for cand in ${ac_tool_prefix}$user_adac $user_adac      \
            ${ac_tool_prefix}gcc        gcc             \
            ${ac_tool_prefix}gnatgcc    gnatgcc         \
            ${ac_tool_prefix}cc         cc              \
            ${ac_tool_prefix}gnatcc     gnatcc          ; do
  # There is a bug in all released versions of GCC which causes the
  # driver to exit successfully when the appropriate language module
  # has not been installed.  This is fixed in 2.95.4, 3.0.2, and 3.1.
  # Therefore we must check for the error message as well as an
  # unsuccessful exit.
  errors=`$cand -c conftest.adb 2>&1 || echo failure`
  if test x"$errors" = x; then
    gcc_cv_prog_adac=$cand
    break
  fi
  gcc_cv_prog_adac=no
done

(oops, the last two lines should be switched.)  It iterates over a
series of four (normally) possible candidates for the Ada compiler
driver.  Each is asked to compile a trivial Ada procedure.  The first
one that exits successfully and produces no output is taken to work.
We then set up ADAC appropriately.

The stuff with ${ac_tool_prefix} is to simulate the effect of
AC_CHECK_TOOL: if we were cross compiling we would probably want
something named powerpc-eabi-gnatgcc, for instance.

zw