cxx-lt-demo.sh

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Hash : 34001a98
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Date : 2013-01-09T23:16:53

compile: use 'compile' script when "-c -o" is used with losing compilers

Do so seen when only source files in the "current" directory are present.

This commit is part of a series of related changes addressing automake
bug#13378 (see also the plan 'PLANS/subdir-objects.txt').

Before this change, Automake-generated C compilation rules mistakenly
passed the "-c -o" options combination unconditionally (even to losing
compiler) when the 'subdir-objects' was used but sources were only
present in the top-level directory.  Issue spotted by Nick Bowler:

  <http://debbugs.gnu.org/cgi/bugreport.cgi?bug=13378#35>
  <http://debbugs.gnu.org/cgi/bugreport.cgi?bug=13378#44>

We fix this by having Automake redefine AC_PROG_CC to take over the role
of AM_PROG_CC_C_O and to require the 'compile' script unconditionally
(albeit that will continue to be invoked only when inferior compilers
are detected).

Among other things, this means AM_PROG_CC_C_O explicitly is no longer
required; that macro is still supported for backward-compatibility, but
calling it is basically a no-op now.

This change has some pros and some cons (obviously, we believe the former
outweighs the latter).  Here are the most relevant ones:

+ Pros 1:
  Some logic in the Automake script has been simplified.
+ Pros 2:
  That simplification has automatically fixed an actual bug (see
  Nick's mails referenced above; admittedly, that was present only in
  corner-case situations, but still); the test 't/ccnoco4.sh', which
  demonstrated the bug and has been failing so far, now passes.
+ Pros 3:
  Things works more "automagically" now (no need to manually add the
  AM_PROG_CC_C_O macro to configure.ac anymore).

* Cons 1:
  The 'compile' script will be required in all projects using C
  compilation; this will only be a problem for packages not using
  '--add-missing'.  However, such packages are definitely more rare
  than the ones using '--add-missing', and adjusting them will be
  trivial -- just copy the compile script over from the new Automake
  installation.
* Cons 2:
  The copy & paste of autoconf internals hack this change has introduced
  in our "rewrite" of AC_PROG_CC is really an egregious abomination.  It
  can only be justified with the fact that we expect future versions of
  autoconf to implement the semantics we need directly in AC_PROG_CC, so
  that we'll be able to leverage that (since Automake 1.14 will require
  the latest Autoconf version released).

Now, the detailed list of file-by-file changes ...

* automake.in ($seen_cc_c_o): Remove this global variable.
(scan_autoconf_traces): Don't set it, and do not trace the
'AM_PROG_CC_C_O' m4 macro.
(lang_c_rewrite): Remove, no longer needed.
* doc/automake.texi: Adjust expected "autoreconf --install" output
in the amhello example.  Remove statements about the need for the
AM_PROG_CC_C_O macro.  Report it is obsolete now.
* m4/init.m4: Re-write AC_PROG_CC to append checks about whether the
C compiler supports "-c -o" together.  These checks have basically
been ripped out (with adaptations) from the 'AC_PROG_CC_C_O' macro
of Autoconf and ...
* m4/minuso.m4 (AM_PROG_CC_C_O): ... this macro of ours, which has
thus basically become a no-op.
* t/ax/am-test-lib.sh (am_setup_testdir): Also copy the 'compile'
script in the test directory; if we don't do so, every test using
AC_PROG_CC should call automake with the "--add-missing" option, or
copy the 'compile' script itself.
* t/cond11.sh: No need to create a dummy 'compile' script: that is
already brought in by 'am_setup_testdir()', that is automatically
invoked when 'test-lib.sh' is sourced.
* t/add-missing.tap: Adjust: we expect the 'compile' script to be
required by a mere AC_PROG_CC call now.
* t/dist-auxdir-many-subdirs.sh: Likewise.
* t/specflg6.sh: Likewise.
* t/subobj4.sh: Likewise.
* t/cxx-lt-demo.sh: Likewise, and update comments to match.
* t/distcom2.sh: Enhance a little.
* t/dollarvar2.sh: Adjust.
* t/extra-portability.sh: Likewise.
* t/libobj19.sh: Likewise.
* t/per-target-flags.sh: Likewise.
* t/repeated-options.sh: Likewise.
* t/subobj.sh: Likewise, and enhance a little.
* t/ccnoco2.sh: Remove as obsolete.
* t/list-of-tests.mk (handwritten_TESTS): Adjust.
(XFAIL_TESTS): Remove 't/ccnoco4.sh'.
* NEWS: Update.

Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>

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t/cxx-lt-demo.sh

#! /bin/sh
# Copyright (C) 2012-2013 Free Software Foundation, Inc.
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2, or (at your option)
# any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

# Demo on Libtool/C++ support.

required='libtoolize c++'
am_create_testdir=empty
. test-init.sh

cat > configure.ac << 'END'
AC_INIT([GNU C++/Libtool Demo], [0.73], [bug-automake@gnu.org])
AC_CONFIG_SRCDIR([lib/libfoo.c++])
AC_CONFIG_AUX_DIR([ax])
AM_INIT_AUTOMAKE
AC_CANONICAL_HOST
AC_CANONICAL_BUILD
AC_PROG_CXX
AM_PROG_AR
LT_INIT
AC_CONFIG_FILES([
  Makefile
  src/Makefile
  lib/Makefile
  try.sh:try.in
])
AC_OUTPUT
END

mkdir ax lib src

cat > Makefile.am <<'END'
SUBDIRS = lib src

AUTOMAKE_OPTIONS = parallel-tests
TEST_EXTENSIONS = .sh
SH_LOG_COMPILER = $(SHELL) -ex
TESTS = try.sh

.PHONY: test-objs
check-local: test-objs
test-objs:
	test -f src/main.$(OBJEXT)
	test -f lib/libfoo.lo
END

cat > src/Makefile.am << 'END'
bin_PROGRAMS = zardoz
zardoz_SOURCES = main.cc
zardoz_LDADD = $(top_builddir)/lib/libfoo.la
AM_CPPFLAGS = -I$(top_builddir)/lib
END

cat > lib/Makefile.am << 'END'
lib_LTLIBRARIES = libfoo.la
nodist_libfoo_la_SOURCES = libfoo.h++
libfoo_la_SOURCES = libfoo.c++
libfoo.h++: $(srcdir)/libfoo.c++
	echo '#include <string>' >$@-t
	grep "target *(" "$(srcdir)/libfoo.c++" >>$@-t
	echo ';' >>$@-t
	chmod a-w $@-t && mv -f $@-t $@
BUILT_SOURCES = libfoo.h++
DISTCLEANFILES = $(BUILT_SOURCES)
END

cat > try.in << 'END'
#!/bin/sh
set -e
if test x"$host_alias" = x || test x"$build_alias" = x"$host_alias"; then
  ./src/zardoz
  test "`./src/zardoz`" = 'Howdy, Testsuite!'
else
  echo "Skip: cannot run a cross-compiled program"
  exit 77
fi
END

libtoolize --copy
$ACLOCAL
$AUTOCONF
$AUTOMAKE --add-missing --copy

ls -l . ax # For debugging.
# Ideally, the 'compile' script should not be required by C++ compilers.
# But alas, LT_INIT seems to invoke AC_PROG_CC anyway, and that brings in
# that script.
for f in ltmain.sh depcomp compile config.guess config.sub; do
  test -f ax/$f && test ! -h ax/$f || exit 1
done

cat > src/main.cc << 'END'
#include "libfoo.h++"
#include <iostream>
using namespace std;
int main (void)
{
  cout << "Howdy, " << target () << "!" << endl;
  return 0;
}
END

cat > lib/libfoo.c++ << 'END'
#include "libfoo.h++"
#include <string>
std::string target (void)
{
  std::string s1 = "Test";
  std::string s2 = "suite";
  return (s1 + s2);
}
END

./configure
CC=false $MAKE -e
ls -l . src lib # For debugging.
$MAKE test-objs
VERBOSE=yes $MAKE check-TESTS
grep 'Howdy.*Testsuite' try.log || grep 'Skip:.*cross-compiled' try.log

$MAKE distcheck

:

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