Add testing for slimcc compiler

New compiler support testing for Slimcc, which is based on existing link
order testing.

See https://debbugs.gnu.org/cgi/bugreport.cgi?bug=79216

Makefile.am

@@ -679,6 +679,7 @@ TESTSUITE_AT	= tests/testsuite.at \
 		  tests/inherited_flags.at \
 		  tests/link-order.at \
 		  tests/link-order2.at \
+		  tests/slimcc.at \
 		  tests/fail.at \
 		  tests/shlibpath.at \
 		  tests/runpath-in-lalib.at \

tests/slimcc.at

@@ -0,0 +1,101 @@
+# slimcc.at - Link order check for the slimcc compiler   -*- Autotest -*-
+#
+#   Copyright (C) 2025 Free Software Foundation, Inc.
+#
+#   This file is part of GNU Libtool.
+#
+# GNU Libtool 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 of
+# the License, or (at your option) any later version.
+#
+# GNU Libtool 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 GNU Libtool.  If not, see <https://www.gnu.org/licenses/>.
+####
+
+
+AT_SETUP([Link order slimcc test])
+AT_KEYWORDS([slimcc])
+eval `$LIBTOOL --config | $EGREP '^(hardcode_direct|hardcode_direct_absolute|shrext_cmds)='`
+LDFLAGS="$LDFLAGS -no-undefined"
+
+module=no
+eval shared_ext=\"$shrext_cmds\"
+
+AT_CHECK([$LIBTOOL --config | $EGREP '^CC=slimcc' || exit 77], 1)
+
+prefix_old=`pwd`/old
+prefix_new=`pwd`/new
+mkdir src $prefix_old $prefix_new $prefix_old/lib $prefix_new/lib
+
+AT_DATA(src/c.c,
+[[int c = 1;
+]])
+
+$LIBTOOL --mode=compile $CC $CPPFLAGS $CFLAGS -c src/c.c -o src/c.lo
+$LIBTOOL --mode=link $CC $CFLAGS $LDFLAGS -o src/libcee.la src/c.lo -rpath $prefix_old/lib
+$LIBTOOL --mode=install cp src/libcee.la $prefix_old/lib/libcee.la
+
+for i in old new; do
+  rm -rf src
+  mkdir src
+
+  cat >src/a_$i.c <<EOF
+extern int c;
+extern int b_$i();
+int a_$i() { return c + b_$i(); }
+EOF
+
+  cat >src/b_$i.c <<EOF
+extern int c;
+int b_$i() { return 1 + c; }
+EOF
+
+  prefix=`eval echo \\$prefix_$i`
+  $LIBTOOL --mode=compile $CC $CPPFLAGS $CFLAGS -c src/a_$i.c -o src/a.lo
+  $LIBTOOL --mode=compile $CC $CPPFLAGS $CFLAGS -c src/b_$i.c -o src/b.lo
+  $LIBTOOL --mode=link $CC $CFLAGS $LDFLAGS -o src/libb.la src/b.lo \
+      -L$prefix_old/lib -lcee -rpath $prefix/lib
+  $LIBTOOL --mode=link $CC $CFLAGS $LDFLAGS -o src/liba.la src/a.lo \
+      src/libb.la -L$prefix_old/lib -lcee -rpath $prefix/lib
+  $LIBTOOL --mode=install cp src/libb.la $prefix/lib/libb.la
+  AT_CHECK([$LIBTOOL --mode=install cp src/liba.la $prefix/lib/liba.la],
+	[0], [stdout], [stderr])
+done
+
+$LIBTOOL --mode=clean rm -f src/libb.la
+$LIBTOOL --mode=clean rm -f src/liba.la
+
+# Do not error if we do not relink (e.g. static-only systems)
+case $hardcode_direct$hardcode_direct_absolute in
+yesno)
+  AT_CHECK([if $EGREP relinking stderr; then
+       $EGREP " .*/new/lib/libb$shared_ext .*/old/lib/libcee$shared_ext" stdout
+     else :; fi], [0], [ignore], [], [echo "wrong link order"])
+  ;;
+*)
+  AT_CHECK([if $EGREP relinking stderr; then
+       $EGREP " -L.*/new/lib -lb -L.*/old/lib -lcee" stdout
+     else :; fi], [0], [ignore], [], [echo "wrong link order"])
+  ;;
+esac
+
+for i in old new; do
+  cat >src/main_$i.c <<EOF
+extern int a_$i();
+int main(void) { return a_$i() != 3; }
+EOF
+
+  prefix=`eval echo \\$prefix_$i`
+  $LIBTOOL --mode=compile $CC $CPPFLAGS $CFLAGS -c src/main_$i.c -o src/main_$i.lo
+  AT_CHECK($LIBTOOL --mode=link $CC $CFLAGS $LDFLAGS -o src/main_$i$EXEEXT src/main_$i.lo -L$prefix/lib -la,
+	   [0], [ignore], [ignore])
+  LT_AT_EXEC_CHECK([src/main_$i])
+done
+
+AT_CLEANUP