-# We want no optimization with C++, too.
-CXXFLAGS='@O0CXXFLAGS@ @WARNING_CXXFLAGS@ @WERROR_CFLAGS@'
+# Whether the compiler supports POSIXLY_CORRECT defined.
+: ${C_COMPILER_POSIXLY_CORRECT='@C_COMPILER_POSIXLY_CORRECT@'}
+: ${CXX_COMPILER_POSIXLY_CORRECT='@CXX_COMPILER_POSIXLY_CORRECT@'}
+
+if $POSIXLY_CORRECT_IS_EXPORTED; then
+ $C_COMPILER_POSIXLY_CORRECT ||
+ BISON_C_WORKS="as_fn_error 77 POSIXLY_CORRECT"
+ $CXX_COMPILER_POSIXLY_CORRECT ||
+ BISON_CXX_WORKS="as_fn_error 77 POSIXLY_CORRECT"
+fi
+
+# Handle --compile-c-with-cxx here, once CXX and CXXFLAGS are known.
+if "$at_arg_compile_c_with_cxx"; then
+ CC_IS_CXX=1
+ CC=$CXX
+ NO_WERROR_CFLAGS=$NO_WERROR_CXXFLAGS
+ CFLAGS=$CXXFLAGS
+ BISON_C_WORKS=$BISON_CXX_WORKS
+else
+ CC_IS_CXX=0
+fi
+
+
+## ------- ##
+## Other. ##
+## ------- ##
+
+# Empty if no javac was found
+CONF_JAVAC='@CONF_JAVAC@'
+
+# Empty if no Java VM was found
+CONF_JAVA='@CONF_JAVA@'
+
+# We need egrep and perl.
+: ${EGREP='@EGREP@'}
+: ${PERL='@PERL@'}
+
+# Use simple quotes (lib/quote.c).
+LC_CTYPE=C
+export LC_CTYPE