+# Sometimes a test group needs to ignore gcc warnings, so it locally
+# sets CFLAGS to this.
+ NO_WERROR_CFLAGS='@CFLAGS@ @WARN_CFLAGS@ @WARN_CFLAGS_TEST@'
+NO_WERROR_CXXFLAGS='@CXXFLAGS@ @WARN_CXXFLAGS@ @WARN_CXXFLAGS_TEST@'
+
+# But most of the time, we want -Werror.
+ CFLAGS="$NO_WERROR_CFLAGS @WERROR_CFLAGS@"
+CXXFLAGS="$NO_WERROR_CXXFLAGS @WERROR_CXXFLAGS@"
+
+# If 'exit 77'; skip all C++ tests; otherwise ':'.
+BISON_CXX_WORKS='@BISON_CXX_WORKS@'
+
+# 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