Refuse to compile when curve not selected.

Author: aleksejspopovs

libff/common/default_types/ec_pp.hpp

@@ -16,38 +16,47 @@
 /************************ Pick the elliptic curve ****************************/
 
 #ifdef CURVE_ALT_BN128
+#define LIBFF_DEFAULT_EC_PP_DEFINED
 #include <libff/algebra/curves/alt_bn128/alt_bn128_pp.hpp>
 namespace libff {
 typedef alt_bn128_pp default_ec_pp;
 } // libff
 #endif
 
 #ifdef CURVE_BN128
+#define LIBFF_DEFAULT_EC_PP_DEFINED
 #include <libff/algebra/curves/bn128/bn128_pp.hpp>
 namespace libff {
 typedef bn128_pp default_ec_pp;
 } // libff
 #endif
 
 #ifdef CURVE_EDWARDS
+#define LIBFF_DEFAULT_EC_PP_DEFINED
 #include <libff/algebra/curves/edwards/edwards_pp.hpp>
 namespace libff {
 typedef edwards_pp default_ec_pp;
 } // libff
 #endif
 
 #ifdef CURVE_MNT4
+#define LIBFF_DEFAULT_EC_PP_DEFINED
 #include <libff/algebra/curves/mnt/mnt4/mnt4_pp.hpp>
 namespace libff {
 typedef mnt4_pp default_ec_pp;
 } // libff
 #endif
 
 #ifdef CURVE_MNT6
+#define LIBFF_DEFAULT_EC_PP_DEFINED
 #include <libff/algebra/curves/mnt/mnt6/mnt6_pp.hpp>
 namespace libff {
 typedef mnt6_pp default_ec_pp;
 } // libff
 #endif
 
+#ifndef LIBFF_DEFAULT_EC_PP_DEFINED
+#error You must define one of the CURVE_* symbols to pick a curve for pairings.
+#endif
+
 #endif // EC_PP_HPP_