configure.ac: fix -DNO_BIG_INT setup to recognize $ENABLED_SP_MATH.

wolfcrypt/test/test.c: fix gating around modLen in rsa_test().

wolfssl/openssl/bn.h: remove superfluous WOLFSSL_SP_MATH gate around mp_int mpi
  in struct WOLFSSL_BIGNUM definition.

wolfssl/wolfcrypt/wolfmath.h: add check for "Conflicting MPI settings.", add
  initial check for WOLFSSL_SP_MATH_ALL || WOLFSSL_SP_MATH to include sp_int.h,
  and remove superfluous WOLFSSL_SP_MATH gate on "common math functions".

configure.ac

@@ -9809,8 +9809,8 @@ AS_IF([test "x$ENABLED_16BIT" = "xyes" && \
 ################################################################################
 # Update CFLAGS based on options                                               #
 ################################################################################
-AS_IF([test "x$ENABLED_SP_MATH_ALL" = "xno" && test "x$ENABLED_FASTMATH" = "xno" &&
-    test "x$ENABLED_HEAPMATH" = "xno"],
+AS_IF([test "$ENABLED_SP_MATH" = "no" && test "$ENABLED_SP_MATH_ALL" = "no" &&
+       test "$ENABLED_FASTMATH" = "no" && test "$ENABLED_HEAPMATH" = "no"],
       [AM_CFLAGS="$AM_CFLAGS -DNO_BIG_INT"])
 
 AS_IF([test "x$ENABLED_CERTS" = "xno"],

wolfcrypt/test/test.c

@@ -22109,13 +22109,15 @@ WOLFSSL_TEST_SUBROUTINE wc_test_ret_t rsa_test(void)
         ERROR_OUT(WC_TEST_RET_ENC_EC(ret), exit_rsa);
 #endif
 
-#if !defined(NO_SIG_WRAPPER) && !defined(NO_SHA256)
+#ifndef NO_SIG_WRAPPER
+#ifndef NO_SHA256
     ret = rsa_sig_test(key, sizeof *key, modLen, &rng);
     if (ret != 0)
         goto exit_rsa;
-#else
+#else /* NO_SHA256 */
     (void)modLen;
-#endif
+#endif /* NO_SHA256 */
+#endif /* !NO_SIG_WRAPPER */
 
 #ifdef WC_RSA_NONBLOCK
     ret = rsa_nb_test(key, in, inLen, out, outSz, plain, plainSz, &rng);

wolfssl/openssl/bn.h

@@ -40,7 +40,7 @@
 typedef struct WOLFSSL_BIGNUM {
     int neg;        /* openssh deference */
     void *internal; /* our big num */
-#if !defined(NO_BIG_INT) || defined(WOLFSSL_SP_MATH)
+#if !defined(NO_BIG_INT)
     mp_int mpi;
 #endif
 } WOLFSSL_BIGNUM;

wolfssl/wolfcrypt/wolfmath.h

@@ -42,6 +42,13 @@ This library provides big integer math functions.
 
 #if defined(NO_BIG_INT)
     /* MPI globally disabled -- no PK algorithms supported. */
+    #if defined(USE_FAST_MATH) || defined(USE_INTEGER_HEAP_MATH) || \
+        defined(WOLFSSL_SP_MATH_ALL) || defined(WOLFSSL_SP_MATH) || \
+        defined(HAVE_WOLF_BIGINT) || defined(WOLFSSL_EXPORT_INT)
+        #error Conflicting MPI settings.
+    #endif
+#elif defined(WOLFSSL_SP_MATH_ALL) || defined(WOLFSSL_SP_MATH)
+    #include <wolfssl/wolfcrypt/sp_int.h>
 #elif defined(USE_FAST_MATH)
     #include <wolfssl/wolfcrypt/tfm.h>
 #elif defined(USE_INTEGER_HEAP_MATH)
@@ -74,7 +81,7 @@ This library provides big integer math functions.
     extern const wc_ptr_t wc_off_on_addr[2];
 #endif
 
-#if !defined(NO_BIG_INT) || defined(WOLFSSL_SP_MATH)
+#if !defined(NO_BIG_INT)
 /* common math functions */
 MP_API int get_digit_count(const mp_int* a);
 MP_API mp_digit get_digit(const mp_int* a, int n);