diff --git a/bn_mp_div_d.c b/bn_mp_div_d.c
index 569f59407..a1f1212c4 100644
--- a/bn_mp_div_d.c
+++ b/bn_mp_div_d.c
@@ -43,12 +43,10 @@ mp_err mp_div_d(const mp_int *a, mp_digit b, mp_int *c, mp_digit *d)
       return MP_OKAY;
    }
 
-#ifdef BN_MP_DIV_3_C
    /* three? */
-   if (b == 3u) {
+   if (MP_HAS(MP_DIV_3) && b == 3u) {
       return mp_div_3(a, c, d);
    }
-#endif
 
    /* no easy answer [c'est la vie].  Just division */
    if ((err = mp_init_size(&q, a->used)) != MP_OKAY) {
diff --git a/bn_mp_exptmod.c b/bn_mp_exptmod.c
index 95a1dcb62..f6846ccea 100644
--- a/bn_mp_exptmod.c
+++ b/bn_mp_exptmod.c
@@ -19,10 +19,13 @@ mp_err mp_exptmod(const mp_int *G, const mp_int *X, const mp_int *P, mp_int *Y)
 
    /* if exponent X is negative we have to recurse */
    if (X->sign == MP_NEG) {
-#ifdef BN_MP_INVMOD_C
       mp_int tmpG, tmpX;
       mp_err err;
 
+      if (!MP_HAS(MP_INVMOD)) {
+         return MP_VAL;
+      }
+
       /* first compute 1/G mod P */
       if ((err = mp_init(&tmpG)) != MP_OKAY) {
          return err;
@@ -46,50 +49,32 @@ mp_err mp_exptmod(const mp_int *G, const mp_int *X, const mp_int *P, mp_int *Y)
       err = mp_exptmod(&tmpG, &tmpX, P, Y);
       mp_clear_multi(&tmpG, &tmpX, NULL);
       return err;
-#else
-      /* no invmod */
-      return MP_VAL;
-#endif
    }
 
    /* modified diminished radix reduction */
-#if defined(BN_MP_REDUCE_IS_2K_L_C) && defined(BN_MP_REDUCE_2K_L_C) && defined(BN_S_MP_EXPTMOD_C)
-   if (mp_reduce_is_2k_l(P) == MP_YES) {
+   if (MP_HAS(MP_REDUCE_IS_2K_L) && MP_HAS(MP_REDUCE_2K_L) && MP_HAS(S_MP_EXPTMOD) &&
+       mp_reduce_is_2k_l(P) == MP_YES) {
       return s_mp_exptmod(G, X, P, Y, 1);
    }
-#endif
 
-#ifdef BN_MP_DR_IS_MODULUS_C
-   /* is it a DR modulus? */
-   dr = (mp_dr_is_modulus(P) == MP_YES) ? 1 : 0;
-#else
-   /* default to no */
-   dr = 0;
-#endif
+   /* is it a DR modulus? default to no */
+   dr = MP_HAS(MP_DR_IS_MODULUS) && mp_dr_is_modulus(P) == MP_YES ? 1 : 0;
 
-#ifdef BN_MP_REDUCE_IS_2K_C
    /* if not, is it a unrestricted DR modulus? */
-   if (dr == 0) {
+   if (MP_HAS(MP_REDUCE_IS_2K) && dr == 0) {
       dr = (mp_reduce_is_2k(P) == MP_YES) ? 2 : 0;
    }
-#endif
 
    /* if the modulus is odd or dr != 0 use the montgomery method */
-#ifdef BN_S_MP_EXPTMOD_FAST_C
-   if (MP_IS_ODD(P) || (dr !=  0)) {
+   if (MP_HAS(S_MP_EXPTMOD_FAST) && (MP_IS_ODD(P) || (dr != 0))) {
       return s_mp_exptmod_fast(G, X, P, Y, dr);
-   } else {
-#endif
-#ifdef BN_S_MP_EXPTMOD_C
+   } else if (MP_HAS(S_MP_EXPTMOD)) {
       /* otherwise use the generic Barrett reduction technique */
       return s_mp_exptmod(G, X, P, Y, 0);
-#else
+   } else {
       /* no exptmod for evens */
       return MP_VAL;
-#endif
-#ifdef BN_S_MP_EXPTMOD_FAST_C
    }
-#endif
 }
 
 #endif
diff --git a/bn_mp_invmod.c b/bn_mp_invmod.c
index d5d6bbc03..7b35a2431 100644
--- a/bn_mp_invmod.c
+++ b/bn_mp_invmod.c
@@ -11,17 +11,13 @@ mp_err mp_invmod(const mp_int *a, const mp_int *b, mp_int *c)
       return MP_VAL;
    }
 
-#ifdef BN_S_MP_INVMOD_FAST_C
    /* if the modulus is odd we can use a faster routine instead */
-   if (MP_IS_ODD(b)) {
+   if (MP_HAS(S_MP_INVMOD_FAST) && MP_IS_ODD(b)) {
       return s_mp_invmod_fast(a, b, c);
    }
-#endif
 
-#ifdef BN_S_MP_INVMOD_SLOW_C
-   return s_mp_invmod_slow(a, b, c);
-#else
-   return MP_VAL;
-#endif
+   return MP_HAS(S_MP_INVMOD_SLOW)
+          ? s_mp_invmod_slow(a, b, c)
+          : MP_VAL;
 }
 #endif
diff --git a/bn_mp_mul.c b/bn_mp_mul.c
index f0ca04af4..a09a68bf9 100644
--- a/bn_mp_mul.c
+++ b/bn_mp_mul.c
@@ -6,80 +6,46 @@
 /* high level multiplication (handles sign) */
 mp_err mp_mul(const mp_int *a, const mp_int *b, mp_int *c)
 {
-   mp_err  err;
-   mp_sign neg;
-#ifdef BN_S_MP_BALANCE_MUL_C
-   int len_b, len_a;
-#endif
-   neg = (a->sign == b->sign) ? MP_ZPOS : MP_NEG;
-#ifdef BN_S_MP_BALANCE_MUL_C
-   len_a = a->used;
-   len_b = b->used;
-
-   if (len_a == len_b) {
-      goto GO_ON;
-   }
-   /*
-    * Check sizes. The smaller one needs to be larger than the Karatsuba cut-off.
-    * The bigger one needs to be at least about one KARATSUBA_MUL_CUTOFF bigger
-    * to make some sense, but it depends on architecture, OS, position of the
-    * stars... so YMMV.
-    * Using it to cut the input into slices small enough for fast_s_mp_mul_digs
-    * was actually slower on the author's machine, but YMMV.
-    */
-   if ((MP_MIN(len_a, len_b) < MP_KARATSUBA_MUL_CUTOFF)
-       || ((MP_MAX(len_a, len_b) / 2) < MP_KARATSUBA_MUL_CUTOFF)) {
-      goto GO_ON;
-   }
-   /*
-    * Not much effect was observed below a ratio of 1:2, but again: YMMV.
-    */
-   if ((MP_MAX(len_a, len_b) /  MP_MIN(len_a, len_b)) < 2) {
-      goto GO_ON;
-   }
-
-   err = s_mp_balance_mul(a,b,c);
-   goto END;
-
-GO_ON:
-#endif
+   mp_err err;
+   int min_len = MP_MIN(a->used, b->used),
+       max_len = MP_MAX(a->used, b->used),
+       digs = a->used + b->used + 1;
+   mp_sign neg = (a->sign == b->sign) ? MP_ZPOS : MP_NEG;
 
-   /* use Toom-Cook? */
-#ifdef BN_S_MP_TOOM_MUL_C
-   if (MP_MIN(a->used, b->used) >= MP_TOOM_MUL_CUTOFF) {
+   if (MP_HAS(S_MP_BALANCE_MUL) &&
+       /* Check sizes. The smaller one needs to be larger than the Karatsuba cut-off.
+        * The bigger one needs to be at least about one MP_KARATSUBA_MUL_CUTOFF bigger
+        * to make some sense, but it depends on architecture, OS, position of the
+        * stars... so YMMV.
+        * Using it to cut the input into slices small enough for fast_s_mp_mul_digs
+        * was actually slower on the author's machine, but YMMV.
+        */
+       (min_len >= MP_KARATSUBA_MUL_CUTOFF) &&
+       (max_len / 2 >= MP_KARATSUBA_MUL_CUTOFF) &&
+       /* Not much effect was observed below a ratio of 1:2, but again: YMMV. */
+       (max_len >= (2 * min_len))) {
+      err = s_mp_balance_mul(a,b,c);
+   } else if (MP_HAS(S_MP_TOOM_MUL) &&
+              (min_len >= MP_TOOM_MUL_CUTOFF)) {
       err = s_mp_toom_mul(a, b, c);
-   } else
-#endif
-#ifdef BN_S_MP_KARATSUBA_MUL_C
-      /* use Karatsuba? */
-      if (MP_MIN(a->used, b->used) >= MP_KARATSUBA_MUL_CUTOFF) {
-         err = s_mp_karatsuba_mul(a, b, c);
-      } else
-#endif
-      {
-         /* can we use the fast multiplier?
-          *
-          * The fast multiplier can be used if the output will
-          * have less than MP_WARRAY digits and the number of
-          * digits won't affect carry propagation
-          */
-         int     digs = a->used + b->used + 1;
-
-#ifdef BN_S_MP_MUL_DIGS_FAST_C
-         if ((digs < MP_WARRAY) &&
-             (MP_MIN(a->used, b->used) <= MP_MAXFAST)) {
-            err = s_mp_mul_digs_fast(a, b, c, digs);
-         } else
-#endif
-         {
-#ifdef BN_S_MP_MUL_DIGS_C
-            err = s_mp_mul_digs(a, b, c, a->used + b->used + 1);
-#else
-            err = MP_VAL;
-#endif
-         }
-      }
-END:
+   } else if (MP_HAS(S_MP_KARATSUBA_MUL) &&
+              (min_len >= MP_KARATSUBA_MUL_CUTOFF)) {
+      err = s_mp_karatsuba_mul(a, b, c);
+   } else if (MP_HAS(S_MP_MUL_DIGS_FAST) &&
+              /* can we use the fast multiplier?
+               *
+               * The fast multiplier can be used if the output will
+               * have less than MP_WARRAY digits and the number of
+               * digits won't affect carry propagation
+               */
+              (digs < MP_WARRAY) &&
+              (min_len <= MP_MAXFAST)) {
+      err = s_mp_mul_digs_fast(a, b, c, digs);
+   } else if (MP_HAS(S_MP_MUL_DIGS)) {
+      err = s_mp_mul_digs(a, b, c, digs);
+   } else {
+      err = MP_VAL;
+   }
    c->sign = (c->used > 0) ? neg : MP_ZPOS;
    return err;
 }
diff --git a/bn_mp_reduce.c b/bn_mp_reduce.c
index 574855091..3c669d491 100644
--- a/bn_mp_reduce.c
+++ b/bn_mp_reduce.c
@@ -26,21 +26,17 @@ mp_err mp_reduce(mp_int *x, const mp_int *m, const mp_int *mu)
       if ((err = mp_mul(&q, mu, &q)) != MP_OKAY) {
          goto CLEANUP;
       }
-   } else {
-#ifdef BN_S_MP_MUL_HIGH_DIGS_C
+   } else if (MP_HAS(S_MP_MUL_HIGH_DIGS)) {
       if ((err = s_mp_mul_high_digs(&q, mu, &q, um)) != MP_OKAY) {
          goto CLEANUP;
       }
-#elif defined(BN_S_MP_MUL_HIGH_DIGS_FAST_C)
+   } else if (MP_HAS(S_MP_MUL_HIGH_DIGS_FAST)) {
       if ((err = s_mp_mul_high_digs_fast(&q, mu, &q, um)) != MP_OKAY) {
          goto CLEANUP;
       }
-#else
-      {
-         err = MP_VAL;
-         goto CLEANUP;
-      }
-#endif
+   } else {
+      err = MP_VAL;
+      goto CLEANUP;
    }
 
    /* q3 = q2 / b**(k+1) */
diff --git a/bn_mp_sqr.c b/bn_mp_sqr.c
index d4c7d171b..d99caccd2 100644
--- a/bn_mp_sqr.c
+++ b/bn_mp_sqr.c
@@ -7,35 +7,21 @@
 mp_err mp_sqr(const mp_int *a, mp_int *b)
 {
    mp_err err;
-
-#ifdef BN_S_MP_TOOM_SQR_C
-   /* use Toom-Cook? */
-   if (a->used >= MP_TOOM_SQR_CUTOFF) {
+   if (MP_HAS(S_MP_TOOM_SQR) && /* use Toom-Cook? */
+       a->used >= MP_TOOM_SQR_CUTOFF) {
       err = s_mp_toom_sqr(a, b);
-      /* Karatsuba? */
-   } else
-#endif
-#ifdef BN_S_MP_KARATSUBA_SQR_C
-      if (a->used >= MP_KARATSUBA_SQR_CUTOFF) {
-         err = s_mp_karatsuba_sqr(a, b);
-      } else
-#endif
-      {
-#ifdef BN_S_MP_SQR_FAST_C
-         /* can we use the fast comba multiplier? */
-         if ((((a->used * 2) + 1) < MP_WARRAY) &&
-             (a->used < (MP_MAXFAST / 2))) {
-            err = s_mp_sqr_fast(a, b);
-         } else
-#endif
-         {
-#ifdef BN_S_MP_SQR_C
-            err = s_mp_sqr(a, b);
-#else
-            err = MP_VAL;
-#endif
-         }
-      }
+   } else if (MP_HAS(S_MP_KARATSUBA_SQR) &&  /* Karatsuba? */
+              a->used >= MP_KARATSUBA_SQR_CUTOFF) {
+      err = s_mp_karatsuba_sqr(a, b);
+   } else if (MP_HAS(S_MP_SQR_FAST) && /* can we use the fast comba multiplier? */
+              (((a->used * 2) + 1) < MP_WARRAY) &&
+              (a->used < (MP_MAXFAST / 2))) {
+      err = s_mp_sqr_fast(a, b);
+   } else if (MP_HAS(S_MP_SQR)) {
+      err = s_mp_sqr(a, b);
+   } else {
+      err = MP_VAL;
+   }
    b->sign = MP_ZPOS;
    return err;
 }
diff --git a/bn_prime_tab.c b/bn_prime_tab.c
index 008e9c38a..a6c07f8da 100644
--- a/bn_prime_tab.c
+++ b/bn_prime_tab.c
@@ -44,7 +44,7 @@ const mp_digit ltm_prime_tab[] = {
 #endif
 };
 
-#if defined(__GNUC__) && (__GNUC__ * 100 + __GNUC_MINOR__ >= 301)
+#if defined(__GNUC__) && __GNUC__ >= 4
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
 const mp_digit *s_mp_prime_tab = ltm_prime_tab;
diff --git a/bn_s_mp_exptmod.c b/bn_s_mp_exptmod.c
index 5d5510fc8..ee82d7a8c 100644
--- a/bn_s_mp_exptmod.c
+++ b/bn_s_mp_exptmod.c
@@ -5,8 +5,10 @@
 
 #ifdef MP_LOW_MEM
 #   define TAB_SIZE 32
+#   define MAX_WINSIZE 5
 #else
 #   define TAB_SIZE 256
+#   define MAX_WINSIZE 0
 #endif
 
 mp_err s_mp_exptmod(const mp_int *G, const mp_int *X, const mp_int *P, mp_int *Y, int redmode)
@@ -35,11 +37,7 @@ mp_err s_mp_exptmod(const mp_int *G, const mp_int *X, const mp_int *P, mp_int *Y
       winsize = 8;
    }
 
-#ifdef MP_LOW_MEM
-   if (winsize > 5) {
-      winsize = 5;
-   }
-#endif
+   winsize = MAX_WINSIZE ? MP_MIN(MAX_WINSIZE, winsize) : winsize;
 
    /* init M array */
    /* init first cell */
diff --git a/bn_s_mp_exptmod_fast.c b/bn_s_mp_exptmod_fast.c
index 43a2ba116..56e2b2be2 100644
--- a/bn_s_mp_exptmod_fast.c
+++ b/bn_s_mp_exptmod_fast.c
@@ -13,8 +13,10 @@
 
 #ifdef MP_LOW_MEM
 #   define TAB_SIZE 32
+#   define MAX_WINSIZE 5
 #else
 #   define TAB_SIZE 256
+#   define MAX_WINSIZE 0
 #endif
 
 mp_err s_mp_exptmod_fast(const mp_int *G, const mp_int *X, const mp_int *P, mp_int *Y, int redmode)
@@ -48,11 +50,7 @@ mp_err s_mp_exptmod_fast(const mp_int *G, const mp_int *X, const mp_int *P, mp_i
       winsize = 8;
    }
 
-#ifdef MP_LOW_MEM
-   if (winsize > 5) {
-      winsize = 5;
-   }
-#endif
+   winsize = MAX_WINSIZE ? MP_MIN(MAX_WINSIZE, winsize) : winsize;
 
    /* init M array */
    /* init first cell */
@@ -73,52 +71,46 @@ mp_err s_mp_exptmod_fast(const mp_int *G, const mp_int *X, const mp_int *P, mp_i
 
    /* determine and setup reduction code */
    if (redmode == 0) {
-#ifdef BN_MP_MONTGOMERY_SETUP_C
-      /* now setup montgomery  */
-      if ((err = mp_montgomery_setup(P, &mp)) != MP_OKAY) {
+      if (MP_HAS(MP_MONTGOMERY_SETUP)) {
+         /* now setup montgomery  */
+         if ((err = mp_montgomery_setup(P, &mp)) != MP_OKAY) {
+            goto LBL_M;
+         }
+      } else {
+         err = MP_VAL;
          goto LBL_M;
       }
-#else
-      err = MP_VAL;
-      goto LBL_M;
-#endif
 
       /* automatically pick the comba one if available (saves quite a few calls/ifs) */
-#ifdef BN_S_MP_MONTGOMERY_REDUCE_FAST_C
-      if ((((P->used * 2) + 1) < MP_WARRAY) &&
+      if (MP_HAS(S_MP_MONTGOMERY_REDUCE_FAST) &&
+          (((P->used * 2) + 1) < MP_WARRAY) &&
           (P->used < MP_MAXFAST)) {
          redux = s_mp_montgomery_reduce_fast;
-      } else
-#endif
-      {
-#ifdef BN_MP_MONTGOMERY_REDUCE_C
+      } else if (MP_HAS(MP_MONTGOMERY_REDUCE)) {
          /* use slower baseline Montgomery method */
          redux = mp_montgomery_reduce;
-#else
+      } else {
          err = MP_VAL;
          goto LBL_M;
-#endif
       }
    } else if (redmode == 1) {
-#if defined(BN_MP_DR_SETUP_C) && defined(BN_MP_DR_REDUCE_C)
-      /* setup DR reduction for moduli of the form B**k - b */
-      mp_dr_setup(P, &mp);
-      redux = mp_dr_reduce;
-#else
-      err = MP_VAL;
-      goto LBL_M;
-#endif
-   } else {
-#if defined(BN_MP_REDUCE_2K_SETUP_C) && defined(BN_MP_REDUCE_2K_C)
+      if (MP_HAS(MP_DR_SETUP) && MP_HAS(MP_DR_REDUCE)) {
+         /* setup DR reduction for moduli of the form B**k - b */
+         mp_dr_setup(P, &mp);
+         redux = mp_dr_reduce;
+      } else {
+         err = MP_VAL;
+         goto LBL_M;
+      }
+   } else if (MP_HAS(MP_REDUCE_2K_SETUP) && MP_HAS(MP_REDUCE_2K)) {
       /* setup DR reduction for moduli of the form 2**k - b */
       if ((err = mp_reduce_2k_setup(P, &mp)) != MP_OKAY) {
          goto LBL_M;
       }
       redux = mp_reduce_2k;
-#else
+   } else {
       err = MP_VAL;
       goto LBL_M;
-#endif
    }
 
    /* setup result */
@@ -134,20 +126,20 @@ mp_err s_mp_exptmod_fast(const mp_int *G, const mp_int *X, const mp_int *P, mp_i
     */
 
    if (redmode == 0) {
-#ifdef BN_MP_MONTGOMERY_CALC_NORMALIZATION_C
-      /* now we need R mod m */
-      if ((err = mp_montgomery_calc_normalization(&res, P)) != MP_OKAY) {
-         goto LBL_RES;
-      }
+      if (MP_HAS(MP_MONTGOMERY_CALC_NORMALIZATION)) {
+         /* now we need R mod m */
+         if ((err = mp_montgomery_calc_normalization(&res, P)) != MP_OKAY) {
+            goto LBL_RES;
+         }
 
-      /* now set M[1] to G * R mod m */
-      if ((err = mp_mulmod(G, &res, P, &M[1])) != MP_OKAY) {
+         /* now set M[1] to G * R mod m */
+         if ((err = mp_mulmod(G, &res, P, &M[1])) != MP_OKAY) {
+            goto LBL_RES;
+         }
+      } else {
+         err = MP_VAL;
          goto LBL_RES;
       }
-#else
-      err = MP_VAL;
-      goto LBL_RES;
-#endif
    } else {
       mp_set(&res, 1uL);
       if ((err = mp_mod(G, P, &M[1])) != MP_OKAY) {
diff --git a/bn_s_mp_mul_high_digs.c b/bn_s_mp_mul_high_digs.c
index e5e1ba472..2bb2a5098 100644
--- a/bn_s_mp_mul_high_digs.c
+++ b/bn_s_mp_mul_high_digs.c
@@ -16,12 +16,11 @@ mp_err s_mp_mul_high_digs(const mp_int *a, const mp_int *b, mp_int *c, int digs)
    mp_digit tmpx, *tmpt, *tmpy;
 
    /* can we use the fast multiplier? */
-#ifdef BN_S_MP_MUL_HIGH_DIGS_FAST_C
-   if (((a->used + b->used + 1) < MP_WARRAY)
+   if (MP_HAS(S_MP_MUL_HIGH_DIGS_FAST)
+       && ((a->used + b->used + 1) < MP_WARRAY)
        && (MP_MIN(a->used, b->used) < MP_MAXFAST)) {
       return s_mp_mul_high_digs_fast(a, b, c, digs);
    }
-#endif
 
    if ((err = mp_init_size(&t, a->used + b->used + 1)) != MP_OKAY) {
       return err;
diff --git a/bn_s_mp_rand_platform.c b/bn_s_mp_rand_platform.c
index 1349b7c61..950faed15 100644
--- a/bn_s_mp_rand_platform.c
+++ b/bn_s_mp_rand_platform.c
@@ -8,11 +8,16 @@
  * - Windows
  */
 #if defined(__FreeBSD__) || defined(__OpenBSD__) || defined(__NetBSD__) || defined(__DragonFly__)
-#  define MP_ARC4RANDOM
+#define BN_S_READ_ARC4RANDOM_C
+static mp_err s_read_arc4random(void *p, size_t n)
+{
+   arc4random_buf(p, n);
+   return MP_OKAY;
+}
 #endif
 
 #if defined(_WIN32) || defined(_WIN32_WCE)
-#define MP_WIN_CSP
+#define BN_S_READ_WINCSP_C
 
 #ifndef _WIN32_WINNT
 #define _WIN32_WINNT 0x0400
@@ -33,7 +38,7 @@
 # pragma warning(pop)
 #endif
 
-static mp_err s_read_win_csp(void *p, size_t n)
+static mp_err s_read_wincsp(void *p, size_t n)
 {
    static HCRYPTPROV hProv = 0;
    if (hProv == 0) {
@@ -50,9 +55,9 @@ static mp_err s_read_win_csp(void *p, size_t n)
 }
 #endif /* WIN32 */
 
-#if !defined(MP_WIN_CSP) && defined(__linux__) && defined(__GLIBC_PREREQ)
+#if !defined(BN_S_READ_WINCSP_C) && defined(__linux__) && defined(__GLIBC_PREREQ)
 #if __GLIBC_PREREQ(2, 25)
-#define MP_GETRANDOM
+#define BN_S_READ_GETRANDOM_C
 #include <sys/random.h>
 #include <errno.h>
 
@@ -78,7 +83,8 @@ static mp_err s_read_getrandom(void *p, size_t n)
 /* We assume all platforms besides windows provide "/dev/urandom".
  * In case yours doesn't, define MP_NO_DEV_URANDOM at compile-time.
  */
-#if !defined(MP_WIN_CSP) && !defined(MP_NO_DEV_URANDOM)
+#if !defined(BN_S_READ_WINCSP_C) && !defined(MP_NO_DEV_URANDOM)
+#define BN_S_READ_URANDOM_C
 #ifndef MP_DEV_URANDOM
 #define MP_DEV_URANDOM "/dev/urandom"
 #endif
@@ -86,7 +92,7 @@ static mp_err s_read_getrandom(void *p, size_t n)
 #include <errno.h>
 #include <unistd.h>
 
-static mp_err s_read_dev_urandom(void *p, size_t n)
+static mp_err s_read_urandom(void *p, size_t n)
 {
    int fd;
    char *q = (char *)p;
@@ -115,6 +121,7 @@ static mp_err s_read_dev_urandom(void *p, size_t n)
 #endif
 
 #if defined(MP_PRNG_ENABLE_LTM_RNG)
+#define B_S_READ_LTM_RNG
 unsigned long (*ltm_rng)(unsigned char *out, unsigned long outlen, void (*callback)(void));
 void (*ltm_rng_callback)(void);
 
@@ -128,37 +135,21 @@ static mp_err s_read_ltm_rng(void *p, size_t n)
 }
 #endif
 
+mp_err s_read_arc4random(void *p, size_t n);
+mp_err s_read_wincsp(void *p, size_t n);
+mp_err s_read_getrandom(void *p, size_t n);
+mp_err s_read_urandom(void *p, size_t n);
+mp_err s_read_ltm_rng(void *p, size_t n);
+
 mp_err s_mp_rand_platform(void *p, size_t n)
 {
-#if defined(MP_ARC4RANDOM)
-   arc4random_buf(p, n);
-   return MP_OKAY;
-#else
-
-   mp_err res = MP_ERR;
-
-#if defined(MP_WIN_CSP)
-   res = s_read_win_csp(p, n);
-   if (res == MP_OKAY) return res;
-#endif
-
-#if defined(MP_GETRANDOM)
-   res = s_read_getrandom(p, n);
-   if (res == MP_OKAY) return res;
-#endif
-
-#if defined(MP_DEV_URANDOM)
-   res = s_read_dev_urandom(p, n);
-   if (res == MP_OKAY) return res;
-#endif
-
-#if defined(MP_PRNG_ENABLE_LTM_RNG)
-   res = s_read_ltm_rng(p, n);
-   if (res == MP_OKAY) return res;
-#endif
-
-   return res;
-#endif
+   mp_err err = MP_ERR;
+   if ((err != MP_OKAY) && MP_HAS(S_READ_ARC4RANDOM)) err = s_read_arc4random(p, n);
+   if ((err != MP_OKAY) && MP_HAS(S_READ_WINCSP))     err = s_read_wincsp(p, n);
+   if ((err != MP_OKAY) && MP_HAS(S_READ_GETRANDOM))  err = s_read_getrandom(p, n);
+   if ((err != MP_OKAY) && MP_HAS(S_READ_URANDOM))    err = s_read_urandom(p, n);
+   if ((err != MP_OKAY) && MP_HAS(S_READ_LTM_RNG))    err = s_read_ltm_rng(p, n);
+   return err;
 }
 
 #endif
diff --git a/demo/test.c b/demo/test.c
index 11f243fa0..7ea3225f9 100644
--- a/demo/test.c
+++ b/demo/test.c
@@ -50,6 +50,49 @@ static uint64_t uabs64(int64_t x)
    return x > 0 ? (uint64_t)x : -(uint64_t)x;
 }
 
+/* This function prototype is needed
+ * to test dead code elimination
+ * which is used for feature detection.
+ *
+ * If the feature detection does not
+ * work as desired we will get a linker error.
+ */
+void does_not_exist(void);
+
+static int test_feature_detection(void)
+{
+#define BN_TEST_FEATURE1_C
+   if (!MP_HAS(TEST_FEATURE1)) {
+      does_not_exist();
+      return EXIT_FAILURE;
+   }
+
+#define BN_TEST_FEATURE2_C 1
+   if (MP_HAS(TEST_FEATURE2)) {
+      does_not_exist();
+      return EXIT_FAILURE;
+   }
+
+#define BN_TEST_FEATURE3_C 0
+   if (MP_HAS(TEST_FEATURE3)) {
+      does_not_exist();
+      return EXIT_FAILURE;
+   }
+
+#define BN_TEST_FEATURE4_C something
+   if (MP_HAS(TEST_FEATURE4)) {
+      does_not_exist();
+      return EXIT_FAILURE;
+   }
+
+   if (MP_HAS(TEST_FEATURE5)) {
+      does_not_exist();
+      return EXIT_FAILURE;
+   }
+
+   return EXIT_SUCCESS;
+}
+
 static int test_trivial_stuff(void)
 {
    mp_int a, b, c, d;
@@ -2046,6 +2089,7 @@ int unit_tests(int argc, char **argv)
       int (*fn)(void);
    } test[] = {
 #define T(n) { #n, test_##n }
+      T(feature_detection),
       T(trivial_stuff),
       T(mp_get_set_i32),
       T(mp_get_set_i64),
diff --git a/makefile.msvc b/makefile.msvc
index e6938344b..736cc1071 100644
--- a/makefile.msvc
+++ b/makefile.msvc
@@ -14,7 +14,7 @@ PREFIX    = c:\devel
 CFLAGS    = /Ox
 
 #Compilation flags
-LTM_CFLAGS  = /nologo /I./ /D_CRT_SECURE_NO_WARNINGS /D_CRT_NONSTDC_NO_DEPRECATE /D__STDC_WANT_SECURE_LIB__=1 /D_CRT_HAS_CXX17=0 /Wall /wd4146 /wd4127 /wd4710 /wd4711 /wd4820 /WX $(CFLAGS)
+LTM_CFLAGS  = /nologo /I./ /D_CRT_SECURE_NO_WARNINGS /D_CRT_NONSTDC_NO_DEPRECATE /D__STDC_WANT_SECURE_LIB__=1 /D_CRT_HAS_CXX17=0 /Wall /wd4146 /wd4127 /wd4710 /wd4711 /wd4820 /wd4003 /WX $(CFLAGS)
 LTM_LDFLAGS = advapi32.lib
 
 #Libraries to be created (this makefile builds only static libraries)
diff --git a/tommath.h b/tommath.h
index 1c00ade9a..8efb9f931 100644
--- a/tommath.h
+++ b/tommath.h
@@ -206,7 +206,7 @@ TOOM_SQR_CUTOFF;
 #  endif
 #endif
 
-#if defined(__GNUC__) && (__GNUC__ * 100 + __GNUC_MINOR__ >= 301)
+#if defined(__GNUC__) && (__GNUC__ * 100 + __GNUC_MINOR__ >= 405)
 #  define MP_DEPRECATED(x) __attribute__((deprecated("replaced by " #x)))
 #  define PRIVATE_MP_DEPRECATED_PRAGMA(s) _Pragma(#s)
 #  define MP_DEPRECATED_PRAGMA(s) PRIVATE_MP_DEPRECATED_PRAGMA(GCC warning s)
diff --git a/tommath_class.h b/tommath_class.h
index ae4405f99..cc94e1601 100644
--- a/tommath_class.h
+++ b/tommath_class.h
@@ -860,6 +860,7 @@
 #   define BN_MP_SUB_C
 #   define BN_S_MP_MUL_DIGS_C
 #   define BN_S_MP_MUL_HIGH_DIGS_C
+#   define BN_S_MP_MUL_HIGH_DIGS_FAST_C
 #   define BN_S_MP_SUB_C
 #endif
 
diff --git a/tommath_private.h b/tommath_private.h
index 3271d7e11..4c25fa082 100644
--- a/tommath_private.h
+++ b/tommath_private.h
@@ -17,7 +17,7 @@
  *
  * On Win32 a .def file must be used to specify the exported symbols.
  */
-#if defined (MP_PRIVATE_SYMBOLS) && __GNUC__ >= 4
+#if defined (MP_PRIVATE_SYMBOLS) && defined(__GNUC__) && __GNUC__ >= 4
 #   define MP_PRIVATE __attribute__ ((visibility ("hidden")))
 #else
 #   define MP_PRIVATE
@@ -140,6 +140,11 @@ extern void *MP_CALLOC(size_t nmemb, size_t size);
 extern void MP_FREE(void *mem, size_t size);
 #endif
 
+/* feature detection macro */
+#define MP_STRINGIZE(x)  MP__STRINGIZE(x)
+#define MP__STRINGIZE(x) ""#x""
+#define MP_HAS(x)        (sizeof(MP_STRINGIZE(BN_##x##_C)) == 1)
+
 /* TODO: Remove private_mp_word as soon as deprecated mp_word is removed from tommath. */
 #undef mp_word
 typedef private_mp_word mp_word;