Merge pull request #289 from libtom/static-assert

add MP_STATIC_ASSERT

Author: sjaeckel

bn_mp_shrink.c

@@ -6,10 +6,8 @@
 /* shrink a bignum */
 mp_err mp_shrink(mp_int *a)
 {
-   static int static_check[-(MP_PREC < MP_MIN_PREC)];
    mp_digit *tmp;
    int alloc = MP_MAX(MP_MIN_PREC, a->used);
-   (void)static_check;
    if (a->alloc != alloc) {
       if ((tmp = (mp_digit *) MP_REALLOC(a->dp,
                                          (size_t)a->alloc * sizeof(mp_digit),

tommath_private.h

@@ -151,6 +151,9 @@ typedef private_mp_word mp_word;
 #define MP_MIN(x, y) (((x) < (y)) ? (x) : (y))
 #define MP_MAX(x, y) (((x) > (y)) ? (x) : (y))
 
+/* Static assertion */
+#define MP_STATIC_ASSERT(msg, cond) typedef char mp_static_assert_##msg[-(!(cond))];
+
 /* ---> Basic Manipulations <--- */
 #define MP_IS_ZERO(a) ((a)->used == 0)
 #define MP_IS_EVEN(a) (((a)->used == 0) || (((a)->dp[0] & 1u) == 0u))
@@ -162,6 +165,8 @@ typedef private_mp_word mp_word;
 /* Minimum number of available digits in mp_int, MP_PREC >= MP_MIN_PREC */
 #define MP_MIN_PREC ((((CHAR_BIT * (int)sizeof(long long)) + MP_DIGIT_BIT) - 1) / MP_DIGIT_BIT)
 
+MP_STATIC_ASSERT(prec_geq_min_prec, MP_PREC >= MP_MIN_PREC)
+
 /* random number source */
 extern MP_PRIVATE mp_err(*s_mp_rand_source)(void *out, size_t size);