Commit 5d735465 authored by Geoff Thorpe's avatar Geoff Thorpe
Browse files

The efforts to eliminate the dual-representation of zero and to ensure 

bignums are passed in and out of functions and APIs in a consistent form
has highlighted that zero-valued bignums don't need any allocated word
data. The use of BN_set_word() to initialise a bignum to zero causes
needless allocation and gives it a return value that must be checked. This
change converts BN_zero() to a self-contained macro that has no
return/expression value and does not cause any expansion of bignum data.

Note, it would be tempting to rewrite the deprecated version as a
success-valued comma expression, such as;
   #define BN_zero(a) ((a)->top = (a)->neg = 0, 1)
However, this evaluates 'a' twice and would confuse initialisation loops
(eg. while(..) { BN_zero(bn++) } ). As such, the deprecated version
continues to use BN_set_word().
parent 9e051bac

crypto/bn/bn.h

+10 −0
Original line number Diff line number Diff line
@@ -372,7 +372,17 @@ int BN_GENCB_call(BN_GENCB *cb, int a, int b); 
#define BN_is_odd(a)	    (((a)->top > 0) && ((a)->d[0] & 1))



#define BN_one(a)	(BN_set_word((a),1))

#define BN_zero_ex(a) \

	do { \

		BIGNUM *_tmp_bn = (a); \

		_tmp_bn->top = 0; \

		_tmp_bn->neg = 0; \

	} while(0)

#ifdef OPENSSL_NO_DEPRECATED

#define BN_zero(a)	BN_zero_ex(a)

#else

#define BN_zero(a)	(BN_set_word((a),0))

#endif

/* BN_set_sign(BIGNUM *, int) sets the sign of a BIGNUM

 * (0 for a non-negative value, 1 for negative) */

#define BN_set_sign(a,b) ((a)->neg = (b))