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field: Static-assert that int args affecting magnitude are constant

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See #1001.
This commit is contained in:
Tim Ruffing
2023-06-13 13:34:49 +02:00
parent 67214f5f7d
commit be8ff3a02a
6 changed files with 43 additions and 18 deletions
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24
src/field.h
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@@ -88,8 +88,8 @@ static const secp256k1_fe secp256k1_const_beta = SECP256K1_FE_CONST(
# define secp256k1_fe_set_b32_mod secp256k1_fe_impl_set_b32_mod
# define secp256k1_fe_set_b32_limit secp256k1_fe_impl_set_b32_limit
# define secp256k1_fe_get_b32 secp256k1_fe_impl_get_b32
# define secp256k1_fe_negate secp256k1_fe_impl_negate
# define secp256k1_fe_mul_int secp256k1_fe_impl_mul_int
# define secp256k1_fe_negate_unchecked secp256k1_fe_impl_negate_unchecked
# define secp256k1_fe_mul_int_unchecked secp256k1_fe_impl_mul_int_unchecked
# define secp256k1_fe_add secp256k1_fe_impl_add
# define secp256k1_fe_mul secp256k1_fe_impl_mul
# define secp256k1_fe_sqr secp256k1_fe_impl_sqr
@@ -214,11 +214,17 @@ static void secp256k1_fe_get_b32(unsigned char *r, const secp256k1_fe *a);
/** Negate a field element.
*
* On input, r does not need to be initialized. a must be a valid field element with
* magnitude not exceeding m. m must be an integer in [0,31].
* magnitude not exceeding m. m must be an integer constant expression in [0,31].
* Performs {r = -a}.
* On output, r will not be normalized, and will have magnitude m+1.
*/
static void secp256k1_fe_negate(secp256k1_fe *r, const secp256k1_fe *a, int m);
#define secp256k1_fe_negate(r, a, m) ASSERT_INT_CONST_AND_DO(m, secp256k1_fe_negate_unchecked(r, a, m))
/** Like secp256k1_fe_negate_unchecked but m is not checked to be an integer constant expression.
*
* Should not be called directly outside of tests.
*/
static void secp256k1_fe_negate_unchecked(secp256k1_fe *r, const secp256k1_fe *a, int m);
/** Add a small integer to a field element.
*
@@ -229,12 +235,18 @@ static void secp256k1_fe_add_int(secp256k1_fe *r, int a);
/** Multiply a field element with a small integer.
*
* On input, r must be a valid field element. a must be an integer in [0,32].
* On input, r must be a valid field element. a must be an integer constant expression in [0,32].
* The magnitude of r times a must not exceed 32.
* Performs {r *= a}.
* On output, r's magnitude is multiplied by a, and r will not be normalized.
*/
static void secp256k1_fe_mul_int(secp256k1_fe *r, int a);
#define secp256k1_fe_mul_int(r, a) ASSERT_INT_CONST_AND_DO(a, secp256k1_fe_mul_int_unchecked(r, a))
/** Like secp256k1_fe_mul_int but a is not checked to be an integer constant expression.
*
* Should not be called directly outside of tests.
*/
static void secp256k1_fe_mul_int_unchecked(secp256k1_fe *r, int a);
/** Increment a field element by another.
*