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Merge #533: Make sure we're not using an uninitialized variable in secp256k1_wnaf_const(...)

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248f046 Make sure we're not using an uninitialized variable in secp256k1_wnaf_const(...) (practicalswift)

Pull request description:

  Make sure we're not using an uninitialized variable in `secp256k1_wnaf_const(...)`:

  ```
  In file included from src/secp256k1.c:15:0,
                   from src/tests.c:17:
  src/ecmult_const_impl.h: In function ‘secp256k1_wnaf_const’:
  src/ecmult_const_impl.h:117:20: warning: ‘u’ may be used uninitialized in this function [-Wmaybe-uninitialized]
       wnaf[word] = u * global_sign;
                      ^
  ```

  **Note to reviewers:** Perhaps an `assert(…);` is a bit drastic. What would be a more graceful way to handle this? :-)

Tree-SHA512: 536cd7cc5b87a84fbaac578cecbba81b8d82e4672a30a2db9a674b82856132e79b0158a6a88609bc24942ebdbf1fcd2c4399a4c31ab0654b88ace9c0e6f1eaf3
This commit is contained in:
Gregory Maxwell 2019-05-22 04:43:53 +00:00
commit 5df77a0eda
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1 changed files with 6 additions and 2 deletions
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8
src/ecmult_const_impl.h
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@ -61,6 +61,10 @@ static int secp256k1_wnaf_const(int *wnaf, const secp256k1_scalar *scalar, int w
int bit;
secp256k1_scalar s;
int not_neg_one;
VERIFY_CHECK(w > 0);
VERIFY_CHECK(size > 0);
/* Note that we cannot handle even numbers by negating them to be odd, as is
* done in other implementations, since if our scalars were specified to have
* width < 256 for performance reasons, their negations would have width 256
@ -94,7 +98,7 @@ static int secp256k1_wnaf_const(int *wnaf, const secp256k1_scalar *scalar, int w
/* 4 */
u_last = secp256k1_scalar_shr_int(&s, w);
while (word * w < size) {
do {
int sign;
int even;
@ -110,7 +114,7 @@ static int secp256k1_wnaf_const(int *wnaf, const secp256k1_scalar *scalar, int w
wnaf[word++] = u_last * global_sign;
u_last = u;
}
} while (word * w < size);
wnaf[word] = u * global_sign;
VERIFY_CHECK(secp256k1_scalar_is_zero(&s));