Skip to content

build: fix clang -Wshorten-64-to-32 warnings #1801

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
csjones wants to merge 4 commits into
base: master
Choose a base branch
from
Open

build: fix clang -Wshorten-64-to-32 warnings #1801

Show file tree
Hide file tree
Changes from 2 commits
Commits
Show all changes
4 commits
Select commit Hold shift + click to select a range
66452d4
fix: change w variable type from uint32_t to uint64_t in modinv64 imp…
csjones Jun 6, 2025
3ddc5be
fix: use explicit casts for 'implicit conversion loses integer precis…
csjones Jan 14, 2026
4a84fb7
fix: use explicit casts for 'implicit conversion loses integer precis…
csjones Jan 14, 2026
da9db68
refactor: preserve unsigned arithmetic and add VERIFY_CHECKs before c…
csjones Jan 22, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
4 changes: 2 additions & 2 deletions src/modinv64_impl.h
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -240,7 +240,7 @@ static int64_t secp256k1_modinv64_divsteps_62_var(int64_t eta, uint64_t f0, uint
/* Transformation matrix; see comments in secp256k1_modinv64_divsteps_62. */
uint64_t u = 1, v = 0, q = 0, r = 1;
uint64_t f = f0, g = g0, m;
uint32_t w;
uint64_t w;
int i = 62, limit, zeros;

for (;;) {
Expand Down Expand Up @@ -326,7 +326,7 @@ static int64_t secp256k1_modinv64_posdivsteps_62_var(int64_t eta, uint64_t f0, u
/* Transformation matrix; see comments in secp256k1_modinv64_divsteps_62. */
uint64_t u = 1, v = 0, q = 0, r = 1;
uint64_t f = f0, g = g0, m;
uint32_t w;
uint64_t w;
int i = 62, limit, zeros;
int jac = *jacp;

Expand Down
8 changes: 4 additions & 4 deletions src/scalar_4x64_impl.h
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -109,7 +109,7 @@ static int secp256k1_scalar_add(secp256k1_scalar *r, const secp256k1_scalar *a,
secp256k1_u128_accum_u64(&t, a->d[3]);
secp256k1_u128_accum_u64(&t, b->d[3]);
r->d[3] = secp256k1_u128_to_u64(&t); secp256k1_u128_rshift(&t, 64);
overflow = secp256k1_u128_to_u64(&t) + secp256k1_scalar_check_overflow(r);
overflow = (int)secp256k1_u128_to_u64(&t) + secp256k1_scalar_check_overflow(r);
Comment thread
csjones marked this conversation as resolved.
Outdated
VERIFY_CHECK(overflow == 0 || overflow == 1);
secp256k1_scalar_reduce(r, overflow);

Expand Down Expand Up @@ -634,7 +634,7 @@ static void secp256k1_scalar_reduce_512(secp256k1_scalar *r, const uint64_t *l)
sumadd_fast(n3);
extract_fast(m5);
VERIFY_CHECK(c0 <= 1);
m6 = c0;
m6 = (uint32_t)c0;

/* Reduce 385 bits into 258. */
/* p[0..4] = m[0..3] + m[4..6] * SECP256K1_N_C. */
Expand All @@ -654,7 +654,7 @@ static void secp256k1_scalar_reduce_512(secp256k1_scalar *r, const uint64_t *l)
muladd_fast(m6, SECP256K1_N_C_1);
sumadd_fast(m5);
extract_fast(p3);
p4 = c0 + m6;
p4 = (uint32_t)c0 + m6;
VERIFY_CHECK(p4 <= 2);
Comment on lines +658 to 659
Copy link
Copy Markdown
Contributor

@real-or-random real-or-random Jan 21, 2026

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Suggested change
p4 = (uint32_t)c0 + m6;
VERIFY_CHECK(p4 <= 2);
VERIFY_CHECK(c0 <= 1 && m6 <= 1);
p4 = (uint32_t)c0 + m6;

Copy link
Copy Markdown
Author

@csjones csjones Jan 22, 2026

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Change made

Copy link
Copy Markdown
Author

@csjones csjones Jan 22, 2026

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

I ended up removing m6 <= 1 because it's already verified at line 637. The CI failed with c0 <= 1 and after running the ci script locally a few times, I changed it to c0 <= 2, which is consistent with the original p4 <= 2 check (since p4 = c0 + m6 and m6 <= 1). I also restored the p4 <= 2 check.

Copy link
Copy Markdown
Contributor

@real-or-random real-or-random Jan 22, 2026

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Hm, I see. I have no idea how the algorithm works. Still, this is a bit surprising to me because that means m6 == 0 always (but then it probably wouldn't be there in the first place) or m6 == 0 iff c0 == 2, and I don't see why the latter should hold.

Perhaps @sipa can provide some insights..


/* Reduce 258 bits into 256. */
Expand All @@ -674,7 +674,7 @@ static void secp256k1_scalar_reduce_512(secp256k1_scalar *r, const uint64_t *l)
#endif

/* Final reduction of r. */
secp256k1_scalar_reduce(r, c + secp256k1_scalar_check_overflow(r));
secp256k1_scalar_reduce(r, (unsigned int)c + secp256k1_scalar_check_overflow(r));
Comment thread
csjones marked this conversation as resolved.
}

static void secp256k1_scalar_mul_512(uint64_t *l8, const secp256k1_scalar *a, const secp256k1_scalar *b) {
Expand Down