tests: Improve secp256k1_scalar_check_overflow tests (Issue #1812) by therohityadav · Pull Request #1819 · bitcoin-core/secp256k1

therohityadav · 2026-02-04T07:51:19Z

This Pull Request improves the tests for secp256k1_scalar_check_overflow as requested in #1812.

Changes:

Removed the redundant "all ones" check from run_scalar_tests.
Added a new dedicated test function test_scalar_check_overflow.
Added static checks for edge cases: 0, N-1, N, N+1, and MAX.
Added random input tests that verify check_overflow against a manual byte comparison.

Fixes #1812.

hebasto

Trailing spaces should be removed to pass the CI.

src/tests.c

therohityadav · 2026-02-04T10:52:50Z

Trailing spaces should be removed to pass the CI.

Thank you, I have removed the trailing whitespace and all the tests passed.

real-or-random

Concept ACK

src/tests.c

real-or-random · 2026-02-04T11:05:15Z

Thank you, I have removed the trailing whitespace and all the tests passed.

Thanks, and please squash your commits. :)

therohityadav · 2026-02-04T13:01:00Z

Thank you, I have removed the trailing whitespace and all the tests passed.

Thanks, and please squash your commits. :)

Thanks for the Concept ACK and the review! I have addressed all the feedback:

Restored the global count variable and used it for the loop iteration.
Switched to testrand256 for randomness.
Used secp256k1_group_order_bytes to avoid duplicating constants.
Squashed the commits into one.

real-or-random · 2026-02-04T14:06:54Z

I don't see any diff compared to your last push. (See https://github.com/bitcoin-core/secp256k1/compare/58be14be2de04cc39df0f286826f0b19b8809fe0..83568d863521ba25a2f3bc791f0776a898cdb2cb)

But I see you squashed. Did you push the wrong commit?

real-or-random

Thanks for the update, I have just one more comment

real-or-random · 2026-02-04T16:10:08Z

src/tests.c

+    CHECK(secp256k1_scalar_check_overflow(&n_plus_1) == 1);
+    CHECK(secp256k1_scalar_check_overflow(&max) == 1);
+
+    for (i = 0; i < count; i++) {


I literally meant COUNT, a global variable in the tests. This loop could run 2 * COUNT times, I think.

I literally meant COUNT, a global variable in the tests. This loop could run 2 * COUNT times, I think.

Thank you for the catch. I have removed the local count variable and updated the loop to use the global COUNT with 2 * COUNT iterations.

theStack

Concept and code-review ACK 6b49efd

As a follow-up idea, maybe a deduplication of these scalar constants with other tests could make sense (see e.g. $ git grep -i 0xbaeedce6).

theStack · 2026-02-04T18:02:26Z

src/tests.c

+
 static void run_scalar_tests(void) {
    int i;
+    test_scalar_check_overflow();


non-blocking nit: could add a newline before to separate the declaration block

non-blocking nit: could add a newline before to separate the declaration block

I have added the newline to separate the declaration block.

Regarding the scalar constant deduplication: I am looking into doing that in a follow-up PR to keep this one focused.

theStack

re-ACK f47bbc0

real-or-random

utACK f47bbc0

real-or-random · 2026-02-04T19:25:49Z

Thanks for your contribution!

hebasto reviewed Feb 4, 2026

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real-or-random added assurance tweak/refactor labels Feb 4, 2026

therohityadav force-pushed the test-overflow branch from 58be14b to 83568d8 Compare February 4, 2026 12:05

therohityadav force-pushed the test-overflow branch from 83568d8 to 1cee90f Compare February 4, 2026 14:53

real-or-random reviewed Feb 4, 2026

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therohityadav force-pushed the test-overflow branch from 1cee90f to 6b49efd Compare February 4, 2026 16:26

theStack approved these changes Feb 4, 2026

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therohityadav force-pushed the test-overflow branch from 6b49efd to 1e7dfc0 Compare February 4, 2026 18:23

test: add unit tests for secp256k1_scalar_check_overflow

f47bbc0

therohityadav force-pushed the test-overflow branch from 1e7dfc0 to f47bbc0 Compare February 4, 2026 18:31

theStack approved these changes Feb 4, 2026

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real-or-random approved these changes Feb 4, 2026

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real-or-random merged commit 1d146ac into bitcoin-core:master Feb 4, 2026
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therohityadav mentioned this pull request Feb 5, 2026

test: deduplicate scalar and field constants for n-1 and p-1 #1820

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