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Upstream PRs 1824, 1777, 1834, 1837, 1839, 1841#356

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Upstream PRs 1824, 1777, 1834, 1837, 1839, 1841#356
real-or-random wants to merge 15 commits intomasterfrom
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This PR has been created by a GitHub Actions workflow without human involvement.

[bitcoin-core/secp256k1#1824]: util: introduce and use ARRAY_SIZE macro
[bitcoin-core/secp256k1#1777]: Make SHA256 compression runtime pluggable
[bitcoin-core/secp256k1#1834]: ecmult: Document and test ng=NULL in ecmult
[bitcoin-core/secp256k1#1837]: tests: Fix function pointer initialization C89 error in ellswift tests
[bitcoin-core/secp256k1#1839]: ecdsa: VERIFY_CHECK result of _fe_set_b32_limit
[bitcoin-core/secp256k1#1841]: gha: Bump deprecated GHA workflow dependencies

Tips:

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  • Use git read-tree --reset -u <pr-branch> to replay these resolutions during the conflict resolution stage when recreating the PR branch locally.
    Be aware that this may discard your index as well as the uncommitted changes and untracked files in your worktree.

theStack and others added 15 commits February 17, 2026 00:21
The macro definition matches the one used in Linux, see e.g.
https://github.com/torvalds/linux/blob/9702969978695d9a699a1f34771580cdbb153b33/include/linux/array_size.h#L11
(without the additional check rejecting pointers, as we would need
 GNU C for that, see e.g. https://stackoverflow.com/a/19455169)
This is purely a mechanical change with no behavior change.

It introduces a secp256k1_hash_ctx struct inside secp256k1_context
and propagates it to all SHA256-related operations.

This sets up the ability to provide a hardware-optimized SHA256
compression function at runtime in a follow-up commit.
This introduces `secp256k1_context_set_sha256_compression()`,
which allows users to provide their own SHA256 block-compression
function at runtime.

This is useful in setups where the fastest implementation can only
be determined dynamically based on the available CPU features, and
rebuilding the library is not possible.

The callback is installed on the `secp256k1_context` and is then used
by all operations that compute SHA256 hashes. As part of the setup,
the library performs sanity checks to ensure that the supplied
function is equivalent to the default transform.

Passing NULL to the callback setter restores the built-in
implementation.
Multiple 64-byte blocks can now be compressed directly
from the input buffer, without copying them into the
internal buffer.
…E` macro

921b971 util: introduce and use `ARRAY_SIZE` macro (Sebastian Falbesoner)

Pull request description:

  This PR is another tiny improvement found while working on #1765, with the goal to avoid code repetition.

  The `ARRAY_SIZE` macro definition is pretty wide-spread in C projects and e.g. matches the one [used in the Linux Kernel](https://github.com/torvalds/linux/blob/9702969978695d9a699a1f34771580cdbb153b33/include/linux/array_size.h#L11)  (without the additional check to reject pointers, as we would need GNU C for that, see e.g. https://stackoverflow.com/a/19455169; not sure if a useful counterpart exists that only relies on C89). Replacement instances were identified via `$ git grep sizeof.*/.*sizeof`.

ACKs for top commit:
  w0xlt:
    ACK 921b971
  real-or-random:
    utACK 921b971

Tree-SHA512: 44b6bf0132cf00fade526a3fc04e03dc896d04874123614c032206b61f97c81f94d139b6cc0c108eceaa699251580c19420d230b3150607303ca2cb7ab9a0bcb
…uggable

4d92a08 sha256: speed up writes using multi-block compression (furszy)
0753f8b Add API to override SHA256 compression at runtime (furszy)
fdb6a91 Introduce hash context to support pluggable SHA256 compression (furszy)

Pull request description:

  Tackling the long-standing request #702.

  Right now we ship our own SHA256 implementation, a standard baseline version that does not take advantage of any hardware-optimized instruction, and it cannot be accessed by the embedding application - it is for internal usage only.

  This means embedding applications often have to implement or include a different version for their use cases, wasting space on constrained environments, and in performance-sensitive setups it forces them to use a slower path than what the platform provides. Many projects already rely on tuned SHA-NI / ARMv8 / or other hardware-optimized code, so always using the baseline implementation we ship within the library is not ideal.

  These changes allow users to supply their own SHA256 compression function at runtime, while preserving the existing default behavior for everyone else. This is primarily intended for environments where the available SHA256 implementation is detected dynamically and recompiling the library with a different implementation is not feasible (equivalent build-time functionality will come in a follow-up PR).

  It introduces a new API:

  ```C89
  secp256k1_context_set_sha256_transform_callback(ctx, fn_transform)
  ```

  This function installs the optimized SHA256 compression into the `secp256k1_context`, which is then used by all internal computations. Important: The provided function is verified to be output-equivalent to the original one.

  As a quick example, using this functionality in Bitcoin-Core will be very straightforward: furszy/bitcoin-core@f68bef0

ACKs for top commit:
  real-or-random:
    ACK 4d92a08
  w0xlt:
    ACK 4d92a08
  theStack:
    ACK 4d92a08

Tree-SHA512: 058e2e82071f1ca77254b684458292c621e60d65bbcc5500574429717e7db75bc9f3221129fafd11eb5d33e666a5efec5e9844460d3b194ef3b6b16f2df28fb9
…in ecmult

3a40363 eckey: Call ecmult with NULL instead of zero scalar (Tim Ruffing)
7e68c0c ecmult: Document and test ng=NULL in ecmult (Tim Ruffing)

Pull request description:

ACKs for top commit:
  theStack:
    re-ACK 3a40363

Tree-SHA512: 954928d4dfa120845c6e899c1a69ad0408072809551d42735eac491b8bc41249eb25d7c57cfa4f44763167620b5cb78639b5c396c0a342c47b0afc48a088c755
This also avoids a spurious "-Wmaybe-uninitialized" warning emitted by
gcc 16 (snapshot) when compiling with -DDETERMINISTIC.
…lization C89 error in ellswift tests

b84635e tests: Fix C89 function pointer initialization in ellswift tests (mllwchrry)

Pull request description:

  Fixes a C89 pedantic compliance error in `src/modules/ellswift/tests_impl.h` where function pointer array initialization is not allowed at declaration time.

  This error was exposed while I was testing the improved test coverage in CI. The initial plan was to simplify the configuration of modules in CI by enabling all modules by default and testing the disabling of each module independently.

  Error: src/modules/ellswift/tests_impl.h:442:110: error: initializer element is not computable at load time [-Wpedantic].

  The error occurred when running the `x86_64_debian` GitHub Actions CI job, which uses GCC 16 (snapshot) with strict flags (-std=c89 -pedantic -pedantic-errors -Werror). See this action run for reference: https://github.com/mllwchrry/secp256k1/actions/runs/23301905657/job/67769464566.

  The fix uses `if/else` to assign function pointers after declaration, matching the pattern already used in the same file.

  While this is a minor C89 compliance issue, it blocks the potential CI simplification.

ACKs for top commit:
  real-or-random:
    utACK b84635e
  theStack:
    ACK b84635e

Tree-SHA512: 61e42afe9c3a215f817b1bf475ea66c103b4af6c598a9d7ee9e1a97789ac6f4e025260b4cd0e2ec219bd73706c7aa2799c58ab904916d9594626cf3c07e4b983
…set_b32_limit

43fca0f ecdsa: VERIFY_CHECK result of _fe_set_b32_limit (Tim Ruffing)

Pull request description:

  This also avoids a spurious `-Wmaybe-uninitialized` warning emitted by gcc 16 (snapshot) when compiling with `-DDETERMINISTIC`.

  Alternative to #1838 by @mllwchrry who tried very a similar thing as this PR but couldn't convince the compiler. (The GCC snapshot is very annoying: a simple `VERIFY_CHECK(secp256k1_fe_set_b32_limit(&xr, c))` doesn't do the trick. I found this variant here with a local store rather by accident.)

ACKs for top commit:
  mllwchrry:
    ACK 43fca0f
  theStack:
    utACK 43fca0f

Tree-SHA512: 2550043e953675db7614f98bbdffb706721834967ef36f7c905f7cbfeee5d88189a9acfcd64865ef822bb0e3272d228440bdfb1124228afe083e025056e53212
…dependencies

c5cd9d6 gha: Bump deprecated GHA workflow dependencies (Tim Ruffing)

Pull request description:

  Deprecation notice:
  https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/

  Changelogs (no entries relevant to us):
    * https://github.com/docker/setup-buildx-action/releases/tag/v4.0.0
    * https://github.com/docker/build-push-action/releases/tag/v7.0.0
    * https://github.com/actions/cache#v5

ACKs for top commit:
  hebasto:
    ACK c5cd9d6.

Tree-SHA512: d21509503a617344f5f93a87fe229774e5ab5322ae2f322b38c7fdaef54ab3386a5eaa9901cb1b15f32c7891d2587aab709c70df9f5aaedc7524710496981311
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4 participants