#36190 test: Check bitcoin wrapper child exit status on windows

Adds functional tests to tool_bitcoin.py to verify that the Windows bitcoin wrapper preserves child process exit status and reports errors on spawn failure. Specifically, it tests that exit codes 0, 1, and -1 are properly passed through by using cmd.exe as a mock child executable, and confirms that startup errors produce an exit code of 1 with an error message on stderr.

Problem: Without dedicated test coverage on Windows, regressions in process execution and exit-code forwarding in the bitcoin wrapper can go unnoticed, such as conflating child exit status -1 with process spawn errors under the Windows CRT.

Evidence of importance:

• PR description: 'The case worth covering is exit code -1. The first version of the wrapper used _spawnvp(_P_WAIT), which returns -1 both when the spawn fails and when the child started fine and exited with -1, so bitcoin.exe reported a startup error and exited 1 instead of passing -1 through.'
• Commit 7395505c2f: 'This detects a bug that was present in the original implementation of the earlier commit "Fix ExecVp on Windows to wait for child process"'

Scope: The PR branch currently includes the prerequisite commits from #36105; the unique changes belonging to this PR are the new test cases added to test/functional/tool_bitcoin.py.

Risk of a mistake: low (tests). A mistake in the new tests would only cause functional test failures on Windows environments and does not impact node runtime logic.

Changed since the previous assessment: Rebased on updated commits from #36105 with no functional changes to the tests.

Ready · Review #36105 first

Stacked on #36105; the base PR's changes are included in this diff.

Waiting on (from the thread read):

• author: rebase and mark ready for review after #36105 lands 2026-09-23

Strong

substantive support, no open objection (cyb3ralbert, ryanofsky)

Thread notes: ryanofsky reviewed and ACKed the test commits, and converted the PR to draft status pending #36105.

Objections, suggestions, and questions:

Support:

• cyb3ralbert (contributor) (ACK, 2026-09-13) [tested: tool_bitcoin.py]: Ran tool_bitcoin.py against this head on Linux and on a windows-2022 runner with cross-built binaries (both CRTs), confirming all tests pass and the new launch failure test is reached in each.
• ryanofsky (member) (ACK, 2026-09-23) [read: last 2 commits]: Both tests are well written and add useful coverage.

Participants:

• ryanofsky (member, support, 5 statements 2026-09-09 to 2026-09-23): ACKed the test commits and converted the PR to draft pending #36105
• cyb3ralbert (contributor, support, 2 statements 2026-09-11 to 2026-09-13): tested on Linux and Windows, suggested adding coverage for failed child launches, and ACKed the updated PR

Depends on: #36105

Based on (shares commits with): #36105

73 lines under test/bench/ci.

• test/functional/tool_bitcoin.py +41/-10
• test/functional/interface_gui.py +6/-7
• src/util/exec.cpp +11/-1
• src/bitcoin.cpp +4/-1
• src/qt/test/CMakeLists.txt +3/-1
• test/functional/test_framework/test_framework.py +4/-0
• test/config.ini.in +1/-0

The short text the ranking pass compares across PRs.

This PR adds functional tests in tool_bitcoin.py to verify that the Windows bitcoin wrapper process correctly preserves child exit statuses and reports launch failures. It tests that exit codes 0, 1, and -1 are forwarded intact without injecting unexpected stderr output, and verifies that failure to start the child process returns an exit code of 1 with an informative execvp error. The tests specifically guard against a bug in Windows CRT process handling where an exit code of -1 was conflated with process spawn failure. It depends on runtime fixes in #36105.

P3 · test coverage

Adds Windows functional test coverage for child exit status propagation in the bitcoin wrapper. As noted in the description, this 'detects a bug that was present in the original implementation' where child exit code -1 was conflated with spawn failures under the Windows CRT.

Membership: Tests process execution and exit status preservation for the bitcoin wrapper executable, which is explicitly covered under IPC.

Factors: security/stability 0, bug 0, performance 0, user value 0, leverage 0

P3 · test coverage

Verifies exit code forwarding and error handling for the bitcoin CLI wrapper on Windows. Citing the PR description, it ensures exit codes 0, 1, and -1 are preserved and verifies that spawn errors return exit code 1 with diagnostic output on stderr.

Membership: Directly tests the bitcoin wrapper CLI tool in test/functional/tool_bitcoin.py.

Factors: security/stability 0, bug 0, performance 0, user value 0, leverage 0

P3 · test coverage

Provides test coverage for the process execution utility handling on Windows. The description highlights covering an edge case where spawn failure and exit code -1 were previously conflated.

Membership: Carries the Utils/log/libs maintainer label and validates Windows child process execution utilities (ExecVp).

Factors: security/stability 0, bug 0, performance 0, user value 0, leverage 0