Add util::ResultPtr class

ryanofsky commented at 3:57 pm on September 6, 2022: contributor

This is based on #25665. The non-base commits are:

The util::ResultPtr class is a wrapper for util::Result providing syntax sugar to make it less awkward to use with returned pointers. Instead of needing to be deferenced twice with **result or (*result)->member, it only needs to be dereferenced once with *result or result->member. Also when it is used in a boolean context, instead of evaluating to true when there is no error and the pointer is null, it evaluates to false so it is straightforward to determine whether the result points to something.

This PR is only partial a solution to #26004 because while it makes it easier to check for null pointer values, it does not make it impossible to return a null pointer value inside a successful result. It would be possible to enforce that successful results always contain non-null pointers by using a not_null type (https://github.com/bitcoin/bitcoin/issues/24423) in combination with ResultPtr, though.

ryanofsky commented at 3:57 pm on September 6, 2022: contributor

In draft state because it’s a partial solution to #26004 and could be discussed more

DrahtBot commented at 11:11 pm on September 6, 2022: contributor

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For details see: https://corecheck.dev/bitcoin/bitcoin/pulls/26022.

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Conflicts

Reviewers, this pull request conflicts with the following ones:

#32061 (Replace libevent with our own HTTP and socket-handling implementation by pinheadmz)
#30595 (kernel: Introduce initial C header API by TheCharlatan)

If you consider this pull request important, please also help to review the conflicting pull requests. Ideally, start with the one that should be merged first.

DrahtBot added the label Needs rebase on Sep 19, 2022

ryanofsky force-pushed on Sep 20, 2022

ryanofsky commented at 6:28 pm on September 20, 2022: contributor

Rebased 4b8ee99dea4d990ac21dd6074a15511bc7842a8e -> 123788cf6dd74510e2a5b4ea3c566dc512a871ef (pr/bresult-ptr.1 -> pr/bresult-ptr.2, compare) due to conflict with #26005

DrahtBot removed the label Needs rebase on Sep 20, 2022

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ryanofsky commented at 11:29 pm on February 21, 2024: contributor

Rebased a1dddc5a2a86908d9ea677875ad67a79d2c71d14 -> 8ecac0885ef5b6fc2313cd2f8dfb48c10a05db27 (pr/bresult-ptr.3 -> pr/bresult-ptr.4, compare) on top of #25665.

I also rewrote the commit and PR description. I think this is in a good state to review, despite being based on another PR.

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ryanofsky force-pushed on May 1, 2024

ryanofsky commented at 5:56 pm on May 1, 2024: contributor

Rebased 8ecac0885ef5b6fc2313cd2f8dfb48c10a05db27 -> 9f58eb795ec5592c59f9af3269f004e589a2368f (pr/bresult-ptr.4 -> pr/bresult-ptr.5, compare) on top of latest #25665 (no other changes)

DrahtBot removed the label Needs rebase on May 1, 2024

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ryanofsky force-pushed on Jun 17, 2024

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ryanofsky force-pushed on Jul 18, 2024

DrahtBot commented at 10:16 pm on July 18, 2024: contributor

🚧 At least one of the CI tasks failed. Debug: https://github.com/bitcoin/bitcoin/runs/27633993409

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DrahtBot commented at 5:21 am on August 29, 2024: contributor

🚧 At least one of the CI tasks failed. Debug: https://github.com/bitcoin/bitcoin/runs/27663380898

Make sure to run all tests locally, according to the documentation.

The failure may happen due to a number of reasons, for example:

Possibly due to a silent merge conflict (the changes in this pull request being incompatible with the current code in the target branch). If so, make sure to rebase on the latest commit of the target branch.
A sanitizer issue, which can only be found by compiling with the sanitizer and running the affected test.
An intermittent issue.

Leave a comment here, if you need help tracking down a confusing failure.

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ryanofsky force-pushed on Nov 4, 2024

ryanofsky commented at 1:34 pm on November 4, 2024: contributor

Rebased 5f6f91c5fd848fecdc71db25ce1c5ddbedc78f29 -> c7e73097f4a8336e23d098c2fb4296319aba318e (pr/bresult-ptr.8 -> pr/bresult-ptr.9, compare) on top of updated base PR (no changes or conflicts) Rebased c7e73097f4a8336e23d098c2fb4296319aba318e -> f8254e78c140f5756fbd981994d17f6a91ee027b (pr/bresult-ptr.9 -> pr/bresult-ptr.10, compare) on top of updated base PR (no changes or conflicts) Rebased f8254e78c140f5756fbd981994d17f6a91ee027b -> f44cb2416fe98a6ffafba2b37ee8e1a18b731a1f (pr/bresult-ptr.10 -> pr/bresult-ptr.11, compare) on top of updated base PR (no changes or conflicts) Rebased f44cb2416fe98a6ffafba2b37ee8e1a18b731a1f -> 06512c44b6264f4ece4108dfcb572c0a90ec55b9 (pr/bresult-ptr.11 -> pr/bresult-ptr.12, compare) due to silent conflict with #31061

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ryanofsky force-pushed on Dec 6, 2024

DrahtBot removed the label Needs rebase on Dec 6, 2024

DrahtBot added the label Needs rebase on Jan 17, 2025

refactor: Add util::Result failure values

Add util::Result support for returning more error information. For better error
handling, adds the ability to return a value on failure, not just a value on
success. This is a key missing feature that made the result class not useful
for functions like LoadChainstate() which produce different errors that need to
be handled differently.

This change also makes some more minor improvements:

- Smaller type size. util::Result<int> is 16 bytes, and util::Result<void> is 8
  bytes. Previously util::Result<int> and util::Result<void> were 72 bytes.

- More documentation and tests.

4d90ce54e7

wallet: fix clang-tidy warning performance-no-automatic-move

Previous commit causes the warning to be triggered, but the suboptimal return
from const statement was added earlier in 517e204bacd9d.

Warning was causing CI failure https://cirrus-ci.com/task/6159914970644480

4140f871d6

refactor: Add util::Result::Update() method

Add util::Result Update method to make it possible to change the value of an
existing Result object. This will be useful for functions that can return
multiple error and warning messages, and want to be able to change the result
value while keeping existing messages.

6a18bcfcf8

refactor: Use util::Result class in LoadChainstate and VerifyLoadedChainstate 48949d1c60

refactor: Add util::Result multiple error and warning messages

Add util::Result support for returning warning messages and multiple errors,
not just a single error string. This provides a way for functions to report
errors and warnings in a standard way, and simplifies interfaces.

The functionality is unit tested here, and put to use in followup PR
https://github.com/bitcoin/bitcoin/pull/25722

4599760cc6

test: add static test for util::Result memory usage

Suggested by Martin Leitner-Ankerl <martin.ankerl@gmail.com>
https://github.com/bitcoin/bitcoin/pull/25722#discussion_r1174298529

Co-authored-by: Martin Leitner-Ankerl <martin.ankerl@gmail.com>

69b14c8122

Merge remote-tracking branch 'origin/pull/25665/head' 26a264e24a

Add util::ResultPtr class

The util::ResultPtr class is a wrapper for util::Result providing syntax sugar
to make it less awkward to use with returned pointers. Instead of needing to be
deferenced twice with **result or (*result)->member, it only needs to be
dereferenced once with *result or result->member. Also when it is used in a
boolean context, instead of evaluating to true when there is no error and the
pointer is null, it evaluates to false so it is straightforward to determine
whether the result points to something.

This PR is only partial a solution to #26004 because while it makes it easier
to check for null pointer values, it does not make it impossible to return a
null pointer value inside a successful result. It would be possible to enforce
that successful results always contain non-null pointers by using a not_null
type (https://github.com/bitcoin/bitcoin/issues/24423) in combination with
ResultPtr, though.

86607f813d

Use ResultPtr<unique_ptr> instead of Result<unique_ptr> 06512c44b6

ryanofsky force-pushed on Mar 12, 2025

DrahtBot removed the label Needs rebase on Mar 12, 2025

Add util::ResultPtr class #26022

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