5057adf22f
3a61fc56a0refactor: move CBlockIndex#ToString() from header to implementation (Jon Atack)57865eb512CDiskBlockIndex: rename GetBlockHash() to ConstructBlockHash() (Jon Atack)99e8ec8721CDiskBlockIndex: remove unused ToString() class member (Jon Atack)14aeece462CBlockIndex: ensure phashBlock is not nullptr before dereferencing (Jon Atack) Pull request description: Fix a few design issues, potential footguns and inconsistent behavior in the CBlockIndex and CDiskBlockIndex classes. - Ensure phashBlock in `CBlockIndex#GetBlockHash()` is not nullptr before dereferencing and remove a now-redundant assert preceding a GetBlockHash() caller. This protects against UB here, and in case of failure (which would indicate a consensus bug), the debug log will print `bitcoind: chain.h:265: uint256 CBlockIndex::GetBlockHash() const: Assertion 'phashBlock != nullptr' failed. Aborted` instead of `Segmentation fault`. - Remove the unused `CDiskBlockIndex#ToString()` class member, and mark the inherited `CBlockIndex#ToString()` public interface member as deleted to disallow calling it in the derived CDiskBlockIndex class. - Rename the `CDiskBlockIndex GetBlockHash()` class member to `ConstructBlockHash()`, which also makes sense as they perform different operations to return a blockhash, and mark the inherited `CBlockIndex#GetBlockHash()` public interface member as deleted to disallow calling it in the derived CDiskBlockIndex class. - Move `CBlockIndex#ToString()` from header to implementation, which also allows dropping `tinyformat.h` from the header file. Rationale and discussion regarding the CDiskBlockIndex changes: Here is a failing test on master that demonstrates the inconsistent behavior of the current design: calling the same inherited public interface functions on the same CDiskBlockIndex object should yield identical behavior, but does not. ```diff diff --git a/src/test/validation_chainstatemanager_tests.cpp b/src/test/validation_chainstatemanager_tests.cpp index 6dc522b421..dac3840f32 100644 --- a/src/test/validation_chainstatemanager_tests.cpp +++ b/src/test/validation_chainstatemanager_tests.cpp @@ -240,6 +240,15 @@ BOOST_FIXTURE_TEST_CASE(chainstatemanager_activate_snapshot, TestChain100Setup) const CBlockIndex* tip = chainman.ActiveTip(); BOOST_CHECK_EQUAL(tip->nChainTx, au_data.nChainTx); + // CDiskBlockIndex "is a" CBlockIndex, as it publicly inherits from it. + // Test that calling the same inherited interface functions on the same + // object yields identical behavior. + CDiskBlockIndex index{tip}; + CBlockIndex *pB = &index; + CDiskBlockIndex *pD = &index; + BOOST_CHECK_EQUAL(pB->GetBlockHash(), pD->GetBlockHash()); + BOOST_CHECK_EQUAL(pB->ToString(), pD->ToString()); ``` (build and run: `$ ./src/test/test_bitcoin -t validation_chainstatemanager_tests`) The GetBlockHash() test assertion only passes on master because the different methods invoked by the current design happen to return the same result. If one of the two is changed, it fails like the ToString() assertion does. Redefining inherited non-virtual functions is well-documented as incorrect design to avoid inconsistent behavior (see Scott Meyers, Effective C++, Item 36). Class usage is confusing when the behavior depends on the pointer definition instead of the object definition (static binding happening where dynamic binding was expected). This can lead to unsuspected or hard-to-track bugs. Outside of critical hot spots, correctness usually comes before optimisation, but the current design dates back to main.cpp and it may possibly have been chosen to avoid the overhead of dynamic dispatch. This solution does the same: the class sizes are unchanged and no vptr or vtbl is added. There are better designs for doing this that use composition instead of inheritance, or that separate the public interface from the private implementations. One example of the latter would be a non-virtual public interface that calls private virtual implementation methods, i.e. the Template pattern via the Non-Virtual Interface (NVI) idiom. ACKs for top commit: vasild: ACK3a61fc56a0Tree-SHA512: 9ff358ab0a6d010b8f053ad8303c6d4d061e62d9c3755a56b9c9f5eab855d02f02bee42acc77dfa0cbf4bb5cb775daa72d675e1560610a29bd285c46faa85ab7
Unit tests
The sources in this directory are unit test cases. Boost includes a unit testing framework, and since Bitcoin Core already uses Boost, it makes sense to simply use this framework rather than require developers to configure some other framework (we want as few impediments to creating unit tests as possible).
The build system is set up to compile an executable called test_bitcoin
that runs all of the unit tests. The main source file for the test library is found in
util/setup_common.cpp.
Compiling/running unit tests
Unit tests will be automatically compiled if dependencies were met in ./configure
and tests weren't explicitly disabled.
After configuring, they can be run with make check.
To run the unit tests manually, launch src/test/test_bitcoin. To recompile
after a test file was modified, run make and then run the test again. If you
modify a non-test file, use make -C src/test to recompile only what's needed
to run the unit tests.
To add more unit tests, add BOOST_AUTO_TEST_CASE functions to the existing
.cpp files in the test/ directory or add new .cpp files that
implement new BOOST_AUTO_TEST_SUITE sections.
To run the GUI unit tests manually, launch src/qt/test/test_bitcoin-qt
To add more GUI unit tests, add them to the src/qt/test/ directory and
the src/qt/test/test_main.cpp file.
Running individual tests
test_bitcoin accepts the command line arguments from the boost framework.
For example, to run just the getarg_tests suite of tests:
test_bitcoin --log_level=all --run_test=getarg_tests
log_level controls the verbosity of the test framework, which logs when a
test case is entered, for example. test_bitcoin also accepts the command
line arguments accepted by bitcoind. Use -- to separate both types of
arguments:
test_bitcoin --log_level=all --run_test=getarg_tests -- -printtoconsole=1
The -printtoconsole=1 after the two dashes redirects the debug log, which
would normally go to a file in the test datadir
(BasicTestingSetup::m_path_root), to the standard terminal output.
... or to run just the doubledash test:
test_bitcoin --run_test=getarg_tests/doubledash
Run test_bitcoin --help for the full list.
Adding test cases
To add a new unit test file to our test suite you need
to add the file to src/Makefile.test.include. The pattern is to create
one test file for each class or source file for which you want to create
unit tests. The file naming convention is <source_filename>_tests.cpp
and such files should wrap their tests in a test suite
called <source_filename>_tests. For an example of this pattern,
see uint256_tests.cpp.
Logging and debugging in unit tests
make check will write to a log file foo_tests.cpp.log and display this file
on failure. For running individual tests verbosely, refer to the section
above.
To write to logs from unit tests you need to use specific message methods
provided by Boost. The simplest is BOOST_TEST_MESSAGE.
For debugging you can launch the test_bitcoin executable with gdb or lldb and
start debugging, just like you would with any other program:
gdb src/test/test_bitcoin
Segmentation faults
If you hit a segmentation fault during a test run, you can diagnose where the fault
is happening by running gdb ./src/test/test_bitcoin and then using the bt command
within gdb.
Another tool that can be used to resolve segmentation faults is valgrind.
If for whatever reason you want to produce a core dump file for this fault, you can do
that as well. By default, the boost test runner will intercept system errors and not
produce a core file. To bypass this, add --catch_system_errors=no to the
test_bitcoin arguments and ensure that your ulimits are set properly (e.g. ulimit -c unlimited).
Running the tests and hitting a segmentation fault should now produce a file called core
(on Linux platforms, the file name will likely depend on the contents of
/proc/sys/kernel/core_pattern).
You can then explore the core dump using
gdb src/test/test_bitcoin core
(gbd) bt # produce a backtrace for where a segfault occurred