Rubber duck debugging in a hotel room in Darmstadt @ ESA 2019 Space debris conference
Making it work: debugging
- Finding bugs before they happen
- Finding bugs after they happen
- Finding bugs while they happen
Today we will cover
Making it work: debugging
So what is a "bug"
And thus and the term "bug in the computer" caught on
Making it work: debugging
So what is a "bug"
Today it means "unwanted behaviour"
Making it work: debugging
- Finding bugs before they happen
- Finding bugs after they happen
- Finding bugs while they happen
Making it work: debugging
- Finding bugs before they happen
The most common methods
- Reading the code
- Static code analyzers
- Tests
Making it work: debugging
- Finding bugs before they happen
- Reading the code
- You reviewing your code
- Others reviewing your code
Making it work: debugging
- Finding bugs before they happen
- Reading the code
- You reviewing your code
- Others reviewing your code
Making it work: debugging
- Finding bugs before they happen
- Reading the code
- You reviewing your code
- Others reviewing your code
Make a routine out of it!
We are practicing this now with the homework
Making it work: debugging
- Finding bugs before they happen
- Static code analyzers
- mypy (Python)
- flake8 / ruff (Python)
- Any LSP server (clangd, pylsp, ...)
- Any compiler (clang, gcc, rustc) !
- ikos (C/C++)
- CodeQL (C/C++, Java, JavaScript, Python)
- [commercial] Cppcheck (C/C++)
- [commercial] Sonar (C/C++, Java, JavaScript, Python)
github analysis-tools-dev has a long list!
Making it work: debugging
- Finding bugs before they happen
- Static code analyzers
We are already doing this (right?!) after our tooling lecture!
Making it work: debugging
- Finding bugs before they happen
- Tests
- Unit testing
- Integration testing
- End-to-end testing
- Compatibility testing
- Performance testing
- Stress testing
- Security testing
- ...
Practical examples
Making it work: debugging
- Finding bugs before they happen
- Tests
Unit testing
class TestAnomalies(unittest.TestCase):
def test_eccentric_true_inverse(self):
nu0 = 1.2345
e = 0.5
nu = kep.eccentric_to_true(kep.true_to_eccentric(nu0, e), e)
self.assertAlmostEqual(nu0, nu)
Making it work: debugging
- Finding bugs before they happen
- Tests
Integration testing
class TestKeplerSolver(unittest.TestCase):
@pytest.mark.slow
def test_laguerre_solve_kepler(self):
E = np.linspace(0.0, 2.0*np.pi, num=300, dtype=np.float64)
e = np.linspace(0, 0.99, num=500, dtype=np.float64)
for eit in e:
for Eit in E:
M = kep.eccentric_to_mean(Eit, eit)
E0 = kep.kepler_guess(M, eit)
E_calc, it = kep.laguerre_solve_kepler(E0, M, eit, tol=1e-12)
fun_err = np.abs(M - E_calc + eit*np.sin(E_calc))
nt.assert_almost_equal(Eit, E_calc, decimal = 1e-9)
assert fun_err < 1e-11
Making it work: debugging
- Finding bugs before they happen
- Tests
End-to-end testing
Making it work: debugging
- Finding bugs before they happen
- Tests
Compatibility testing
test_python_3_10:
image: python:3.10
before_script:
- pip install virtualenv
- virtualenv venv
- source venv/bin/activate
- pip install .
script:
- pip install pytest
- pytest
rules:
- if: $CI_COMMIT_BRANCH == "main"
Making it work: debugging
- Finding bugs before they happen
- Tests
Compatibility testing
Making it work: debugging
- Finding bugs before they happen
- Tests
Performance testing
Next lecture!
Making it work: debugging
- Finding bugs before they happen
- Tests
Stress testing
class TestServer(unittest.TestCase):
...
def test_connect_client(self):
clients = []
for ind in range(10_000):
clients.append(
self.launch_client_request_thread()
)
for client in clients:
self.close_and_validate(client)
Making it work: debugging
- Finding bugs before they happen
- Tests
Security testing
danielk@IRF081-danielk ~/g/pyorb (main)> grype dir:.
✔ Vulnerability DB [updated]
✔ Indexed file system .
✔ Cataloged contents cdb4ee2aea69cc6a83331bbe96dc2caa9a299d21329efb0336fc02a82e1839a8
├── ✔ Packages [1 packages]
├── ✔ Executables [0 executables]
├── ✔ File metadata [2 locations]
└── ✔ File digests [2 files]
✔ Scanned for vulnerabilities [0 vulnerability matches]
├── by severity: 0 critical, 0 high, 0 medium, 0 low, 0 negligible
└── by status: 0 fixed, 0 not-fixed, 0 ignored
No vulnerabilities found
For example grype (podcast in handouts)
Making it work: debugging
- Finding bugs before they happen
- Tests
We are already doing this (right?!) after our testing homework and tooling lecture!
Making it work: debugging
- Finding bugs before they happen
- Finding bugs after they happen
- Finding bugs while they happen
Making it work: debugging
- Finding bugs after they happen
The most common methods
- Logging
-
Examining program output
(plots, data, real world actions, ...) - Asserts and exceptions
Making it work: debugging
- Finding bugs after they happen
The most common methods
- Logging
-
Examining program output
(plots, data, real world actions, ...) - Asserts and exceptions
Next lecture!
This is the default - no need to cover here
A quick second look (we covered syntax before)
Making it work: debugging
- Finding bugs after they happen
- Asserts and exceptions
def stack(logger, file: Path, output_folder=Path | None, duration=1.0, clobber=False):
...
if frame_cnt == 0:
raise EmptyVideoFile("Empty video file, cannot produce stack")
...
def worker(file, output_folder, duration, clobber):
logger = logging.getLogger("allsky7station.processing.stack")
logger.info(f"Processing {file.name}")
try:
stack(logger, file, output_folder=output_folder, duration=duration, clobber=clobber)
except EmptyVideoFile:
logger.warning(f"Empty video-file {file}, not writing output stack")
except FileExistsError:
logger.warning(f"{file} exists, not making stack")
Making it work: debugging
- Finding bugs after they happen
- Asserts and exceptions
Making it work: debugging
- Finding bugs after they happen
- Asserts and exceptions
python -O my_code.py
python cmdline -O: remove asserts and __debug__ code
Making it work: debugging
- Finding bugs after they happen
- Asserts and exceptions
mypy understands "type narrowing"
def function(arg: Any):
assert isinstance(arg, int)
reveal_type(arg) # Revealed type: "builtins.int"
Making it work: debugging
- Finding bugs after they happen
- Asserts and exceptions
Assertion heavy coding! (video in handouts)
# val should never be nan here
vs
assert not np.isnan(val), "this should never happen?!"
Making it work: debugging
- Finding bugs after they happen
- Bonus method: post-mortem
# automatically enter post-mortem if abnormal exit
python -m pdb -c continue my_code.py
It will enter debugger with current state at point of error
pdb.post_mortem
Making it work: debugging
- Finding bugs before they happen
- Finding bugs after they happen
- Finding bugs while they happen
Making it work: debugging
- Finding bugs while they happen
The most common methods
- Dynamic/runtime analyzers
- Debuggers
Making it work: debugging
- Finding bugs while they happen
- Dynamic/runtime analyzers
- tracemalloc (python)
- valgrind (C/C++)
- ...
Making it work: debugging
- Finding bugs while they happen
- Dynamic/runtime analyzers
- tracemalloc (python)
import tracemalloc
tracemalloc.start()
# ... code
snapshot = tracemalloc.take_snapshot()
top_stats = snapshot.statistics('lineno')
print("[ Top 10 ]")
for stat in top_stats[:10]:
print(stat)
Making it work: debugging
- Finding bugs while they happen
- Debuggers
Practical example! Go to handout