e1fb03f3e2
This patch fixes a bug in the VM when breaking within a try-finally. The
bug has to do with executing a break within the finally block of a
try-finally statement. For example:
def f():
for x in (1,):
print('a', x)
try:
raise Exception
finally:
print(1)
break
print('b', x)
f()
Currently in uPy the above code will print:
a 1
1
1
segmentation fault (core dumped) micropython
Not only is there a seg fault, but the "1" in the finally block is printed
twice. This is because when the VM executes a finally block it doesn't
really know if that block was executed due to a fall-through of the try (no
exception raised), or because an exception is active. In particular, for
nested finallys the VM has no idea which of the nested ones have active
exceptions and which are just fall-throughs. So when a break (or continue)
is executed it tries to unwind all of the finallys, when in fact only some
may be active.
It's questionable whether break (or return or continue) should be allowed
within a finally block, because they implicitly swallow any active
exception, but nevertheless it's allowed by CPython (although almost never
used in the standard library). And uPy should at least not crash in such a
case.
The solution here relies on the fact that exception and finally handlers
always appear in the bytecode after the try body.
Note: there was a similar bug with a return in a finally block, but that
was previously fixed in
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| .. | ||
| basics | ||
| bench | ||
| cmdline | ||
| cpydiff | ||
| extmod | ||
| feature_check | ||
| float | ||
| import | ||
| inlineasm | ||
| io | ||
| jni | ||
| micropython | ||
| misc | ||
| net_hosted | ||
| net_inet | ||
| pyb | ||
| pybnative | ||
| stress | ||
| thread | ||
| unicode | ||
| unix | ||
| wipy | ||
| README | ||
| run-bench-tests | ||
| run-tests | ||
| run-tests-exp.py | ||
| run-tests-exp.sh | ||
This directory contains tests for various functionality areas of MicroPython. To run all stable tests, run "run-tests" script in this directory. Tests of capabilities not supported on all platforms should be written to check for the capability being present. If it is not, the test should merely output 'SKIP' followed by the line terminator, and call sys.exit() to raise SystemExit, instead of attempting to test the missing capability. The testing framework (run-tests in this directory, test_main.c in qemu_arm) recognizes this as a skipped test. There are a few features for which this mechanism cannot be used to condition a test. The run-tests script uses small scripts in the feature_check directory to check whether each such feature is present, and skips the relevant tests if not. When creating new tests, anything that relies on float support should go in the float/ subdirectory. Anything that relies on import x, where x is not a built-in module, should go in the import/ subdirectory.