New submission from STINNER Victor <[EMAIL PROTECTED]>:
I would like to be able to catch SIGSEGV in my Python code! So I
started to hack Python trunk to support this feature. The idea is to
use a signal handler which call longjmp(), and add setjmp() at
Py_EvalFrameEx() enter.
See attached ("small") patch: segfault.patch
Example read.py with the *evil* ctypes module of invalid memory read:
------------------- 8< --------------
from ctypes import string_at
def fault():
text = string_at(1, 10)
print("text = {0!r}".format(text))
def test():
print("test: 1")
try:
fault()
except MemoryError, err:
print "ooops!"
print err
print("test: 2")
try:
fault()
except MemoryError, err:
print "ooops!"
print err
print("test: end")
def main():
test()
if __name__ == "__main__":
main()
------------------- 8< --------------
Result:
------------------- 8< --------------
$ python read.py
test: 1
sizeof()=160
ooops!
segmentation fault
test: 2
sizeof()=160
ooops!
segmentation fault
test: end
------------------- 8< --------------
Example bug1.py of a stack overflow:
----------
loop = None,
for i in xrange(10**5):
loop = loop, None
----------
Result:
----------
$ python -i bug1.py
(((((((((...Traceback (most recent call last):
File "<stdin>", line 1, in <module>
MemoryError: segmentation fault
----------
Python is able to restore a valid state (stack/heap) after a
segmentation fault and raise a classical Python exception (I choosed
MemoryError, but it could be a specific exception).
On my computer (Ubuntu Gutsy/i386), each segfault_frame takes
sizeof(sigjmpbuf) + sizeof(void*) = 160 bytes, allocated on the stack.
I don't know if it's huge or not, but that will limit the number of
recursive calls. The feature can be optional if we add a configure
option and some #ifdef/#endif. A dedicated stack is needed to be call
the signal handler on stack overflow error. I choosed 4 KB, but since
I only call longjmp(), smaller stack might also works.
Does other VM support such feature? JVM, Mono, .NET, etc. ?
I had the idea of catching SIGSEGV after reading the issue 1069092
(stack overflow because of too many recursive calls).
----------
files: segfault.patch
keywords: patch
messages: 74060
nosy: haypo
severity: normal
status: open
title: Real segmentation fault handler
Added file: http://bugs.python.org/file11659/segfault.patch
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Python tracker <[EMAIL PROTECTED]>
<http://bugs.python.org/issue3999>
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