Attached patch implements an handler for the signal SIGSEGV. It uses its own stack to be able to allocate memory on the stack (eg. call a function), even on stack overflow.

The patch requires sigaction() and sigaltstack() functions, but I didn't patched configure.in script. These functions are available on Linux, but should be available on other UNIX OSes.

segfault() signal handler supposes that the thread state is consistent (interp->frame chained list). It calls indirectly PyUnicode_EncodeUTF8() and so call PyBytes_FromStringAndSize() which allocates memory on the heap. It clears PyUnicode "defenc" attribute (the result of PyUnicode_EncodeUTF8()) to free directly the memory.

To test it, try some scripts in Lib/test/crashers/.

One example:
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$ ./python Lib/test/crashers/recursive_call.py
Fatal Python error: segmentation fault

Traceback (most recent call first):
  File "Lib/test/crashers/recursive_call.py", line 12, depth 15715
  File "Lib/test/crashers/recursive_call.py", line 12, depth 15714
  File "Lib/test/crashers/recursive_call.py", line 12, depth 15713
...
  File "Lib/test/crashers/recursive_call.py", line 12, depth 3
  File "Lib/test/crashers/recursive_call.py", line 12, depth 2
  File "Lib/test/crashers/recursive_call.py", line 9, depth 1
Segmentation fault
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