15.21 诊断分析代码错误

The interpreter violently crashes with a segmentation fault, bus error, access violation,

or other fatal error. You would like to get a Python traceback that shows you where your

program was running at the point of failure.

The faulthandler module can be used to help you solve this problem. Include the

import faulthandler

faulthandler.enable()

Alternatively, run Python with the -Xfaulthandler option such as this:

bash % python3 -Xfaulthandler program.py

Last, but not least, you can set the PYTHONFAULTHANDLER environment variable.

With faulthandler enabled, fatal errors in C extensions will result in a Python trace‐

back being printed on failures. For example:

Although this won’t tell you where in the C code things went awry, at least it can tell you

how it got there from Python.

The faulthandler will show you the stack traceback of the Python code executing at

the time of failure. At the very least, this will show you the top-level extension function

that was invoked. With the aid of pdb or other Python debugger, you can investigate the

flow of the Python code leading to the error.

faulthandler will not tell you anything about the failure from C. For that, you will

need to use a traditional C debugger, such as gdb. However, the information from the

faulthandler traceback may give you a better idea of where to direct your attention.

It should be noted that certain kinds of errors in C may not be easily recoverable. For

example, if a C extension trashes the stack or program heap, it may render faulthan

dler inoperable and you’ll simply get no output at all (other than a crash). Obviously,

your mileage may vary.