Rogi <r...@linuxmail.org> added the comment: I reviewed teh problem and rewrote teh text to better explain what is happening. Also, I noticed teh change to teh docs, and in fact it is not correct that teh functions call exit() on SystemError.
*** From teh docs: http://docs.python.org/c-api/veryhigh.html int Py_Main(int argc, char **argv)¶ The main program for the standard interpreter. This is made available for programs which embed Python. The argc and argv parameters should be prepared exactly as those which are passed to a C program¿s main() function. It is important to note that the argument list may be modified (but the contents of the strings pointed to by the argument list are not). The return value will be the integer passed to the sys.exit() function, 1 if the interpreter exits due to an exception, or 2 if the parameter list does not represent a valid Python command line. Note that if an otherwise unhandled SystemError is raised, this function will not return 1, but exit the process, as long as Py_InspectFlag is not set. *** Teh problem: Teh Py_Main() function does not return on any unhandled exception. If a unhandled exception is caught, teh function prints teh error and go to teh prompt. Try: ... >>> raise(SystemError) Traceback (most recent call last): File "<stdin>", line 1, in <module> SystemError >>> Consequently, Py_Main() does not return on unhandled SystemExit. But not only that. It calls exit() which terminate teh process. Try: ... Py_Main(argc, argv); fprintf(stderr, "reached!"); ... ... >>> raise(SystemExit) $ note it did not print after Py_Main() termination. *** Analysis: After greping python source, I found that this behaviour is triggered in function PyErr_PrintEx(). For some reason, SystemExit is handled here, in a function that, from its name, should print, not handle, and its handling involves a call to exit(), which terminate teh teh process. Also, not only Py_Main() is affected by this, but any other function that calls PyErr_PrintEx(), such as PyRun_SimpleString(). I tried to fix this but it would require some rewriting. I think this could be accomplished with some set/longjmp, but still some rewriting would be needed to fix other functions that rely on PyErr_PrintEx() behaviour. *** Possible solutions: * fix teh source to match teh docs * fix teh docs to match teh source *** Proposed solution: Teh current behaviour hit me when I was writing an app which had Py_Main() running on a thread. If teh user typed exit() in Python, teh program would crash from exiting on a bad place. Based on this I propose a review of teh source that adhere to teh following: 1 - PyErr_PrintEx() should not be handling any kind of exception. This should be done by a function liek PyErr_HandleException(). 2 - In functions liek PyRun_SimpleString(), teh default exception handling should only occur after giving teh programmer a chance to handle and clear teh exception himself. 3 - No calls to exit() should be made by teh Python interpreter, except, maybe, in some function which is a explicit wrapper. Since proposing is easy and doing is not, It would be nice to have, for now, a warning at teh docs for every bad behaving function, specially those which call exit(). ---------- _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue6498> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
