| #ifndef Py_PYFPE_H |
| #define Py_PYFPE_H |
| #ifdef __cplusplus |
| extern "C" { |
| #endif |
| /* |
| --------------------------------------------------------------------- |
| / Copyright (c) 1996. \ |
| | The Regents of the University of California. | |
| | All rights reserved. | |
| | | |
| | Permission to use, copy, modify, and distribute this software for | |
| | any purpose without fee is hereby granted, provided that this en- | |
| | tire notice is included in all copies of any software which is or | |
| | includes a copy or modification of this software and in all | |
| | copies of the supporting documentation for such software. | |
| | | |
| | This work was produced at the University of California, Lawrence | |
| | Livermore National Laboratory under contract no. W-7405-ENG-48 | |
| | between the U.S. Department of Energy and The Regents of the | |
| | University of California for the operation of UC LLNL. | |
| | | |
| | DISCLAIMER | |
| | | |
| | This software was prepared as an account of work sponsored by an | |
| | agency of the United States Government. Neither the United States | |
| | Government nor the University of California nor any of their em- | |
| | ployees, makes any warranty, express or implied, or assumes any | |
| | liability or responsibility for the accuracy, completeness, or | |
| | usefulness of any information, apparatus, product, or process | |
| | disclosed, or represents that its use would not infringe | |
| | privately-owned rights. Reference herein to any specific commer- | |
| | cial products, process, or service by trade name, trademark, | |
| | manufacturer, or otherwise, does not necessarily constitute or | |
| | imply its endorsement, recommendation, or favoring by the United | |
| | States Government or the University of California. The views and | |
| | opinions of authors expressed herein do not necessarily state or | |
| | reflect those of the United States Government or the University | |
| | of California, and shall not be used for advertising or product | |
| \ endorsement purposes. / |
| --------------------------------------------------------------------- |
| */ |
| |
| /* |
| * Define macros for handling SIGFPE. |
| * Lee Busby, LLNL, November, 1996 |
| * busby1@llnl.gov |
| * |
| ********************************************* |
| * Overview of the system for handling SIGFPE: |
| * |
| * This file (Include/pyfpe.h) defines a couple of "wrapper" macros for |
| * insertion into your Python C code of choice. Their proper use is |
| * discussed below. The file Python/pyfpe.c defines a pair of global |
| * variables PyFPE_jbuf and PyFPE_counter which are used by the signal |
| * handler for SIGFPE to decide if a particular exception was protected |
| * by the macros. The signal handler itself, and code for enabling the |
| * generation of SIGFPE in the first place, is in a (new) Python module |
| * named fpectl. This module is standard in every respect. It can be loaded |
| * either statically or dynamically as you choose, and like any other |
| * Python module, has no effect until you import it. |
| * |
| * In the general case, there are three steps toward handling SIGFPE in any |
| * Python code: |
| * |
| * 1) Add the *_PROTECT macros to your C code as required to protect |
| * dangerous floating point sections. |
| * |
| * 2) Turn on the inclusion of the code by adding the ``--with-fpectl'' |
| * flag at the time you run configure. If the fpectl or other modules |
| * which use the *_PROTECT macros are to be dynamically loaded, be |
| * sure they are compiled with WANT_SIGFPE_HANDLER defined. |
| * |
| * 3) When python is built and running, import fpectl, and execute |
| * fpectl.turnon_sigfpe(). This sets up the signal handler and enables |
| * generation of SIGFPE whenever an exception occurs. From this point |
| * on, any properly trapped SIGFPE should result in the Python |
| * FloatingPointError exception. |
| * |
| * Step 1 has been done already for the Python kernel code, and should be |
| * done soon for the NumPy array package. Step 2 is usually done once at |
| * python install time. Python's behavior with respect to SIGFPE is not |
| * changed unless you also do step 3. Thus you can control this new |
| * facility at compile time, or run time, or both. |
| * |
| ******************************** |
| * Using the macros in your code: |
| * |
| * static PyObject *foobar(PyObject *self,PyObject *args) |
| * { |
| * .... |
| * PyFPE_START_PROTECT("Error in foobar", return 0) |
| * result = dangerous_op(somearg1, somearg2, ...); |
| * PyFPE_END_PROTECT(result) |
| * .... |
| * } |
| * |
| * If a floating point error occurs in dangerous_op, foobar returns 0 (NULL), |
| * after setting the associated value of the FloatingPointError exception to |
| * "Error in foobar". ``Dangerous_op'' can be a single operation, or a block |
| * of code, function calls, or any combination, so long as no alternate |
| * return is possible before the PyFPE_END_PROTECT macro is reached. |
| * |
| * The macros can only be used in a function context where an error return |
| * can be recognized as signaling a Python exception. (Generally, most |
| * functions that return a PyObject * will qualify.) |
| * |
| * Guido's original design suggestion for PyFPE_START_PROTECT and |
| * PyFPE_END_PROTECT had them open and close a local block, with a locally |
| * defined jmp_buf and jmp_buf pointer. This would allow recursive nesting |
| * of the macros. The Ansi C standard makes it clear that such local |
| * variables need to be declared with the "volatile" type qualifier to keep |
| * setjmp from corrupting their values. Some current implementations seem |
| * to be more restrictive. For example, the HPUX man page for setjmp says |
| * |
| * Upon the return from a setjmp() call caused by a longjmp(), the |
| * values of any non-static local variables belonging to the routine |
| * from which setjmp() was called are undefined. Code which depends on |
| * such values is not guaranteed to be portable. |
| * |
| * I therefore decided on a more limited form of nesting, using a counter |
| * variable (PyFPE_counter) to keep track of any recursion. If an exception |
| * occurs in an ``inner'' pair of macros, the return will apparently |
| * come from the outermost level. |
| * |
| */ |
| |
| #ifdef WANT_SIGFPE_HANDLER |
| #include <signal.h> |
| #include <setjmp.h> |
| #include <math.h> |
| extern jmp_buf PyFPE_jbuf; |
| extern int PyFPE_counter; |
| extern double PyFPE_dummy(void *); |
| |
| #define PyFPE_START_PROTECT(err_string, leave_stmt) \ |
| if (!PyFPE_counter++ && setjmp(PyFPE_jbuf)) { \ |
| PyErr_SetString(PyExc_FloatingPointError, err_string); \ |
| PyFPE_counter = 0; \ |
| leave_stmt; \ |
| } |
| |
| /* |
| * This (following) is a heck of a way to decrement a counter. However, |
| * unless the macro argument is provided, code optimizers will sometimes move |
| * this statement so that it gets executed *before* the unsafe expression |
| * which we're trying to protect. That pretty well messes things up, |
| * of course. |
| * |
| * If the expression(s) you're trying to protect don't happen to return a |
| * value, you will need to manufacture a dummy result just to preserve the |
| * correct ordering of statements. Note that the macro passes the address |
| * of its argument (so you need to give it something which is addressable). |
| * If your expression returns multiple results, pass the last such result |
| * to PyFPE_END_PROTECT. |
| * |
| * Note that PyFPE_dummy returns a double, which is cast to int. |
| * This seeming insanity is to tickle the Floating Point Unit (FPU). |
| * If an exception has occurred in a preceding floating point operation, |
| * some architectures (notably Intel 80x86) will not deliver the interrupt |
| * until the *next* floating point operation. This is painful if you've |
| * already decremented PyFPE_counter. |
| */ |
| #define PyFPE_END_PROTECT(v) PyFPE_counter -= (int)PyFPE_dummy(&(v)); |
| |
| #else |
| |
| #define PyFPE_START_PROTECT(err_string, leave_stmt) |
| #define PyFPE_END_PROTECT(v) |
| |
| #endif |
| |
| #ifdef __cplusplus |
| } |
| #endif |
| #endif /* !Py_PYFPE_H */ |
