annotate Python/fmod.c @ 8358:da4bdceeaad7 legacy-trunk

Another veeeeeery old patch... Date: Thu, 14 Sep 1995 12:18:20 -0400 From: Alan Morse <alan@dvcorp.com> To: python-list@cwi.nl Subject: getargs bug in 1.2 and 1.3 BETA We have found a bug in the part of the getargs code that we added and submitted, and which was incorporated into 1.1. The parsing of "O?" format specifiers is not handled correctly; there is no "else" for the "if" and therefore it can never fail. What's worse, the advancing of the varargs pointer is not handled properly, so from then on it is out of sync, wreaking all sorts of havoc. (If it had failed properly, then the out-of-sync varargs would not have been an issue.) Below is the context diff for the change. Note that I have made a few stylistic changes beyond adding the else case, namely: 1) Making the "O" case follow the convention established by the other format specifiers of getting all their vararg arguments before performing the test, rather than getting some before and some after the test passes. 2) Making the logic of the tests parallel, so the "if" part indicates that the format is accepted and the "else" part indicates that the format has failed. They were inconsistent with each other and with the the other format specifiers. -Alan Morse (amorse@dvcorp.com)
author Guido van Rossum <guido@python.org>
date Fri, 15 May 1998 22:04:07 +0000
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1 /***********************************************************
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2 Copyright 1991-1995 by Stichting Mathematisch Centrum, Amsterdam,
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3 The Netherlands.
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5 All Rights Reserved
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6
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7 Permission to use, copy, modify, and distribute this software and its
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8 documentation for any purpose and without fee is hereby granted,
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9 provided that the above copyright notice appear in all copies and that
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10 both that copyright notice and this permission notice appear in
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11 supporting documentation, and that the names of Stichting Mathematisch
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12 Centrum or CWI or Corporation for National Research Initiatives or
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13 CNRI not be used in advertising or publicity pertaining to
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14 distribution of the software without specific, written prior
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15 permission.
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17 While CWI is the initial source for this software, a modified version
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18 is made available by the Corporation for National Research Initiatives
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19 (CNRI) at the Internet address ftp://ftp.python.org.
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21 STICHTING MATHEMATISCH CENTRUM AND CNRI DISCLAIM ALL WARRANTIES WITH
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22 REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF
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23 MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL STICHTING MATHEMATISCH
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24 CENTRUM OR CNRI BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL
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25 DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
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26 PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
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27 TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
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28 PERFORMANCE OF THIS SOFTWARE.
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30 ******************************************************************/
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32 /* Portable fmod(x, y) implementation for systems that don't have it */
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34 #include "config.h"
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36 #include "mymath.h"
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37 #include <errno.h>
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39 double
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40 fmod(double x, double y)
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41 {
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42 double i, f;
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43
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44 if (y == 0.0) {
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45 errno = EDOM;
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46 return 0.0;
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47 }
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49 /* return f such that x = i*y + f for some integer i
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50 such that |f| < |y| and f has the same sign as x */
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51
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52 i = floor(x/y);
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53 f = x - i*y;
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54 if ((x < 0.0) != (y < 0.0))
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55 f = f-y;
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56 return f;
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57 }