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Overview
Comment:Added comment on floating point precision compile option for MSVC. (CVS 5448)
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SHA1: e20f2b8c6a13aa826703441cf340d0ee03bf9f64
User & Date: shane 2008-07-22 05:15:53.000
Context
2008-07-22
05:18
Changed a few loop counters to unsigned ints to remove compiler warnings. (CVS 5449) (check-in: 16f51f9b39 user: shane tags: trunk)
05:15
Added comment on floating point precision compile option for MSVC. (CVS 5448) (check-in: e20f2b8c6a user: shane tags: trunk)
05:13
Add assertion check for NaN support at startup. (CVS 5447) (check-in: 8474cde34b user: shane tags: trunk)
Changes
Side-by-Side Diff Ignore Whitespace Patch
Changes to src/util.c.
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**
*************************************************************************
** Utility functions used throughout sqlite.
**
** This file contains functions for allocating memory, comparing
** strings, and stuff like that.
**
** $Id: util.c,v 1.238 2008/07/11 16:19:10 drh Exp $
** $Id: util.c,v 1.239 2008/07/22 05:15:53 shane Exp $
*/
#include "sqliteInt.h"
#include <stdarg.h>
#include <ctype.h>


/*
** Return true if the floating point value is Not a Number.
** Return true if the floating point value is Not a Number (NaN).
*/
int sqlite3IsNaN(double x){
  /* This NaN test sometimes fails if compiled on GCC with -ffast-math.
  ** On the other hand, the use of -ffast-math comes with the following
  ** warning:
  **
  **      This option [-ffast-math] should never be turned on by any
  **      -O option since it can result in incorrect output for programs
  **      which depend on an exact implementation of IEEE or ISO 
  **      rules/specifications for math functions.
  **
  ** Under MSVC, this NaN test may fail if compiled with a floating-
  ** point precision mode other than /fp:precise.  From the MSDN 
  ** documentation:
  **
  **      The compiler [with /fp:precise] will properly handle comparisons 
  **      involving NaN. For example, x != x evaluates to true if x is NaN 
  **      ...
  */
#ifdef __FAST_MATH__
# error SQLite will not work correctly with the -ffast-math option of GCC.
#endif
  volatile double y = x;
  volatile double z = y;
  return y!=z;
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