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Top Forums Programming Strange value of the double type variable: -nan(0x8000000000000) Post 302903832 by 915086731 on Friday 30th of May 2014 03:25:22 AM
Old 05-30-2014
Strange value of the double type variable: -nan(0x8000000000000)

I am confused by the value of "currdisk->currangle" after adding operation. Initially the value of "currdisk->currangle" is 0.77500000000000013, but after adding operation, it's changed to "-nan(0x8000000000000)", Can anyone explain ? Thanks! The following is the occasion of gdb debugging.

Code:
3338          currdisk->currangle += (simtime - seg->time) / currdisk->rotatetime;
(gdb) p currdisk->currangle
$28 = 0.77500000000000013
(gdb) p (simtime - seg->time) / currdisk->rotatetime
$29 = 0.00833333333333325
(gdb) p (simtime - seg->time) 
$30 = 0.092592592592591672
(gdb) p currdisk->rotatetime
$31 = 11.111111111111111
(gdb) n

(gdb) p currdisk->currangle 
$32 = -nan(0x8000000000000)
(gdb) p/x (char[8])currdisk->currangle 
$52 = {0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0xf8, 0xff}
(gdb)

Then I change
currdisk->currangle += (simtime - seg->time) / currdisk->rotatetime ;
to
double tmp1 = (simtime - seg->time) / currdisk->rotatetime;
currdisk->currangle += tmp1;

The value of currdisk->currangle is normal. Can anyone explain the confusing phenomenon ?

---------- Post updated 05-30-14 at 02:25 AM ---------- Previous update was 05-29-14 at 10:56 PM ----------

All are double type.
 

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GZEXE(1)						      General Commands Manual							  GZEXE(1)

NAME
gzexe - compress executable files in place SYNOPSIS
gzexe name ... DESCRIPTION
The gzexe utility allows you to compress executables in place and have them automatically uncompress and execute when you run them (at a penalty in performance). For example if you execute ``gzexe /usr/bin/gdb'' it will create the following two files: -rwxr-xr-x 1 root root 1026675 Jun 7 13:53 /usr/bin/gdb -rwxr-xr-x 1 root root 2304524 May 30 13:02 /usr/bin/gdb~ /usr/bin/gdb~ is the original file and /usr/bin/gdb is the self-uncompressing executable file. You can remove /usr/bin/gdb~ once you are sure that /usr/bin/gdb works properly. This utility is most useful on systems with very small disks. OPTIONS
-d Decompress the given executables instead of compressing them. SEE ALSO
gzip(1), znew(1), zmore(1), zcmp(1), zforce(1) CAVEATS
The compressed executable is a shell script. This may create some security holes. In particular, the compressed executable relies on the PATH environment variable to find gzip and some standard utilities (basename, chmod, ln, mkdir, mktemp, rm, sleep, and tail). BUGS
gzexe attempts to retain the original file attributes on the compressed executable, but you may have to fix them manually in some cases, using chmod or chown. GZEXE(1)
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