Wrong arithmetic conversion

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Article #1139

#1139

From: Abramo Bagnara
Date: Wed, 08 Nov 2006 09:50

38 lines
3104 bytes

When evaluating comparison expressions, the "usual arithmetic
conversions" mandated by C standard (ISO/IEC 9899 #6.3.1.8) are NOT done.

In the cases below note that GDB returns the mathematically correct
result, but this is not conforming to C standard and to GDB
documentation that says:

"The usual way to examine data in your program is with the `print'
command (abbreviated `p'), or its synonym `inspect'.  It evaluates and
prints the value of an expression of the language your program is
written in"

GNU gdb Red Hat Linux (6.3.0.0-1.134.fc5rh)
Copyright 2004 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain
conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for details.
This GDB was configured as "i386-redhat-linux-gnu"...Using host
libthread_db library "/lib/libthread_db.so.1".

(gdb) print (float)123456792.0 > 123456789
$1 = true
(gdb) print (float)123456792.0 > (float)123456789
$2 = false
(gdb) print 123456789123456784.0 < 123456789123456789LL
$3 = true
(gdb) print 123456789123456784.0 < (double)123456789123456789LL
$4 = false


-- 
Abramo Bagnara                       mailto:abramobagnara@tin.it

Opera Unica                          Phone: +39.0546.656023
Via Emilia Interna, 140
48014 Castel Bolognese (RA) - Italy

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From: Abramo Bagnara <abramobagnara@tin.it>
Newsgroups: gnu.gdb.bug
Subject: Wrong arithmetic conversion
Date: Wed, 08 Nov 2006 10:50:19 +0100
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