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From: "sogartary at yahoo dot com" <sourceware-bugzilla@sourceware.org>
To: gdb-prs@sourceware.org
Subject: [Bug gdb/15318] New: Printing floating point numbers as hexadecimal
 outputs wrongly the integer conversion
Date: Thu, 28 Mar 2013 12:31:00 -0000
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X-Bugzilla-Who: sogartary at yahoo dot com
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X-Bugzilla-Priority: P2
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http://sourceware.org/bugzilla/show_bug.cgi?id=15318

             Bug #: 15318
           Summary: Printing floating point numbers as hexadecimal outputs
                    wrongly the integer conversion
           Product: gdb
           Version: 7.5
            Status: NEW
          Severity: normal
          Priority: P2
         Component: gdb
        AssignedTo: unassigned@sourceware.org
        ReportedBy: sogartary@yahoo.com
    Classification: Unclassified


When printing a float or a double as a hexadecimal the number is first cast to
integer and then the integer is printed in hex.
The correct behaviour is to take the bits of the floating point value,
reinterpret them as integer and print them in hex.

Here is an example. We have the following code:

double dd = 0.00014335116245 + 0x1FFF;

then in GDB after breaking on the next line we issue the following commands:

(gdb) p dd
$1 = 8191.0001433511625

(gdb) p/x 8191
$2 = 0x1fff

(gdb) p/x dd
$3 = 0x1fff

(gdb) p/x *reinterpret_cast<int64_t*>(&dd)
$4 = 0x40bfff000965088e

On the third command GDB should return the same as the result from the fourth
command.

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