[Bug gdb/15318] New: Printing floating point numbers as hexadecimal outputs wrongly the integer conversion

[Bug gdb/15318] New: Printing floating point numbers as hexadecimal outputs wrongly the integer conversion

[sogartary at yahoo dot com]

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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[Bug gdb/15318] Printing floating point numbers as hexadecimal outputs wrongly the integer conversion

[sogartary at yahoo dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=15318

sogartary at yahoo dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |sogartary at yahoo dot com

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[Bug gdb/15318] Printing floating point numbers as hexadecimal outputs wrongly the integer conversion

[sogartary at yahoo dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=15318

--- Comment #1 from Sogartar <sogartary at yahoo dot com> 2013-03-28 12:35:23 UTC ---
I can reproduce this in version 7.4 also.

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[Bug c++/15318] Printing floating point numbers as hexadecimal outputs wrongly the integer conversion

[sogartary at yahoo dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=15318

Sogartar <sogartary at yahoo dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|gdb                         |c++

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[Bug c++/15318] Printing floating point numbers as hexadecimal outputs wrongly the integer conversion

[tromey at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=15318

Tom Tromey <tromey at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |tromey at redhat dot com

--- Comment #2 from Tom Tromey <tromey at redhat dot com> 2013-03-28 16:07:12 UTC ---
I agree the current behavior is weird, but
I'm not sure that this should act like the
reinterpret_cast.  Instead maybe it should
print a hex floating point representation.

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[Bug c++/15318] Printing floating point numbers as hexadecimal outputs wrongly the integer conversion

[sogartary at yahoo dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=15318

--- Comment #3 from Sogartar <sogartary at yahoo dot com> 2013-04-05 15:49:47 UTC ---
Then this is will be a change of the given feature, since the documentation
specifies:
"Regard the bits of the value as an integer, and print the integer in
hexadecimal."

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[Bug c++/15318] Printing floating point numbers as hexadecimal outputs wrongly the integer conversion

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=15318

Tom Tromey <tromey at sourceware dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |DUPLICATE
                 CC|                            |tromey at sourceware dot org

--- Comment #5 from Tom Tromey <tromey at sourceware dot org> ---
Dup.

*** This bug has been marked as a duplicate of bug 16242 ***

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