[Bug gdb/18318] New: Printing an hexadecimal floating constant with negative exponent gives wrong result

[Bug gdb/18318] New: Printing an hexadecimal floating constant with negative exponent gives wrong result

[olivier.gay at a3 dot epfl.ch]

https://sourceware.org/bugzilla/show_bug.cgi?id=18318

            Bug ID: 18318
           Summary: Printing an hexadecimal floating constant with
                    negative exponent gives wrong result
           Product: gdb
           Version: 7.9
            Status: NEW
          Severity: normal
          Priority: P2
         Component: gdb
          Assignee: unassigned at sourceware dot org
          Reporter: olivier.gay at a3 dot epfl.ch

Printing an hexadecimal floating constant with positive exponent is OK:

(gdb) p/f 0x00.1p0
$1 = 0.0625
(gdb) p/f 0x00.1p1
$2 = 0.125

but if the exponent is negative then the result is wrong:

(gdb) p/f 0x00.1p-1
$3 = -0.9375

The expected result is 0.031250.

Tested with gdb 7.9.

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[Bug gdb/18318] Printing an hexadecimal floating constant with negative exponent gives wrong result

[olivier.gay at a3 dot epfl.ch]

https://sourceware.org/bugzilla/show_bug.cgi?id=18318

--- Comment #1 from Olivier Gay <olivier.gay at a3 dot epfl.ch> ---
The question originally came from:
http://stackoverflow.com/questions/29846835/can-gdb-correcly-parse-c-style-hexadecimal-floating-point-numbers/29848357

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[Bug gdb/18318] Printing an hexadecimal floating constant with negative exponent gives wrong result

[huguesdelassus at hotmail dot fr]

https://sourceware.org/bugzilla/show_bug.cgi?id=18318

Hugues de Lassus Saint-Geniès <huguesdelassus at hotmail dot fr> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |huguesdelassus at hotmail dot fr

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https://sourceware.org/bugzilla/show_bug.cgi?id\x18273

--- Comment #2 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Nick Clifton <nickc@sourceware.org>:

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;hcc72d1ae497cdf43db5347464a97164e720b83f

commit 63c72d1ae497cdf43db5347464a97164e720b83f
Author: Nick Clifton <nickc@redhat.com>
Date:   Fri Apr 24 15:31:36 2015 +0100

    Fix typo in check for valid register number in RX sim.

        PR sim/18273
        * reg.c (put_reg): Fix check for valid register number.

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[Bug gdb/18318] Printing an hexadecimal floating constant with negative exponent gives wrong result

[huguesdelassus at hotmail dot fr]

https://sourceware.org/bugzilla/show_bug.cgi?id=18318

--- Comment #2 from Hugues de Lassus Saint-Geniès <huguesdelassus at hotmail dot fr> ---
I have encountered the same bug with explicitly positive exponents:

(gdb) p 0x1.8480000000000p+6
$1 = 7.517578125
(gdb) p 0x1.8480000000000p6
$2 = 97.125

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https://sourceware.org/bugzilla/show_bug.cgi?id\x17768

Yao Qi <qiyao at gcc dot gnu.org> changed:

           What    |Removed                     |Added
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             Status|NEW                         |WAITING
                 CC|                            |qiyao at gcc dot gnu.org

--- Comment #6 from Yao Qi <qiyao at gcc dot gnu.org> ---
(In reply to Mark Manning from comment #5)
> Created attachment 8034 [details]
> attachment-28523-0.html
>
> actually, there is still something wrong, i set a breakpoint on address
> 0xnnnn and the breakpoint gets inserted somewhere else close by but within
> a few opcodes, not at the specified location.  I can not supply you with
> anything other than my executable and a description of how to reproduce the
> problem.

Can you show us the gdb session, including the gdb commands you typed and the
output.  Please point out which part isn't what you expected.

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[Bug gdb/18318] Printing an hexadecimal floating constant with negative exponent gives wrong result

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=18318

Tom Tromey <tromey at sourceware dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |tromey at sourceware dot org
           Assignee|unassigned at sourceware dot org   |tromey at sourceware dot org

--- Comment #3 from Tom Tromey <tromey at sourceware dot org> ---
I have a patch.  It was a bug in the C lexer.

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[Bug gdb/18318] Printing an hexadecimal floating constant with negative exponent gives wrong result

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=18318

--- Comment #4 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Tom Tromey <tromey@sourceware.org>:

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=2b4e6a3f4b66284556254f548716c7b21b93524a

commit 2b4e6a3f4b66284556254f548716c7b21b93524a
Author: Tom Tromey <tom@tromey.com>
Date:   Thu Jun 11 10:34:31 2020 -0600

    Fix hex floating point lexing

    PR gdb/18318 notes that gdb will sometimes incorrectly handle hex
    floating point input.  This turns out to be a bug in the C lexer; the
    'p' was not being correctly recognized, and so the exponent was not
    always passed to the floating point "from_string" method.

    Tested by the buildbot "Fedora-x86_64-m64" builder.

    gdb/ChangeLog
    2020-06-11  Tom Tromey  <tom@tromey.com>

            PR gdb/18318:
            * c-exp.y (lex_one_token): Handle 'p' like 'e'.

    gdb/testsuite/ChangeLog
    2020-06-11  Tom Tromey  <tom@tromey.com>

            PR gdb/18318:
            * gdb.base/printcmds.exp (test_float_accepted): Add more hex
            floating point tests.

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[Bug gdb/18318] Printing an hexadecimal floating constant with negative exponent gives wrong result

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=18318

Tom Tromey <tromey at sourceware dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |10.1
         Resolution|---                         |FIXED
             Status|NEW                         |RESOLVED

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

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