[Bug symtab/15391] New: DW_OP_GNU_implicit_pointer bug

[Bug symtab/15391] New: DW_OP_GNU_implicit_pointer bug

[jan.kratochvil at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=15391

             Bug #: 15391
           Summary: DW_OP_GNU_implicit_pointer bug
           Product: gdb
           Version: HEAD
            Status: NEW
          Severity: normal
          Priority: P2
         Component: symtab
        AssignedTo: unassigned@sourceware.org
        ReportedBy: jan.kratochvil@redhat.com
                CC: tromey@redhat.com
    Classification: Unclassified
            Target: x86_64-unknown-linux-gnu


struct S { short a; char b, c; };
volatile int v;
void foo (int x)
{
  struct S s = { x, x + 2, x + 3 };
  char *p = &s.b;
  s.a++;
  v++; /* line 8 */
}
int main ()
{
  foo (1);
  return 0;
}

gcc-4.8.0-2.fc19.x86_64
gcc -g -O2 -fno-inline -fno-ipa-cp -o implptr implptr.c -Wall

gdb ./implptr -ex 'b 8' -ex r -ex 'p p[-1]' -ex c -ex q -q

Actual:
$1 = 3 '\003'

Expected:
$1 = 0 '\000'

Bugreported by Jakub Jelinek.


Abbrev Number: 7 (DW_TAG_variable)
 DW_AT_name     : s  
 DW_AT_location : (DW_OP_breg5 (rdi): 1; DW_OP_stack_value; DW_OP_piece: 2;
DW_OP_breg5 (rdi): 2; DW_OP_stack_value; DW_OP_piece: 1; DW_OP_breg5 (rdi): 3;
DW_OP_stack_value; DW_OP_piece: 1)

Abbrev Number: 7 (DW_TAG_variable)
 DW_AT_name     : p  
 DW_AT_location : (DW_OP_GNU_implicit_pointer: <0x88> 2)

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[Bug symtab/15391] DW_OP_GNU_implicit_pointer bug

[tromey at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=15391

Tom Tromey <tromey at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at sourceware    |tromey at redhat dot com
                   |dot org                     |

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[Bug symtab/15391] DW_OP_GNU_implicit_pointer bug

[cvs-commit at gcc dot gnu.org]

http://sourceware.org/bugzilla/show_bug.cgi?id=15391

--- Comment #1 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
CVSROOT:    /cvs/src
Module name:    src
Changes by:    tromey@sourceware.org    2013-06-18 18:11:19

Modified files:
    gdb            : ChangeLog dwarf2loc.c utils.c utils.h 
    gdb/testsuite  : ChangeLog 
    gdb/testsuite/gdb.dwarf2: implptrconst.exp 
    gdb/testsuite/lib: dwarf.exp 
Added files:
    gdb/testsuite/gdb.dwarf2: implptrpiece.exp 

Log message:
    Fix PR symtab/15391

    PR symtab/15391 is a failure with the DW_OP_GNU_implicit_pointer
    feature.

    I tracked it down to a logic error in read_pieced_value.  The code
    truncates this_size_bits according to the type size and offset too
    early -- it should do it after taking bits_to_skip into account.

    This patch fixes the bug.

    While testing this, I also tripped across a latent bug because
    indirect_pieced_value does not sign-extend where needed.  This patch
    fixes this bug as well.

    Finally, Pedro pointed out that a previous version implemented sign
    extension incorrectly.  This version introduces a new gdb_sign_extend
    function for this.  A couple of notes on this function:

    * It has the gdb_ prefix to avoid clashes with various libraries that
    felt free to avoid proper namespacing.  There is a "sign_extend"
    function in a Tile GX header, in an SOM-related BFD header (and in
    sh64-tdep.c and as a macro in arm-wince-tdep.c, but those are
    ours...)

    * I looked at all the sign extensions in gdb and didn't see ones that
    I felt comfortable converting to use this function; in large part
    because I don't have a good way to test the conversion.

    Built and regtested on x86-64 Fedora 18.  New test cases included;
    this required a minor addition to the DWARF assembler.  Note that the
    DWARF CU made by implptrpiece.exp uses a funny pointer size in order
    to show the sign-extension bug on all platforms.

    * dwarf2loc.c (read_pieced_value): Truncate this_size_bits
    after taking bits_to_skip into account.  Sign extend byte_offset.
    * utils.h (gdb_sign_extend): Declare.
    * utils.c (gdb_sign_extend): New function.

    * gdb.dwarf2/implptrpiece.exp: New file.
    * gdb.dwarf2/implptrconst.exp (d): New variable.
    Print d.
    * lib/dwarf2.exp (Dwarf::_location): Handle DW_OP_piece.

Patches:
http://sourceware.org/cgi-bin/cvsweb.cgi/src/gdb/ChangeLog.diff?cvsroot=src&r1=1.15708&r2=1.15709
http://sourceware.org/cgi-bin/cvsweb.cgi/src/gdb/dwarf2loc.c.diff?cvsroot=src&r1=1.173&r2=1.174
http://sourceware.org/cgi-bin/cvsweb.cgi/src/gdb/utils.c.diff?cvsroot=src&r1=1.300&r2=1.301
http://sourceware.org/cgi-bin/cvsweb.cgi/src/gdb/utils.h.diff?cvsroot=src&r1=1.8&r2=1.9
http://sourceware.org/cgi-bin/cvsweb.cgi/src/gdb/testsuite/ChangeLog.diff?cvsroot=src&r1=1.3696&r2=1.3697
http://sourceware.org/cgi-bin/cvsweb.cgi/src/gdb/testsuite/gdb.dwarf2/implptrpiece.exp.diff?cvsroot=src&r1=NONE&r2=1.1
http://sourceware.org/cgi-bin/cvsweb.cgi/src/gdb/testsuite/gdb.dwarf2/implptrconst.exp.diff?cvsroot=src&r1=1.3&r2=1.4
http://sourceware.org/cgi-bin/cvsweb.cgi/src/gdb/testsuite/lib/dwarf.exp.diff?cvsroot=src&r1=1.9&r2=1.10

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[Bug symtab/15391] DW_OP_GNU_implicit_pointer bug

[tromey at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=15391

Tom Tromey <tromey at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED
   Target Milestone|---                         |7.7

--- Comment #2 from Tom Tromey <tromey at redhat dot com> ---
Fixed.

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