[Bug tui/10829] New: Confusing results printed when a subexpression is optimized out

["ajax at redhat dot com" <sourceware-bugzilla at sourceware dot org>]

In the X server during request processing, where "stuff" is a struct xReq * with
a member named class:

(gdb) print stuff
$3 = <value optimized out>
(gdb) print stuff->class
Cannot access memory at address 0x16

The naïve conclusion for the user is that "stuff" somehow became NULL, which is
not in fact true; its value is merely being flattened to zero before computing
the offset of the "class" member.  The second print statement should be more
along the lines of "Cannot evaluate subexpression foo".

gdb version:

% rpm -q gdb
gdb-6.8.91.20090921-1.fc12.i686

-- 
           Summary: Confusing results printed when a subexpression is
                    optimized out
           Product: gdb
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: tui
        AssignedTo: unassigned at sourceware dot org
        ReportedBy: ajax at redhat dot com
                CC: gdb-prs at sourceware dot org


http://sourceware.org/bugzilla/show_bug.cgi?id=10829

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