[Bug translator/13186] New: systemtap does not correctly point out offending structure when accidentally dereferencing a structure as a string

[Bug translator/13186] New: systemtap does not correctly point out offending structure when accidentally dereferencing a structure as a string

[anish at chelsio dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=13186

             Bug #: 13186
           Summary: systemtap does not correctly point out offending
                    structure when accidentally dereferencing a structure
                    as a string
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: translator
        AssignedTo: systemtap@sourceware.org
        ReportedBy: anish@chelsio.com
    Classification: Unclassified


probe point :
printf("%s : %s\n",thread_indent(1),kernel_string($kobj->dentry->d_name))

error message :
Pass 1: parsed user script and 76 library script(s) using
138788virt/22212res/2784shr kb, in 140usr/10sys/152real ms.
semantic error: 'struct qstr' is being accessed instead of a member: identifier
'$kobj' at /tmp/sysfs.stp:14:53
        source:                 printf("%s :
%s\n",thread_indent(1),kernel_string($kobj->dentry->d_name))
                                     ^

Here d_name is a structure of type qstr; which is the offending dereference
however the translator points to $kobj instead of d_name.

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[Bug translator/13186] systemtap does not correctly point out offending structure when accidentally dereferencing a structure as a string

[anish at chelsio dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=13186

--- Comment #1 from Anish Bhatt <anish at chelsio dot com> 2011-09-13 19:50:03 UTC ---
Complete script as follows :

probe kernel.function("sysfs_create_group@fs/sysfs/group.c") {
       printf("%s :
%s\n",thread_indent(1),kernel_string($kobj->dentry->d_name))
}

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[Bug translator/13186] systemtap does not correctly point out offending structure when accidentally dereferencing a structure as a string

[jistone at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=13186

--- Comment #2 from Josh Stone <jistone at redhat dot com> 2011-09-13 19:53:16 UTC ---
(In reply to comment #0)
> semantic error: 'struct qstr' is being accessed instead of a member: identifier
> '$kobj' at /tmp/sysfs.stp:14:53
>         source:                 printf("%s :
> %s\n",thread_indent(1),kernel_string($kobj->dentry->d_name))
>                                      ^
> 
> Here d_name is a structure of type qstr; which is the offending dereference
> however the translator points to $kobj instead of d_name.

The message is generated by dwflpp::translate_final_fetch_or_store, using the
token of the overall expression (e->tok).  It should be possible to use the
token of the last dereferencing e->component instead, falling back to e->tok
only if there are no components.

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