[Bug translator/17860] New: foreach loop fails -p4 if array slice is an expression

[Bug translator/17860] New: foreach loop fails -p4 if array slice is an expression

[jlebon at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=17860

            Bug ID: 17860
           Summary: foreach loop fails -p4 if array slice is an expression
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: translator
          Assignee: systemtap at sourceware dot org
          Reporter: jlebon at redhat dot com

The following script runs successfully:

global arr

probe oneshot {
   i = 1
   arr[1] = 2
   foreach (var in arr[i] limit 1) {
      println("iterating")
   }
}

But if we change the subscript of arr to arr[i++] in the foreach statement, we
get the following p4 failures:

/tmp/stappEHxIa/stap_b1cc5d80db2fc511db3feaaaf7d971a3_1314_src.c: In function
‘probe_2463’:
/tmp/stappEHxIa/stap_b1cc5d80db2fc511db3feaaaf7d971a3_1314_src.c:205:6: error:
‘struct probe_2463_locals’ has no member named ‘__tmp8’
     l->__tmp8 = 0LL;
      ^
/tmp/stappEHxIa/stap_b1cc5d80db2fc511db3feaaaf7d971a3_1314_src.c:221:12: error:
‘struct probe_2463_locals’ has no member named ‘__tmp8’
       if (l->__tmp8++ >= l->__tmp7) goto break_0;
            ^
make[1]: *** [/tmp/stappEHxIa/stap_b1cc5d80db2fc511db3feaaaf7d971a3_1314_src.o]
Error 1

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[Bug translator/17860] foreach loop fails -p4 if array slice is an expression

[jlebon at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=17860

--- Comment #1 from Jonathan Lebon <jlebon at redhat dot com> ---
The reason this fails is that the logic in c_tmpcounter::visit_foreach_loop()
is not exactly matched with c_unparser::visit_foreach_loop(). The order in
which tmpvars are declared is not the same as the order in which they are used
up during unparsing.

This doesn't cause an issue in the working case above since tmpcounter declares
and unparser uses 4 tmpvars in consecutive order. However, when i++ is used,
tmpcounter introduces two new vars for the post_crement, one of which it ends
up not declaring. When c_unparser then tries to use this same numbered tmpvar
we get the failures above.

Currently testing a patch for this.

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[Bug translator/17860] foreach loop fails -p4 if array slice is an expression

[jlebon at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=17860

Jonathan Lebon <jlebon at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED

--- Comment #2 from Jonathan Lebon <jlebon at redhat dot com> ---
Fixed in commit 39495c1.

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