[Bug translator/20672] New: buildok/dentry-embedded.stp regression

[Bug translator/20672] New: buildok/dentry-embedded.stp regression

[mcermak at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=20672

            Bug ID: 20672
           Summary: buildok/dentry-embedded.stp regression
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: translator
          Assignee: systemtap at sourceware dot org
          Reporter: mcermak at redhat dot com
  Target Milestone: ---

On rhel6, buildok/dentry-embedded.stp regressed.  The new error is:

=======
spawn stap -p4 --compatible=2.9
/root/systemtap/testsuite/buildok/dentry-embedded.stp
semantic error: while processing function real_mount

semantic error: type definition 'mount' not found in 'kernel': operator '@cast'
at /usr/local/share/systemtap/tapset/type_defined.stpm:6:16
        source:     @defined(& @cast(0, @type) -> @member)
                               ^
        in expansion of macro: operator '@type_member_defined' at
/usr/local/share/systemtap/tapset/linux/dentry.stp:160:6
        source:         if (@type_member_defined("mount", mnt_parent)) {
                            ^

Pass 2: analysis failed.  [man error::pass2]
wait results: 12735 exp6 0 1
FAIL: buildok/dentry-embedded.stp
=======

The regression seems to be caused by following commit:

=======
commit 056cb27baac1ce3ab4d675dbbe4881afde801ca3
Author: Frank Ch. Eigler <fche@redhat.com>
Date:   Wed Jun 22 11:43:33 2016 -0400

    PR18079: support nested autocast / @defined

    We now perform const-folding & dead-code-elision during the type
    resolution loop, whenever an autocast expression gets evaluated.  This
    way, @defined(foo()->mm) type expressions can work as nature intended.

    This requires @defined() not to be short-circuit evaluated to 0 during
    a random const_folding process, so a flag is introduced to control its
    preservation or collapsing.  For the last (assert_resolvability) pass
    in the type resolution loop, this flag is set to true, so that
    genuinely unresolvable @defined($expressions) do get mapped to 0 in
    time for a last elision.
=======

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[Bug translator/20672] @defined(@cast()) regression

[mcermak at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=20672

Martin Cermak <mcermak at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|buildok/dentry-embedded.stp |@defined(@cast())
                   |regression                  |regression

--- Comment #1 from Martin Cermak <mcermak at redhat dot com> ---
Another problem this aforementioned commit 056cb27baac1 is causing is, that it
breaks the compileability of sys.stp (part of syscall.exp) on rhel6:

=======
 6.8 Server x86_64 # stap -I $HOME/src/testsuite/systemtap.syscall/tapset  -p4
$HOME/src/testsuite/systemtap.syscall/sys.stp
semantic error: while processing probe
kernel.function("sys32_mmap@arch/x86/ia32/sys_ia32.c:155") from: syscall.mmap32
from: syscall.*

semantic error: type definition 'mmap_arg_struct32' not found in 'kernel':
operator '@cast' at
/usr/local/share/systemtap/tapset/linux/x86_64/syscalls.stp:169:15
        source:         if (@defined(@cast($arg, "mmap_arg_struct32")->addr)) {
                                     ^

Pass 2: analysis failed.  [man error::pass2]
 6.8 Server x86_64 #
=======

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[Bug translator/20672] @defined(@cast()) regression

[fche at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=20672

Frank Ch. Eigler <fche at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |fche at redhat dot com

--- Comment #2 from Frank Ch. Eigler <fche at redhat dot com> ---
Just for the record, this is not exactly a regression, but the exposure of a
latent bug:

probe kernel.function("sys_sendto").return { println(@defined(@entry($foobar)))
}

fails under quite old systemtap too.

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[Bug translator/20672] @defined(@cast()) regression

[fche at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=20672

Frank Ch. Eigler <fche at redhat dot com> changed:

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

--- Comment #3 from Frank Ch. Eigler <fche at redhat dot com> ---
monster commit 16aa72d9adf4 reworks some rewriting passes

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[Bug translator/20672] @defined(@cast()) regression

[penguin-kernel@i-love.sakura.ne.jp]

https://sourceware.org/bugzilla/show_bug.cgi?id=20672

Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |penguin-kernel@i-love.sakur
                   |                            |a.ne.jp

--- Comment #4 from Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp> ---
Hello.

This commit is causing a regression (presumably infinite loop)
with python probes.

---------- /tmp/test.py start ----------
def func1(a, b):
  return a + b;

print(func1(1, 2));
---------- /tmp/test.py end ----------

# time PYTHONPATH=/tmp /usr/bin/stap -e 'probe
python2.module("test").function("*") { printf("%s %s\n", pn(), $$parms); }' -c
'python -m HelperSDT /tmp/test.py'



Bisect log:

# bad: [e81970274b46cf3e20586751bf58195258f31518] Add timestamp to
nfsd-trace.stp example.
# good: [9f950728d1a921e32d53cc8dabcbc0684d0256ee] Update lookup_bad_addr() to
avoid a kernel warning.
git bisect start 'HEAD' '9f950728d1a921e32d53cc8dabcbc0684d0256ee'
# good: [4fb0437d6e19bc5b7c917af5f542938d68968828] testsuite: more adaptation
to $var -> @entry($var) in .return probes
git bisect good 4fb0437d6e19bc5b7c917af5f542938d68968828
# bad: [16aa72d9adf420e973cfb3370f4cb9dacd3922fd] PR20627: rework several code
rewriting passes
git bisect bad 16aa72d9adf420e973cfb3370f4cb9dacd3922fd
# good: [15528f73d31f4fdd5257016957ac2e4cfaac8cd0] testsuite: tweak bz1027459
git bisect good 15528f73d31f4fdd5257016957ac2e4cfaac8cd0
# first bad commit: [16aa72d9adf420e973cfb3370f4cb9dacd3922fd] PR20627: rework
several code rewriting passes

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[Bug translator/20672] @defined(@cast()) regression

[fche at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=20672

Frank Ch. Eigler <fche at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |dsmith at redhat dot com

--- Comment #5 from Frank Ch. Eigler <fche at redhat dot com> ---
This appears to be fixed in commit f90352b.
It was caused by interesting infinite recursion of the python
variable-expander in-place mapping 

$var3
to
python2_get_var_obj(Py2Object_Repr($arg3, "arg3"))

and then the nested $arg3 ad infinitum.

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