[Varnish] #1800: PRIV_TASK in a vmod object method leads to code that cannot be compiled/linked

[Varnish]

#1800: PRIV_TASK in a vmod object method leads to code that cannot be
compiled/linked
-------------------+--------------------
 Reporter:  geoff  |       Type:  defect
   Status:  new    |   Priority:  normal
Milestone:  Later  |  Component:  vmod
  Version:  4.1.0  |   Severity:  normal
 Keywords:         |
-------------------+--------------------
 This diff in the vcc declaration of vmod_debug:

 {{{
 diff --git a/lib/libvmod_debug/vmod.vcc b/lib/libvmod_debug/vmod.vcc
 index dad36ec..9dd9f5b 100644
 --- a/lib/libvmod_debug/vmod.vcc
 +++ b/lib/libvmod_debug/vmod.vcc
 @@ -89,6 +89,8 @@ $Method TIME .date()

  You never know when you need a date.

 +$Method VOID .task(PRIV_TASK)
 +
  $Function VOID rot52(HTTP hdr)

  Encrypt the HTTP header with quad-ROT13 encryption,
 }}}

 ... causes about 25 vtc tests to fail, all of them with this error
 message:

 {{{
 **** v1    0.2 CLI RX| Message from VCC-compiler:\n
 **** v1    0.2 CLI RX| Could not load VMOD debug\n
 **** v1    0.2 CLI RX| \tFile name: /home/geoff/Develop/varnish/varnish-
 cache/lib/libvmod_debug/.libs/libvmod_debug.so\n
 **** v1    0.2 CLI RX| \tdlerror:: /home/geoff/Develop/varnish/varnish-
 cache/lib/libvmod_debug/.libs/libvmod_debug.so: undefined symbol:
 vmod_obj_task\n
 **** v1    0.2 CLI RX| ('input' Line 5 Pos 16)\n
 **** v1    0.2 CLI RX|         import debug from
 "/home/geoff/Develop/varnish/varnish-
 cache/lib/libvmod_debug/.libs/libvmod_debug.so";\n
 **** v1    0.2 CLI RX|
 ---------------#####-------------------------------------------------------------------------------------------\n
 **** v1    0.2 CLI RX| \n
 **** v1    0.2 CLI RX| Running VCC-compiler failed, exited with 2\n
 **** v1    0.2 CLI RX| VCL compilation failed
 ---- v1    0.2 FAIL VCL does not compile
 }}}

 In my own VMOD I'm getting a compile error for the C code generated for
 the VMOD:

 {{{
 **** v1    0.3 CLI RX| Message from C-compiler:\n
 **** v1    0.3 CLI RX| vgc.c: In function
 \xe2\x80\x98VGC_function_vcl_backend_response\xe2\x80\x99:\n
 **** v1    0.3 CLI RX| vgc.c:1178:31: error:
 \xe2\x80\x98VGC_vmod_bar\xe2\x80\x99 undeclared (first use in this
 function)\n
 **** v1    0.3 CLI RX|            VRT_priv_task(ctx, &VGC_vmod_bar),\n
 **** v1    0.3 CLI RX|                                ^\n
 **** v1    0.3 CLI RX| vgc.c:1178:31: note: each undeclared identifier is
 reported only once for each function it appears in\n
 **** v1    0.3 CLI RX| vgc.c: In function
 \xe2\x80\x98VGC_function_vcl_recv\xe2\x80\x99:\n
 **** v1    0.3 CLI RX| vgc.c:1429:31: error:
 \xe2\x80\x98VGC_vmod_foobar\xe2\x80\x99 undeclared (first use in this
 function)\n
 **** v1    0.3 CLI RX|            VRT_priv_task(ctx, &VGC_vmod_foobar),\n
 **** v1    0.3 CLI RX|                                ^\n
 **** v1    0.3 CLI RX| vgc.c:1439:31: error:
 \xe2\x80\x98VGC_vmod_snafu\xe2\x80\x99 undeclared (first use in this
 function)\n
 **** v1    0.3 CLI RX| [2 lines truncated]\n
 **** v1    0.3 CLI RX| Running C-compiler failed, exited with 1\n
 **** v1    0.3 CLI RX| VCL compilation failed
 ---- v1    0.3 FAIL VCL does not compile
 }}}

 The vmodtool doesn't throw any errors, but the generated code is
 defective. Evidently a symbol is generated for the private object that is
 not declared.

 The use case is a VMOD object that is intended to have state across method
 calls within a "task" (client or backend context). In my case, it's for a
 regex VMOD with a backref call meant to refer back to captured expressions
 in a previous match call (https://code.uplex.de/uplex-varnish/libvmod-re).
 The VCC interface is something like this:

 {{{
 $Object regex(STRING)
 $Method BOOL .match(PRIV_TASK, STRING)
 $Method STRING .backref(PRIV_TASK, INT)
 }}}

 With usage like this:

 {{{
 import re;

 sub vcl_init {
     # compile a regex
     new myregex = re.regex("foo(bar)");
 }

 sub vcl_recv {
     if (myregex.match(req.http.Foo)) {
         set req.http.Bar = myregex.backref(1);
 }
 }}}

 The immediate defect is that code is generated that either can't be
 compiled or linked. More generally, it seems very intuitive to me that
 object methods should be able to maintain a state with task scope -- the
 regex example is basic stuff. Up to now, I'd been maintaining state by
 using pthread-local keys, but I thought using PRIV_TASK would be the more
 natural, Varnishy solution.

-- 
Ticket URL: <https://www.varnish-cache.org/trac/ticket/1800>
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