Thanks Kenton,
An update on this. I am leaning to think it is an stack overflow, although
I couldn't confirm 100%. The truth is that, calling the same code from the
main(), with the same exact objects and encoding routine, doesn't crash.
However, when the encode() method is called from a thread that is created
by an external library, I consistently get a SIGSEGV. I've tried the
typical ulimit / pthread_attr_setstacksize() without much of a success (not
sure why though).
Re-arranging the code so that the encode() is called with less stack (I cut
2 or 3 frames), I get past the point of libstdc++, but I consistenly crash
here:
(gdb) bt
#0 0x00000000009d4e46 in capnp::_::DirectWireValue<unsigned int>::get
*(this=0x0)* at /home/marc/target/rootfs/include/capnp/endian.h:80
#1 0x0000000001e64d37 in
capnp::_::WirePointer::target(capnp::_::SegmentReader*) const ()
#2 0x0000000001e6a83c in
capnp::_::WireHelpers::readStructPointer(capnp::_::SegmentReader*,
capnp::_::CapTableReader*, capnp::_::WirePointer const*, capnp::word const*
, int) ()
#3 0x0000000001e5e7e7 in capnp::_::PointerReader::getStruct(capnp::word
const*) const ()
#4 0x0000000001e7fe61 in capnp::_::PointerHelpers<capnp::schema::Node,
(capnp::Kind)3>::get(capnp::_::PointerReader, capnp::word const*) ()
#5 0x0000000001e7f6ec in capnp::ReaderFor_<capnp::schema::Node,
(kind<capnp::schema::Node>)()>::Type
capnp::AnyPointer::Reader::getAs<capnp::schema::Node>() const ()
#6 0x0000000001e7de31 in capnp::schema::Node::Reader
capnp::readMessageUnchecked<capnp::schema::Node>(capnp::word const*) ()
#7 0x0000000001e780db in capnp::Schema::getProto() const ()
#8 0x0000000001e7995f in capnp::EnumSchema::getEnumerants() const ()
#9 0x0000000001e8068f in capnp::DynamicEnum::getEnumerant() const ()
#10 0x0000000001e45c74 in
capnp::JsonCodec::encode(capnp::DynamicValue::Reader, capnp::Type,
capnp::JsonValue::Builder) const ()
Really odd... So I think it is not related to capnproto code
Thanks
marc
On Saturday, March 3, 2018 at 1:19:15 AM UTC+1, Kenton Varda wrote:
>
> Sorry, I don't really have any ideas here. The stack trace is deep in STL
> code for the type handler map, inside find(). If you've registered no type
> handlers, that map should be empty. It's hard to imagine how find() on an
> empty std::unordered_map could ever segfault...
>
> -Kenton
>
> On Fri, Mar 2, 2018 at 11:07 AM, Marc Sune <ma...@voltanet.io
> <javascript:>> wrote:
>
>> Kenton,
>>
>> On Friday, March 2, 2018 at 7:27:30 PM UTC+1, Kenton Varda wrote:
>>>
>>> Hi Marc,
>>>
>>> Do you have any custom type handlers registered via addTypeHandler()? Is
>>> it possible that the handler class has gone out-of-scope (been destroyed)
>>> by the time the encoder is executed?
>>>
>>
>> No, I am not using custom handlers. I am just dumping the Builder like
>> this (simplified):
>>
>> template<typename T>
>> void dump_msg(T& msg){
>> try{
>> capnp::JsonCodec enc;
>> enc.setPrettyPrint(PPRINT);
>> auto t = enc.encode(msg);
>> fprintf(stderr, "MSG: %s\n", t.cStr());
>> }catch(...){}
>> }
>>
>> Where, in this case, msg is:
>>
>> 147 capnp::MallocMessageBuilder builder;
>>
>> 148 auto msg = builder.initRoot<Message>();
>>
>> //Fill it
>>
>> 254 dump_msg(msg);
>>
>> So the builder and encoder al valid, I believe in the entire dumping.
>> Moreover, valgrind would complain before the SEGFAULT if something would be
>> out of the stack, and the only thing I get is the direct SEGFAULT.
>>
>> Any thoughts? I will keep trying to isolate the problem
>>
>> marc
>>
>> -Kenton
>>>
>>> On Fri, Mar 2, 2018 at 10:18 AM, Marc Sune <ma...@voltanet.io> wrote:
>>>
>>>> > That's about all that I can get, even though capnproto is compiled
>>>> with DEBUG.
>>>>
>>>> Or shall I say, it should :/
>>>>
>>>>
>>>> On Friday, March 2, 2018 at 7:17:02 PM UTC+1, Marc Sune wrote:
>>>>>
>>>>> Hi guys,
>>>>>
>>>>> I am experiencing a _very_ strange segfault during JSON encoding of
>>>>> message:
>>>>>
>>>>> ```
>>>>> Program received signal SIGSEGV, Segmentation fault.
>>>>> [Switching to Thread 27946]
>>>>> 0x0000000001e4b81a in std::__detail::_Hashtable_ebo_helper<1,
>>>>> capnp::(anonymous namespace)::TypeHash,
>>>>> true>::_S_cget(std::__detail::_Hashtable_ebo_helper<1, capnp::(anonymous
>>>>> namespace)::TypeHash, true> const&) ()
>>>>> (gdb) bt
>>>>> #0 0x0000000001e4b81a in std::__detail::_Hashtable_ebo_helper<1,
>>>>> capnp::(anonymous namespace)::TypeHash,
>>>>> true>::_S_cget(std::__detail::_Hashtable_ebo_helper<1, capnp::(anonymous
>>>>> namespace)::TypeHash, true> const&) ()
>>>>> #1 0x0000000001e4b11a in std::__detail::_Hash_code_base<capnp::Type,
>>>>> std::pair<capnp::Type const, capnp::JsonCodec::HandlerBase*>,
>>>>> std::__detail::_Select1st, capnp::(anonymous namespace)::TypeHash,
>>>>> std::__detail::_Mod_range_hashing, std::__detail::_Default_ranged_hash,
>>>>> true>::_M_h1() const ()
>>>>> #2 0x0000000001e4a976 in std::__detail::_Hash_code_base<capnp::Type,
>>>>> std::pair<capnp::Type const, capnp::JsonCodec::HandlerBase*>,
>>>>> std::__detail::_Select1st, capnp::(anonymous namespace)::TypeHash,
>>>>> std::__detail::_Mod_range_hashing, std::__detail::_Default_ranged_hash,
>>>>> true>::_M_hash_code(capnp::Type const&) const ()
>>>>> #3 0x0000000001e4a401 in std::_Hashtable<capnp::Type,
>>>>> std::pair<capnp::Type const, capnp::JsonCodec::HandlerBase*>,
>>>>> std::allocator<std::pair<capnp::Type const,
>>>>> capnp::JsonCodec::HandlerBase*>
>>>>> >, std::__detail::_Select1st, std::equal_to<capnp::Type>,
>>>>> >capnp::(anonymous
>>>>> namespace)::TypeHash, std::__detail::_Mod_range_hashing,
>>>>> std::__detail::_Default_ranged_hash, std::__detail::_Prime_rehash_policy,
>>>>> std::__detail::_Hashtable_traits<true, false, true> >::find(capnp::Type
>>>>> const&) const ()
>>>>> #4 0x0000000001e483a3 in std::unordered_map<capnp::Type,
>>>>> capnp::JsonCodec::HandlerBase*, capnp::(anonymous namespace)::TypeHash,
>>>>> std::equal_to<capnp::Type>, std::allocator<std::pair<capnp::Type const,
>>>>> capnp::JsonCodec::HandlerBase*> > >::find(capnp::Type const&) const ()
>>>>> #5 0x0000000001e443d5 in
>>>>> capnp::JsonCodec::encode(capnp::DynamicValue::Reader, capnp::Type,
>>>>> capnp::JsonValue::Builder) const ()
>>>>> #6 0x0000000001e44a6f in
>>>>> capnp::JsonCodec::encode(capnp::DynamicValue::Reader, capnp::Type,
>>>>> capnp::JsonValue::Builder) const ()
>>>>> #7 0x0000000001e45a36 in
>>>>> capnp::JsonCodec::encodeField(capnp::StructSchema::Field,
>>>>> capnp::DynamicValue::Reader, capnp::JsonValue::Builder) const ()
>>>>> #8 0x0000000001e45377 in
>>>>> capnp::JsonCodec::encode(capnp::DynamicValue::Reader, capnp::Type,
>>>>> capnp::JsonValue::Builder) const ()
>>>>> #9 0x0000000001e45a36 in
>>>>> capnp::JsonCodec::encodeField(capnp::StructSchema::Field,
>>>>> capnp::DynamicValue::Reader, capnp::JsonValue::Builder) const ()
>>>>> #10 0x0000000001e45377 in
>>>>> capnp::JsonCodec::encode(capnp::DynamicValue::Reader, capnp::Type,
>>>>> capnp::JsonValue::Builder) const ()
>>>>> #11 0x0000000001e45a36 in
>>>>> capnp::JsonCodec::encodeField(capnp::StructSchema::Field,
>>>>> capnp::DynamicValue::Reader, capnp::JsonValue::Builder) const ()
>>>>> #12 0x0000000001e45377 in
>>>>> capnp::JsonCodec::encode(capnp::DynamicValue::Reader, capnp::Type,
>>>>> capnp::JsonValue::Builder) const ()
>>>>> #13 0x0000000001e45a36 in
>>>>> capnp::JsonCodec::encodeField(capnp::StructSchema::Field,
>>>>> capnp::DynamicValue::Reader, capnp::JsonValue::Builder) const ()
>>>>> #14 0x0000000001e45618 in
>>>>> capnp::JsonCodec::encode(capnp::DynamicValue::Reader, capnp::Type,
>>>>> capnp::JsonValue::Builder) const ()
>>>>> #15 0x0000000001e45a36 in
>>>>> capnp::JsonCodec::encodeField(capnp::StructSchema::Field,
>>>>> capnp::DynamicValue::Reader, capnp::JsonValue::Builder) const ()
>>>>> #16 0x0000000001e45618 in
>>>>> capnp::JsonCodec::encode(capnp::DynamicValue::Reader, capnp::Type,
>>>>> capnp::JsonValue::Builder) const ()
>>>>> #17 0x0000000001e43fcc in
>>>>> capnp::JsonCodec::encode(capnp::DynamicValue::Reader, capnp::Type) const
>>>>> ()
>>>>> #18 0x00000000009e02c7 in capnp::JsonCodec::encode<Message::Builder
>>>>> const&> (this=0x7ffff22e1210, value=...) at
>>>>> /home/marc/.../capnp/compat/json.h:216
>>>>> ```
>>>>>
>>>>> That's about all that I can get, even though capnproto is compiled
>>>>> with DEBUG.
>>>>>
>>>>> The message trying to be encoded (sorry, I am not sure I can share the
>>>>> entire set of schemas), is a series of simple objects, which in the
>>>>> inner-most object contains a list that is initialized normally:
>>>>>
>>>>> 115 s.initIfaceType(1);
>>>>>
>>>>> The funny part; not initializing it, doesn't make JsonCodec crash. But
>>>>> initializing it, or initializing it + setting a value (valid one),
>>>>> produces
>>>>> the crash always.
>>>>>
>>>>> Valgrind etc... doesn't complain until that point.
>>>>>
>>>>> I am trying to isolate the problem, to make it reproducible, but I am
>>>>> not able yet.
>>>>>
>>>>> Any ideas on this?
>>>>>
>>>>> Thanks
>>>>>
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