Re: Protobuf string serialization bug with statically linked protobuf 2.5.0

[Tomasz Wiszkowski <tomasz.wiszkowski@gmail.com>]

I gather this package bug is not exactly interesting here, but i'll
share a final update.

The package is likely built inaccurately, or is linked against library
that changed ABI over time.

Downloading and compiling protocol buffers library manually does not
expose any of the serialization problems.
furthermore, manual compilation does not introduce an artificial
dependency on cygprotobuf.dll library.

the protobuf package needs to be rebuilt.

thank you for your attention, i will not be disturbing the list with
further updates.

--
"My definition of an expert in any field is a person who knows enough
about what's really going on to be scared" - P. J. Plauger


2016-02-11 15:20 GMT-08:00 Tomasz Wiszkowski <tomasz.wiszkowski@gmail.com>:
> A brief correction.
>
> I tried to identify further the problem by selectively linking
> libraries. (-Wl,-Bstatic -lprotobuf.dll -Wl,-Bdynamic) and it turns
> out the problem emerges the moment i statically link both protobuf
> _and_ the c++ library. linking everything statically except for libc++
> seems to work just fine.
>
> i checked if protobuf loads cygc++-6 separately, which would easily
> explain the problem, but it does not seem to. the problem clearly
> seems to be interaction between these two.
>
> linking libc++ dynamically resolves the problem, but that would also
> mean shipping the software with artificial add-on... i suspect
> recompilation still might resolve the issue...
>
>
> --
> "My definition of an expert in any field is a person who knows enough
> about what's really going on to be scared" - P. J. Plauger
>
>
> 2016-02-10 10:54 GMT-08:00 Tomasz Wiszkowski <tomasz.wiszkowski@gmail.com>:
>> Dear all,
>>
>> I'm having problems with statically linked executables that use
>> protocol buffers.
>> I suspect the problem may be related to incompatibility between
>> std::string implementation used to compile the library vs. current. If
>> that's the case, the problem would likely go away with recompilation
>> of the protocol buffer libraries (protobuf-lite is also exposing the
>> same problem).
>>
>> I have attached a test case as you requested. the example program
>> compiles two variants - one dynamically linked (works fine) and one
>> statically linked that crashes upon first attempt to serialize the
>> protocol buffer.
>>
>> It would be great if someone could take a look and possibly rebuild
>> the static libraries for protocol buffers.
>>
>> Best regards,
>> Tomasz
>>
>> -------- example.proto ------------
>> syntax = "proto2";
>>
>> package example;
>>
>> message ExampleMsg {
>>   optional int32 argc = 1;
>>   optional string argv0 = 2;
>> };
>>
>> -------- main.cc ------------
>> #include <iostream>
>> #include <string>
>>
>> #include "example.pb.h"
>>
>> int main(int argc, char** argv) {
>>   example::ExampleMsg message;
>>
>>   message.set_argc(argc);
>>   message.set_argv0(argv[0]);
>>
>>   std::cout << "Serializing protocol buffer." << std::endl;
>>   std::string serialized;
>>   message.SerializeToString(&serialized);  // static variant crashes here.
>>   std::cout << "Serialized length: " << serialized.length() << std::endl;
>>
>>   message.Clear();
>>
>>   std::cout << "Deserializing protocol buffer." << std::endl;
>>   message.ParseFromString(serialized);  // static variant also crashes here.
>>   std::cout << "Deserialized content: argc=" << message.argc() << ", argv0="
>>             << message.argv0();
>>
>>   return 0;
>> }
>>
>> -------- Makefile ------------
>> CFLAGS += -Wall
>> CXXFLAGS := $(CFLAGS)
>> CC = g++
>> LIBS = -lprotobuf.dll
>>
>> all: clean example example-bug
>>
>> example.pb.cc: example.proto
>>         protoc --cpp_out=. $^
>>
>> clean:
>>         rm -f *.o *.pb.* *.exe*
>>
>> example: example.pb.o main.o
>>         $(CC) $(CFLAGS) $^ -o $@ $(LIBS)
>>
>> example-bug: example.pb.o main.o
>>         $(CC) $(CFLAGS) -static $^ -o $@ $(LIBS)

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