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Date:	Thu, 11 Feb 2016 15:20:06 -0800
Message-ID:	<CAPqrHhqeBD1ho_CFjUTHT+NbZnftrKJ0Qj9+OEuXBMf2BWU2Xw@mail.gmail.com>
Subject:	Re: Protobuf string serialization bug with statically linked protobuf 2.5.0
From:	Tomasz Wiszkowski <tomasz DOT wiszkowski AT gmail DOT com>
To:	cygwin AT cygwin DOT 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 DOT wiszkowski AT gmail DOT 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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