Mutate function produced an error

Hi,

I wrote a parser function P, a renderer function R and try to use the mutate function.

Given an input I, if I call m = P(I), and J = R(m), I am able to produce a string J = I.

If I have m = P(I), mutator.Mutate(&m, 100), J = R(m), at execution, mutator.Mutate(&m, 100) would produce a system error. The message is:

#########################################
terminate called after throwing an instance of 'std::system_error'
what(): Unknown error -1
Aborted (core dumped)
##########################################

I installed libprotobuf-mutator two years ago, and the mutator worked fine. Using the recent version, I got this error. I am not sure why I received this error.

Here is the stack trace:
################################################################
#0 __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:51
#1 0x00007f8ecaeb6801 in __GI_abort () at abort.c:79
#2 0x00007f8ecb50b957 in ?? () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#3 0x00007f8ecb511ab6 in ?? () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#4 0x00007f8ecb511af1 in std::terminate() ()
from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#5 0x00007f8ecb511d24 in __cxa_throw ()
from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#6 0x00007f8ecb50da19 in ?? () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#7 0x00007f8ecb97dce3 in std::call_once (
__f=@0x7f8ecb988800: {void (const google::protobuf::internal::DescriptorTable *)} 0x7f8ecb988800 , __once=...)
at /usr/include/c++/7/mutex:698
#8 google::protobuf::internal::AssignDescriptors (table=)
at google/protobuf/generated_message_reflection.cc:2407
#9 0x00005622487fa7dd in input::Group::GetMetadataStatic() ()
#10 0x00005622487f3b85 in input::Group::GetMetadata() const ()
#11 0x000056224880e6f9 in google::protobuf::Message::GetDescriptor() const ()
#12 0x0000562248808ebe in protobuf_mutator::(anonymous namespace)::MutationSampler::Sample(google::protobuf::Message*) ()
#13 0x0000562248808dfb in protobuf_mutator::(anonymous namespace)::MutationSampl---Type to continue, or q to quit---return
er::MutationSampler(bool, std::linear_congruential_engine*, google::protobuf::Message*) ()
#14 0x0000562248809e59 in protobuf_mutator::Mutator::MutateImpl(google::protobuf::Message*, unsigned long) ()
#15 0x0000562248809b51 in protobuf_mutator::Mutator::Mutate(google::protobuf::Message*, unsigned long) ()
#16 0x00005622487a8c92 in main ()
#########################################################

Thanks!