reused rosbag::Bag instance crashes

[denwi248]

I'm on Ubuntu 16.04 with ros kinetic 1.12.14.

A minimal reproducible example is:

#include <rosbag/bag.h>
#include <rosbag/view.h>
#include <std_msgs/Int32.h>

rosbag::Bag bag;

// generate first bag file
bag.open("test.bag", rosbag::bagmode::Write);

std_msgs::Int32 msg;

for ( unsigned int i = 0; i < 10; ++i ) {
    msg.data = i;
    bag.write("numbers", ros::Time::now(), msg);
}

bag.close();

// generate second bag file
bag.open("test2.bag", rosbag::bagmode::Write);

for ( unsigned int i = 10; i < 20; ++i ) {
    msg.data = i;
    bag.write("numbers2", ros::Time::now(), msg);
}

bag.close();

// read in first bag file
bag.open("test.bag", rosbag::bagmode::Read);

for ( rosbag::MessageInstance const m : rosbag::View(bag) ) {
    std_msgs::Int32::ConstPtr i = m.instantiate<std_msgs::Int32>();
    if ( i != nullptr )
      std::cout << "bag1: " << i->data << std::endl;
}

bag.close();

// read in second bag file
bag.open("test2.bag", rosbag::bagmode::Read);

for ( rosbag::MessageInstance const m : rosbag::View(bag) ) {
    std_msgs::Int32::ConstPtr i = m.instantiate<std_msgs::Int32>();
    if ( i != nullptr )
      std::cout << "bag2: " << i->data << std::endl;
}

bag.close();

I create two bag files and want to read them in later. All with the same rosbag::Bag instance. This works until I open the second bag file and crashes with the error message:

Error: Received an invalid TCPROS header. Each element must be prepended by a 4-byte length.
at line 88 in /tmp/binarydeb/ros-kinetic-cpp-common-0.6.11/src/header.cpp
terminate called after throwing an instance of 'rosbag::BagFormatException'
what(): Error parsing header

I found a workaround by using a new instance of rosbag::Bag for the second rosbag file. This is working as expected.

Strange side note:
when I change the topic name in the second bag file from numbers2 to numbers, then it does not crash but it is printing two times numbers from 0-9 instead 0-9 and 10-19. So it looks like it has opened the first bag file again.

[racko]

Fixed in lunar: #1192

[denwi248]

Thanks for the hint. Will that fix be ported to kinetic, too?

[racko]

The PR is referenced by changes between 1.12.7 and 1.13.4 for backporting. There, #1192 is listed as "Not backported":

patch would require other changes to be backported or patch to be rewritten

[dirk-thomas]

I will close this ticket for now since as mentioned above the necessary changes aren't available in Kinetic.