C terminate called without an active exception

Question

I am getting a C   error with threading   terminate called without an active exception Aborted   Here is the code    include  lt queue gt   include  lt thread gt   include  lt mutex gt   include  lt condition variable gt   template lt typename TYPE gt  class blocking stream   public      blocking stream size t max buffer size               max buffer size max buffer size                         PUSH data into the buffer     blocking stream  amp operator lt  lt  TYPE  amp other                std  unique lock lt std  mutex gt  mtx lock mtx            while buffer size   gt  max buffer size              stop if full wait mtx lock            buffer push std  move other             mtx lock unlock            stop if empty notify one            return  this              POP data out of the buffer      blocking stream  amp operator gt  gt  TYPE  amp other                std  unique lock lt std  mutex gt  mtx lock mtx           while buffer empty                stop if empty wait mtx lock            other swap buffer front              buffer pop             mtx lock unlock            stop if full notify one            return  this         private      size t max buffer size      std  queue lt TYPE gt  buffer      std  mutex mtx      std  condition variable stop if empty                              stop if full      bool eof          I modeled my code around this example  http   www justsoftwaresolutions co uk threading implementing-a-thread-safe-queue-using-condition-variables html  What am I doing wrong and how do I fix the error

User · Answer

First you define a thread  And if you never call join   or detach   before calling the thread destructor  the program will abort   As follows  calling a thread destructor without first calling join  to wait for it to finish  or detach is guarenteed to immediately call std  terminate and end the program      Either implicitly detaching or joining a joinable   thread in its   destructor could result in difficult to debug correctness  for detach    or performance  for join  bugs encountered only when an exception is   raised  Thus the programmer must ensure that the destructor is never   executed while the thread is still joinable

User · Answer

When a thread object goes out of scope and it is in joinable state  the program is terminated  The Standard Committee had two other options for the destructor of a joinable thread  It could quietly join -- but join might never return if the thread is stuck  Or it could detach the thread  a detached thread is not joinable   However  detached threads are very tricky  since they might survive till the end of the program and mess up the release of resources  So if you don t want to terminate your program  make sure you join  or detach  every thread

User · Answer

How to reproduce that error    include  lt iostream gt   include  lt stdlib h gt   include  lt string gt   include  lt thread gt  using namespace std  void task1 std  string msg     cout  lt  lt   task1 says     lt  lt  msg    int main        std  thread t1 task1   hello       return 0      Compile and run   el defiant   foo4 39 threading   g   -o s s cpp -pthread -std c  11 el defiant   foo4 39 threading     s terminate called without an active exception Aborted  core dumped    You get that error because you didn t join or detach your thread     One way to fix it  join the thread like this    include  lt iostream gt   include  lt stdlib h gt   include  lt string gt   include  lt thread gt  using namespace std  void task1 std  string msg     cout  lt  lt   task1 says     lt  lt  msg    int main        std  thread t1 task1   hello       t1 join      return 0      Then compile and run   el defiant   foo4 39 threading   g   -o s s cpp -pthread -std c  11 el defiant   foo4 39 threading     s task1 says  hello   The other way to fix it  detach it like this    include  lt iostream gt   include  lt stdlib h gt   include  lt string gt   include  lt unistd h gt   include  lt thread gt  using namespace std  void task1 std  string msg     cout  lt  lt   task1 says     lt  lt  msg    int main                       std  thread t1 task1   hello             t1 detach              thread handle is destroyed here  as goes out of scope        usleep 1000000     wait so that hello can be printed      Compile and run    el defiant   foo4 39 threading   g   -o s s cpp -pthread -std c  11 el defiant   foo4 39 threading     s task1 says  hello   Read up on detaching C   threads and joining C   threads

User · Answer

Eric Leschinski and Bartosz Milewski have given the answer already  Here  I will try to present it in a more beginner friendly manner   Once a thread has been started within a scope  which itself is running on a thread   one must explicitly ensure one of the following happens before the thread goes out of scope    The runtime exits the scope  only after that thread finishes executing  This is achieved by joining with that thread  Note the language  it is the outer scope that joins with that thread  The runtime leaves the thread to run on its own  So  the program will exit the scope  whether this thread finished executing or not  This thread executes and exits by itself  This is achieved by detaching the thread  This could lead to issues  for example  if the thread refers to variables in that outer scope    Note  by the time the thread is joined with or detached  it may have well finished executing  Still either of the two operations must be performed explicitly

User · Answer

year  the thread must be join    when the main exit

User · Answer

As long as your program die  then without detach or join of the thread  this error will occur  Without detaching and joining the thread  you should give endless loop after creating thread   int main     std  thread t thread 1    while 1       t detach    return 0     It is also interesting that  after sleeping or looping  thread can be detach or join  Also with this way you do not get this error    Below example also shows that  third thread can not done his job before main die  But this error can not happen also  as long as you detach somewhere in the code   Third thread sleep for 8 seconds but main will die in 5 seconds   void thread int n   std  this thread  sleep for  std  chrono  seconds n      int main     std  cout  lt  lt   Start main n   std  thread t thread 1   std  thread t2 thread 3   std  thread t3 thread 8   sleep 5    t detach    t2 detach    t3 detach    return 0

[c++] C++ terminate called without an active exception

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