When does a process get SIGABRT signal 6

Question

What are the scenarios where a process gets a SIGABRT in C     Does this signal always come from within the process or can this signal be sent from one process to another   Is there a way to identify which process is sending this signal

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It usually happens when there is a problem with memory allocation    It happened to me when my program was trying to allocate an array with negative size

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abort   sends the calling process the SIGABRT signal  this is how abort   basically works    abort   is usually called by library functions which detect an internal error or some seriously broken constraint  For example malloc   will call abort   if its internal structures are damaged by a heap overflow

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Regarding the first question  What are the scenarios where a process gets a SIGABRT in C    I can think of two special cases where a C   program is aborted automatically -- not by directly calling std  abort   or std  terminate    One  Throw an exception while an exception is being handled  try       throw  quot abc quot     catch             throw  quot def quot       abort here    Two  An uncaught exception that attempts to propagates outside main    int main int argc  char   argv        throw  quot abc quot       abort here    C   experts could probably name more special cases  There is also a lot of good info on these reference pages   https   en cppreference com w cpp utility program abort https   en cppreference com w cpp error terminate

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As   sarnold   aptly pointed out  any process can send signal to any other process  hence  one process can send SIGABORT to other process  amp  in that case the receiving process is unable to distinguish whether its coming because of its own tweaking of memory etc  or someone else has  unicastly   send to it   In one of the systems I worked there is one deadlock detector which actually detects if process is coming out of some task by giving heart beat or not  If not  then it declares the process is in deadlock state and sends SIGABORT to it   I just wanted to share this prospective with reference to question asked

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SIGABRT is commonly used by libc and other libraries to abort the program in case of critical errors  For example  glibc sends an SIGABRT in case of a detected double-free or other heap corruptions   Also  most assert implementations make use of SIGABRT in case of a failed assert   Furthermore  SIGABRT can be sent from any other process like any other signal  Of course  the sending process needs to run as same user or root

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There s another simple cause in case of c     std  thread   thread      if  joinable             std  terminate         i e  scope of thread ended but you forgot to call either   thread  join      or  thread  detach

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The GNU libc will print out information to  dev tty regarding some fatal conditions before it calls abort    which then triggers SIGABRT   but if you are running your program as a service or otherwise not in a real terminal window  these message can get lost  because there is no tty to display the messages    See my post on redirecting libc to write to stderr instead of  dev tty   Catching libc error messages  redirecting from  dev tty

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I will give my answer from a competitive programming cp  perspective  but it applies to other domains as well  Many a times while doing cp  constraints are quite large  For example   I had a question with a variables N  M  Q such that 1   N  M  Q  lt  10 5  The mistake I was making was I declared a 2D integer array of size 10000 x 10000 in C   and struggled with the SIGABRT error at Codechef for almost 2 days  Now  if we calculate    Typical size of an integer   4 bytes No  of cells in our array   10000 x 10000 Total size  in bytes    400000000 bytes   4 10 8    400 MB  Your solutions to such questions will work on your PC not always  as it can afford this size  But the resources at coding sites online judges  is limited to few KBs  Hence  the SIGABRT error and other such errors  Conclusion  In such questions  we ought not to declare an array or vector or any other DS of this size  but our task is to make our algorithm such efficient that it works without them DS  or with less memory  PS   There might be other reasons for this error  above was one of them

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You can send any signal to any process using the kill 2  interface   kill -SIGABRT 30823  30823 was a dash process I started  so I could easily find the process I wanted to kill      bin dash   Aborted   The Aborted output is apparently how dash reports a SIGABRT   It can be sent directly to any process using kill 2   or a process can send the signal to itself via assert 3   abort 3   or raise 3

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In my case  it was due to an input in an array at an index equal to the length of the  array   string x 5    for int i 1  i lt  5  i          cin gt  gt x i        x 5  is being accessed which is not present

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A case when process get SIGABRT from itself  Hrvoje mentioned about a buried pure virtual being called from ctor generating an abort  i recreated an example for this  Here when d is to be constructed  it first calls its base class A ctor  and passes inside pointer to itself  the A ctor calls pure virtual method before table was filled with valid pointer   because d is not constructed yet    include lt iostream gt  using namespace std  class A   public   A A  pa  pa- gt f      virtual void f   0     class D   public A   public   D   A this     virtual void f    cout lt  lt  D  f n       int main     D d   A  pa    amp d   pa- gt f     return 0      compile  g   -o aa aa cpp  ulimit -c unlimited  run    aa  pure virtual method called terminate called without an active exception Aborted  core dumped    now lets quickly see the core file  and validate that SIGABRT was indeed called   gdb aa core   see regs   i r rdx            0x6      6 rsi            0x69a    1690 rdi            0x69a    1690 rip            0x7feae3170c37   check code   disas 0x7feae3170c37  mov     0xea  eax    234   lt - this is the kill syscall  sends signal to process syscall    lt -----   http   blog rchapman org posts Linux System Call Table for x86 64   234 sys tgkill  pid t tgid  pid t pid   int sig   6   SIGABRT

[c++] When does a process get SIGABRT (signal 6)?

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