stop-the-world

LD_PRELOAD base library for stopping(send SIGTSTP) the program before starting main()

for what?

• lazy gdb attach pid
• get pid for pmap to see memory mapping
• to set pid to tasks file of cgroup

how to run

# linux
LD_PRELOAD=./target/debug/libstop_the_world.so ls
# darwin
DYLD_FORCE_FLAT_NAMESPACE=1 DYLD_INSERT_LIBRARIES=./target/debug/libstop_the_world.dylib ls

# if your environment has no output log of background process pid, set below environment variable
STOP_THE_WORLD_PIDFILE=$(tty)

# environment variable
STOP_THE_WORLD_INIT=1 # (default is enable)
STOP_THE_WORLD_TERM=0 # (default is disable)
STOP_THE_WORLD_PIDFILE="" # (default is no output)

how to send SIGCONT signal

fg
# or
kill -SIGCONT $PID
# or
pkill -SIGCONT $PNAME

FYI

• some rust program: NG(no sleep)
• some c++ program: OK
• kill -SIGSEGV to sleep: OK

#include <chrono>
#include <csignal>
#include <thread>

void segv_handler(int sig) {
  std::this_thread::sleep_for(std::chrono::seconds(3600 * 24));
}

namespace internal {
struct Segvstop {
  Segvstop() {
    struct sigaction sa;
    sa.sa_flags   = 0;
    sa.sa_handler = segv_handler;
    sigemptyset(&sa.sa_mask);
    sigaction(SIGSEGV, &sa, nullptr);
  }
  ~Segvstop() {}
};

static Segvstop segvstop;
}  // namespace internal

---

gdb上で再現しないセグフォをgdbで追跡する - Qiita

darwin

g++ -shared -fPIC -std=c++11 segvstop.cpp -o libsegvstop.dylib
DYLD_FORCE_FLAT_NAMESPACE=1 DYLD_INSERT_LIBRARIES=./libsegvstop.dylib XXX