implement __set_backtrace_on_abort and define more operators for pthr…

…ead_t (#57)

* src: implement __set_backtrace_on_abort(true|false)

This is to avoid zoslib's abort() from calling
__display_backtrace() if the current process already
had function in place that does that (so avoid a
duplicate backtrace from being output).

* include: define operators for pthread_t ==|!= int

include/zos-base.h

@@ -149,6 +149,11 @@ int gettid();
  */
 void __display_backtrace(int fd);
 
+/**
+ * Enable or disable abort() from calling display_backtrace(). Default is true.
+ */
+void __set_backtrace_on_abort(bool flag);
+
 /**
  * Execute a file.
  * \param [in] name used to construct a pathname that identifies the new
@@ -578,6 +583,12 @@ inline bool operator<(const pthread_t &_a, const pthread_t &_b) {
 inline bool operator>(const pthread_t &_a, const pthread_t &_b) {
   return _a.__ > _b.__;
 }
+inline bool operator==(const pthread_t &_a, const int _b) {
+  return _a.__ == static_cast<unsigned long long>(_b);
+}
+inline bool operator!=(const pthread_t &_a, const int _b) {
+  return _a.__ != static_cast<unsigned long long>(_b);
+}
 
 struct zoslibEnvar {
   std::string envarName;

src/zos.cc

@@ -64,6 +64,7 @@ static char **__argv = nullptr;
 static int __argc = -1;
 static pthread_t _timer_tid;
 static int *__main_thread_stack_top_address = 0;
+static bool __is_backtrace_on_abort = true;
 
 #if defined(BUILD_VERSION)
 const char *__zoslib_version = BUILD_VERSION;
@@ -659,11 +660,17 @@ extern "C" void *__dlcb_entry_addr(void *dlcb) {
 }
 
 extern "C" void abort(void) {
-  __display_backtrace(STDERR_FILENO);
+  if (__is_backtrace_on_abort) {
+    __display_backtrace(STDERR_FILENO);
+  }
   __zinit::getInstance()->__abort();
   exit(-1); // never reach here, suppress clang warning
 }
 
+extern "C" void __set_backtrace_on_abort(bool flag) {
+  __is_backtrace_on_abort = flag;
+}
+
 int __cond_timed_wait(unsigned int secs, unsigned int nsecs,
                       unsigned int event_list, unsigned int *secs_rem,
                       unsigned int *nsecs_rem) {