Make initialization for the "err" library into a subsystem.

src/app/main/main.c

@@ -69,7 +69,6 @@
 #include "lib/container/buffers.h"
 #include "lib/crypt_ops/crypto_rand.h"
 #include "lib/crypt_ops/crypto_s2k.h"
-#include "lib/err/backtrace.h"
 #include "lib/geoip/geoip.h"
 
 #include "lib/process/waitpid.h"
@@ -822,7 +821,6 @@ tor_free_all(int postfork)
   if (!postfork) {
     escaped(NULL);
     esc_router_info(NULL);
-    clean_up_backtrace_handler();
     logs_free_all(); /* free log strings. do this last so logs keep working. */
   }
 }
@@ -1419,14 +1417,6 @@ tor_run_main(const tor_main_configuration_t *tor_cfg)
 #endif /* !defined(_WIN64) */
 #endif /* defined(_WIN32) */
 
-  {
-    int bt_err = configure_backtrace_handler(get_version());
-    if (bt_err < 0) {
-      log_warn(LD_BUG, "Unable to install backtrace handler: %s",
-               strerror(-bt_err));
-    }
-  }
-
 #ifdef EVENT_SET_MEM_FUNCTIONS_IMPLEMENTED
   event_set_mem_functions(tor_malloc_, tor_realloc_, tor_free_);
 #endif

src/app/main/subsystem_list.c

@@ -8,13 +8,15 @@
 #include "lib/cc/compat_compiler.h"
 #include "lib/cc/torint.h"
 
+#include "lib/err/torerr_sys.h"
+
 #include <stddef.h>
 
 /**
  * Global list of the subsystems in Tor, in the order of their initialization.
  **/
 const subsys_fns_t *tor_subsystems[] = {
-   NULL // placeholder.
+  &sys_torerr,
 };
 
 const unsigned n_tor_subsystems = ARRAY_LENGTH(tor_subsystems);

src/lib/err/.may_include

@@ -1,3 +1,5 @@
 orconfig.h
 lib/cc/*.h
 lib/err/*.h
+lib/subsys/*.h
+lib/version/*.h

src/lib/err/include.am

@@ -7,7 +7,8 @@ endif
 
 src_lib_libtor_err_a_SOURCES =			\
 	src/lib/err/backtrace.c			\
-	src/lib/err/torerr.c
+	src/lib/err/torerr.c			\
+	src/lib/err/torerr_sys.c
 
 src_lib_libtor_err_testing_a_SOURCES = \
 	$(src_lib_libtor_err_a_SOURCES)
@@ -16,4 +17,5 @@ src_lib_libtor_err_testing_a_CFLAGS = $(AM_CFLAGS) $(TEST_CFLAGS)
 
 noinst_HEADERS +=					\
 	src/lib/err/backtrace.h				\
-	src/lib/err/torerr.h
+	src/lib/err/torerr.h				\
+	src/lib/err/torerr_sys.h

src/lib/err/torerr.c

@@ -122,6 +122,16 @@ tor_log_set_sigsafe_err_fds(const int *fds, int n)
   n_sigsafe_log_fds = n;
 }
 
+/**
+ * Reset the list of emergency error fds to its default.
+ */
+void
+tor_log_reset_sigsafe_err_fds(void)
+{
+  int fds[] = { STDERR_FILENO };
+  tor_log_set_sigsafe_err_fds(fds, 1);
+}
+
 /**
  * Set the granularity (in ms) to use when reporting fatal errors outside
  * the logging system.

src/lib/err/torerr.h

@@ -39,6 +39,7 @@ void tor_raw_assertion_failed_msg_(const char *file, int line,
 void tor_log_err_sigsafe(const char *m, ...);
 int tor_log_get_sigsafe_err_fds(const int **out);
 void tor_log_set_sigsafe_err_fds(const int *fds, int n);
+void tor_log_reset_sigsafe_err_fds(void);
 void tor_log_sigsafe_err_set_granularity(int ms);
 
 int format_hex_number_sigsafe(unsigned long x, char *buf, int max_len);

src/lib/err/torerr_sys.c

@@ -0,0 +1,39 @@
+/* Copyright (c) 2018, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+/**
+ * \file torerr_sys.c
+ * \brief Subsystem object for the error handling subsystem.
+ **/
+
+#include "orconfig.h"
+#include "lib/err/backtrace.h"
+#include "lib/err/torerr.h"
+#include "lib/err/torerr_sys.h"
+#include "lib/subsys/subsys.h"
+#include "lib/version/torversion.h"
+
+#include <stddef.h>
+
+static int
+torerr_subsys_init(void)
+{
+  configure_backtrace_handler(get_version());
+  tor_log_reset_sigsafe_err_fds();
+
+  return 0;
+}
+static void
+torerr_subsys_shutdown(void)
+{
+  tor_log_reset_sigsafe_err_fds();
+  clean_up_backtrace_handler();
+}
+
+const subsys_fns_t sys_torerr = {
+  .name = "err",
+  .level = -100,
+  .supported = true,
+  .initialize = torerr_subsys_init,
+  .shutdown = torerr_subsys_shutdown
+};

src/lib/err/torerr_sys.h

@@ -0,0 +1,14 @@
+/* Copyright (c) 2018, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+/**
+ * \file torerr_sys.h
+ * \brief Declare subsystem object for torerr.c
+ **/
+
+#ifndef TOR_TORERR_SYS_H
+#define TOR_TORERR_SYS_H
+
+extern const struct subsys_fns_t sys_torerr;
+
+#endif /* !defined(TOR_TORERR_SYS_H) */