1 files changed, 29 insertions, 15 deletions

diff --git a/src/common/backtrace.c b/src/common/backtrace.c
index 3a073a8ff5..3b762b68e3 100644
--- a/src/common/backtrace.c
+++ b/src/common/backtrace.c
@@ -1,6 +1,18 @@
-/* Copyright (c) 2013, The Tor Project, Inc. */
+/* Copyright (c) 2013-2016, The Tor Project, Inc. */
 /* See LICENSE for licensing information */
 
+/**
+ * \file backtrace.c
+ *
+ * \brief Functions to produce backtraces on bugs, crashes, or assertion
+ * failures.
+ *
+ * Currently, we've only got an implementation here using the backtrace()
+ * family of functions, which are sometimes provided by libc and sometimes
+ * provided by libexecinfo.  We tie into the sigaction() backend in order to
+ * detect crashes.
+ */
+
 #define __USE_GNU
 #define _GNU_SOURCE 1
 
@@ -62,16 +74,16 @@ static tor_mutex_t cb_buf_mutex;
  * ucontext_t structure.
  */
 void
-clean_backtrace(void **stack, int depth, const ucontext_t *ctx)
+clean_backtrace(void **stack, size_t depth, const ucontext_t *ctx)
 {
 #ifdef PC_FROM_UCONTEXT
 #if defined(__linux__)
-  const int n = 1;
+  const size_t n = 1;
 #elif defined(__darwin__) || defined(__APPLE__) || defined(__OpenBSD__) \
   || defined(__FreeBSD__)
-  const int n = 2;
+  const size_t n = 2;
 #else
-  const int n = 1;
+  const size_t n = 1;
 #endif
   if (depth <= n)
     return;
@@ -80,6 +92,7 @@ clean_backtrace(void **stack, int depth, const ucontext_t *ctx)
 #else
   (void) depth;
   (void) ctx;
+  (void) stack;
 #endif
 }
 
@@ -88,14 +101,14 @@ clean_backtrace(void **stack, int depth, const ucontext_t *ctx)
 void
 log_backtrace(int severity, int domain, const char *msg)
 {
-  int depth;
+  size_t depth;
   char **symbols;
-  int i;
+  size_t i;
 
   tor_mutex_acquire(&cb_buf_mutex);
 
   depth = backtrace(cb_buf, MAX_DEPTH);
-  symbols = backtrace_symbols(cb_buf, depth);
+  symbols = backtrace_symbols(cb_buf, (int)depth);
 
   tor_log(severity, domain, "%s. Stack trace:", msg);
   if (!symbols) {
@@ -119,7 +132,7 @@ static void
 crash_handler(int sig, siginfo_t *si, void *ctx_)
 {
   char buf[40];
-  int depth;
+  size_t depth;
   ucontext_t *ctx = (ucontext_t *) ctx_;
   int n_fds, i;
   const int *fds = NULL;
@@ -138,7 +151,7 @@ crash_handler(int sig, siginfo_t *si, void *ctx_)
 
   n_fds = tor_log_get_sigsafe_err_fds(&fds);
   for (i=0; i < n_fds; ++i)
-    backtrace_symbols_fd(cb_buf, depth, fds[i]);
+    backtrace_symbols_fd(cb_buf, (int)depth, fds[i]);
 
   abort();
 }
@@ -173,8 +186,8 @@ install_bt_handler(void)
      * libc has pre-loaded the symbols we need to dump things, so that later
      * reads won't be denied by the sandbox code */
     char **symbols;
-    int depth = backtrace(cb_buf, MAX_DEPTH);
-    symbols = backtrace_symbols(cb_buf, depth);
+    size_t depth = backtrace(cb_buf, MAX_DEPTH);
+    symbols = backtrace_symbols(cb_buf, (int) depth);
     if (symbols)
       free(symbols);
   }
@@ -214,9 +227,10 @@ int
 configure_backtrace_handler(const char *tor_version)
 {
   tor_free(bt_version);
-  if (!tor_version)
-    tor_version = "";
-  tor_asprintf(&bt_version, "Tor %s", tor_version);
+  if (tor_version)
+    tor_asprintf(&bt_version, "Tor %s", tor_version);
+  else
+    tor_asprintf(&bt_version, "Tor");
 
   return install_bt_handler();
 }