cmake,common: flag for stack trace

By default the flag is enabled whenever libunwind is found on the
system, with the exception of static build on OSX (for which we can't
install the throw hook #932 due to lack of support for --wrap in OSX
ld64 linker).

src/common/CMakeLists.txt

@@ -31,8 +31,11 @@ set(common_sources
   command_line.cpp
   dns_utils.cpp
   util.cpp
-  i18n.cpp
-  stack_trace.cpp)
+  i18n.cpp)
+
+if (STACK_TRACE)
+  list(APPEND common_sources stack_trace.cpp)
+endif()
 
 set(common_headers)
 

src/common/stack_trace.cpp

@@ -28,10 +28,8 @@
 
 #include "common/stack_trace.h"
 #include "misc_log_ex.h"
-#ifdef HAVE_LIBUNWIND
 #define UNW_LOCAL_ONLY
 #include <libunwind.h>
-#endif
 #include <cxxabi.h>
 #ifndef STATICLIB
 #include <dlfcn.h>
@@ -96,7 +94,6 @@ void set_stack_trace_log(const std::string &log)
 
 void log_stack_trace(const char *msg)
 {
-#ifdef HAVE_LIBUNWIND
   unw_context_t ctx;
   unw_cursor_t cur;
   unw_word_t ip, off;
@@ -136,7 +133,6 @@ void log_stack_trace(const char *msg)
     LOG_PRINT2(log, "  " << std::setw(4) << level << std::setbase(16) << std::setw(20) << "0x" << ip << " " << (!status && dsym ? dsym : sym) << " + " << "0x" << off, LOG_LEVEL_0);
     free(dsym);
   }
-#endif
 }
 
 }  // namespace tools