Found by -fsanitize=undefined as

  $ burrGui
  lua/luaclass.cpp:60:17: runtime error: execution reached the end of a value-returning function without returning a value

which with Clang leads to

  * thread #1: tid = 100272, 0x00000000005d0d2d burrGui`luaClass_c::doString(this=0x00007fffffffd6e0, code="windowposh = 600") + 125 at luaclass.cpp:61, stop reason = signal SIGILL: privileged instruction
      frame #0: 0x00000000005d0d2d burrGui`luaClass_c::doString(this=0x00007fffffffd6e0, code="windowposh = 600") + 125 at luaclass.cpp:61
     58     luaL_loadfile(L, fname) || lua_pcall(L, 0, 0, 0);
     59   }
     60   int luaClass_c::doString(const char *code) {
  -> 61     luaL_loadbuffer(L, code, strlen(code), "line") || lua_pcall(L, 0, 0, 0);
     62   }
     63
     64   /* functions that allow calling lua functions
  (lldb) bt
  * thread #1: tid = 100272, 0x00000000005d0d2d burrGui`luaClass_c::doString(this=0x00007fffffffd6e0, code="windowposh = 600") + 125 at luaclass.cpp:61, stop reason = signal SIGILL: privileged instruction
    * frame #0: 0x00000000005d0d2d burrGui`luaClass_c::doString(this=0x00007fffffffd6e0, code="windowposh = 600") + 125 at luaclass.cpp:61
      frame #1: 0x0000000000416735 burrGui`configuration_c::parse(this=0x00000000008e5a18) + 165 at configuration.cpp:65
      frame #2: 0x0000000000416fbb burrGui`configuration_c::configuration_c(this=0x00000000008e5a18) + 939 at configuration.cpp:144
      frame #3: 0x0000000000417877 burrGui`::__cxx_global_var_init() + 23 at configuration.cpp:266
      frame #4: 0x00000000004178b9 burrGui`_GLOBAL__sub_I_configuration.cpp + 9 at configuration.cpp:0
      frame #5: 0x00000000006221e2 burrGui`__do_global_ctors_aux + 34
      frame #6: 0x000000000040e986 burrGui

--- src/lua/luaclass.cpp.orig	2013-05-08 19:02:06 UTC
+++ src/lua/luaclass.cpp
@@ -54,10 +54,10 @@ bool luaClass_c::getBool(const char *nam
 }
 
 /* functions to evaluate lua code */
-int luaClass_c::doFile(const char *fname) {
+void luaClass_c::doFile(const char *fname) {
   luaL_loadfile(L, fname) || lua_pcall(L, 0, 0, 0);
 }
-int luaClass_c::doString(const char *code) {
+void luaClass_c::doString(const char *code) {
   luaL_loadbuffer(L, code, strlen(code), "line") || lua_pcall(L, 0, 0, 0);
 }
 
--- src/lua/luaclass.h.orig	2013-05-08 19:02:06 UTC
+++ src/lua/luaclass.h
@@ -45,8 +45,8 @@ class luaClass_c {
     bool getBool(const char *name);
 
     /* functions to evaluate lua code */
-    int doFile(const char *fname);
-    int doString(const char *code);
+    void doFile(const char *fname);
+    void doString(const char *code);
 
     /* functions that allow calling lua functions
      *