Only call malloc_usable_size under linux

and not under OSX or other systems that may not support it.

Author: petr-bauch

src/memory-analyzer/gdb_api.cpp

@@ -59,6 +59,14 @@ gdb_apit::~gdb_apit()
 
 size_t gdb_apit::query_malloc_size(const std::string &pointer_expr)
 {
+#ifndef __linux__
+  // The memory analyzer can be compiled under OSX and other systems that can
+  // interact with the machine interface of gdb but `malloc_usable_size` is only
+  // available under linux. Under non-linux system we simple return 1, i.e. as
+  // if the \p pointer_expr was not dynamically allocated.
+  return 1;
+#endif
+
   write_to_gdb("-var-create tmp * malloc_usable_size(" + pointer_expr + ")");
 
   if(!was_command_accepted())