Cast void pointer before deallocating with delete[]

The stack memory is a `void*` which creates a warning when using
the delete[] operator because it is unable to call the destructor of
of an unkown object type.

Author: hugueskamba

rtos/source/Thread.cpp

@@ -19,6 +19,8 @@
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  * SOFTWARE.
  */
+
+#include <stdlib.h>
 #include "rtos/Thread.h"
 #include "rtos/ThisThread.h"
 #include "rtos_idle.h"
@@ -113,7 +115,8 @@ osStatus Thread::start(mbed::Callback<void()> task)
     _tid = osThreadNew(Thread::_thunk, this, &_attr);
     if (_tid == nullptr) {
         if (_dynamic_stack) {
-            delete[] _attr.stack_mem;
+            // Cast before deallocation as delete[] does not accept void*
+            delete[] static_cast<uint32_t *>(_attr.stack_mem);
             _attr.stack_mem = nullptr;
         }
         _mutex.unlock();
@@ -417,7 +420,8 @@ Thread::~Thread()
     // terminate is thread safe
     terminate();
     if (_dynamic_stack) {
-        delete[] _attr.stack_mem;
+        // Cast before deallocation as delete[] does not accept void*
+        delete[] static_cast<uint32_t *>(_attr.stack_mem);
         _attr.stack_mem = nullptr;
     }
 }