diff --git a/os/common/ports/ARMCMx/compilers/GCC/rules.mk b/os/common/ports/ARMCMx/compilers/GCC/rules.mk
index a9228e393..1d6def961 100644
--- a/os/common/ports/ARMCMx/compilers/GCC/rules.mk
+++ b/os/common/ports/ARMCMx/compilers/GCC/rules.mk
@@ -23,6 +23,9 @@ ifeq ($(USE_LTO),yes)
 endif
 
 # FPU-related options
+ifeq ($(USE_FPU),)
+  USE_FPU = no
+endif
 ifneq ($(USE_FPU),no)
   OPT += -mfloat-abi=$(USE_FPU) -mfpu=fpv4-sp-d16 -fsingle-precision-constant
   DDEFS += -DCORTEX_USE_FPU=TRUE
diff --git a/os/nil/ports/ARMCMx/nilcore.h b/os/nil/ports/ARMCMx/nilcore.h
index 9d9c643b4..60202222a 100644
--- a/os/nil/ports/ARMCMx/nilcore.h
+++ b/os/nil/ports/ARMCMx/nilcore.h
@@ -42,6 +42,11 @@
  */
 #define PORT_ARCHITECTURE_ARM
 
+/* The following code is not processed when the file is included from an
+   asm module because those intrinsic macros are not necessarily defined
+   by the assembler too.*/
+#if !defined(_FROM_ASM_)
+
 /**
  * @brief   Compiler name and version.
  */
@@ -57,6 +62,9 @@
 #else
 #error "unsupported compiler"
 #endif
+
+#endif /* !defined(_FROM_ASM_) */
+
 /** @} */
 
 /**
diff --git a/os/rt/include/ch.h b/os/rt/include/ch.h
index 11c75c407..a8cc7ac81 100644
--- a/os/rt/include/ch.h
+++ b/os/rt/include/ch.h
@@ -62,10 +62,6 @@
 #define CH_KERNEL_PATCH         0
 /** @} */
 
-/* Forward declarations.*/
-typedef struct thread thread_t;
-typedef struct virtual_timer virtual_timer_t;
-
 /* Core headers.*/
 #include "chtypes.h"
 #include "chconf.h"
diff --git a/os/rt/include/chschd.h b/os/rt/include/chschd.h
index bcca26d85..fe85f76cb 100644
--- a/os/rt/include/chschd.h
+++ b/os/rt/include/chschd.h
@@ -69,22 +69,29 @@
 /*===========================================================================*/
 
 /**
- * @brief   Generic threads single link list, it works like a stack.
+ * @extends threads_queue_t
+ *
+ * @brief   Type of a thread structure.
  */
-typedef struct {
-  thread_t              *p_next;    /**< @brief Next in the list/queue.     */
-} threads_list_t;
+typedef struct thread thread_t;
 
 /**
  * @extends threads_list_t
  *
- * @brief   Generic threads bidirectional linked list header and element.
+ * @brief   Type of a generic threads bidirectional linked list header and element.
  */
 typedef struct {
   thread_t              *p_next;    /**< @brief Next in the list/queue.     */
   thread_t              *p_prev;    /**< @brief Previous in the queue.      */
 } threads_queue_t;
 
+/**
+ * @brief   Type of a generic threads single link list, it works like a stack.
+ */
+typedef struct {
+  thread_t              *p_next;    /**< @brief Next in the list/queue.     */
+} threads_list_t;
+
 /**
  * @extends threads_queue_t
  *
@@ -106,14 +113,12 @@ typedef struct {
 } ready_list_t;
 
 /**
- * @extends threads_queue_t
- *
  * @brief   Structure representing a thread.
  * @note    Not all the listed fields are always needed, by switching off some
  *          not needed ChibiOS/RT subsystems it is possible to save RAM space
- *          by shrinking the @p thread_t structure.
+ *          by shrinking this structure.
  */
-typedef struct thread {
+struct thread {
   thread_t              *p_next;    /**< @brief Next in the list/queue.     */
   /* End of the fields shared with the threads_list_t structure.*/
   thread_t              *p_prev;    /**< @brief Previous in the queue.      */
@@ -246,7 +251,32 @@ typedef struct thread {
   /* Extra fields defined in chconf.h.*/
   CH_CFG_THREAD_EXTRA_FIELDS
 #endif
-} thread_t;
+};
+
+/**
+ * @brief   Type of a Virtual Timer callback function.
+ */
+typedef void (*vtfunc_t)(void *);
+
+/**
+ * @brief   Type of a Virtual Timer structure.
+ */
+typedef struct virtual_timer virtual_timer_t;
+
+/**
+ * @extends virtual_timers_list_t
+ *
+ * @brief   Virtual Timer descriptor structure.
+ */
+struct virtual_timer {
+  virtual_timer_t       *vt_next;   /**< @brief Next timer in the list.     */
+  virtual_timer_t       *vt_prev;   /**< @brief Previous timer in the list. */
+  systime_t             vt_delta;   /**< @brief Time delta before timeout.  */
+  vtfunc_t              vt_func;    /**< @brief Timer callback function
+                                                pointer.                    */
+  void                  *vt_par;    /**< @brief Timer callback function
+                                                parameter.                  */
+};
 
 /**
  * @brief   Virtual timers list header.
diff --git a/os/rt/include/chvt.h b/os/rt/include/chvt.h
index 5c2d49d31..471ba22ee 100644
--- a/os/rt/include/chvt.h
+++ b/os/rt/include/chvt.h
@@ -87,31 +87,6 @@
 /* Module data structures and types.                                         */
 /*===========================================================================*/
 
-/**
- * @brief   Type of a Virtual Timer callback function.
- */
-typedef void (*vtfunc_t)(void *);
-
-/**
- * @brief   Type of a Virtual Timer structure.
- */
-typedef struct virtual_timer virtual_timer_t;
-
-/**
- * @extends virtual_timers_list_t
- *
- * @brief   Virtual Timer descriptor structure.
- */
-struct virtual_timer {
-  virtual_timer_t       *vt_next;   /**< @brief Next timer in the list.     */
-  virtual_timer_t       *vt_prev;   /**< @brief Previous timer in the list. */
-  systime_t             vt_delta;   /**< @brief Time delta before timeout.  */
-  vtfunc_t              vt_func;    /**< @brief Timer callback function
-                                                pointer.                    */
-  void                  *vt_par;    /**< @brief Timer callback function
-                                                parameter.                  */
-};
-
 /*===========================================================================*/
 /* Module macros.                                                            */
 /*===========================================================================*/
diff --git a/os/rt/ports/ARMCMx/chcore.h b/os/rt/ports/ARMCMx/chcore.h
index ca6ae60e7..0e5ed6933 100644
--- a/os/rt/ports/ARMCMx/chcore.h
+++ b/os/rt/ports/ARMCMx/chcore.h
@@ -42,6 +42,11 @@
  */
 #define PORT_ARCHITECTURE_ARM
 
+/* The following code is not processed when the file is included from an
+   asm module because those intrinsic macros are not necessarily defined
+   by the assembler too.*/
+#if !defined(_FROM_ASM_)
+
 /**
  * @brief   Compiler name and version.
  */
@@ -57,6 +62,9 @@
 #else
 #error "unsupported compiler"
 #endif
+
+#endif /* !defined(_FROM_ASM_) */
+
 /** @} */
 
 /**
diff --git a/os/rt/ports/ARMCMx/chcore_v6m.h b/os/rt/ports/ARMCMx/chcore_v6m.h
index e80efc9b9..fa6476084 100644
--- a/os/rt/ports/ARMCMx/chcore_v6m.h
+++ b/os/rt/ports/ARMCMx/chcore_v6m.h
@@ -254,7 +254,7 @@ struct port_intctx {
   struct port_intctx *r13 = (struct port_intctx *)__get_PSP();              \
   if ((stkalign_t *)(r13 - 1) < (otp)->p_stklimit)                          \
     chSysHalt("stack overflow");                                            \
-  _port_switch(ntp, otp);                                                   \
+  _port_switch((void *)ntp, (void *)otp);                                   \
 }
 #endif
 
@@ -266,10 +266,10 @@ struct port_intctx {
 extern "C" {
 #endif
   void _port_irq_epilogue(regarm_t lr);
+  void _port_switch(void *ntp, void *otp);
+  void _port_thread_start(void);
   void _port_switch_from_isr(void);
   void _port_exit_from_isr(void);
-  void _port_switch(thread_t *ntp, thread_t *otp);
-  void _port_thread_start(void);
 #ifdef __cplusplus
 }
 #endif
diff --git a/os/rt/ports/ARMCMx/chcore_v7m.h b/os/rt/ports/ARMCMx/chcore_v7m.h
index 404e87411..9e0b1e9cd 100644
--- a/os/rt/ports/ARMCMx/chcore_v7m.h
+++ b/os/rt/ports/ARMCMx/chcore_v7m.h
@@ -344,7 +344,7 @@ struct port_intctx {
   struct port_intctx *r13 = (struct port_intctx *)__get_PSP();              \
   if ((stkalign_t *)(r13 - 1) < (otp)->p_stklimit)                          \
     chSysHalt("stack overflow");                                            \
-  _port_switch(ntp, otp);                                                   \
+  _port_switch((void *)ntp, (void *)otp);                                   \
 }
 #endif
 
@@ -356,7 +356,7 @@ struct port_intctx {
 extern "C" {
 #endif
   void _port_irq_epilogue(void);
-  void _port_switch(thread_t *ntp, thread_t *otp);
+  void _port_switch(void *ntp, void *otp);
   void _port_thread_start(void);
   void _port_switch_from_isr(void);
   void _port_exit_from_isr(void);
diff --git a/os/rt/ports/e200/chcore.h b/os/rt/ports/e200/chcore.h
index 0255a0f1d..a043bb0b0 100644
--- a/os/rt/ports/e200/chcore.h
+++ b/os/rt/ports/e200/chcore.h
@@ -340,7 +340,7 @@ struct context {
   register struct port_intctx *sp asm ("%r1");                              \
   if ((stkalign_t *)(sp - 1) < otp->p_stklimit)                             \
     chDbgPanic("stack overflow");                                           \
-  _port_switch(ntp, otp);                                                   \
+  _port_switch((void *)ntp, (void *)otp);                                   \
 }
 #endif
 
@@ -373,7 +373,7 @@ struct context {
 #ifdef __cplusplus
 extern "C" {
 #endif
-  void _port_switch(thread_t *ntp, thread_t *otp);
+  void _port_switch(void *ntp, void *otp);
   void _port_thread_start(void);
 #ifdef __cplusplus
 }
diff --git a/os/rt/src/chvt.c b/os/rt/src/chvt.c
index e87c2d12c..d20e20d91 100644
--- a/os/rt/src/chvt.c
+++ b/os/rt/src/chvt.c
@@ -136,8 +136,9 @@ void chVTDoSetI(virtual_timer_t *vtp, systime_t delay,
   while (p->vt_delta < delay) {
     delay -= p->vt_delta;
     p = p->vt_next;
-  }
-
  /* The timer is inserted in the delta list.*/
+  }
+
+  /* The timer is inserted in the delta list.*/
   vtp->vt_prev = (vtp->vt_next = p)->vt_prev;
   vtp->vt_prev->vt_next = p->vt_prev = vtp;
   vtp->vt_delta = delay