Workaround 'uninitialized variable sp passed to APPROX_SP' cppcheck FP

(fix of commit 0fb49af)

* include/private/gc_priv.h (APPROX_SP): Rename to STORE_APPROX_SP_TO;
change argument type from ptr_t* to ptr_t& (lvalue); update comment.
* mark_rts.c (GC_approx_sp): Use STORE_APPROX_SP_TO(sp) instead of
APPROX_SP(&sp).
* misc.c (GC_call_with_stack_base): Likewise.
* misc.c [!THREADS] (GC_call_with_gc_active): Likewise.
* pthread_support.c (GC_call_with_gc_active): Likewise.
* tools/setjmp_t.c (nested_sp, main): Likewise.

include/private/gc_priv.h

@@ -1946,23 +1946,23 @@ GC_INNER void GC_push_all_register_sections(
 /* Return the current stack pointer, approximately. */
 GC_INNER ptr_t GC_approx_sp(void);
 
-/* Same as GC_approx_sp() but a macro.  sp_ptr should be a pointer  */
-/* to a local variable of volatile ptr_t type.                      */
+/* Same as GC_approx_sp() but a macro.  sp should be a local        */
+/* variable of volatile ptr_t type.                                 */
 #if (defined(E2K) && defined(__clang__)         \
      || (defined(S390) && __clang_major__ < 8)) \
     && !defined(CPPCHECK)
 /* Workaround some bugs in clang:                                   */
 /* "undefined reference to llvm.frameaddress" error (clang-9/e2k);  */
 /* a crash in SystemZTargetLowering of libLLVM-3.8 (s390).          */
-#  define APPROX_SP(sp_ptr) (void)(*(sp_ptr) = (ptr_t)(sp_ptr))
+#  define STORE_APPROX_SP_TO(sp) (void)(sp = (ptr_t)(&sp))
 #elif defined(CPPCHECK)                          \
     || (__GNUC__ >= 4 /* GC_GNUC_PREREQ(4, 0) */ \
         && !defined(STACK_NOT_SCANNED))
 /* TODO: Use GC_GNUC_PREREQ after fixing a bug in cppcheck. */
-#  define APPROX_SP(sp_ptr) \
-    (void)(*(sp_ptr) = (ptr_t)__builtin_frame_address(0))
+/* Note: lvalue is passed instead of pointer to sp (because of cppcheck). */
+#  define STORE_APPROX_SP_TO(sp) (void)(sp = (ptr_t)__builtin_frame_address(0))
 #else
-#  define APPROX_SP(sp_ptr) (void)(*(sp_ptr) = (ptr_t)(sp_ptr))
+#  define STORE_APPROX_SP_TO(sp) (void)(sp = (ptr_t)(&sp))
 #endif
 
 GC_INNER GC_bool GC_should_collect(void);

mark_rts.c

@@ -543,7 +543,7 @@ GC_approx_sp(void)
   /* This also forces stack to grow if necessary.  Otherwise the      */
   /* later accesses might cause the kernel to think we are doing      */
   /* something wrong.                                                 */
-  APPROX_SP(&sp);
+  STORE_APPROX_SP_TO(sp);
   return (/* no volatile */ ptr_t)sp;
 }
 

misc.c

@@ -2396,7 +2396,7 @@ GC_call_with_stack_base(GC_stack_base_func fn, void *arg)
   struct GC_stack_base base;
   void *result;
 
-  APPROX_SP((volatile ptr_t *)&base.mem_base);
+  STORE_APPROX_SP_TO(*(volatile ptr_t *)&base.mem_base);
 #ifdef IA64
   base.reg_base = GC_save_regs_in_stack();
   /* TODO: Unnecessarily flushes register stack,    */
@@ -2438,7 +2438,7 @@ GC_call_with_gc_active(GC_fn_type fn, void *client_data)
   /* Adjust our stack bottom pointer (this could happen if    */
   /* GC_get_main_stack_base() is unimplemented or broken for  */
   /* the platform).  Note: stacksect variable is reused here. */
-  APPROX_SP((volatile ptr_t *)&stacksect.saved_stack_ptr);
+  STORE_APPROX_SP_TO(*(volatile ptr_t *)&stacksect.saved_stack_ptr);
   if (HOTTER_THAN(GC_stackbottom, stacksect.saved_stack_ptr))
     GC_stackbottom = stacksect.saved_stack_ptr;
 

pthread_support.c

@@ -2163,7 +2163,7 @@ GC_call_with_gc_active(GC_fn_type fn, void *client_data)
   /* GC_get_stack_base() was used which returned GC_SUCCESS). */
   stack_end = crtn->stack_end; /* read of a volatile field */
   GC_ASSERT(stack_end != NULL);
-  APPROX_SP((volatile ptr_t *)&stacksect.saved_stack_ptr);
+  STORE_APPROX_SP_TO(*(volatile ptr_t *)&stacksect.saved_stack_ptr);
   if (HOTTER_THAN(stack_end, stacksect.saved_stack_ptr)) {
     crtn->stack_end = stacksect.saved_stack_ptr;
 #  if defined(I386) && defined(GC_WIN32_THREADS)

tools/setjmp_t.c

@@ -70,7 +70,7 @@ nested_sp(void)
 {
   volatile ptr_t sp;
 
-  APPROX_SP(&sp);
+  STORE_APPROX_SP_TO(sp);
   return ADDR(sp);
 }
 
@@ -101,7 +101,7 @@ main(void)
   static volatile int y = 0;
 #endif
 
-  APPROX_SP(&sp);
+  STORE_APPROX_SP_TO(sp);
   printf("This appears to be a %s running %s\n", MACH_TYPE, OS_TYPE);
 #if defined(CPPCHECK)
   (void)nested_sp(); /* to workaround a bug in cppcheck */