toolchain: define ZRESTRICT for restrict aliasing

restrict keyword is not supported in C++, however
GNUC does support __restrict for C/C++ so we can use that,
however the complexity of toolchains requires a ZRESTRICT
symbol that should be used throughout the codebase to not
cause any conflicts or redefinition errors

Signed-off-by: Nicholas Lowell <nlowell@lexmark.com>

include/toolchain/common.h

@@ -26,6 +26,14 @@
 #define TASK_ENTRY_CPP  extern "C"
 #endif
 
+#ifndef ZRESTRICT
+#ifndef __cplusplus
+#define ZRESTRICT restrict
+#else
+#define ZRESTRICT
+#endif
+#endif
+
 /*
  * Generate a reference to an external symbol.
  * The reference indicates to the linker that the symbol is required

include/toolchain/gcc.h

@@ -63,6 +63,12 @@
 #define BUILD_ASSERT(EXPR, MSG...)
 #endif
 
+#ifdef __cplusplus
+#define ZRESTRICT __restrict
+#else
+#define ZRESTRICT restrict
+#endif
+
 #include <toolchain/common.h>
 #include <stdbool.h>