command: Support evaluating C expressions in DECL_CONSTANT()

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

src/ctr.h

@@ -14,4 +14,17 @@
     static char __PASTE(_DECLS_, __LINE__)[] __attribute__((used))      \
         __section(".compile_time_request") = (REQUEST)
 
+#define CTR_INT(V, S) ((((uint32_t)(V) >> S) & 0x3f) + 48)
+
+// Declare a compile time request with an integer expression
+#define DECL_CTR_INT(REQUEST, VALUE)                            \
+    static struct { char _r[sizeof(REQUEST)]; char _v[8]; }     \
+        __PASTE(_DECLI_, __LINE__) __attribute__((used))        \
+            __section(".compile_time_request") = {              \
+            REQUEST " ", {                                      \
+                (VALUE) < 0 ? '-' : '+',                        \
+                CTR_INT((VALUE),0), CTR_INT((VALUE),6),         \
+                CTR_INT((VALUE),12), CTR_INT((VALUE),18),       \
+                CTR_INT((VALUE),24), CTR_INT((VALUE),30), 0 } }
+
 #endif // ctr.h