Check for potential address space overlaps (prime windows)

OAR/src/memcheck.c

@@ -6,6 +6,8 @@
 
 void memcheck()
 {
+//#define MEMCHECK
+#ifdef MEMCHECK
     uint32_t patterns[] = {
         0x0,
         0xFFFFFFFF,
@@ -14,6 +16,7 @@ void memcheck()
         0xAA55AA55,
         0x55AA55AA,
     };
+    unsigned primes[] = { 3, 7, 31, 127 };
     size_t space = 512*1024;
     void *p = malloc(space);
     int i;
@@ -36,6 +39,34 @@ void memcheck()
         exit(1);
     }
 
+    // Check potential address space overlaps
+    printf("[MEMCHECK] Checking for potential address space overlap. Window: ");
+    for (i=0; i<sizeof(primes)/sizeof(primes[0]); i++) {
+        uint8_t *pc = p;
+        unsigned prime = primes[i];
+        unsigned bytes = space;
+        unsigned idx = 0;
+        printf("%s%d", i?", ":"", prime);
+        fflush(stdout);
+        while (bytes--) {
+            *pc++ = (idx % prime);
+            idx++;
+        }
+        pc = p;
+        bytes = space;
+        idx = 0;
+        while (bytes--) {
+            if (*pc != (idx % prime)) {
+                printf("[MEMCHECK] Address space wrapped around at 0x%x!\n", (unsigned)pc);
+                fflush(stdout);
+                exit(1);
+            }
+            pc++;
+            idx++;
+        }
+    }
+    puts("");
+
     for(i=0; i<sizeof(patterns)/sizeof(patterns[0]); i++) {
         printf("[MEMCHECK] Checking memory with pattern: 0x%x...\n", (unsigned) patterns[i]);
         uint32_t *pw = p;
@@ -59,4 +90,8 @@ void memcheck()
         }
     }
     free(p);
+#else
+    puts("[MEMCHECK] Memory checks disabled in release mode.");
+    fflush(stdout);
+#endif
 }