ALIGNOF() helper

[ccan] / alignof / _info.c

diff --git a/alignof/_info.c b/alignof/_info.c
new file mode 100644 (file)
index 0000000..b5afa02
--- /dev/null
+++ b/alignof/_info.c
@@ -0,0 +1,45 @@
+#include <stdio.h>
+#include <string.h>
+#include "config.h"
+
+/**
+ * alignof - ALIGNOF() macro to determine alignment of a type.
+ *
+ * Many platforms have requirements that certain types must be aligned
+ * to certain address boundaries, such as ints needing to be on 4-byte
+ * boundaries.  Attempting to access variables with incorrect
+ * alignment may cause performance loss or even program failure (eg. a
+ * bus signal).
+ *
+ * There are times which it's useful to be able to programatically
+ * access these requirements, such as for dynamic allocators.
+ *
+ * Example:
+ *     #include <stdio.h>
+ *     #include "alignof/alignoff.h"
+ *
+ *     int main(int argc, char *argv[])
+ *     {
+ *             char arr[sizeof(int)];
+ *
+ *             if ((unsigned long)arr % ALIGNOF(int)) {
+ *                     printf("arr %p CANNOT hold an int\n", arr);
+ *                     exit(1);
+ *             } else {
+ *                     printf("arr %p CAN hold an int\n", arr);
+ *                     exit(0);
+ *             }
+ *     }
+ */
+int main(int argc, char *argv[])
+{
+       if (argc != 2)
+               return 1;
+
+       if (strcmp(argv[1], "depends") == 0) {
+               printf("build_assert\n");
+               return 0;
+       }
+
+       return 1;
+}