use a simple constant

lib/src/uuid.rs

@@ -33,10 +33,9 @@ pub extern "C" fn tc_uuid_nil() -> TCUuid {
     Uuid::nil().into()
 }
 
-/// Length, in bytes, of a C string containing a TCUuid.
-// TODO: why not a const?
-#[no_mangle]
-pub static TC_UUID_STRING_BYTES: usize = ::uuid::adapter::Hyphenated::LENGTH;
+// NOTE: this must be a simple constant so that cbindgen can evaluate it
+/// Length, in bytes, of the string representation of a UUID (without NUL terminator)
+pub const TC_UUID_STRING_BYTES: usize = 36;
 
 /// Write the string representation of a TCUuid into the given buffer, which must be
 /// at least TC_UUID_STRING_BYTES long.  No NUL terminator is added.

lib/taskchampion.h

@@ -1,5 +1,11 @@
 #include <stdbool.h>
 #include <stdint.h>
+#define TC_UUID_STRING_BYTES 36
+
+/**
+ * Length, in bytes, of the string representation of a UUID (without NUL terminator)
+ */
+#define TC_UUID_STRING_BYTES 36
 
 /**
  * A result combines a boolean success value with
@@ -74,8 +80,6 @@ typedef struct TCUuid {
 extern "C" {
 #endif // __cplusplus
 
-extern const size_t TC_UUID_STRING_BYTES;
-
 /**
  * Create a new TCReplica with an in-memory database.  The contents of the database will be
  * lost when it is freed.