Seems to be happening with gcc 12.2.0-3ubuntu1:
```
lightningd/jsonrpc.c: In function ‘destroy_json_command’:
lightningd/jsonrpc.c:1180:63: error: the comparison will always evaluate as ‘false’ for the address of ‘canary’ will never be NULL [-Werror=address]
lightningd/jsonrpc.c:108:53: note: ‘canary’ declared here
```
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
* It evaluates to @x so you can chain it.
*/
#define tcon_check_ptr(x, canary, expr) \
- (sizeof(&(x)->_tcon[0].canary == (expr)) ? (x) : (x))
-
+ (sizeof((expr) ? (expr) : &(x)->_tcon[0].canary) ? (x) : (x))
/**
* tcon_type - the type within a container (or void *)