(port-revealed (open-input-file "/dev/null")) => 32539
The little investigating I've done so far suggests that this is because scm_i_fdes_to_port calls scm_gc_malloc_pointerless and initializes only the 'fdes' and 'options' fields, leaving 'revealed' uninitialized. The comment above scm_gc_malloc_pointerless does a good job of explaining why this is an issue: /* Allocate SIZE bytes of memory whose contents should not be scanned for pointers (useful, e.g., for strings). Note though that this memory is *not* cleared; be sure to initialize it to prevent information leaks. */ This issue appears to be present both in the 2.2 and 3.0 releases packaged in guix. - reepca