I expect to push something like the attached tomorrow:

stdlib: avoid canonicalize_file_name contradiction
* lib/stdlib.in.h (canonicalize_file_name): Remove the nonnull
attribute from its declaration. tests/test-canonicalize-lgpl.c
passes null_ptr () to it, which (via this contradiction) would
provoke a segfault from GCC 10. See a small reproducer and
discussion in https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93156