serious compiler warnings in mingw64 build of master

[Stephen Leake <stephen_leake@stephe-leake.org>]

I just updated emacs/master (to
bf55b5ac17cd5a40ad5ff2e25af7e050602180bb), and it's giving these
compiler warnings:

   CC       process.o
In file included from process.c:33:
process.c: In function 'Fmake_process':
lisp.h:1561:31: warning: null pointer dereference [-Wnull-dereference]
 1561 |   return XSTRING (string)->u.s.data;
      |          ~~~~~~~~~~~~~~~~~~~~~^~~~~

This is from line 1990 in process.c:
	  new_argv[i] = SSDATA (XCAR (tem));

I have not tried to figure out a fix.


   CC       w32.o
w32.c: In function '_sys_read_ahead':
w32.c:8858:10: warning: 'rc' may be used uninitialized in this function [-Wmaybe-uninitialized]
 8858 |   if (rc == sizeof (char))
      |       ~~~^~~~~~~~~~~~~~~~

The preceding if/elsif block has no final 'else', so rc may not be set.
I'm not clear if the right fix is to init rc to 0, or to add an 'else'
that does something like report an error.


I've been getting mysterious crashes when mail spawns a process to get
more mail, so I'm hoping these are the root cause of that.

-- 
-- Stephe