GCC pointer signedness (and other) warnings

I've noticed a lot of signedness warnings when compiling Postgres
with GCC 4. They may have been there with GCC 3.3 as well, but I
don't recall. Here's a example:

gcc -no-cpp-precomp -O2 -Wall -Wmissing-prototypes -Wpointer-arith -
Wdeclaration-after-statement -Wold-style-definition -Wendif-labels -
fno-strict-aliasing -g -I../../../src/include -I/usr/include/ -c -o
pg_proc.o pg_proc.c
pg_proc.c: In function 'match_prosrc_to_query':
pg_proc.c:724: warning: pointer targets in passing argument 1 of
'pg_mbstrlen_with_len' differ in signedness
pg_proc.c:738: warning: pointer targets in passing argument 1 of
'pg_mbstrlen_with_len' differ in signedness

Here's another:
gcc -no-cpp-precomp -O2 -Wall -Wmissing-prototypes -Wpointer-arith -
Wdeclaration-after-statement -Wold-style-definition -Wendif-labels -
fno-strict-aliasing -g -I../../../../../../src/include -I/usr/
include/ -c -o utf8_and_ascii.o utf8_and_ascii.c
utf8_and_ascii.c: In function 'ascii_to_utf8':
utf8_and_ascii.c:38: warning: pointer targets in initialization
differ in signedness
utf8_and_ascii.c:39: warning: pointer targets in initialization
differ in signedness

I've also noticed some possible uninitialized variable warnings, such
as this:
gcc -no-cpp-precomp -O2 -Wall -Wmissing-prototypes -Wpointer-arith -
Wdeclaration-after-statement -Wold-style-definition -Wendif-labels -
fno-strict-aliasing -g -I../../../../src/interfaces/ecpg/include -
I../../../../src/include/utils -I../../../../src/interfaces/libpq -
I../../../../src/include -I/usr/include/ -DFRONTEND -c -o
datetime.o datetime.c
datetime.c: In function 'PGTYPESdate_defmt_asc':
datetime.c:335: warning: 'tm$tm_mday' may be used uninitialized in
this function
datetime.c:335: warning: 'tm$tm_mon' may be used uninitialized in
this function
datetime.c:335: warning: 'tm$tm_year' may be used uninitialized in
this function

Are these things we could clean up? (Yes, I'm volunteering if it's
something I'm capable of helping out with, though probably not for 8.1.)

Michael Glaesemann
grzm myrealbox com

laughter:~ glaesema$ gcc -v
Reading specs from /usr/lib/gcc/powerpc-apple-darwin8/4.0.0/specs
Configured with: /private/var/tmp/gcc/gcc-4061.obj~8/src/configure --
disable-checking --prefix=/usr --mandir=/share/man --enable-
languages=c,objc,c++,obj-c++ --program-transform-name=/^[cg][^+.-]*$/
s/$/-4.0/ --with-gxx-include-dir=/include/gcc/darwin/4.0/c++ --
build=powerpc-apple-darwin8 --host=powerpc-apple-darwin8 --
target=powerpc-apple-darwin8
Thread model: posix
gcc version 4.0.0 20041026 (Apple Computer, Inc. build 4061)