Here are some potentially significant warnings from 1.8.1 p3

Solaris 9
gcc 3.3.2
CC=gcc -Wall -m64 -mcpu=ultrasparc -fno-strict-aliasing

error.c:645: warning: `init_syserr' declared `static' but never defined

eval.c:9032: warning: `limit' might be used uninitialized in this
function

file.c:329: warning: unsigned int format, different type arg (arg 3)

gc.c:582: warning: unused variable `tmp'
gc.c:658: warning: unused variable `ret'

numeric.c:791: warning: implicit declaration of function `finite'

parse.y:4443: warning: `nodeline' defined but not used

process.c: In function `rb_syswait':
process.c:909: warning: `hfunc' might be used uninitialized in this
function
process.c:909: warning: `qfunc' might be used uninitialized in this
function
process.c:909: warning: `ifunc' might be used uninitialized in this
function

bigdecimal.c:106: warning: int format, different type arg (arg 3)
bigdecimal.c:1582: warning: `VpIsNegDoubleZero' defined but not used
bigdecimal.c:3573: warning: `VpItoV' defined but not used

curses.c:665: warning: `curses_ungetmouse' defined but not used
curses.c:1264: warning: `window_bkgdset' defined but not used
curses.c:1276: warning: `window_bkgd' defined but not used
curses.c:1289: warning: `window_getbkgd' defined but not used

dl.c: In function `dlsizeof':
dl.c:167: warning: subscript has type `char'
dl.c:169: warning: subscript has type `char'

ptr.c: In function `rb_dlptr_define_data_type':
ptr.c:572: warning: subscript has type `char'
ptr.c:574: warning: subscript has type `char'

sym.c:365: warning: unused variable `guard'

iconv.c: In function `iconv_convert':
iconv.c:429: warning: int format, different type arg (arg 3)
iconv.c: In function `Init_iconv':
iconv.c:839: warning: unused variable `metaclass'

pty.c: In function `getDevice':
pty.c:343: warning: unused variable `p'
pty.c:345: warning: unused variable `MasterName'
pty.c: At top level:
pty.c:89: warning: `MasterDevice' defined but not used
pty.c:90: warning: `SlaveDevice' defined but not used
pty.c:91: warning: `deviceNo' defined but not used
pty.c:404: warning: `freeDevice' defined but not used

socket.c: In function `bsock_getsockopt':
socket.c:317: warning: implicit declaration of function `alloca'
socket.c: In function `port_str':
socket.c:599: warning: int format, different type arg (arg 4)
socket.c: In function `ipaddr':
socket.c:660: warning: `addr1' might be used uninitialized in this
function
socket.c: In function `init_inetsock_internal':
socket.c:897: warning: `syscall' might be used uninitialized in this
function
socket.c: In function `sock_s_getaddrinfo':
socket.c:2109: warning: int format, different type arg (arg 4)
socket.c: In function `sock_s_getnameinfo':
socket.c:2228: warning: int format, different type arg (arg 4)

bytecode.re: In function `sycklex_bytecode_utf8':
bytecode.re:218: warning: unused variable `yyaccept'
bytecode.re:413: warning: unused variable `yyaccept'
bytecode.re:436: warning: unused variable `yyaccept'
bytecode.re:136: warning: unused variable `doc_level'
bytecode.re:457: warning: label `yy84' defined but not used
bytecode.re:441: warning: label `yy81' defined but not used
bytecode.re:479: warning: label `yy79' defined but not used
bytecode.re:474: warning: label `yy75' defined but not used
bytecode.re:438: warning: label `yy69' defined but not used
bytecode.re:415: warning: label `yy60' defined but not used
bytecode.re:648: warning: label `yy57' defined but not used
bytecode.re:567: warning: label `yy55' defined but not used
bytecode.re:408: warning: label `yy52' defined but not used
bytecode.re:399: warning: label `yy46' defined but not used
bytecode.re:243: warning: label `yy42' defined but not used
bytecode.re:258: warning: label `yy39' defined but not used
bytecode.re:294: warning: label `yy36' defined but not used
bytecode.re:387: warning: label `yy33' defined but not used
bytecode.re:387: warning: label `yy31' defined but not used
bytecode.re:369: warning: label `yy28' defined but not used
bytecode.re:367: warning: label `yy26' defined but not used
bytecode.re:307: warning: label `yy24' defined but not used
bytecode.re:300: warning: label `yy22' defined but not used
bytecode.re:293: warning: label `yy20' defined but not used
bytecode.re:271: warning: label `yy18' defined but not used
bytecode.re:220: warning: label `yy10' defined but not used
bytecode.re:206: warning: label `yy7' defined but not used
bytecode.re:189: warning: label `yy1' defined but not used
bytecode.re:181: warning: label `Header' defined but not used
bytecode.re:187: warning: `yyaccept' might be used uninitialized in this
function
bytecode.re:397: warning: `yyaccept' might be used uninitialized in this
function
bytecode.re: In function `get_inline':
bytecode.re:509: warning: unused variable `yyaccept'
bytecode.re:520: warning: label `yy92' defined but not used
bytecode.re:511: warning: label `yy86' defined but not used

mplicit.re: In function `syck_match_implicit':
implicit.re:125: warning: label `yy175' defined but not used
implicit.re:124: warning: label `yy174' defined but not used
implicit.re:135: warning: label `yy165' defined but not used
implicit.re:134: warning: label `yy164' defined but not used
implicit.re:182: warning: label `yy156' defined but not used
implicit.re:181: warning: label `yy155' defined but not used
implicit.re:90: warning: label `yy141' defined but not used
implicit.re:334: warning: label `yy139' defined but not used
implicit.re:242: warning: label `yy130' defined but not used
implicit.re:237: warning: label `yy128' defined but not used
implicit.re:314: warning: label `yy97' defined but not used
implicit.re:256: warning: label `yy90' defined but not used
implicit.re:239: warning: label `yy88' defined but not used
implicit.re:195: warning: label `yy74' defined but not used
implicit.re:138: warning: label `yy64' defined but not used
implicit.re:98: warning: label `yy58' defined but not used
implicit.re:111: warning: label `yy56' defined but not used
implicit.re:96: warning: label `yy54' defined but not used
implicit.re:161: warning: label `yy52' defined but not used
implicit.re:143: warning: label `yy50' defined but not used
implicit.re:117: warning: label `yy44' defined but not used
implicit.re:116: warning: label `yy43' defined but not used
implicit.re:148: warning: label `yy38' defined but not used
implicit.re:147: warning: label `yy37' defined but not used
implicit.re:116: warning: label `yy29' defined but not used
implicit.re:233: warning: label `yy27' defined but not used
implicit.re:133: warning: label `yy7' defined but not used
implicit.re:55: warning: label `yy1' defined but not used
implicit.re: In function `syck_type_id_to_uri':
implicit.re:581: warning: label `yy256' defined but not used
implicit.re:454: warning: label `yy249' defined but not used
implicit.re:385: warning: label `yy247' defined but not used
implicit.re:238: warning: label `yy243' defined but not used
implicit.re:284: warning: label `yy236' defined but not used
implicit.re:358: warning: label `yy221' defined but not used
implicit.re:231: warning: label `yy214' defined but not used
implicit.re:161: warning: label `yy212' defined but not used
implicit.re:434: warning: label `yy210' defined but not used
implicit.re:240: warning: label `yy200' defined but not used
implicit.re:134: warning: label `yy194' defined but not used
implicit.re:125: warning: `marker' might be used uninitialized in this
function
implicit.re:132: warning: `yyaccept' might be used uninitialized in this
function

rubyext.c: In function `rb_syck_compile':
rubyext.c:96: warning: implicit declaration of function
`syck_parser_assign_io'
rubyext.c: In function `rb_syck_mktime':
rubyext.c:207: warning: subscript has type `char'
rubyext.c:212: warning: subscript has type `char'
rubyext.c:217: warning: subscript has type `char'
rubyext.c:222: warning: subscript has type `char'
rubyext.c:227: warning: subscript has type `char'
rubyext.c: In function `yaml_org_handler':
rubyext.c:488: warning: subscript has type `char'
rubyext.c:493: warning: subscript has type `char'
rubyext.c: In function `syck_set_model':
rubyext.c:681: warning: implicit declaration of function
`syck_parser_set_input_type'

token.re: In function `sycklex':
token.re:235: warning: control reaches end of non-void function
token.re: In function `sycklex_yaml_utf8':
token.re:840: warning: subscript has type `char'
token.re:934: warning: label `yy206' defined but not used
token.re:944: warning: label `yy204' defined but not used
token.re:856: warning: label `yy198' defined but not used
token.re:862: warning: label `yy193' defined but not used
token.re:742: warning: label `yy181' defined but not used
token.re:717: warning: label `yy176' defined but not used
token.re:736: warning: label `yy173' defined but not used
token.re:740: warning: label `yy169' defined but not used
token.re:728: warning: label `yy166' defined but not used
token.re:639: warning: label `yy155' defined but not used
token.re:619: warning: label `yy149' defined but not used
token.re:562: warning: label `yy139' defined but not used
token.re:524: warning: label `yy133' defined but not used
token.re:542: warning: label `yy127' defined but not used
token.re:542: warning: label `yy124' defined but not used
token.re:542: warning: label `yy121' defined but not used
token.re:490: warning: label `yy109' defined but not used
token.re:632: warning: label `yy106' defined but not used
token.re:473: warning: label `yy103' defined but not used
token.re:460: warning: label `yy93' defined but not used
token.re:389: warning: label `yy87' defined but not used
token.re:403: warning: label `yy82' defined but not used
token.re:420: warning: label `yy77' defined but not used
token.re:448: warning: label `yy74' defined but not used
token.re:436: warning: label `yy71' defined but not used
token.re:456: warning: label `yy66' defined but not used
token.re:440: warning: label `yy61' defined but not used
token.re:445: warning: label `yy57' defined but not used
token.re:424: warning: label `yy54' defined but not used
token.re:421: warning: label `yy52' defined but not used
token.re:527: warning: label `yy50' defined but not used
token.re:379: warning: label `yy44' defined but not used
token.re:449: warning: label `yy42' defined but not used
token.re:353: warning: label `yy36' defined but not used
token.re:303: warning: label `yy33' defined but not used
token.re:317: warning: label `yy26' defined but not used
token.re:319: warning: label `yy8' defined but not used
token.re:343: warning: label `yy6' defined but not used
token.re:289: warning: label `yy1' defined but not used
token.re:458: warning: `yyaccept' might be used uninitialized in this
function
token.re:740: warning: `yyaccept' might be used uninitialized in this
function

Regards,

Dan