Wesley Morgan <[EMAIL PROTECTED]> writes:
> On Wed, 16 Jul 2003, Christian Brueffer wrote:
>
> > ===> lib/libpam/modules/pam_echo
> > cc -O2 -pipe -march=pentium2
> > -I/usr/src/lib/libpam/modules/pam_echo/../../../../contrib/openpam/include
> > -I/usr/src/lib/libpam/modules/pam_echo/../../libpam -Wsystem-headers -Werror
> > -Wall -Wno-format-y2k -W -Wstrict-prototypes -Wmissing-prototypes -Wpointer-arith
> > -Wreturn-type -Wcast-qual -Wwrite-strings -Wswitch -Wshadow -Wcast-align
> > -Wno-uninitialized -c /usr/src/lib/libpam/modules/pam_echo/pam_echo.c
> > /usr/src/lib/libpam/modules/pam_echo/pam_echo.c: In function `_pam_echo':
> > /usr/src/lib/libpam/modules/pam_echo/pam_echo.c:92: warning: dereferencing
> > type-punned pointer will break strict-aliasing rules
> > *** Error code 1
>
> I was just about to report this myself. The breakage only occurs with
> optimization levels of -O2 (and maybe higher). Officially -O2 is not
> supported for world, but in my experience there are real problems with
> code (warnings in this case) that do not show up until the optimizer takes
> a closer look at them.
[snip]
It's my impression that these warnings mean the C code in question is
undefined or implementation-defined according to the C standard,
and the generated assembler may have unexpected behavior.
I get this impression from reading the description of
-fstrict-aliasing (enabled at -O2, -O3, -Os) at:
http://gcc.gnu.org/onlinedocs/gcc-3.3/gcc/Optimize-Options.html#Optimize%20Options
(The relevant warning flag is -Wstrict-aliasing, see
http://gcc.gnu.org/onlinedocs/gcc-3.3/gcc/Warning-Options.html#Warning%20Options
)
_______________________________________________
[EMAIL PROTECTED] mailing list
http://lists.freebsd.org/mailman/listinfo/freebsd-current
To unsubscribe, send any mail to "[EMAIL PROTECTED]"
