Bug 448743

This problem was first seen in the F-9 build of FreeRADIUS when the server
failed to listen on the correct port (bug #446864). It was observed the program
behaved correctly when compiled without optimization.

I have tracked the problem down by examining generating a preprocessed source
file, compiling that under the same options and then looking at the disassembled
code. It appears as though the following statement in the original C code in the
function fr_socket(), line 208, file packet.c):

sa->sin_port = htons((uint16_t) port);

is not generating any code when compiled with -O2 on i386, this leaves the port
unspecified leading to incorrect program behavior. That line when preprocessed
expands to:

sa->sin_port = (__extension__ ({ register unsigned short int __v, __x =
((uint16_t) port); if (__builtin_constant_p (__x)) __v = ((((__x) >> 8) & 0xff)
| (((__x) & 0xff) << 8)); else __asm__ ("rorw $8, %w0" : "=r" (__v) : "0" (__x)
: "cc"); __v; }));

Examination of the disassembled code in GDB shows sa->sin_port is never assigned
(or at least I believe that is the case, it's not always easy to correctly
interpret generated machine code).

I have attached the original C source file (packet.c), the preprocessed file
(packet.i with some annotations correlating it to the original C code), the
object file (packet.o), and the disassembled function (packet.asm).

The compiler version used was (Note this may not be the compiler used on the
build systems when the problem was first seen, but it reproduces with this):

[jdennis@localhost F-9]$ gcc -v
Using built-in specs.
Target: i386-redhat-linux
Configured with: ../configure --prefix=/usr --mandir=/usr/share/man
--infodir=/usr/share/info --with-bugurl=http://bugzilla.redhat.com/bugzilla
--enable-bootstrap --enable-shared --enable-threads=posix
--enable-checking=release --with-system-zlib --enable-__cxa_atexit
--disable-libunwind-exceptions
--enable-languages=c,c++,objc,obj-c++,java,fortran,ada --enable-java-awt=gtk
--disable-dssi --enable-plugin
--with-java-home=/usr/lib/jvm/java-1.5.0-gcj-1.5.0.0/jre
--enable-libgcj-multifile --enable-java-maintainer-mode
--with-ecj-jar=/usr/share/java/eclipse-ecj.jar --disable-libjava-multilib
--with-cpu=generic --build=i386-redhat-linux
Thread model: posix
gcc version 4.3.0 20080428 (Red Hat 4.3.0-8) (GCC) 

The command line to compile the original C codes was:

gcc -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector
--param=ssp-buffer-size=4 -m32 -march=i686 -mtune=generic
-fasynchronous-unwind-tables -fpic -D_LIBRADIUS
-I/home/jdennis/src/fedora/freeradius/F-9/freeradius-server-2.0.3/src -c
packet.c  -fPIC -DPIC -o .libs/packet.o

The command line used to generate the preprocessed file (packet.i) was:

gcc -E -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector
--param=ssp-buffer-size=4 -m32 -march=i386 -mtune=generic
-fasynchronous-unwind-tables -fpic -D_LIBRADIUS 
-I/home/jdennis/src/fedora/freeradius/F-9/freeradius-server-2.0.3/src -c
packet.c  -fPIC -DPIC > ../../../packet.i

The command line used to complile the preprocessed file into machine code was:

gcc -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector
--param=ssp-buffer-size=4 -m32 -march=i386 -mtune=generic
-fasynchronous-unwind-tables -fpic -D_LIBRADIUS 
-I/home/jdennis/src/fedora/freeradius/F-9/freeradius-server-2.0.3/src -c
packet.i  -fPIC -DPIC

I wonder if the culprit is the __extension__ pragma, that is the only statement
which seems to omit generated code.