cannot build with gcc 4.7.1 and -O2

[Brent Garber]

gcc -c -pipe  -O -W -Wall -Wpointer-arith -Wno-unused-parameter -Werror -g -O2 -I src/core -I src/event -I src/event/modules -I src/os/unix -I objs -I src/http -I src/http/modules \
		-o objs/src/http/ngx_http_core_module.o \
		src/http/ngx_http_core_module.c
src/http/ngx_http_core_module.c: In function ‘ngx_http_get_forwarded_addr’:
src/http/ngx_http_core_module.c:2779:13: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
cc1: all warnings being treated as errors
make[1]: *** [objs/src/http/ngx_http_core_module.o] Error 1
make[1]: Leaving directory `/usr/src/nginx-1.3.5'
make: *** [build] Error 2
make -f objs/Makefile install
make[1]: Entering directory `/usr/src/nginx-1.3.5'
gcc -c -pipe  -O -W -Wall -Wpointer-arith -Wno-unused-parameter -Werror -g -O2 -I src/core -I src/event -I src/event/modules -I src/os/unix -I objs -I src/http -I src/http/modules \
		-o objs/src/http/ngx_http_core_module.o \
		src/http/ngx_http_core_module.c
src/http/ngx_http_core_module.c: In function ‘ngx_http_get_forwarded_addr’:
src/http/ngx_http_core_module.c:2779:13: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
cc1: all warnings being treated as errors
make[1]: *** [objs/src/http/ngx_http_core_module.o] Error 1
make[1]: Leaving directory `/usr/src/nginx-1.3.5'
make: *** [install] Error 2

[Brent Garber]

This is GCC 4.7.1

[Brent Garber]

Appeared somewhere between r4623 and r4629 but with different build errors in that range, cannot narrow it down any more.

And only appears when compiling with -O2, -O1 appears to compile w/o errors.

[Ruslan Ermilov]

Replying to Brent Garber <bgarber42@gmail.com>:

This is GCC 4.7.1

What Linux distribution do you use?

According to ​http://www.linode.com/faq.cfm, there's plenty of options.

[Brent Garber]

Debian unstable, GNU toolchain is 4.7.1-7

[Ruslan Ermilov]

Replying to Brent Garber <bgarber42@gmail.com>:

Debian unstable, GNU toolchain is 4.7.1-7, 4.6.3-9 works with -O2 however.

Please try the patch I have attached.

[Brent Garber]

That seems to do the trick:

# ./nginx -V
nginx version: nginx/1.3.5
built by gcc 4.7.1 (Debian 4.7.1-7) 
TLS SNI support enabled
configure arguments: --prefix=/etc/nginx --sbin-path=/usr/sbin/nginx --conf-path=/etc/nginx/nginx.conf --pid-path=/var/run/nginx.pid --lock-path=/var/lock/nginx.lock --error-log-path=/var/log/nginx/error.log --http-log-path=/var/log/nginx/access.log --user=www-data --group=www-data --with-ipv6 --with-http_ssl_module --with-http_gzip_static_module --with-http_stub_status_module --with-pcre-jit --with-sha1-asm --with-sha1=/usr/include --with-cc-opt=-O2 --with-cpu-opt=native

[Ruslan Ermilov]

Thanks for testing!

[Ruslan Ermilov]

In 4829/nginx:

Fixed strict aliasing bugs when dealing with IPv4-mapped IPv6 addresses
(closes #201).

[Maxim Dounin]

In 4858/nginx:

Merge of r4829: fixed strict aliasing with ipv6 (ticket #201).

Fixed strict aliasing bugs when dealing with IPv4-mapped IPv6
addresses.