Bug in nginx 0.7.xx ./configure procedure

[Igor Sysoev]

On Mon, Mar 23, 2009 at 11:03:29PM -0700, Michael Shadle wrote:

> when my "make" runs this is what i see:
> 
> gcc -c -O -pipe  -O -W -Wall -Wpointer-arith -Wno-unused-parameter
> -Wno-unused-function -Wunused-variable -Wunused-value -Werror -g  -I
> src/core -I src/event -I src/event/modules -I src/os/unix -I
> /usr/lib/include -I /usr/include/libxml2 -I objs \
>                 -o objs/src/core/ngx_array.o \
>                 src/core/ngx_array.c
> 
> that is as optimal as it should be for an x86_64 ubuntu linux box,
> basically, right?

Yes, -O is enough.

> 2009/3/23 Igor Sysoev <is at rambler-co.ru>:
> > On Mon, Mar 23, 2009 at 09:56:45PM +0000, Mark Alan wrote:
> >
> >> mike wrote:
> >> >What does this do?
> >> >
> >> ># ensure that there is only one -O in CFLAGS and that it is -O2
> >>
> >> When we use --with-cc-opt= to specify any alternative -On C compiler
> >> optimization, there seems to be a bug (or is it a designed feature?) in
> >> nginx's ./configure that leads to the following line in the created
> >> objs/Makefile file:
> >>
> >> CFLAGS =  -O -pipe  -O -W -Wall -Wpointer-arith -Wno-unused-parameter
> >> -Wno-unused-function -Wunused-variable -Wunused-value -Werror -g -O2
> >>
> >>
> >> If I am not wrong, that line should only have one instance of -O:
> >>
> >> CFLAGS = -pipe -W -Wall -Wpointer-arith -Wno-unused-parameter
> >> -Wno-unused-function -Wunused-variable -Wunused-value -Werror -g -O2
> >>
> >>
> >> Hence the usage of the command sed -i '/CFLAGS/s/ \-O //g' objs/Makefile
> >> to clean the other instances of -O.
> >>
> >> From man cc:
> >> " -O2 Optimize even more.
> >> (...)
> >> As compared to -O, this option increases both compilation time and the
> >> performance of the generated code."
> >
> > As I understand gcc uses the lastest -O option, therefore -O -O2 is the same
> > as -O2. Also you may disable optimizations using -O -O0. As to -O2 itself,
> > I believe you would not see any significant changes in nginx with -O2
> > if compared with just -O. However, -O0 vs -O change is dramatically.
> >
> >
> > --
> > Igor Sysoev
> > http://sysoev.ru/en/
> >
> >
> 
> hen

-- 
Igor Sysoev
http://sysoev.ru/en/