> On 16 Dec 2023, at 06:57, Maxim Dounin <mdou...@mdounin.ru> wrote: > > Hello! > > On Sat, Dec 09, 2023 at 08:42:11AM +0000, J Carter wrote: > >> On Sat, 09 Dec 2023 07:46:10 +0000 >> J Carter <jordanc.car...@outlook.com> wrote: >> >>> # HG changeset patch >>> # User J Carter <jordanc.car...@outlook.com> >>> # Date 1702101635 0 >>> # Sat Dec 09 06:00:35 2023 +0000 >>> # Node ID 1a77698f82d2580aa8b8f62ce89b4dbb6d678c5d >>> # Parent d9275e982a7188a1ea7855295ffa93362ea9830f >>> Win32: extended ngx_random range to 0x7fffffff >>> >>> rand() is used on win32. RAND_MAX is implementation defined. win32's is >>> 0x7fff. >>> >>> Existing uses of ngx_random rely upon 0x7fffffff range provided by >>> posix implementations of random(). >>> >>> diff -r d9275e982a71 -r 1a77698f82d2 src/os/win32/ngx_win32_config.h >>> --- a/src/os/win32/ngx_win32_config.h Sat Dec 09 05:09:07 2023 +0000 >>> +++ b/src/os/win32/ngx_win32_config.h Sat Dec 09 06:00:35 2023 +0000 >>> @@ -280,7 +280,9 @@ >>> >>> #define NGX_HAVE_GETADDRINFO 1 >>> >>> -#define ngx_random rand >>> +#define ngx_random >>> \ >>> + ((rand() << 16) | (rand() << 1) | (rand() >> 14)) >>> + >>> #define ngx_debug_init() >>> >>> >> >> ^ my mistake - copying error.. >> >> # HG changeset patch >> # User J Carter <jordanc.car...@outlook.com> >> # Date 1702111094 0 >> # Sat Dec 09 08:38:14 2023 +0000 >> # Node ID 10ef59a412a330872fc6d46de64f42e32e997b3a >> # Parent d9275e982a7188a1ea7855295ffa93362ea9830f >> Win32: extended ngx_random range to 0x7fffffff > > Nitpicking: > > Win32: extended ngx_random() range to 0x7fffffff. > >> >> rand() is used on win32. RAND_MAX is implementation defined. win32's is >> 0x7fff. >> >> Existing uses of ngx_random rely upon 0x7fffffff range provided by >> posix implementations of random(). > > Thanks for catching this. > > As far as I can see, the only module which actually relies on the > range is the random index module. Relying on the ngx_random() > range generally looks wrong to me, and we might want to change the > code to don't. OTOH, it's the only way to get a completely > uniform distribution, and that's what the module tries to do. As > such, it might be good enough to preserve it as is, at least till > further changes to ngx_random(). > > Either way, wider range for ngx_random() should be beneficial in > other places. > >> >> diff -r d9275e982a71 -r 10ef59a412a3 src/os/win32/ngx_win32_config.h >> --- a/src/os/win32/ngx_win32_config.h Sat Dec 09 05:09:07 2023 +0000 >> +++ b/src/os/win32/ngx_win32_config.h Sat Dec 09 08:38:14 2023 +0000 >> @@ -280,7 +280,9 @@ >> >> #define NGX_HAVE_GETADDRINFO 1 >> >> -#define ngx_random rand >> +#define ngx_random() >> \ > > Nitpicking: the "\" character should be at the 79th column (in > some files at 78th). This ensures that a diff won't wrap on a > standard 80-column terminal. > >> + ((rand() << 16) | (rand() << 1) | (rand() >> 14)) >> + >> #define ngx_debug_init() > > Using "|" for random numbers looks utterly wrong to me, even if > ORed values are guaranteed to not interfere. > > I would rather use "^", and avoid dependency on the particular > value of RAND_MAX (other than POSIX-required minimum of 32767) by > using something like > > 0x7fffffff & ((rand() << 16) ^ (rand() << 8) ^ rand()) > > with proper typecasts. > > Something like this should work: > > diff --git a/src/os/win32/ngx_win32_config.h b/src/os/win32/ngx_win32_config.h > --- a/src/os/win32/ngx_win32_config.h > +++ b/src/os/win32/ngx_win32_config.h > @@ -280,7 +280,11 @@ typedef int sig_atomic_t > > #define NGX_HAVE_GETADDRINFO 1 > > -#define ngx_random rand > +#define ngx_random() > \ > + ((long) (0x7fffffff & ( ((uint32_t) rand() << 16) > \ > + ^ ((uint32_t) rand() << 8) > \ > + ^ ((uint32_t) rand()) ))) > + > #define ngx_debug_init() > >
Nitpicking: you might want to re-align the "^" operator to the first symbol of the left-hand operand (similar to NGX_CONF_TAKE1234, or even NGX_UNIX_ADDRSTRLEN). Other than that, it looks good. -- Sergey Kandaurov _______________________________________________ nginx-devel mailing list nginx-devel@nginx.org https://mailman.nginx.org/mailman/listinfo/nginx-devel
