Hello, Thanks the review and feedback.
On Sat, 16 Dec 2023 05:57:28 +0300 Maxim Dounin <[email protected]> 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 <[email protected]> wrote: > > > > > # HG changeset patch > > > # User J Carter <[email protected]> > > > # 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 <[email protected]> > > # 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. Ah thanks, will include the full stop in future. > > > > > 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. Yes, that was the obvious one - I suspect upstream_random balancers might act strangely in extreme cases (I'm not entirely sure though). Other uses I'm not sure at all, as those are more domain specific (like resolver). > 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(). Yes the alternative would seem to be #ifdefs for win32 vs unix, or adding in an 'ngx_random_max', or writing (or borrowing) a posix random implementation into nginx's codebase. > > 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. Thanks, will note for the future. > > > + ((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. Yep, makes sense. > > 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() > > > Looks good to me. _______________________________________________ nginx-devel mailing list [email protected] https://mailman.nginx.org/mailman/listinfo/nginx-devel
