Date: Tue, 1 May 2007 23:31:46 +0400 From: Andrey Chernov <ache@freebsd.org> To: John Baldwin <jhb@freebsd.org> Cc: Alfred Perlstein <alfred@freebsd.org>, src-committers@freebsd.org, cvs-all@freebsd.org, cvs-src@freebsd.org Subject: Re: cvs commit: src/usr.sbin/sysinstall main.c Message-ID: <20070501193146.GD10323@nagual.pp.ru> In-Reply-To: <200705011210.12839.jhb@freebsd.org> References: <200704301516.l3UFGJbu019162@repoman.freebsd.org> <20070501000242.GA19510@nagual.pp.ru> <20070501100642.GB823@turion.vk2pj.dyndns.org> <200705011210.12839.jhb@freebsd.org>
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On Tue, May 01, 2007 at 12:10:11PM -0400, John Baldwin wrote: > Now, that said, apparently some folks on this list CAN'T READ. > > Linux has the new putenv() algorithm already, so if any software breaks with > this, it is _ALREADY_ broken on Linux. Please consider that before ripping > ache@ a new one here. As much as BSD wants to feel really important, in > truth, most of the software in ports probably runs more often on Linux than > on BSD, so I think the chances of non-trivial real-world breakage are fairly > small. And I already tell exactly so about Linux and ports already portable in the threads. Perhaps they will hear you better, but the changes in question are already backed out and I can't work on them under such pressure. In case anyone brave will be found, feel free to restore, and then I'll promise my help dealing with all bugs they may cause. > So with all that said, it seems we have four groups of usage with respect to > putenv(3): > > - give it a stack allocated or otherwise non-persistent buffer (note that > string constants are persistent, even if they are read-only) as the first > argument. This violates POSIX I guess, and would break on at least Linux and > Solaris (judging by Open Solaris's putenv() implementation). Agreed. > - pass in a persistent buffer (constant, allocated memory, etc.) and change > the contents later expecting that changing the buffer won't change the > environment. This breaks Linux and Solaris and POSIX as well. Agreed. > - pass in a persistent buffer and don't change it afterwards (at least not > until after a later call to putenv or setenv for the same variable). This > works for both impls and is probably the vast majority of usage. Agreed. Most programs don't use the modify-env-on-the-fly feature, but it is at the current moment, just because several putenv() implementations was hanging around when no one standartized. When POSIX explicitly standartize modify-env-on-the-fly feature, more programs will tend to try it at time. > - pass in a persistent buffer and change the contents expecting that it will > change the value returned from getenv(). This doesn't work on BSD, but does > on Linux + Solaris + POSIX + FreeBSD 7. Agreed (but not for FreeBSD7 now). > So we have four groups: 1, 2, 3 (likely the vast majority), and 4. (4) is > fixed by this commit, and works on Linux, Solaris, and POSIX. (1 + 2) are > broken by this commit, but they also don't work on Linux, Solaris, or POSIX. > So the question seems to be, which set is larger, programs that depend on (1 + > 2), or programs that depend on (4)? Also, which set is going to get larger > as time moves on given Linux's implementation? If you assume (as I do), that > most programs fall into (3) anyway, then it really isn't all that important > anyway. Set 3 is larger now, but popularity of set 4 perhaps will be increased in the future because it is standard. Set 1 is small and will be decreased. -- http://ache.pp.ru/
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