This is the mail archive of the
mailing list for the glibc project.
Re: [RFC] Make getenv O(1)
- From: Rich Felker <dalias at aerifal dot cx>
- To: OndÅej BÃlka <neleai at seznam dot cz>
- Cc: libc-alpha at sourceware dot org
- Date: Mon, 14 Oct 2013 12:54:12 -0400
- Subject: Re: [RFC] Make getenv O(1)
- Authentication-results: sourceware.org; auth=none
- References: <20131014155229 dot GA25159 at domone dot podge>
On Mon, Oct 14, 2013 at 05:52:29PM +0200, OndÅej BÃlka wrote:
> Hi, when I browsed getenv i found that it uses linear search.
> But in getenv there is code that uses trees and I have doubts about its
> The getenv/setenv could be easily changed to use hash table, does
> something block us to do so?
> A possible complication would be that we need additionaly maintain
> __environ which causes some code overhead.
In general it's impossible to use anything but linear search because
the application can modify environ directly (although it's
questionable whether this is permissible by the standard) or use
putenv and modify the strings after they're added to the environment
(this is explicitly permitted by POSIX). There may be cases where it's
possible to detect that this does not happen and use a faster
approach; I'm not sure.