commit | af09ff1981063b28705726a86b913dfa98d70942 | [log] [tgz] |
---|---|---|
author | Richard Miller <miller.research@gmail.com> | Mon May 25 10:30:23 2020 +0100 |
committer | David du Colombier <0intro@gmail.com> | Fri Jun 19 11:28:19 2020 +0000 |
tree | 1c0f50ad28534c7c37904c0a6658d05df8420f08 | |
parent | 3dec253783e1211989102ac6abd34cddbf8ba0e6 [diff] |
runtime, syscall: use local cache for Setenv/Getenv in Plan 9 In os.Getenv and os.Setenv, instead of directly reading and writing the Plan 9 environment device (which may be shared with other processes), use a local copy of environment variables cached at the start of execution. This gives the same semantics for Getenv and Setenv as on other operating systems which don't share the environment, making it more likely that Go programs (for example the build tests) will be portable to Plan 9. This doesn't preclude writing non-portable Plan 9 Go programs which make use of the shared environment semantics (for example to have a command which exports variable definitions to the parent shell). To do this, use ioutil.ReadFile("/env/"+key) and ioutil.WriteFile("/env/"+key, value, 0666) in place of os.Getenv(key) and os.Setenv(key, value) respectively. Note that CL 5599054 previously added env cacheing, citing efficiency as the reason. However it made the cache write-through, with Setenv changing the shared environment as well as the cache (so not consistent with Posix semantics), and Clearenv breaking the sharing of the environment between the calling thread and other threads (leading to unpredictable behaviour). Because of these inconsistencies (#8849), CL 158970045 removed the cacheing again. This CL restores cacheing but without write-through. The local cache is initialised at start of execution, manipulated by the standard functions in syscall/env_unix.go to ensure the same semantics, and exported only when exec'ing a new program. Fixes #34971 Fixes #25234 Fixes #19388 Updates #38772 Change-Id: I2dd15516d27414afaf99ea382f0e00be37a570c3 Reviewed-on: https://go-review.googlesource.com/c/go/+/236520 Run-TryBot: David du Colombier <0intro@gmail.com> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Fazlul Shahriar <fshahriar@gmail.com> Reviewed-by: David du Colombier <0intro@gmail.com>
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