0004499: Changes to the environment are invisible to Sys.getenv

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0004499

OCaml

OCaml windows

public

2008-02-05 18:10

2012-09-15 11:57

Reporter

frisch

Assigned To

Priority

normal

Severity

minor

Reproducibility

always

Status

acknowledged

Resolution

open

Platform

Windows

OS Version

Product Version

Target Version

4.00.2+dev

Fixed in Version

Summary

0004499: Changes to the environment are invisible to Sys.getenv

Description

Windows has functions like SetEnvironmentVariable/GetEnvironmentVariable to access the process environment. The MS C runtime library also has getenv/putenv functions, but they operate on a snapshot of the environment taken when the process started. putenv also push modifications to the real environment through SetEnvironmentVariable.

So, if we mix in a single process OCaml code and other native code that set environment variables directly (from .Net, we only have SetEnvironmentVariable, not putenv), these changes are not seen from OCaml, which uses getenv.

A fix would be to use the "native" win32 functions for OCaml (not only for implementing Sys.getenv, but also for all the calls to getenv in the runtime system; and some care is needed for execve).

(At LexiFi, we use a temporary solution: we have a function to "refresh" the local copy of the environment in the libc by fetching all the real environment variable and putenv'ing them.)

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Notes
(0004452) doligez (manager) 2008-02-19 14:49	I could easily argue that this is a bug in the getenv of the MS C runtime library.

(0007582) frisch (developer) 2012-06-20 11:25	> I could easily argue that this is a bug in the getenv of the MS C runtime library. Probably, but it's easier (for us) to work-around the problem on the OCaml side than to convince Microsoft to fix their C runtime. As long as the effort remains reasonable, I think it's good to provide a coherent semantics between all the supported OCaml ports, even if this requires to work around bugs created by third parties.

(0008078) doligez (manager) 2012-09-15 11:57	The right solution is probably to define our own functions sys_getenv and sys_putenv once with system-dependent code, and then use them everywhere. In fact, from your description it seems we only need to redefine getenv.

Issue History
Date Modified	Username	Field	Change
2008-02-05 18:10	frisch	New Issue
2008-02-19 14:49	doligez	Note Added: 0004452
2008-02-19 14:49	doligez	Status	new => acknowledged
2012-06-20 11:20	frisch	Category	OCaml general => OCaml windows
2012-06-20 11:25	frisch	Note Added: 0007582
2012-07-11 15:58	doligez	Target Version	=> 4.01.0+dev
2012-07-31 13:37	doligez	Target Version	4.01.0+dev => 4.00.1+dev
2012-09-15 11:57	doligez	Note Added: 0008078
2012-09-15 11:57	doligez	Target Version	4.00.1+dev => 4.00.2+dev