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From Ed Holyat <ehol...@olf.com>
Subject RE: apr_env_set use of putenv
Date Thu, 22 Apr 2010 23:18:57 GMT
- Windows automatically copies and controls the memory with _putenv, allocating a copy on Windows
should not be done.

- Unix requires a memory allocation, you can free the memory in the environment if you clear
the environment variable.  

e.g.  UNIX

mymem=strdup("FOO=abc");
putenv(mymem);
putenv("FOO=");
free(mymem);

In my opinion it is not worth the coding effort to keep track of the environment variables
you set and then freeing them.  Environment variables should be set once and used for the
life of the program they are not meant to be set and unset over and over again.
UNIX should just be putenv(strdup("FOO=abc"));//set it and forget it.

-----Original Message-----
From: Graham Leggett [mailto:minfrin@sharp.fm] 
Sent: Monday, March 29, 2010 9:55 AM
To: Dan Poirier
Cc: dev@apr.apache.org
Subject: Re: apr_env_set use of putenv

On 29 Mar 2010, at 3:36 PM, Dan Poirier wrote:

> I don't think that's the right pattern to follow.  apr_table is used  
> to
> allocate a new data structure, owned by the caller, and the caller
> certainly should control its lifetime.  apr_env_set() is used to add  
> an
> entry to the OS's environment, which the caller does not own and would
> not expect to have any control over the lifetime of its entries.

 From what I can see of the code right now, the caller is expected to  
control the lifetime of the string that it passes, or set up their own  
cleanup as appropriate to ensure that the environment entry is removed  
if the pool is removed.

The strdup() is by definition a leak, so that isn't ideal at all.

I suspect the docs would need to be updated to warn the caller than if  
they set a string in the environment, they are required to ensure  
their string lives as long as the process, or to register their own  
cleanup if not.

Regards,
Graham
--



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