| Re: IDL/DLM segmentation fault on reset [message #72311] |
Tue, 31 August 2010 08:24  |
Haje Korth
Messages: 651
Registered: May 1997
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Senior Member |
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Hi Karl,
thanks so much for your reply. You are exactly right, the variable
input to putenv is a static char*, and your description of what is
going on makes sense. I will give setenv a shot later today and report
back.
Cheers,
haje
On Aug 31, 10:54 am, Karl <karl.w.schu...@gmail.com> wrote:
> On Aug 30, 6:34 pm, Haje Korth <hajeko...@gmail.com> wrote:
>
>> Hi,
>> Have an interesting problem for DLM programmers out there. I have a C
>> code for Linux that sets an environment variable using putenv() within
>> a DLM. The code executes as designed but when I issue
>> a .full_session_reset I get a segmentation fault and IDL exits
>> ungracefully. I run the same code (with slightly different calling
>> convention) under Windows without problems. Does anyone know why? Do I
>> need some sort of exit handler for the DLM (similar to IDL_Load for
>> startup)?
>
>> Haje
>
> The putenv() function just puts a pointer to the string in the
> environment. It does not make a copy of the string.
>
> The full session reset unloads the DLM. Your string argument to
> putenv() probably resides in a static var in the DLM. The environment
> is just a list of pointers to strings. When the DLM got unloaded, the
> environment is left with an invalid pointer to a string. I can't say
> exactly what was going on when the segmentation fault occurred, but it
> is easy to imagine that some system routine running during the session
> reset was probably walking the environment strings and hit the bogus
> pointer.
>
> You might try using setenv() instead. The setenv() function allocates
> heap memory for environment strings, and thus avoids the string memory
> from getting unallocated by a unload of a module or an automatic
> variable going out of scope.
>
> It worked on Windows because Windows probably stores the environment
> strings differently.
>
> Karl
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