Re: native Win32 guile 1.7.0

[stefan]

On Thu, 12 Jun 2003, Kevin Ryde wrote:

> > I just added a check for unsetenv() in the configure script and used it in
> > posix.c appropiately for mingw32 hosts.  Which means that a
> > putenv("name="); would remove the environment variable 'name'.
>
> I guess this means it's not possible to use putenv("name=") to set
> name to an empty string.  I'm pretty sure it's valid to do so on other
> systems.
>
> On wine, which might not be the same as a real mingw, setting "name= "
> and then changing that space to a \0 does the trick.  Bit nasty to go
> changing putenvs strings like that, but unless there's a setenv or
> some function hiding then there might be no choice.  Eg, (untested),
>
>
>
>       /* If str is "FOO=", ie. attempting to set an empty string, then we
>          need to see if it's been successful.  On MINGW, "FOO=" means remove
>          FOO from the environment.  As a workaround, we set "FOO= ", ie. a
>          space, and then modify the string returned by getenv.  It's not
>          enough just to modify the string we set, because MINGW putenv
>          copies it.  */
>       if (ptr[SCM_STRING_LENGTH(str)-1] == '=')
>         {
>           SCM name = scm_substring (str, SCM_MAKINUM (0),
>                                     SCM_MAKINUM (SCM_STRING_LENGTH (str) - 
> 1));
>           if (getenv (SCM_STRING_CHARS (name)) == NULL)
>             {
>               char  *alt = scm_malloc (SCM_STRING_LENGTH (str) + 2);
>               memcpy (alt, SCM_STRING_CHARS (str), SCM_STRING_LENGTH(str));
>               alt[SCM_STRING_LENGTH(str)] = ' ';
>               alt[SCM_STRING_LENGTH(str)+1] = '\0';
>               rv = putenv (alt);
>               if (rv < 0)
>                 SCM_SYSERROR;
>               free (ptr);   /* don't need the old string we gave to putenv */
>               alt = getenv (SCM_STRING_CHARS (name));
>               alt[SCM_STRING_LENGTH(str)] = '\0';
>             }
>         }

I tested this piece of code on  my Win95 box and modified it a bit to get
it really working.  Then I applied the code CVS.  The (putenv) primitive
now behaves equally on GNU/Linux and Win32.

Cheers,
        address@hidden