extern char **environ and msvc

[Frank Richter]

On 25.05.2011 22:52, Stefan Dösinger wrote:
> I'm sorry for the German, I don't know how to change this. Google finds only 
> other clueless people. Either way it says something like "Inconsistent DLL 
> binding"

I believe the English translation is “inconsistent DLL linkage”.

> 
> The line in stdlib.h declares _environ as
> 
> _CRTIMP extern char ** _environ;    /* pointer to environment table */
> 
> The compiler just writes a warning, but afterwards linking fails:
> 
> 1>loader.obj : error LNK2001: Nicht aufgelöstes externes Symbol "__environ".
> 
> The linker complains about an "unresolved external symbol __environ". Removing 
> our declaration of environ fixes the warning, link error and libwine seems to 
> work OK.
> 
> I don't know what the proper fix is, please advise. Maybe this code shouldn't 
> be compiled at all? I don't think I need the loader code on Windows.

The underlying issue is probably the _CRTIMP - that's most likely
_declspec(dllimport) in MSVC. This matters, as DLL-imported and “plain”
extern variables are handled differently on Windows.
IIRC DLL export/import of variables is indirect - when DLL-importing a
variable you really import a _pointer_ to the variable. So accessing the
variable dereferences some pointer. “extern” variables, otoh, are
accessed directly (resolving the actual variable location is handled at
link-time).

-f.r.

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