On Wed, Apr 27, 2016 at 2:39 AM, Christian Ullrich <ch...@chrullrich.net> wrote:
> * Christian Ullrich wrote:
>> wrong even without considering the debug/release split. If we load a
>> compiled extension built with a CRT we have not seen yet, _after_ the
>> first call to pgwin32_putenv(), that module's CRT's view of its
>> environment will be frozen because we will never attempt to update it.
> Four patches attached:
> master --- 0001 --- 0002 --- 0003
>                          \
>                           `- 0004
> 0001 is just some various fixes to set the stage.
> 0002 fixes this "load race" by not remembering a negative result anymore.
> However, ...

>From 0001, which does not apply anymore on HEAD because of the
integration with MS2015:
                    if (rtmodules[i].putenvFunc == NULL)
-                       CloseHandle(rtmodules[i].hmodule);
                        rtmodules[i].hmodule = INVALID_HANDLE_VALUE;
Nice catch. This portion is a bug and should be backpatched. As far as
I can read from MS docs, GetModuleHandle() retrieves an existing
handle so there is no need to free it. Or that would fail.

And actually, by looking at those patches, isn't it a dangerous
practice to be able to load multiple versions of the same DLL routines
in the same workspace? I have personally very bad souvenirs with that,
and particularly loading multiple versions of msvcr into the same
workspace can cause unwanted crashes and corruptions of processes. In
short I mean this thing: https://en.wikipedia.org/wiki/DLL_Hell.

So, shouldn't we first make the DLL list a little bit more severe
depending on the value of _MSC_VER? I would mean something like that:
#ifdef _MSC_VER >= 1900
{"ucrtbase",    NULL,   NULL},
#elif _MSC_VER >= 1800
{"msvcr120",    NULL,   NULL},
#elif etc, etc.

This would require modules to be built using the same msvc version as
the core server, but that's better than just plain crash if loaded
DLLs corrupt the stack. Am I missing something?

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