Re: [HACKERS] pgsql: Add putenv support for msvcrt from Visual Studio 2013

2016-12-04 Thread Michael Paquier 
On Sun, Dec 4, 2016 at 5:58 AM, Noah Misch  wrote:
> On Wed, Nov 30, 2016 at 04:24:34PM +, Christian Ullrich wrote:
>> * From: Michael Paquier
>> > would be nice to mention in a code comment that this what Noah has
>> > mentioned upthread: if a CRT loads while pgwin32_putenv() is
>> > executing, the newly-loaded CRT will always have the latest value.
>>
>> I fixed the existing comment by removing the last sentence that is in the 
>> wrong place now, but I don't see the point in suddenly starting to explain 
>> why it is done this way and not the other.
>>
>> > Based on that 0006 will need a rebase, nothing huge though.
>>
>> Done, new revisions attached.
>
> I committed patches 1-7 with some comment changes, a pgindent, and other
> cosmetic trivia.  (The file was pgindent-clean before this work.  Patch 6
> still achieved the more-compact formatting you sought.)

Thanks all for helping in closing this item. We have a fine result here.
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Re: [HACKERS] pgsql: Add putenv support for msvcrt from Visual Studio 2013

2016-12-03 Thread Noah Misch 
On Wed, Nov 16, 2016 at 08:45:20PM +, Christian Ullrich wrote:
> * Noah Misch wrote:
> > I prefer the simplicity of abandoning the cache (patch 4), if it
> > performs decently.  Would you compare the performance of patch 1,
> > patches 1+2+3, and patches 1+2+4?  This should measure the right 
> > thing (after substituting @libdir@ for your environment):
> 
> Tested with release builds; Core i7-6700K (quad/HT; 4000 MHz).
> I did three runs each, and they were always within 0.5 % of each
> other's run time.
> 
> - patch 1 (now 1-3): 24 μs/iteration (24 s for 1e6)
> - patch 1+2+3 (now 1-5 + 8): 29 μs/iteration
> - patch 1+2+4 (now 1-7): 30 μs/iteration

Thanks for measuring; 6μs*9=54μs is a negligible addition to Windows backend
startup time.

On Wed, Nov 30, 2016 at 04:24:34PM +, Christian Ullrich wrote:
> * From: Michael Paquier
> > would be nice to mention in a code comment that this what Noah has
> > mentioned upthread: if a CRT loads while pgwin32_putenv() is
> > executing, the newly-loaded CRT will always have the latest value.
> 
> I fixed the existing comment by removing the last sentence that is in the 
> wrong place now, but I don't see the point in suddenly starting to explain 
> why it is done this way and not the other.
> 
> > Based on that 0006 will need a rebase, nothing huge though.
> 
> Done, new revisions attached.

I committed patches 1-7 with some comment changes, a pgindent, and other
cosmetic trivia.  (The file was pgindent-clean before this work.  Patch 6
still achieved the more-compact formatting you sought.)


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Re: [HACKERS] pgsql: Add putenv support for msvcrt from Visual Studio 2013

2016-12-02 Thread Robert Haas 
On Wed, Nov 30, 2016 at 2:56 AM, Michael Paquier
 wrote:
> On Tue, Nov 29, 2016 at 08:45:13PM +0100, Christian Ullrich wrote:
>> * Michael Paquier wrote:
>>
>> > On Wed, Nov 16, 2016 at 12:45 PM, Christian Ullrich
>> >  wrote:
>> >> I also did a debug build with 1+2+4 that came in at 84 μs/iteration.
>> >
>> > Moved to next CF. Christian, perhaps this patch should have an extra
>> > round of reviews?
>>
>> It is significantly different from the last version, so yes, of course.
>
> Patches 0001 (Cosmetic fixes), 0002 (Remove unnecessary CloseHandle)
> and 0003 (support for debug CRTs) look in good shape to me. 0004 (Fix
> load race) is 0002 from the previous set, and this change makes sense
> in itself.

0001 looks fine insofar as it makes things consistent regarding 0 vs.
NULL, but the whitespace changes will be reverted by pgindent.  (I
just tested.)

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Re: [HACKERS] pgsql: Add putenv support for msvcrt from Visual Studio 2013

2016-11-30 Thread Michael Paquier 
On Thu, Dec 1, 2016 at 1:24 AM, Christian Ullrich  wrote:
> * From: Michael Paquier
>
>> With 0005 I am seeing a compilation failure: you need to have the
>> declarations in the _MSC_VER block at the beginning of the routine. It
>
> Sorry, too used to C++.
>
>> would be nice to mention in a code comment that this what Noah has
>> mentioned upthread: if a CRT loads while pgwin32_putenv() is
>> executing, the newly-loaded CRT will always have the latest value.
>
> I fixed the existing comment by removing the last sentence that is in the 
> wrong place now, but I don't see the point in suddenly starting to explain 
> why it is done this way and not the other.
>
>> Based on that 0006 will need a rebase, nothing huge though.
>
> Done, new revisions attached.

Okay, switched as ready for committer.
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Re: [HACKERS] pgsql: Add putenv support for msvcrt from Visual Studio 2013

2016-11-30 Thread Christian Ullrich 
* From: Michael Paquier

> With 0005 I am seeing a compilation failure: you need to have the
> declarations in the _MSC_VER block at the beginning of the routine. It

Sorry, too used to C++.

> would be nice to mention in a code comment that this what Noah has
> mentioned upthread: if a CRT loads while pgwin32_putenv() is
> executing, the newly-loaded CRT will always have the latest value.

I fixed the existing comment by removing the last sentence that is in the wrong 
place now, but I don't see the point in suddenly starting to explain why it is 
done this way and not the other.

> Based on that 0006 will need a rebase, nothing huge though.

Done, new revisions attached.

-- 
Christian



0005-Do-the-process-environment-update-first.patch
Description: 0005-Do-the-process-environment-update-first.patch


0006-Fix-the-unload-race-as-best-we-can.patch
Description: 0006-Fix-the-unload-race-as-best-we-can.patch

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Re: [HACKERS] pgsql: Add putenv support for msvcrt from Visual Studio 2013

2016-11-29 Thread Michael Paquier 
On Tue, Nov 29, 2016 at 08:45:13PM +0100, Christian Ullrich wrote:
> * Michael Paquier wrote:
>
> > On Wed, Nov 16, 2016 at 12:45 PM, Christian Ullrich
> >  wrote:
> >> I also did a debug build with 1+2+4 that came in at 84 μs/iteration.
> >
> > Moved to next CF. Christian, perhaps this patch should have an extra
> > round of reviews?
>
> It is significantly different from the last version, so yes, of course.

Patches 0001 (Cosmetic fixes), 0002 (Remove unnecessary CloseHandle)
and 0003 (support for debug CRTs) look in good shape to me. 0004 (Fix
load race) is 0002 from the previous set, and this change makes sense
in itself.

With 0005 I am seeing a compilation failure: you need to have the
declarations in the _MSC_VER block at the beginning of the routine. It
would be nice to mention in a code comment that this what Noah has
mentioned upthread: if a CRT loads while pgwin32_putenv() is
executing, the newly-loaded CRT will always have the latest value.

Based on that 0006 will need a rebase, nothing huge though.

Removing the caching per the measurements upthread is causing a 1us
regression compared to the full set. Let's do things simple then! This
smells like noise.
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Re: [HACKERS] pgsql: Add putenv support for msvcrt from Visual Studio 2013

2016-11-29 Thread Christian Ullrich 

* Michael Paquier wrote:

> On Wed, Nov 16, 2016 at 12:45 PM, Christian Ullrich
>  wrote:
>> I also did a debug build with 1+2+4 that came in at 84 μs/iteration.
>
> Moved to next CF. Christian, perhaps this patch should have an extra
> round of reviews?

It is significantly different from the last version, so yes, of course.

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Re: [HACKERS] pgsql: Add putenv support for msvcrt from Visual Studio 2013

2016-11-28 Thread Michael Paquier 
On Wed, Nov 16, 2016 at 12:45 PM, Christian Ullrich
 wrote:
> I also did a debug build with 1+2+4 that came in at 84 μs/iteration.

Moved to next CF. Christian, perhaps this patch should have an extra
round of reviews?
-- 
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Re: [HACKERS] pgsql: Add putenv support for msvcrt from Visual Studio 2013

2016-11-16 Thread Christian Ullrich 
* Noah Misch wrote:

> On Tue, Apr 26, 2016 at 07:39:29PM +0200, Christian Ullrich
> wrote:

> > * Christian Ullrich wrote:

> Patch 1 looks good, except that it should be three patches:
> 
> - cosmetic parts: change whitespace and s/0/NULL/
> - remove CloseHandle() call
> - probe for debug CRT modules, not just release CRT modules

Attached as 0001, 0002, 0003, in that order.

0004 is what used to be 0002, it disables caching of "DLL not 
loaded" results.

> I recommend also moving the SetEnvironmentVariable() call before
> the putenv calls.  That way, if a CRT loads while pgwin32_putenv()
> is executing, the newly-loaded CRT will always have the latest
> value.

Agreed, attached as 0005.

0006 was previously known as 0004, removing all caching.

> > Even with patch 0004, there is still a race condition between
> > the main thread and a theoretical additional thread created by
> > some other component that unloads some CRT between
> > GetProcAddress() and the _putenv() call, but that is hardly
> > fixable.
> 
> I think you can fix it by abandoning GetModuleHandle() in favor
> of GetModuleHandleEx() + GetProcessAddress() + FreeLibrary(). 

Attached as 0007.

> > There is another possible fix, ugly as sin, if we really need
> > to keep the whole environment update machinery *and* cannot do 
> > the full loop each time. Patch 0003 pins each CRT when we see 
> > it for the first time.

This is now 0008.

Patch topology: master --- 1 .. 5 --- 6 --- 7
  \
   `- 8

> I prefer the simplicity of abandoning the cache (patch 4), if it
> performs decently.  Would you compare the performance of patch 1,
> patches 1+2+3, and patches 1+2+4?  This should measure the right 
> thing (after substituting @libdir@ for your environment):

Tested with release builds; Core i7-6700K (quad/HT; 4000 MHz).
I did three runs each, and they were always within 0.5 % of each
other's run time.

- patch 1 (now 1-3): 24 μs/iteration (24 s for 1e6)
- patch 1+2+3 (now 1-5 + 8): 29 μs/iteration
- patch 1+2+4 (now 1-7): 30 μs/iteration

I also did a debug build with 1+2+4 that came in at 84 μs/iteration.

--
Christian

... now how do I get all the dangling debris out of the repo ...


0008-getmodulehandleex-pin.patch
Description: 0008-getmodulehandleex-pin.patch


0001-whitespace.patch
Description: 0001-whitespace.patch


0002-closehandle.patch
Description: 0002-closehandle.patch


0003-debug-crt.patch
Description: 0003-debug-crt.patch


0004 no-caching-notfound.patch
Description: 0004 no-caching-notfound.patch


0005-reorder-update.patch
Description: 0005-reorder-update.patch


0006-no-caching-at-all.patch
Description: 0006-no-caching-at-all.patch


0007-getmodulehandleex-correctness.patch
Description: 0007-getmodulehandleex-correctness.patch

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Re: [HACKERS] pgsql: Add putenv support for msvcrt from Visual Studio 2013

2016-11-15 Thread Noah Misch 
On Tue, Apr 26, 2016 at 07:39:29PM +0200, Christian Ullrich 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.

Patch 1 looks good, except that it should be three patches:

- cosmetic parts: change whitespace and s/0/NULL/
- remove CloseHandle() call
- probe for debug CRT modules, not just release CRT modules

Please split along those boundaries.  I plan to back-patch all of that.  I've
seen some gettext builds mysteriously ignore "SET lc_messages = ..."; ignoring
debug CRTs could have been the cause.

> I tested this with a project
> () that contains two DLLs:

That's a pithy test; thanks for assembling it.

> Even with patch 0004, there is still a race condition between the main
> thread and a theoretical additional thread created by some other component
> that unloads some CRT between GetProcAddress() and the _putenv() call, but
> that is hardly fixable.

I think you can fix it by abandoning GetModuleHandle() in favor of
GetModuleHandleEx() + GetProcessAddress() + FreeLibrary().  I recommend also
moving the SetEnvironmentVariable() call before the putenv calls.  That way,
if a CRT loads while pgwin32_putenv() is executing, the newly-loaded CRT will
always have the latest value.  (I'm assuming CRTs populate their environment
from GetEnvironmentStrings(), because I can't think of an alternative.)

As a separate patch, I am inclined to remove the "#ifdef _MSC_VER" directive,
activating its enclosed code under all compilers.  A MinGW-built postgres.exe
has the same need to update all CRTs.

> The fact that master looks like it does means that there have not been many
> (or any) complaints about missing cross-module environment variables. If
> nobody ever needs to see a variable set elsewhere, we have a very simple
> solution: Why don't we simply throw out the whole #ifdef _MSC_VER block?

pgwin32_putenv() originated, in commit 0154345, to make "SET lc_messages =
..." effective when gettext uses a different CRT from postgres.exe.  I suspect
it also makes krb_server_keyfile effective when GSS uses a different CRT.
Those are achievements worth keeping.  I'm not surprised about the lack of
complaints, because environment variables don't often change after backend
startup.  Here are some ways one could notice the difference between master
and patches 2+3 or 2+4:

- Use shared_preload_libraries to load a module that reads LC_CTYPE or
  LC_COLLATE.  CheckMyDatabase() sets those variables subsequent to
  process_shared_preload_libraries().

- Load, at any time, a module that reads LC_MESSAGES.  There's little reason
  to read that variable outside of gettext.  A module could use a gettext DLL
  other than the postgres.exe gettext DLL, but such a module would need to
  work around pg_bindtextdomain() always using the postgres.exe gettext.

- Load, at any time, a module that itself changes environment variables, other
  than LC_MESSAGES, after backend startup.  I suspect PL/Python suffices.

Those are plausible scenarios, but they're sufficiently specialized that
problems could lie unnoticed or undiagnosed for years.  I lean against
back-patching anything from patches 2, 3 or 4.

> There is another possible fix, ugly as sin, if we really need to keep the
> whole environment update machinery *and* cannot do the full loop each time.
> Patch 0003 pins each CRT when we see it for the first time.
> GET_MODULE_HANDLE_EX_FLAG_PIN is documented as "The module stays loaded
> until the process is terminated, no matter how many times FreeLibrary is
> called", so the unload race cannot occur anymore.

I prefer the simplicity of abandoning the cache (patch 4), if it performs
decently.  Would you compare the performance of patch 1, patches 1+2+3, and
patches 1+2+4?  This should measure the right thing (after substituting
@libdir@ for your environment):

CREATE FUNCTION putenv(text)
   RETURNS void
   AS '@libdir@/regress.dll', 'regress_putenv'
   LANGUAGE C STRICT;
\timing on
SELECT count(putenv('foo=' || n)) FROM generate_series(1,100) t(n);

(I'm interested for the sake of backend startup time.  I recall nine putenv()
in every backend startup, seven in main() and two in CheckMyDatabase().)

Thanks,
nm


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Re: [HACKERS] pgsql: Add putenv support for msvcrt from Visual Studio 2013

2016-10-02 Thread Michael Paquier 
On Tue, Sep 6, 2016 at 9:36 PM, Michael Paquier
 wrote:
> OK, let's get to the next step of the game and get a committer to look
> at this patch.

Moved to next CF. It would be good to get a committer on this one. We
have come on a conclusion on what to do. Actually, 0001 can be just
HEAD-only per the lack of complaints.
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Re: [HACKERS] pgsql: Add putenv support for msvcrt from Visual Studio 2013

2016-09-06 Thread Michael Paquier 
(Just remembered to remove pgsql-committers here).

On Tue, Sep 6, 2016 at 9:21 PM, Christian Ullrich  wrote:
> * Michael Paquier wrote:
>
>> On Tue, Sep 6, 2016 at 5:36 PM, Christian Ullrich 
>> wrote:
>>>
>>> * Michael Paquier wrote:
>
 In order to avoid any problems with the load and unload windows, my
 bet goes for 0001, 0002 and 0003, with the last two patches merged
 together, 0001 being only a set of independent fixes. That's ugly, but
 that looks the safest course of actions. I have rebased/rewritten the
 patches as attached. Thoughts?
>>>
>>>
>>> In lieu of convincing you to drop the entire thing, yes, that looks about
>>> right, except for the BOOL thing.
>>
>>
>> Yes, right. Thanks. Patch 0001 is definitely something that should be
>> applied and backpatched, the CloseHandle() call is buggy. Now 0002 and
>> 0003 are improving things, but there have been no reports regarding
>> problems in this area, so this could just be applied to master I
>> guess. Christian, does that sound right?
>
> Yes.

OK, let's get to the next step of the game and get a committer to look
at this patch.
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Re: [HACKERS] pgsql: Add putenv support for msvcrt from Visual Studio 2013

2016-09-06 Thread Christian Ullrich 

* Michael Paquier wrote:


On Tue, Sep 6, 2016 at 5:36 PM, Christian Ullrich  wrote:

* Michael Paquier wrote:



In order to avoid any problems with the load and unload windows, my
bet goes for 0001, 0002 and 0003, with the last two patches merged
together, 0001 being only a set of independent fixes. That's ugly, but
that looks the safest course of actions. I have rebased/rewritten the
patches as attached. Thoughts?


In lieu of convincing you to drop the entire thing, yes, that looks about
right, except for the BOOL thing.


Yes, right. Thanks. Patch 0001 is definitely something that should be
applied and backpatched, the CloseHandle() call is buggy. Now 0002 and
0003 are improving things, but there have been no reports regarding
problems in this area, so this could just be applied to master I
guess. Christian, does that sound right?


Yes.


By the way, how is it decided that a DLL gets unloaded in a process if
it is not pinned? Is that something the OS decides?


Reference counting in LoadLibrary() and FreeLibrary(), among other 
places. For example, GetModuleHandleEx() (but not the non-Ex) will by 
default increment the counter.


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Re: [HACKERS] pgsql: Add putenv support for msvcrt from Visual Studio 2013

2016-09-06 Thread Michael Paquier 
On Tue, Sep 6, 2016 at 5:36 PM, Christian Ullrich  wrote:
> * Michael Paquier wrote:
>> In order to avoid any problems with the load and unload windows, my
>> bet goes for 0001, 0002 and 0003, with the last two patches merged
>> together, 0001 being only a set of independent fixes. That's ugly, but
>> that looks the safest course of actions. I have rebased/rewritten the
>> patches as attached. Thoughts?
>
>
> In lieu of convincing you to drop the entire thing, yes, that looks about
> right, except for the BOOL thing.

Yes, right. Thanks. Patch 0001 is definitely something that should be
applied and backpatched, the CloseHandle() call is buggy. Now 0002 and
0003 are improving things, but there have been no reports regarding
problems in this area, so this could just be applied to master I
guess. Christian, does that sound right?

By the way, how is it decided that a DLL gets unloaded in a process if
it is not pinned? Is that something the OS decides?
-- 
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Re: [HACKERS] pgsql: Add putenv support for msvcrt from Visual Studio 2013

2016-09-06 Thread Christian Ullrich 

* Michael Paquier wrote:


On Thu, Sep 1, 2016 at 4:03 PM, Christian Ullrich  wrote:



My conclusion from April stands:


The fact that master looks like it does means that there have not been
many (or any) complaints about missing cross-module environment
variables. If nobody ever needs to see a variable set elsewhere, we
have a very simple solution: Why don't we simply throw out the whole
#ifdef _MSC_VER block?


Looking at the commit logs and 741e4ad7 that does not sound like a good idea.


Well, I still maintain that if it doesn't work and has never worked, 
getting rid of it is better than making it work six years after the 
fact. OTOH, there may have been cases where it did actually work, 
perhaps those gnuwin32 libraries that were mentioned in the comment 
before it was changed in that commit above, if they were loaded before 
the first call to the function.


OTTH, wouldn't it be funny if fixing it actually broke something that 
worked accidentally because it *didn't* get the updated environment? I 
think that is at least as likely as suddenly getting excited reports 
that something now works that hasn't before.



It is better to avoid !!. See for example 1a7a436 that avoided
problems with VS2015 as far as I recall.


Agreed, thanks for noticing. This change creates a warning, however, 
because GetModuleHandleEx() returns BOOL, not HMODULE. Updated 0003 
attached, simplified over my original one.



In order to avoid any problems with the load and unload windows, my
bet goes for 0001, 0002 and 0003, with the last two patches merged
together, 0001 being only a set of independent fixes. That's ugly, but
that looks the safest course of actions. I have rebased/rewritten the
patches as attached. Thoughts?


In lieu of convincing you to drop the entire thing, yes, that looks 
about right, except for the BOOL thing.


--
Christian

>From dfbe7384b309c20d7733b0d18e6819302a483d95 Mon Sep 17 00:00:00 2001
From: Christian Ullrich 
Date: Tue, 6 Sep 2016 10:02:06 +0200
Subject: [PATCH] Pin any DLL as soon as seen when looking for _putenv()

---
 src/port/win32env.c | 54 ++---
 1 file changed, 35 insertions(+), 19 deletions(-)

diff --git a/src/port/win32env.c b/src/port/win32env.c
index 3f56ba8..7417b60 100644
--- a/src/port/win32env.c
+++ b/src/port/win32env.c
@@ -43,36 +43,37 @@ pgwin32_putenv(const char *envval)
char   *modulename;
HMODULE hmodule;
PUTENVPROC  putenvFunc;
+   BOOLpinned;
}   rtmodules[] =
{
/* Visual Studio 6.0 / mingw */
-   {"msvcrt",  NULL,   NULL},
-   {"msvcrtd", NULL,   NULL},
+   {"msvcrt",  NULL,   NULL,   FALSE},
+   {"msvcrtd", NULL,   NULL,   FALSE},
/* Visual Studio 2002 */
-   {"msvcr70", NULL,   NULL},
-   {"msvcr70d",NULL,   NULL},
+   {"msvcr70", NULL,   NULL,   FALSE},
+   {"msvcr70d",NULL,   NULL,   FALSE},
/* Visual Studio 2003 */
-   {"msvcr71", NULL,   NULL},
-   {"msvcr71d",NULL,   NULL},
+   {"msvcr71", NULL,   NULL,   FALSE},
+   {"msvcr71d",NULL,   NULL,   FALSE},
/* Visual Studio 2005 */
-   {"msvcr80", NULL,   NULL},
-   {"msvcr80d",NULL,   NULL},
+   {"msvcr80", NULL,   NULL,   FALSE},
+   {"msvcr80d",NULL,   NULL,   FALSE},
/* Visual Studio 2008 */
-   {"msvcr90", NULL,   NULL},
-   {"msvcr90d",NULL,   NULL},
+   {"msvcr90", NULL,   NULL,   FALSE},
+   {"msvcr90d",NULL,   NULL,   FALSE},
/* Visual Studio 2010 */
-   {"msvcr100",NULL,   NULL},
-   {"msvcr100d",   NULL,   NULL},
+   {"msvcr100",NULL,   NULL,   FALSE},
+   {"msvcr100d",   NULL,   NULL,   FALSE},
/* Visual Studio 2012 */
-   {"msvcr110",NULL,   NULL},
-   {"msvcr110d",   NULL,   NULL},
+   {"msvcr110",NULL,   NULL,   FALSE},
+   {"msvcr110d",   NULL,   NULL,   FALSE},
/* Visual Studio 2013 */
-   {"msvcr120",NULL,   NULL},
-   {"msvcr120d",   NULL,   NULL},
+   {"msvcr120",NULL,   NULL,   FALSE},
+   {"msvcr120d",   NULL,   NULL,   FALSE},
/* Visual Studio 2015 and later */
-   {"ucrtbase",NULL,   NULL},
-   {"ucrtbased",   NULL,   NULL},
-   {NULL,  NULL,   NULL}
+   {"ucrtbase",NULL,   NULL,   FALSE},
+   {"ucrtbased",   NULL,   N

Re: [HACKERS] pgsql: Add putenv support for msvcrt from Visual Studio 2013

2016-09-06 Thread Michael Paquier 
On Thu, Sep 1, 2016 at 4:03 PM, Christian Ullrich  wrote:
> * Michael Paquier wrote:
>
>> On Wed, Apr 27, 2016 at 2:39 AM, Christian Ullrich 
>> wrote:
>
>>> * Christian Ullrich wrote:
>
>> 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,
>
> No, it is exactly what the version-specific CRTs are meant to allow. Each
> module uses the CRT version it needs, and they don't share any state, so
> absent bugs, they cannot conflict.

Hm. OK.

> That said, introducing this requirement would be a very significant change.
> I'm not sure how many independently maintained compiled extensions there
> are, but this would mean that their developers would have to have the
> matching VS versions for every PG distribution they want to support. Even if
> that's just EDB, it still is a lot of effort.

Yes. FWIW in my stuff everything gets compiled based on the same VS
version and bundled in the same msi, including a set of extensions
compiled from source, but perhaps my sight is too narrow in this
area... Well let's forget about that.

> My conclusion from April stands:
>
>> The fact that master looks like it does means that there have not been
>> many (or any) complaints about missing cross-module environment
>> variables. If nobody ever needs to see a variable set elsewhere, we
>> have a very simple solution: Why don't we simply throw out the whole
>> #ifdef _MSC_VER block?

Looking at the commit logs and 741e4ad7 that does not sound like a good idea.

+   if (!rtmodules[i].pinned)
+   {
+   HMODULE tmp;
+   BOOL res = GetModuleHandleEx(
+   GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS
+   | GET_MODULE_HANDLE_EX_FLAG_PIN,
+   (LPCTSTR)rtmodules[i].hmodule,
+   &tmp);
+   rtmodules[i].pinned = !!res;
+   }
It is better to avoid !!. See for example 1a7a436 that avoided
problems with VS2015 as far as I recall.

In order to avoid any problems with the load and unload windows, my
bet goes for 0001, 0002 and 0003, with the last two patches merged
together, 0001 being only a set of independent fixes. That's ugly, but
that looks the safest course of actions. I have rebased/rewritten the
patches as attached. Thoughts?
-- 
Michael
From b809a0b1c323529c2d7460962a3c688ad8aec3f4 Mon Sep 17 00:00:00 2001
From: Michael Paquier 
Date: Tue, 6 Sep 2016 15:51:55 +0900
Subject: [PATCH 1/3] Cleanups in pgwin32_putenv().

- Added UCRT and all debug CRTs
- Condensed the array to one line per item (it was getting long)
- Test HMODULEs for NULL instead of zero
- Removed unnecessary CloseHandle() call
---
 src/port/win32env.c | 61 +
 1 file changed, 29 insertions(+), 32 deletions(-)

diff --git a/src/port/win32env.c b/src/port/win32env.c
index e64065c..77f8334 100644
--- a/src/port/win32env.c
+++ b/src/port/win32env.c
@@ -45,36 +45,34 @@ pgwin32_putenv(const char *envval)
 		PUTENVPROC	putenvFunc;
 	}			rtmodules[] =
 	{
-		{
-			"msvcrt", 0, NULL
-		},		/* Visual Studio 6.0 / mingw */
-		{
-			"msvcr70", 0, NULL
-		},		/* Visual Studio 2002 */
-		{
-			"msvcr71", 0, NULL
-		},		/* Visual Studio 2003 */
-		{
-			"msvcr80", 0, NULL
-		},		/* Visual Studio 2005 */
-		{
-			"msvcr90", 0, NULL
-		},		/* Visual Studio 2008 */
-		{
-			"msvcr100", 0, NULL
-		},		/* Visual Studio 2010 */
-		{
-			"msvcr110", 0, NULL
-		},		/* Visual Studio 2012 */
-		{
-			"msvcr120", 0, NULL
-		},		/* Visual Studio 2013 */
-		{
-			"ucrtbase", 0, NULL
-		},		/* Visual Studio 2015 and later */
-		{
-			NULL, 0, NULL
-		}
+		/* Visual Studio 6.0 / mingw */
+		{"msvcrt",		NULL,	NULL},
+		{"msvcrtd",		NULL,	NULL},
+		/* Visual Studio 2002 */
+		{"msvcr70",		NULL,	NULL},
+		{"msvcr70d",	NULL,	NULL},
+		/* Visual Studio 2003 */
+		{"msvcr71",		NULL,	NULL},
+		{"msvcr71d",	NULL,	NULL},
+		/* Visual Studio 2005 */
+		{"msvcr80",		NULL,	NULL},
+		{"msvcr80d",	NULL,	NULL},
+		/* Visual Studio 2008 */
+		{"msvcr90",		NULL,	NULL},
+		{"msvcr90d",	NULL,	NULL},
+		/* Visual Studio 2010 */
+		{"msvcr100",	NULL,	NULL},
+		{"msvcr100d",	NULL,	NULL},
+		/* Visual Studio 2012 */
+		{"msvcr110",	NULL,	NULL},
+		{"msvcr110d",	NULL,	NULL},
+		/* Visual Studio 2013 */
+		{"msvcr120",	NULL,	NULL},
+		{"msvcr120d",	NULL,	NULL},
+		/* Visual Studio 2015 and later */
+		{"ucrtbase",	NULL,	NULL},
+		{"ucrtbased",	NULL,	NULL},
+		{NULL,			NULL,	NULL}
 	};
 	int			i;
 
@@ -82,7 +80,7 @@ pgwin32_putenv(const char *envval)
 	{
 		if (rtmodules[i].putenvFunc == NULL)
 		{
-			if (rtmodules[i].hmodule == 0)
+			if (rtmodules[i].hmodule == NULL)
 			{
 /* Not attempted before, so try to find this DLL */
 rtmodules[i].hmodule = GetModuleHan

Re: [HACKERS] pgsql: Add putenv support for msvcrt from Visual Studio 2013

2016-09-01 Thread Christian Ullrich 

* Michael Paquier wrote:

> On Wed, Apr 27, 2016 at 2:39 AM, Christian Ullrich 
 wrote:


>> * Christian Ullrich wrote:

> 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,

No, it is exactly what the version-specific CRTs are meant to allow. 
Each module uses the CRT version it needs, and they don't share any 
state, so absent bugs, they cannot conflict.


Of the processes currently running on my system, 25 have more than one 
CRT loaded (one has three, the others two).


> 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.

That was about DLLs existing in different versions with the same file 
name, and installers replacing them with their own, leading to problems 
with other applications that expected to load their preferred version. 
This does not apply to the multiple-CRT situation, because all minor 
versions of a given CRT are supposed to be ABI compatible.


> 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.
> [...]
> #endif
>
> 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?

Yes: This turns (this part of) pgwin32_putenv() into a great big NOP. We 
call putenv() anyway on the very last line of the function, so if we 
require common-CRT builds, that call alone (together with the 
SetEnvironmentVariable() just above) is sufficient.


That said, introducing this requirement would be a very significant 
change. I'm not sure how many independently maintained compiled 
extensions there are, but this would mean that their developers would 
have to have the matching VS versions for every PG distribution they 
want to support. Even if that's just EDB, it still is a lot of effort.


My conclusion from April stands:

> The fact that master looks like it does means that there have not been
> many (or any) complaints about missing cross-module environment
> variables. If nobody ever needs to see a variable set elsewhere, we
> have a very simple solution: Why don't we simply throw out the whole
> #ifdef _MSC_VER block?

--
Christian



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Re: [HACKERS] pgsql: Add putenv support for msvcrt from Visual Studio 2013

2016-04-26 Thread Christian Ullrich 

* 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, ...



If it can happen that a CRT DLL is unloaded before the process exits,
and we cached the module handle while it was loaded, and later
pgwin32_putenv() is called, that won't end well for the process. This
might be a bit far-fetched; I have to see if I can actually make it happen.


... this *can* and does happen, so fixing the load race alone is not 
enough. 0004 fixes the unload race as well, by dropping the entire DLL 
handle/_putenv pointer cache from the function and going through the 
list of DLLs each time.


I tested this with a project 
() that contains two DLLs:


- The first one is built with VS 2013 (debug), as is the server. It
  does not matter what it is built with, except it must not be the same
  as the second DLL. It exports a single function callable from SQL.

- The second one is built with VS 2015 (debug), and again, the exact
  CRT is not important as long as it is not the same as the server
  or the first DLL.

The function does this:

1. It loads the second DLL. This brings in ucrtbased.dll as well.
2. It calls putenv().
3. It unloads the second DLL. This also causes ucrtbased.dll to be
   unloaded because it is not needed anymore.
4. It calls putenv() again.

   - With current master, this works, because pgwin32_putenv(),
 after the first call somewhere early during backend startup,
 never looks for ucrtbased again (including in step 2).

   - With patch 0002 applied, it crashes because pgwin32_putenv(),
 having detected ucrtbased.dll and cached its HMODULE during
 the call in step 2 above, reuses these values after the DLL
 is long gone.

   - With patch 0004 applied as well, it works again because no
 caching is done anymore.

Even with patch 0004, there is still a race condition between the main 
thread and a theoretical additional thread created by some other 
component that unloads some CRT between GetProcAddress() and the 
_putenv() call, but that is hardly fixable.


The fact that master looks like it does means that there have not been 
many (or any) complaints about missing cross-module environment 
variables. If nobody ever needs to see a variable set elsewhere, we have 
a very simple solution: Why don't we simply throw out the whole #ifdef 
_MSC_VER block?


There is another possible fix, ugly as sin, if we really need to keep 
the whole environment update machinery *and* cannot do the full loop 
each time. Patch 0003 pins each CRT when we see it for the first time. 
GET_MODULE_HANDLE_EX_FLAG_PIN is documented as "The module stays loaded 
until the process is terminated, no matter how many times FreeLibrary is 
called", so the unload race cannot occur anymore.


--
Christian

From d74e778d8abbfea244bacbeb352cadc737032e85 Mon Sep 17 00:00:00 2001
From: Christian Ullrich 
Date: Tue, 26 Apr 2016 15:26:14 +0200
Subject: [PATCH 1/3] Cleanups in pgwin32_putenv().

- Added UCRT and all debug CRTs
- Condensed the array to one line per item (it was getting long)
- Test HMODULEs for NULL instead of zero
- Removed unnecessary CloseHandle() call
---
 src/port/win32env.c | 49 -
 1 file changed, 20 insertions(+), 29 deletions(-)

diff --git a/src/port/win32env.c b/src/port/win32env.c
index 7e4ff62..fd6762e 100644
--- a/src/port/win32env.c
+++ b/src/port/win32env.c
@@ -45,33 +45,25 @@ pgwin32_putenv(const char *envval)
PUTENVPROC  putenvFunc;
}   rtmodules[] =
{
-   {
-   "msvcrt", 0, NULL
-   },  /* Visual 
Studio 6.0 / mingw */
-   {
-   "msvcr70", 0, NULL
-   },  /* Visual 
Studio 2002 */
-   {
-   "msvcr71", 0, NULL
-   },  /* Visual 
Studio 2003 */
-   {
-   "msvcr80", 0, NULL
-   },  /* Visual 
Studio 2005 */
-   {
-   "msvcr90", 0, NULL
-   },  /* Visual 
Studio 2008 */
-   {
-   "msvcr100", 0, NULL
-   },  /* Visual 
Studio 2010 */
-

Re: [HACKERS] pgsql: Add putenv support for msvcrt from Visual Studio 2013

2016-04-25 Thread Christian Ullrich 

* Christian Ullrich wrote:


* Andrew Dunstan wrote:



What if both are present? Is a release build prevented from loading a
debug dll and vice versa?


Debug and release are simply two separate CRTs. If your process contains
a module that needs the one, and another that needs the other, you will
have both loaded at once.


pgwin32_putenv() is the gift that keeps giving.


According to its comment, it is not required that all modules exchanging 
calls with postgres.exe have to be built with the same CRT version (100, 
110, 120, etc.). Is it?


If not, the logic that remembers negative results from GetModuleHandle() 
(i.e. gives up forever on each possible CRT once it does not find it) is 
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.


If that code is in there because it has some noticeable performance 
advantage, the negative results could probably be reset in SQL LOAD, 
rather than just not remembering them anymore.



This comment is also incomplete then:

/*
 * Module loaded, but we did not find the function last time.
 * We're not going to find it this time either...
 */

This else branch is also taken if the module handle is set to 
INVALID_HANDLE_VALUE because the module was not found in a previous call.



If it can happen that a CRT DLL is unloaded before the process exits, 
and we cached the module handle while it was loaded, and later 
pgwin32_putenv() is called, that won't end well for the process. This 
might be a bit far-fetched; I have to see if I can actually make it happen.


One situation I can think of where this could occur is if an extension 
loaded with LOAD creates a COM in-proc server from a DLL built with yet 
another CRT, and when that object is released, either FreeLibrary() 
(transitively) or CoFreeUnusedLibraries() (directly) boots that CRT (if 
they do; it's possible that a CRT, once loaded, stays loaded.)



Finally: A nonzero handle returned from GetModuleHandle() is not 
something that needs to be CloseHandle()d. It is not actually a handle, 
but a pointer to the base (load) address of the module, although the 
documentation for GetModuleHandle() is careful not to admit that.


The value it is compared against to see whether we have seen the module 
before should be NULL, not 0.



It's getting a bit late for me today, but I will do the necessary 
experimentation and try to come up with a POC patch to fix whatever of 
the above I can actually prove to be real. Should anyone know for sure 
that I'm completely off track on something, better yet, everything, 
please let me know.


I should finish thinking before posting, then I would not have to reply 
to myself so often.


--
Christian



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Re: [HACKERS] pgsql: Add putenv support for msvcrt from Visual Studio 2013

2016-04-25 Thread Christian Ullrich 

* Andrew Dunstan wrote:


On 04/25/2016 09:27 AM, Christian Ullrich wrote:

* Magnus Hagander wrote:


On Sun, Apr 24, 2016 at 9:56 PM, Christian Ullrich
 wrote:



Just noticed something. This DLL detection by name has never worked in
debug builds where the DLL names end in "d". Is that important?



That's an interesting point.  I guess our release builds are never with
debugging info - but could it make the buildfarm "wrong"?



What if both are present? Is a release build prevented from loading a
debug dll and vice versa?


Debug and release are simply two separate CRTs. If your process contains 
a module that needs the one, and another that needs the other, you will 
have both loaded at once.


I had hoped they might share state, but they don't, at least as far as 
putenv()/getenv() are concerned.



Alternatively, can we detect at compile time if we are a debug build and
if so add the suffix?


No; same reason as above.

--
Christian



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Re: [HACKERS] pgsql: Add putenv support for msvcrt from Visual Studio 2013

2016-04-25 Thread Christian Ullrich 

* Magnus Hagander wrote:


On Sun, Apr 24, 2016 at 9:56 PM, Christian Ullrich 
wrote:


* Magnus Hagander wrote:

Add putenv support for msvcrt from Visual Studio 2013
http://git.postgresql.org/pg/commitdiff/9f633b404cb3be6139f8dfdea00538489ffef9ab



Just noticed something. This DLL detection by name has never worked in
debug builds where the DLL names end in "d". Is that important?



That's an interesting point.  I guess our release builds are never with
debugging info - but could it make the buildfarm "wrong"?

Fixing it should probably be as easy as trying each dll with the specified
name and also with a "d" as a suffix?


I think so, yes.

Personally, I would have expected that at least the debug/release DLLs 
of a single CRT version would somehow share their environment, but I 
tried it and they don't.


--
Christian





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Re: [HACKERS] pgsql: Add putenv support for msvcrt from Visual Studio 2013

2016-04-25 Thread Magnus Hagander 
On Sun, Apr 24, 2016 at 9:56 PM, Christian Ullrich 
wrote:

> * Magnus Hagander wrote:
>
> Add putenv support for msvcrt from Visual Studio 2013
>>
>> This was missed when VS 2013 support was added.
>>
>> Michael Paquier
>>
>> Branch
>> --
>> master
>>
>> Details
>> ---
>>
>> http://git.postgresql.org/pg/commitdiff/9f633b404cb3be6139f8dfdea00538489ffef9ab
>>
>
> Just noticed something. This DLL detection by name has never worked in
> debug builds where the DLL names end in "d". Is that important?


That's an interesting point.  I guess our release builds are never with
debugging info - but could it make the buildfarm "wrong"?

Fixing it should probably be as easy as trying each dll with the specified
name and also with a "d" as a suffix?

-- 
 Magnus Hagander
 Me: http://www.hagander.net/
 Work: http://www.redpill-linpro.com/

Re: [HACKERS] pgsql: Add putenv support for msvcrt from Visual Studio 2013

2016-04-24 Thread Christian Ullrich 

* Magnus Hagander wrote:


Add putenv support for msvcrt from Visual Studio 2013

This was missed when VS 2013 support was added.

Michael Paquier

Branch
--
master

Details
---
http://git.postgresql.org/pg/commitdiff/9f633b404cb3be6139f8dfdea00538489ffef9ab


Just noticed something. This DLL detection by name has never worked in 
debug builds where the DLL names end in "d". Is that important?


--
Christian



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