Building Windows Server Extensions Using VC++ 2005

Hi everyone,

I've been able to successfully build server extension using Visual
Studio 2005 for Windows Postgresql 8.1. However, it took a few tweaks
which I thought I should document (maybe these issues could be fixed in
future postgresql versions?):

1. There is no lib file for VC++ to link against. This can be created
easily enough by going to src/backend directory and running:

lib /MACHINE:x86 /NAME:postgres.exe /DEF:postgres.def

Note the use of /NAME to tell VC++ it is linking against an executable
and not a dll.

It would be nice if this lib file was automatically installed on windows
when installing postgresql.

2. Requirement on strings.h

In c.h:69 there is this code:

#ifdef HAVE_STRINGS_H
#include <strings.h>
#endif

In pg_config.h:405 this is defined:

/* Define to 1 if you have the <strings.h> header file. */
#define HAVE_STRINGS_H 1

However, Visual Studio 2005 does not include this file. For a
workaround I simply added it but that's a bit of hack.

3. This is a bigger issue, and took a while to figure out. If you try
to use the Version 1 calling convention, your function will be called
but if you try to do anything with the passed in parameters a
segmentation fault will occur. If you use the Version 0 calling
convention things work fine.

The problem is if you use PG_FUNCTION_INFO_V1 postgres does not see the
generated function because it is not exported from the dll and thus
assumes the Version 0 calling convention when in fact your function is
using Version1. The problem is in fmgr.h:298

#define PG_FUNCTION_INFO_V1(funcname) \

extern Pg_finfo_record * CppConcat(pg_finfo_,funcname) (void); \
...

For windows to export this function it must be:

extern __declspec(dllexport) Pg_finfo_record *
CppConcat(pg_finfo_,funcname) (void);

Would it be possible to add a DLLEXPORT macro here to fix this?

4. Last, and the biggest issue, if my function calls pfree it blows
up. What is happening is that pfree somehow ends up pointing to a
random spot in memory - thus when you try to call it you execute invalid
code (in fact you never execute pfree at all as far as I can see). I
worked around this by using pgport_pfree which does work. Haven't a
clue why...

Here is the assembly for successfully calling pgport_pfree:

pgport_pfree(fileName);
100112D3 mov eax,dword ptr [ebp-0Ch]
100112D6 push eax
100112D7 call 100110C3
100112DC add esp,4

100110C3 jmp 1001131A

pgport_pfree:
1001131A jmp dword ptr ds:[10016288h]

005CF140 push ebp
005CF141 mov ebp,esp
005CF143 sub esp,8
005CF146 mov eax,dword ptr [ebp+8]
005CF149 mov dword ptr [esp+4],eax
005CF14D mov eax,dword ptr ds:[006A9F94h]
005CF152 mov dword ptr [esp],eax
005CF155 call 005CF0D0
005CF15A leave
005CF15B ret

And here is pfree. Note at the end the code tries to execute "db" at
005E1560 causing a segmentation fault.

pfree( fileName );
100112D3 mov eax,dword ptr [ebp-0Ch]
100112D6 push eax
100112D7 call 1001110E
100112DC add esp,4

1001110E jmp 10011238

pfree:
10011238 jmp dword ptr ds:[1001628Ch]

005E1560 db ffh

Hope this helps others. It would be great if building postgresql server
extensions with VC++ worked out of the box on Windows (in addition of
course to using MingW) since I think it would open up a wider audience.

Charlie