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