在Windows平台上创建PostgreSQL C扩展

Question

I'm having problems getting some simple test functions for postgres to link and/or run on Windows, having tried both from command line and Visual Studio. I have found little documentation and no working templates for this.

I'm not used to the compiling tools in Windows and I'm new to postgres so I may be missing something very basic. Any directions would be appreciated!

Using: Windows 8.0 (64-bit), cl.exe 18.00.21005.1, link.exe 12.00.21005.1, PostgreSQL v.9.3.4 (binary install).

This is the sample code from the documentation just to have something simple, I only added the PGDLLEXPORT invocation:

#include "postgres.h"
#include "fmgr.h"

PG_MODULE_MAGIC;
PG_FUNCTION_INFO_V1(add_one);

PGDLLEXPORT Datum
add_one(PG_FUNCTION_ARGS)
{
    int32   arg = PG_GETARG_INT32(0);

    PG_RETURN_INT32(arg + 1);
}

In my cl command file I collected the following include paths:

/I "C:\Program Files\PostgreSQL\9.3\include\server\port\win32_msvc"
/I "C:\Program Files\PostgreSQL\9.3\include\server\port\win32"
/I "C:\Program Files\PostgreSQL\9.3\include\server\port"
/I "C:\Program Files\PostgreSQL\9.3\include\server"
/I "C:\Program Files\PostgreSQL\9.3\include"

And then running:

cl /c add.c @includes
link /DLL add.obj "C:\Program Files\PostgreSQL\9.3\lib\postgres.lib"

It compiles and links without errors or warnings. I put the created add.dll in the postgres \\lib directory and define the corresponding function logged in with psql as user postgres:

CREATE FUNCTION add_one(integer) RETURNS integer
AS 'add','add_one'
LANGUAGE C STRICT;

Where I get the following error:

ERROR:  could not load library "C:/Program Files/PostgreSQL/9.3/lib/add.dll": %1 is not a valid Win32 application.

The result is the same when building the dll in Visual Studio.

The extensions I originally intended to write were more complex and included also "funcapi.h" for using composite arguments and returns. In that case it also compiled without problems, but failed at the linking stage with errors of this type:

error LNK2019: unresolved external symbol _get_call_result_type ...
error LNK2019: unresolved external symbol _BlessTupleDesc ...
error LNK2019: unresolved external symbol _heap_form_tuple ...

Same wether using command line or MSVC, and checking lib path and trying adding all the possible .lib dependencies in \\lib to the command line. I tried also different calling conventions.

But, anyway, I need to get simple DLL-exports working first, and maybe the solutions are related to the same issue.

I guess it may have something to do with system defaults included by cl that doesn't match (32/64-bit?), but since the source only includes headers from the postgres project I'd hoped that was automatically resolved and I don't know how to proceed with this.

Answer 1

I wrote a blog on this topic that may be useful; see Compiling PostgreSQL extensions on Windows with Visual Studio .

The issue with the headers you mention is fixed in the 9.4 series. I'll see about getting it backpatched for back branches.

Rather than hacking ch you should instead just specify the define on the command line:

/DWIN32

You should also ensure the code is compiled as plain C :

/Tc

and of course you must be running under the correct Visual Studio command prompt environment, with the x86 or x64 compiler depending on the desired target. If you're not sure, you can check by running cl.exe without arguments; it'll print the target architecture.

Answer 2

Actually this works (the command line method).

I just used the wrong version of the Command Prompt, so when using the VS2012 x64 Cross Tools Command Prompt with the same procedure as above I could get all the example functions from the postgres documentation to work.

EDIT: If you get the compile error C2011: 'timezone':'struct' type redefinition that I'm commenting on below, see Craig Ringers answer for better way of handling it.

If somebody else is getting stuck on this I can also tell that I had to modify one header file, include\\ch, adding this:

#if defined(_WIN32)
#define WIN32
#endif

right before this part in the code:

#if !defined(WIN32) && !defined(__CYGWIN__)     /* win32 includes further down */
#include "pg_config_os.h"       /* must be before any system header files */
#endif

Without it you get compile error.

(I got this from this thread: error C2011: 'timezone':'struct' type redefinition (postgres) , in the accepted answer, link to mailing list with attached diff)

I don't know if this is the best way for building extensions in Windows, but at least you don't need to compile the whole source tree to get going and learning.