I write my dll files in visual studio 2010.
The dll file (name fservice.dll), which has an external function, code write in c++ (VS2010, I have dll and lib files)
char * convert(char *)
Dll file witch has c-function, who exports and imports to postgresql:
typedef char* (__cdecl *MYPROC)(char * value);
PG_FUNCTION_INFO_V1(transform);
Datum
transform (PG_FUNCTION_ARGS)
{
HINSTANCE hinstLib= LoadLibrary("fservice.dll");
char * pointer;
text *t = PG_GETARG_TEXT_P(0);
if (hinstLib != NULL)
{
ProcAdd = (MYPROC) GetProcAddress(hinstLib, "convert");
pointer=ProcAdd("text");
FreeLibrary(hinstLib);
}
/*
* code
*/
PG_RETURN_TEXT_P(new_t);
}
I have a problem because, mod is doesn't exists. Path to dll file I check before write.
Compile this c-function, and when i debug i saw it HINSTANCE hinstLib it wasn't created. It wasn't NULL or any value, It wasn't exist. Finally my c-function doesn't use my function form external dll.
How load dll and use my external function ?
My external function form dll and LoadLibrary() is not called by dll program with called by Postgresql, Why?
this may be a simple answer, but what I don't see is a create function call. It would be something like:
CREATE OR REPLACE FUNCTION transform(text) RETURNS text LANGUAGE C AS
'/path/to/dll', 'transform';
Until you create the function, PostgreSQL doesn't know to dynamically load the dll....
Related
I am using (Unicode) Inno Setup 6.0.5 on Windows 10 64-bit.
The exported symbol, I want to use has the signature:
typedef int(__stdcall *GetDirVST2x86) (LPWSTR lpString1);
The Inno Setup [Code] section has its declaration as:
function GetDirVST2x86(var lpString1: String): Integer;
external 'GetDirVST2x86#files:R2RINNO.DLL stdcall setuponly';
where, lpString1 will contain a pointer to the wide-string after the function returns and R2RINNO.DLL is a 32-bit DLL.
Now my problem is, if I compile and run this setup, a read access violation occurs right when I try to retrieve the value. I get the correct result when I execute this same function from a C program. Removing the var from the prototype declaration in Inno script fetches an empty (or possibly) empty or blank string, so that doesn't help either.
I don't have the source for the DLL I wish to use, and I figured out the signature from IDA. The scripting engine Inno Setup seems hopelessly inadequate as it doesn't support pointers at all.
One interesting thing I observed was if I changed the type of lpString1 to Cardinal or Integer and used IntToStr to fetch the string I got the value of the directory in which the setup was getting created.
Here's a working C code:
#include <windows.h>
#include <stdio.h>
#define _UNICODE
#define UNICODE
typedef int(WINAPI *GetDirVST2x86) (LPWSTR );
int main() {
HMODULE hModule = LoadLibrary("R2RINNO.DLL");
if (NULL != hModule) {
GetDirVST2x86 pGetDirVST2x86 = (GetDirVST2x86) GetProcAddress (hModule, "GetDirVST2x86");
if (NULL != pGetDirVST2x86) {
LPWSTR lpszVST2x86;
pGetDirVST2x86(lpszVST2x86);
wprintf(lpszVST2x86);
}
FreeLibrary(hModule);
}
}
Here's the output:
C:\Program Files (x86)\Steinberg\VstPlugins
Here's the IDA screenshot of the function I want to use:
Pascal Script equivalent of the C declaration should be:
function GetDirVST2x86(lpString1: string): Integer;
external 'GetDirVST2x86#files:R2RINNO.DLL stdcall setuponly';
(i.e. no var, as it is an input character pointer argument).
Assuming the function contract is that you (as a caller) allocate a buffer and provide it to the function to be filled in, you should call the function like this:
var
Buf: string;
begin
{ Allocate buffer for the result large enough according to the API specification }
SetLength(Buf, 1000);
GetDirVST2x86(Buf);
SetLength(Result, Pos(#0, Result) - 1);
end;
See also How to return a string from a DLL to Inno Setup?
Hi everyone and thank you for your time. This was created in Visual Studio 2012,and I'm using the standard Windows Libraries.
I am attempting to call a DLL function explicitly and I believe the code I've written is correct; however, I am receiving an error. I'm not sure if it's an error in something that I've written in the small C console application or from the DLL which I do not have access to the internal workings of.
//global area
HINSTANCE _createInstance;
typedef UINT (CALLBACK* LPFNDLLFUNCLOOKUP)(AccuInput*, AccuOut*);
LPFNDLLFUNCLOOKUP lpfnDllFuncCASSLookup;
typedef UINT (CALLBACK* LPFNDLLFUNCINIT)(BSTR);
LPFNDLLFUNCINIT lpfnDllFuncInit;
typedef UINT (CALLBACK* LPFNDLLFUNCCLOSE)();
LPFNDLLFUNCCLOSE lpfnDllFuncClose;
HMODULE unmanagedLib;
Here is my main function:
int main() {
// Load Library
BSTR configFile;
unmanagedLib = LoadLibraryA((LPCSTR) "AccuAddressUnMgd.dll");
// Initialize AccuAddress COM dll
lpfnDllFuncInit = (LPFNDLLFUNCINIT)GetProcAddress(unmanagedLib, (LPCSTR)"Init");
// This function will lookup the address
lpfnDllFuncCASSLookup = (LPFNDLLFUNCLOOKUP)GetProcAddress(unmanagedLib, (LPCSTR)"AccuCassLookup");
// This function will call AccuAddress COM DLL Close function
lpfnDllFuncClose = (LPFNDLLFUNCCLOSE)GetProcAddress(unmanagedLib, (LPCSTR)"Close");
// Append “config.acu” file path.
configFile = SysAllocString(L"C:\PathTo\Config.acu");
printf("ConfigPath created");
lpfnDllFuncInit(configFile);
printf("ConfigFile consumed");
SysFreeString(configFile);
return 0;
}
This is the error that I receive:
Unhandled exception at at 0x75D4C54F in RDISample1.exe: Microsoft C++ exception: _com_error at memory location 0x001AFAC0.
The error occurs at:
lpfnDllFuncInit(configFile);
So, I guess my question is two parts. Based off the code can I say for a fact that the error is in the DLL function?
Second question, when calling GetProcAddress what would be the point (if any) for encapsulating the string in LPCSTR like a function versus typecasting?
ie
lpfnDllFuncClose = (LPFNDLLFUNCCLOSE)GetProcAddress(unmanagedLib, LPCSTR("Close"));
Thanks again for the help. I've been doing a fair amount of research yet DLLs still have been puzzled.
The initial error is caused by the library you're using failing to correctly handle a file that doesn't exist.
The path you gave contains single slashes \, which are treated as escape characters, not path separators. Path separators must be escaped, i.e. \\ to be treated correctly.
There is no point casting a string literal to LPCSTR.
As for the _com_error that is definitely coming from the DLL. I would suggest wrapping that in a:
try
{
...
} catch(_com_error const & e)
{
wprintf(L"Caught a com error: %s\r\n", e.ErrorMessage());
}
And then you might be able to figure out what is wrong.
I am trying to write a small extension for PostgreSQL.
As a way to test if my module loads correctly I am writing some stuff in files in the void _PG_init(void) and void _PG_fini(void) functions. Here is the code of these two functions:
#include "postgres.h"
#include "executor\executor.h"
#include "fmgr.h"
#include "funcapi.h"
#include <stdio.h>
PG_MODULE_MAGIC;
extern void _PG_init(void);
extern void _PG_fini(void);
static void myExecutorStart(QueryDesc *queryDesc, int eflags);
static void myExecutorRun(QueryDesc *queryDesc, ScanDirection direction, uint64 count);
static void myExecutorFinish(QueryDesc *queryDesc);
static void myExecutorEnd(QueryDesc *queryDesc);
static ExecutorStart_hook_type prevExecutorStart = NULL;
static ExecutorRun_hook_type prevExecutorRun = NULL;
static ExecutorFinish_hook_type prevExecutorFinish = NULL;
static ExecutorEnd_hook_type prevExecutorEnd = NULL;
void _PG_init(void) {
FILE *file = NULL;
file = fopen("F:\\init.txt", "a+");
fprintf(file, "Init started!\n");
fclose(file);
prevExecutorStart = ExecutorStart_hook;
ExecutorStart_hook = myExecutorStart;
prevExecutorRun = ExecutorRun_hook;
ExecutorRun_hook = myExecutorRun;
prevExecutorFinish = ExecutorFinish_hook;
ExecutorFinish_hook = myExecutorFinish;
prevExecutorEnd = ExecutorEnd_hook;
ExecutorEnd_hook = myExecutorEnd;
}
void _PG_fini(void) {
FILE *file = NULL;
file = fopen("F:\\fini.txt", "a+");
fprintf(file, "Fini started!\n");
fclose(file);
ExecutorStart_hook = prevExecutorStart;
ExecutorRun_hook = prevExecutorRun;
ExecutorFinish_hook = prevExecutorFinish;
ExecutorEnd_hook = prevExecutorEnd;
}
Those functions are in a file called "myextension.c", compiled into "myextension.dll". I built it in Visual Studio 2015, with following settings:
Configuration Properties -> General, “Configuration Type” = “Dynamic
Library (.dll)”.
C/C++ -> Code Generation, “Enable C++ Exceptions” = “No”,“Advanced”
set “Compile As” = “Compile as C Code (/TC)”.
Linker -> Manifest File, “Generate Manifest” = “No”.
Linker -> Input -> Additional Dependencies, added “postgres.lib” to the
library list.
Configuration Properties -> C/C++ -> General, Additional Include
Directories, added: “include\server\port\win32_msvc”, “include\server\port\win32”, “include\server”, “include”
Solution configuration = Release
Solution Platform = x64 (Installed 64 bit version of PostgreSQL 9.6 on
Windows 10)
In myExecutorXXX functions I check if there are previous ExecutorXXX functions, call them if they exist, if they don't I call the standard_ExecutorXXX function. Here is an example of one of the functions:
static void myExecutorStart(QueryDesc *queryDesc, int eflags) {
if (prevExecutorStart) prevExecutorStart(queryDesc, eflags);
else standard_ExecutorStart(queryDesc, eflags);
FILE *file = NULL;
file = fopen("F:\\query.txt", "a+");
fprintf(file, "Query: %s started!\n", queryDesc->sourceText);
fclose(file);
}
I copied the "myextension.dll" in "../PostgreSQL/9.6/lib" directory, and added a "myextension.control" and "myextension--1.0.sql" to "../PostgreSQL/9.6/share/extension" directory.
myextension.control:
# pg_extension extension
comment = 'myextension!!!'
default_version = '1.0'
myextension--1.0.sql:
-- complain if script is sourced in psql, rather than via CREATE EXTENSION
\echo Use "CREATE EXTENSION myextension" to load this file. \quit
In the "postgresql.conf" I added shared_preload_libraries = 'myextension'. After that I connected to a test DB and ran: CREATE EXTENSION myextension;, and restarted the server.
If anyone has any idea what might be causing this, please help.
A couple of comments to get you on the right track:
_PG_fini() will never get called, because modules don't get unloaded.
_PG_init(), however, does get called when the module is loaded. Your main question seems to be why nothing is written to F:\init.txt and other files you use for logging.
On Windows, PostgreSQL normally runs as service. I suspect that the operating system user doesn't have the privileges to write to these files. I know little about Windows and its permission management, but I notice that you do not check the return code of fopen(), so it might well have silently failed.
My recommendation is to use the logging infrastructure instead, e.g. with
elog(LOG, "Init started!");
That will write the message to the PostgreSQL server log and is much more comfortable and less error prone.
Two more comments:
There is no point in creating an extension, because your code does not provide any SQL functions. CREATE EXTENSION myextension is a no-operation.
Don't forget to restart the PostgreSQL server after changing shared_preload_libraries.
I want to use a dll-file in my C-Code, but are very confused about the syntax.
My Story: I made a simple function in Matlab ( f(x1,x2)=x1*x2 ), with the "Matlab Coder" I translated it to C-Code and generated an exe, I could run it from the terminal with arguments.Now I generated a dll instead of an exe and want to use the dll.
Since now I could not make Code explanations, I googled, make work for me. I look up Syntax in http://en.cppreference.com/w/ but for my surprise there wasn't even an entry for e.g. GetProcAddress or LoadLirbary.
Here is the C-Code in which I would like to use the dll:
#include <stdio.h>
#include <stdlib.h>
/*
* In my dream I would load the dll function here
* with something like Load(mytimes4.dll)
*/
int main(int argc, char *argv[]) {
double x1,x2,myresult;
//Load Arguments from Terminal
sscanf(argv[1], "%lf", &x1);
sscanf(argv[2], "%lf", &x2);
// Use and print the function from mytimes4.dll
myresult = mytimes4(x1,x2);
printf("%3.2f\n",myresult);
return 0;
}
After generating the dll, Matlab gave me the following folder:
"dll-folder" produced by Matlab
Can someone give me a most simple but complete Code that would work with my example? What files are needed (maybe .def or .exp)? Also for Explanations of the lines involved using the dll I would be gratefull. Or if not, you maybe have some background knowledge that makes the complex syntax reasonable.Thanks in advance!
System information: Windows 7 Pro 64, Matlab 64 2016b, gcc cygwin 64, eclipse ide.
With the link of thurizas I could solve my problem.
https://msdn.microsoft.com/en-us/library/windows/desktop/ms686944(v=vs.85).aspx
I copied the code from the side. Below you can see the code with additional comments of mine and with ,in my opinion, more clearly naming. Thus it is probably easier to use for beginners as I am.
#include <stdio.h>
#include <stdlib.h>
#include <windows.h>
/*Declaration of the function,contained in dll, as pointer with the arbitrary pointer name
"*MYFUNCTIONPOINTER" (not sure if it has to be in big letters).
In my case the function means simply f(x1,x2) = x1*x2 and is thus as double declared*/
typedef double (*MYFUNCTIONPOINTER)(double, double);
int main() {
HINSTANCE hinstLib;
//"myfunction" is the arbitrary name the function will be called later
MYFUNCTIONPOINTER myfunction;
BOOL fFreeResult, fRunTimeLinkSuccess = FALSE;
//Tell the dll file
hinstLib = LoadLibrary(TEXT("mypersonal.dll"));
if (hinstLib != NULL)
{
/* At this line "myfunction" gets its definition from "MYFUNCTIONPOINTER"
and can be used as any other function.The relevant function in the dll has
to be told here.*/
myfunction = (MYFUNCTIONPOINTER) GetProcAddress(hinstLib, "mydllfunction");
// If the function address is valid, call the function.
if (NULL != myfunction)
{
fRunTimeLinkSuccess = TRUE;
// The function can be used.
double myoutput;
myoutput = myfunction(5,7);
printf("%f\n",myoutput);
getchar();
}
// Free the DLL module.
fFreeResult = FreeLibrary(hinstLib);
}
// If unable to call the DLL function, use an alternative.
if (! fRunTimeLinkSuccess)
printf("Message printed from executable\n");
return 0;
}
How can I use the functions in a DLL in C without a LIB file to go with it? I know all of the function prototypes and their names.
Yes you can. You should use the GetProcAddress function, to call the function directly in the DLL, without involving the LIB
Processes explicitly linking to a DLL call GetProcAddress to obtain
the address of an exported function in the DLL. You use the returned
function pointer to call the DLL function.
To quote the Example from the above link:
typedef UINT (CALLBACK* LPFNDLLFUNC1)(DWORD,UINT);
...
HINSTANCE hDLL; // Handle to DLL
LPFNDLLFUNC1 lpfnDllFunc1; // Function pointer
DWORD dwParam1;
UINT uParam2, uReturnVal;
hDLL = LoadLibrary("MyDLL");
if (hDLL != NULL)
{
lpfnDllFunc1 = (LPFNDLLFUNC1)GetProcAddress(hDLL,
"DLLFunc1");
if (!lpfnDllFunc1)
{
// handle the error
FreeLibrary(hDLL);
return SOME_ERROR_CODE;
}
else
{
// call the function
uReturnVal = lpfnDllFunc1(dwParam1, uParam2);
}
}
You can use LoadLibrary() and GetProcAddress() as described in the answer by DarkXphenomenon. Or, another alternative is to create your own import library for the DLL by creating a .def file then running that through the LIB command to generate an import library. Additional details here:
http://support.microsoft.com/kb/131313