https://docs.perl6.org/language/nativecall
"As you may have predicted by now, a NULL pointer
is represented by the type object of the struct type."
https://learn.microsoft.com/en-us/windows/win32/api/winreg/nf-winreg-regqueryvalueexw
C++
LSTATUS RegQueryValueExW(
HKEY hKey,
LPCWSTR lpValueName,
LPDWORD lpReserved,
LPDWORD lpType,
LPBYTE lpData,
LPDWORD lpcbData
);
lpReserved
This parameter is reserved and must be NULL.
With "native", how do I satisfy the "NULL" requirement?
constant WCHAR := uint16;
constant DWORD := int32;
sub RegQueryValueExW( DWORD, WCHARS, DWORD, DWORD, DWORD is rw, DWORD is rw ) is native("Kernel32.dll") returns DWORD { * };
$RtnCode = RegQueryValueExW( $Handle, $lpValueName, int32, REG_DWORD, $lpData, $lpcbData );
"int32" returns:
Cannot unbox a type object (int32) to int in method
CALL-ME at C:\rakudo\share\perl6\sources \947BDAB9F96E0E5FCCB383124F9
23A6BF6F8D76B (NativeCall) line 587
Many thanks,
-T
To pass a pointer to a DWORD you can use a CArray[DWORD]. For example, here I created a test library libmylib.so with a foo() function taking DWORD * (aka int32_t *) argument:
#include <stdio.h>
#include <stdint.h>
void foo (int32_t *bar) {
if ( bar == NULL ) {
printf( "Got NULL pointer\n" );
}
else {
printf("Got bar: %d\n", bar[0]);
}
}
Then test a Raku interface to this library using:
use v6;
use NativeCall;
constant DWORD := int32;
sub foo(CArray[DWORD]) is native("./libmylib.so") { * };
my #bar := CArray[DWORD].new;
#bar[0] = 1;
foo(#bar);
foo(CArray[DWORD]); # <-- Use a type object to pass a NULL pointer
Output:
Got bar: 1
Got NULL pointer
JJ and Brad on the Perl6 mailing list were correct. For a NULL, just pass it a zero. I had a booboo somewhere else.
Related
This is a follow-up question to "How to declare native array of fixed size in Perl 6?".
In that question it was discussed how to incorporate an array of a fixed size into a CStruct. In this answer it was suggested to use HAS to inline a CArray in the CStruct. When I tested this idea, I ran into some strange behavior that could not be resolved in the comments section below the question, so I decided to write it up as a new question. Here is is my C test library code:
slib.c:
#include <stdio.h>
struct myStruct
{
int A;
int B[3];
int C;
};
void use_struct (struct myStruct *s) {
printf("sizeof(struct myStruct): %ld\n", sizeof( struct myStruct ));
printf("sizeof(struct myStruct *): %ld\n", sizeof( struct myStruct *));
printf("A = %d\n", s->A);
printf("B[0] = %d\n", s->B[0]);
printf("B[1] = %d\n", s->B[1]);
printf("B[2] = %d\n", s->B[2]);
printf("C = %d\n", s->C);
}
To generate a shared library from this i used:
gcc -c -fpic slib.c
gcc -shared -o libslib.so slib.o
Then, the Perl 6 code:
p.p6:
use v6;
use NativeCall;
class myStruct is repr('CStruct') {
has int32 $.A is rw;
HAS int32 #.B[3] is CArray is rw;
has int32 $.C is rw;
}
sub use_struct(myStruct $s) is native("./libslib.so") { * };
my $s = myStruct.new();
$s.A = 1;
$s.B[0] = 2;
$s.B[1] = 3;
$s.B[2] = 4;
$s.C = 5;
say "Expected size of Perl 6 struct: ", (nativesizeof(int32) * 5);
say "Actual size of Perl 6 struct: ", nativesizeof( $s );
say 'Number of elements of $s.B: ', $s.B.elems;
say "B[0] = ", $s.B[0];
say "B[1] = ", $s.B[1];
say "B[2] = ", $s.B[2];
say "Calling library function..";
say "--------------------------";
use_struct( $s );
The output from the script is:
Expected size of Perl 6 struct: 20
Actual size of Perl 6 struct: 24
Number of elements of $s.B: 3
B[0] = 2
B[1] = 3
B[2] = 4
Calling library function..
--------------------------
sizeof(struct myStruct): 20
sizeof(struct myStruct *): 8
A = 1
B[0] = 0 # <-- Expected 2
B[1] = 653252032 # <-- Expected 3
B[2] = 22030 # <-- Expected 4
C = 5
Questions:
Why does nativesizeof( $s ) give 24 (and not the expected value of 20)?
Why is the content of the array B in the structure not as expected when printed from the C function?
Note:
I am using Ubuntu 18.04 and Perl 6 Rakudo version 2018.04.01, but have also tested with version 2018.05
Your code is correct. I just fixed that bug in MoarVM, and added tests to rakudo, similar to your code:
In C:
typedef struct {
int a;
int b[3];
int c;
} InlinedArrayInStruct;
In Perl 6:
class InlinedArrayInStruct is repr('CStruct') {
has int32 $.a is rw;
HAS int32 #.b[3] is CArray;
has int32 $.c is rw;
}
See these patches:
https://github.com/MoarVM/MoarVM/commit/ac3d3c76954fa3c1b1db14ea999bf3248c2eda1c
https://github.com/rakudo/rakudo/commit/f8b79306cc1900b7991490eef822480f304a56d9
If you are not building rakudo (and also NQP and MoarVM) directly from latest source from github, you probably have to wait for the 2018.08 release that will appear here: https://rakudo.org/files
When I compiled the following program like:
g++ -O2 -s -static 2.cpp it gave me the warning ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result].
But when I remove -02 from copiling statement no warning is shown.
My 2.cpp program:
#include<stdio.h>
int main()
{
int a,b;
scanf("%d%d",&a,&b);
printf("%d\n",a+b);
return 0;
}
What is the meaning of this warning and what is the meaning of -O2 ??
It means that you do not check the return value of scanf.
It might very well return 1 (only a is set) or 0 (neither a nor b is set).
The reason that it is not shown when compiled without optimization is that the analytics needed to see this is not done unless optimization is enabled. -O2 enables the optimizations - http://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html.
Simply checking the return value will remove the warning and make the program behave in a predicable way if it does not receive two numbers:
if( scanf( "%d%d", &a, &b ) != 2 )
{
// do something, like..
fprintf( stderr, "Expected at least two numbers as input\n");
exit(1);
}
I took care of the warning by making an if statement that matches the number of arguments:
#include <iostream>
#include <cstdio>
using namespace std;
int main() {
int i;
long l;
long long ll;
char ch;
float f;
double d;
//6 arguments expected
if(scanf("%d %ld %lld %c %f %lf", &i, &l, &ll, &ch, &f, &d) == 6)
{
printf("%d\n", i);
printf("%ld\n", l);
printf("%lld\n", ll);
printf("%c\n", ch);
printf("%f\n", f);
printf("%lf\n", d);
}
return 0;
}
I override the function library kernel32.dll in Pascal and OpenProcess function returns 0. Function GetLastError() returns 87 error, that means
ERROR_INVALID_PARAMETER
87 (0x57)
The parameter is incorrect.
What could be wrong?
Program UODll;
const search_window = 'Ultima Online - xxx (The Abyss)';
function FindWindow(C1, C2: PChar): Longint; external 'FindWindowA#user32.dll stdcall';
function GetWindowThreadProcessId(hWnd: Longint; opt: Word): Word; external 'GetWindowThreadProcessId#user32.dll stdcall';
function OpenProcess(dwDesiredAccess: Word; inherit: Byte; pid: Word): Longint; external 'OpenProcess#kernel32.dll stdcall';
function GetProcessId(proc: Longint): Word; external 'GetProcessId#kernel32.dll stdcall';
function GetLastError(): Word; external 'GetLastError#kernel32.dll stdcall';
var
res, err: Word;
wnd, proc: Longint;
Begin
wnd := Findwindow('', search_window);
if (wnd > 0) then
begin
res := GetWindowThreadProcessId(wnd, res);
proc := OpenProcess($0400,0,res);
err := GetLastError();
writeln(IntToStr(proc));
writeln(IntToStr(err));
end;
End.
Im trying to use LongWord and Cardinal, but i have the same error.. Who can help me?)
P.S. its not delphi.. i dont know what is this :) Programm calls UOScript
OpenProcess has declaration
HANDLE WINAPI OpenProcess(
_In_ DWORD dwDesiredAccess,
_In_ BOOL bInheritHandle,
_In_ DWORD dwProcessId
);
dwDesiredAccess and pid are double words that are
typedef unsigned long DWORD;
i.e. 32bit on x86, according to this answer.
But Delphi/Pascal Word type is 16bit.
Also, BOOL is defined as
typedef int BOOL;
So, you should use Integer for inherit instead of Byte
So, your function declaration is incorrect.
Seems you should use Cardinal or LongWord instead of Word in your declarations.
If you use Delphi, you can import Windows module that has all Win API functions defined.
I am trying to code an alternative to LoadLibrary function, based on the idea of calling the function LdrLoadDll from ntdll.
This function needs as a parameter the dll file to load, in a UNICODE_STRING format.
I really can't get what I am doing wrong here (string seems to be correctly initialized), but when LdrLoadDll is called, I get the following error:
Unhandled exception in "Test.exe" (NTDLL.DLL): 0xC0000005: Access Violation.
I use Visual C++ 6.0 for this test, and I am using Windows 7 64 bit.
I post full code here, thanks in advance for any help:
#include <Windows.h>
typedef LONG NTSTATUS; //To be used with VC++ 6, since NTSTATUS type is not defined
typedef struct _UNICODE_STRING { //UNICODE_STRING structure
USHORT Length;
USHORT MaximumLength;
PWSTR Buffer;
} UNICODE_STRING;
typedef UNICODE_STRING *PUNICODE_STRING;
typedef NTSTATUS (WINAPI *fLdrLoadDll) //LdrLoadDll function prototype
(
IN PWCHAR PathToFile OPTIONAL,
IN ULONG Flags OPTIONAL,
IN PUNICODE_STRING ModuleFileName,
OUT PHANDLE ModuleHandle
);
/**************************************************************************
* RtlInitUnicodeString (NTDLL.#)
*
* Initializes a buffered unicode string.
*
* RETURNS
* Nothing.
*
* NOTES
* Assigns source to target->Buffer. The length of source is assigned to
* target->Length and target->MaximumLength. If source is NULL the length
* of source is assumed to be 0.
*/
void WINAPI RtlInitUnicodeString(
PUNICODE_STRING target, /* [I/O] Buffered unicode string to be initialized */
PCWSTR source) /* [I] '\0' terminated unicode string used to initialize target */
{
if ((target->Buffer = (PWSTR) source))
{
unsigned int length = lstrlenW(source) * sizeof(WCHAR);
if (length > 0xfffc)
length = 0xfffc;
target->Length = length;
target->MaximumLength = target->Length + sizeof(WCHAR);
}
else target->Length = target->MaximumLength = 0;
}
NTSTATUS LoadDll( LPCSTR lpFileName)
{
HMODULE hmodule = GetModuleHandleA("ntdll.dll");
fLdrLoadDll _LdrLoadDll = (fLdrLoadDll) GetProcAddress ( hmodule, "LdrLoadDll" );
int AnsiLen = lstrlenA(lpFileName);
BSTR WideStr = SysAllocStringLen(NULL, AnsiLen);
::MultiByteToWideChar(CP_ACP, 0, lpFileName, AnsiLen, WideStr, AnsiLen);
UNICODE_STRING usDllFile;
RtlInitUnicodeString(&usDllFile, WideStr); //Initialize UNICODE_STRING for LdrLoadDll function
::SysFreeString(WideStr);
NTSTATUS result = _LdrLoadDll(NULL, LOAD_WITH_ALTERED_SEARCH_PATH, &usDllFile,0); //Error on this line!
return result;
}
void main()
{
LoadDll("Kernel32.dll");
}
in
_LdrLoadDll(NULL, LOAD_WITH_ALTERED_SEARCH_PATH, &usDllFile,0);
last parameter can't be zero
you can't call SysFreeString before you call _LdrLoadDll,
since the usDllFile.buffer parameter points to this string
I've written a C++/CLI wrapper for a C++-DLL to use this DLL in a C# programm.
However, when I call a function, which takes a char* I get a AccessViolation
int Wrapper::Net_methodX(int a, String^ key, long v)
{
IntPtr ptr = Marshal::StringToHGlobalAnsi(key);
pin_ptr<char> cKey = static_cast<char*>(ptr.ToPointer());
int val = methodX(a,cKey, v); // AccessViolation here
Marshal::FreeHGlobal(ptr);
return val;
}
The signature of the C++-function is
int methodX(int a, char *Key, long v);
EDIT 1
Just to "pin" like the following didn't work either:
int Wrapper::Net_methodX(int a, String^ key, long v)
{
IntPtr ptr = Marshal::StringToHGlobalAnsi(key);
char* cKey = static_cast<char*>(ptr.ToPointer());
pin_ptr<char> pinned = cKey;
int val = methodX(a,cKey, v);
Marshal::FreeHGlobal(ptr);
return val;
}
EDIT 1 END
EDIT 2
I tried also PtrToStringChars the following way (Thanks Matt, found also some doc here):
int Wrapper::Net_methodX(int a, String^ key, long v)
{
pin_ptr<const wchar_t> wkey = PtrToStringChars(key);
size_t convertedChars = 0;
size_t sizeInBytes = ((key->Length + 1) * 2);
errno_t err = 0;
char * ckey = (char * ) malloc(sizeInBytes);
err = wcstombs_s(&convertedChars, ckey, sizeInBytes, wkey, sizeInBytes);
int val = methodX(A_Symbol_Table,ckey, Value);
return val;
}
AccessViolation still occurs, maybe it's an error in methodX() (which is a Third-party-DLL).
EDIT 2 END
I have read some related questions here, but did not find a solution yet.
Any hints?
Thank you.
I know this is an old question, but for anyone who stumble upon this question looking for an answer, here are some simpler solutions.
Simply use sprintf to do the conversion like this: sprintf(cStr, "%s", clrString);. See my answer to this question for a complete example.
Read KB311259 as suggested by Matt Smith. If you are using VS 2008 or higher, use marshal_as<> (Method #4 in the KB). It's much simpler than the other methods in that document.
Simon,
I tried out your example and I do not get an Access Violation. Here's my code:
using namespace System;
using namespace System::Runtime::InteropServices;
ref class Wrapper
{
public:
static int Net_methodX(int a, String^ key, long v);
};
int methodX(int a, char * pKey, long v)
{
IntPtr ptr = static_cast<IntPtr>(pKey);
String ^ pString = Marshal::PtrToStringAnsi(ptr);
System::Console::WriteLine(pString);
return a;
}
int Wrapper::Net_methodX(int a, String^ pKey, long v)
{
IntPtr ptr = Marshal::StringToHGlobalAnsi(pKey);
pin_ptr<char> cKey = static_cast<char*>(ptr.ToPointer());
int val = methodX(a,cKey, v); // AccessViolation here
Marshal::FreeHGlobal(ptr);
return val;
}
void main()
{
Wrapper wrapper;
String ^ p = gcnew String("Hello");
wrapper.Net_methodX(0, p, 0);
}
Also, I have a few comments:
Read here: http://support.microsoft.com/kb/311259
You are using a pin_ptr to native memory. The StringToHGlobalAnsi method returns native memory, so I don't think using a pin_ptr makes sense here. A pin_ptr would make sense if you were using a method that gives you back a pointer to managed memory (like PtrToStringChars). Unless you are modifying the string, you probably want to go with the PtrToStringChars approach anyways--to avoid unnecessary allocation and copying.
Would you post an example version of methodX that causes the problem? If I can reproduce the issue, I might be able to be more helpful.
Simon
I think there is a problem with the following code
pin_ptr<char> cKey = static_cast<char*>(ptr.ToPointer());
You might want to read this http://social.msdn.microsoft.com/forums/en-US/vclanguage/thread/0bd049fe-844a-4cb6-b9f6-c8f5107bc957
Let me know if it helped you.
Sujay