I am trying to compile a DLL library on Windows that can be used with NativeCall in Raku. Here is a minimal C code (my_c_dll.c
):
#include <stdio.h>
#define EXPORTED __declspec(dllexport)
extern __declspec(dllexport) void foo();
void foo()
{
printf("Hello from C\n");
}
I am on Windows 10 and have installed Build Tools for Visual Studio 2019. To compile the DLL I open a "Developer Command Prompt for VS 2019" and run:
> cl.exe /c my_c_dll.c
> link /DLL /OUT:my_c_dll.dll my_c_dll.obj
This creates a DLL my_c_dll.dll
, then I try to use this from Raku (test-dll.raku
):
use v6.d;
use NativeCall;
sub foo() is native("./my_c_dll.dll"){ * }
foo();
but when I run this (I have installed Rakudo version 2020.05.1) I get:
> raku test-dll.raku
Cannot locate native library '(null)': error 0xc1
in method setup at C:\rakudo\share\perl6\core\sources\947BDAB9F96E0E5FCCB383124F923A6BF6F8D76B (NativeCall) line 298
in block foo at C:\rakudo\share\perl6\core\sources\947BDAB9F96E0E5FCCB383124F923A6BF6F8D76B (NativeCall) line 594
in block <unit> at test-dll.raku line 9
What can be the problem here?
Cannot locate native library '(null)': error 0xc1
The error code 0xc1
is a Windows system error code :
ERROR_BAD_EXE_FORMAT
193 (0xC1)
%1 is not a valid Win32 application.
By inspecting the header of the DLL using dumpbin
> dumpbin /headers my_c_dll.dll
Microsoft (R) COFF/PE Dumper Version 14.26.28806.0
Copyright (C) Microsoft Corporation. All rights reserved.
Dump of file my_c_dll.dll
PE signature found
File Type: DLL
FILE HEADER VALUES
14C machine (x86)
4 number of sections
6043A8CB time date stamp Sat Mar 6 17:07:39 2021
0 file pointer to symbol table
0 number of symbols
E0 size of optional header
2102 characteristics
Executable
32 bit word machine
DLL
I observe that it says machine (x86)
and 32 bit word machine
, so I suspect the DLL is a 32-bit DLL. However, I am on a 64 bit machine:
> PowerShell -Command "systeminfo | perl -nE 'say if /System Type/'"
System Type: x64-based PC
It turns out that the Build Tools for Visual Studio 2019
installed some more developer prompts in addition to the "Developer Command Prompt for VS 2019", namely:
By opening a "x64 Native Tools Command Prompt for VS 2019" and recompiling the DLL here, I now get:
> dumpbin /headers my_c_dll.dll
Microsoft (R) COFF/PE Dumper Version 14.26.28806.0
Copyright (C) Microsoft Corporation. All rights reserved.
Dump of file my_c_dll.dll
PE signature found
File Type: DLL
FILE HEADER VALUES
8664 machine (x64)
6 number of sections
6043AAA2 time date stamp Sat Mar 6 17:15:30 2021
0 file pointer to symbol table
0 number of symbols
F0 size of optional header
2022 characteristics
Executable
Application can handle large (>2GB) addresses
DLL
Notice that the output now says machine (x64)
and Application can handle large (>2GB) addresses
, and this also seems to fix the problem:
> raku test-dll.raku
Hello from C
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