Can WCL386 create Windows' DLLs

[CyberSimian]

I want to create a 32-bit Windows DLL to run on 64-bit Windows 10. I thought that I could use WCL386, but I cannot get it to work. So I have created a simple test program to illustrate the problem. Here is the C file "mydll.c":

#include <stddef.h>
#include "windows.h"
BOOL APIENTRY DllMain(HINSTANCE instance, DWORD reason, PVOID reserved)
{
  return(TRUE);
}

Here is the LNK file "mydll.lnk":

system nt_dll
file mydll.obj

Here is the command that I used:

wcl386 /bd /bcl=nt mydll.c @mydll.lnk

Here is the response from WCL386 (waffle omitted):

Open Watcom C/C++ x86 32-bit Compile and Link Utility
Version 2.0 beta Aug 30 2025 02:25:02 (32-bit)
        wcc386 mydll.c  -bd -bt=nt
Open Watcom C x86 32-bit Optimizing Compiler
Version 2.0 beta Aug 30 2025 02:21:47 (32-bit)
mydll.c: 7 lines, included 102670, 0 warnings, 0 errors
Code size: 18
        wlink @__wcl_00.lnk
Open Watcom Linker Version 2.0 beta Aug 30 2025 02:19:26 (32-bit)
Error! E3057: system block nt_dll: executable format has been established
Error: Unable to invoke "D:\tools\watcom\ow200b_20250830\binnt\wlink.exe"

I have tried various combinations of command-line options and link-file directives, but none of them work. The E3057 error is the problem. However, using WCC386 plus WLINK I can successfully create the DLL:

wcc386 /bd /bt=nt mydll.c
wlink @mydll.lnk

So this problem is not a "show stopper" for me. But I am curious why WCL386 does not work. I should mention that OW 1.9 fails in the same way, so the most likely explanation is that I am not using the correct combination of options and directives. If anyone can create the DLL using WCL386, please describe what options and directives you used. Thank you!

-- from CyberSimian in the UK

[jmalak]

It looks like some misconfiguration of OW.
Please check your environment setup for variables
PATH
INCLUDE
LIB

It looks like you use 32-bit version of OW.
That PATH should include %WATCOM%\binnt;%WATCOM%\binw;
INCLUDE should include %WATCOM%\h;%WATCOM%\h\nt;
LIB should be blank

[jmalak]

Anyway you should use folowing options for wcl386 to properly create NT DLL.
wcl386 -bd -bt=nt -l=nt_dll

I tested with your source sample
wcl386 -bd -bt=nt -l=nt_dll x.c

and no problem, no errors or warnings

[CyberSimian]

Thank you! That has solved it.

I checked the environment variables, and they were all correct. It is the command options and link file that were not correct. I think that I now understand it:

• /bt=nt with system nt_dll in the LNK file gives the error.
• /bt=nt without the LNK file works without error, but creates an EXE and not a DLL.
• /bcl=nt with system nt_dll in the LNK file gives the error.
• /bcl=nt without the LNK file works without error, but creates an EXE and not a DLL.
• /bcl=nt_dll without the LNK file works without error and creates a DLL. However, WCL386 inserts /bt=nt_dll for the compile phase, which might produce a result different from /bt=nt.
• /bt=nt with /l=nt_dll but without the LNK file works without error and creates a DLL. Also, it retains nt as the target os.
• /bt=nt with /l=nt_dll with a LNK file that does not contain the system directive works without error and creates a DLL.

So my error was to specify a LNK file containing a system directive. There is an implicit system directive provided by WCL386, so a system directive in the LNK file is a duplicate and causes the error.

Well, I am glad that we got that sorted! Thanks again for your help.

-- from CyberSimian in the UK

[CyberSimian]

/bt specify target for compiler, /l specify target for linker; you must specify both for DLL because compiler and linker target is different; only in case that /bt and /l is same then you can use /bcl

Before I created this thread, I did read the sections in the manuals describing the compiler and linker options, but this limitation in the use of /bcl was not mentioned anywhere. Also, the need to omit the system directive when using WCL386 was not mentioned anywhere. The documentation could usefully be updated to correct these omissions, but I recognise that the documentation is the lowest priority work item in volunteer projects.

-- from CyberSimian in the UK

[jmalak]

This is not a limitation, there are just examples of common executables where /bt and /l are mostly the same as /bcl.
Note that Open Watcom is inherently a cross-compiler/linker that you can compile and link for any target without any configuration change.
This is controlled by the /bt and /l options. Mostly it is related to the default configuration (for host operating system) that doesn't need to be specified in this case.
For example, if you have OW installed on Windows, then it will compile and link for Windows without specifying /bcl or /bt and /l.
However, if you want to create executable for DOS, then you need to specify /bt=dos and with /l the DOS Extender you want to use, etc.
If you use /bt and /l then it works same way with OW installed on any host OS, because default is defined by host OS and depend on installation. On DOS are defaults for DOS on Linux are defaults for Linux etc. but /bt and /l works everywhere same way.

I'll look into the documentation and edit it to make it clearer and include a DLL example.

[jmalak]

I copy this discussion to issue #1506 as documentation enhancement.

[jmalak]

/bt specify target for compiler, /l specify target for linker; you must specify both for DLL because compiler and linker target is different; only in case that /bt and /l is same then you can use /bcl

Before I created this thread, I did read the sections in the manuals describing the compiler and linker options, but this limitation in the use of /bcl was not mentioned anywhere. Also, the need to omit the system directive when using WCL386 was not mentioned anywhere. The documentation could usefully be updated to correct these omissions, but I recognise that the documentation is the lowest priority work item in volunteer projects.

-- from CyberSimian in the UK

I forgot, but we have good on-line documentation in Wiki about OW usage

• OW tools usage Overview
• OW tools usage with CMake
• OW tools usage with Visual Studio Code

[CyberSimian]

I forgot, but we have good on-line documentation in Wiki about OW usage

I have bookmarked the link for the OW Wiki. Thank you.

-- from CyberSimian in the UK