Call HtmlHelp API from C++ compiled with SCC

I have an existing hybrid Fortran / C++ app that calls WinHelp.

I have rewritten the API call from WinHelp to HtmlHelp as we are now using the newer help format.

Unfortunately I cannot get the SCC / SLINK combination to bring in the HtmlHelp library.

In the C++ code I have 'Include 'HtmlHelp.h'' at the top and reworked the API call, this passes through the compiler OK.

The problem comes when I link using SLINK, it is finding and using the htmlhelp.lib file fine, but this has a further dependency on some other API calls with odd prefixes. I've included the command 'lo htmlhelp.lib' to reference the file.

The errors generated are;

WARNING the following symbols are missing:
_imp__GetProcAddress                     H:\MyApp\htmlhelp.lib (/0             )
                                              (release/init.obj)
_imp__LoadLibraryA                       H:\MyApp\htmlhelp.lib (/0             )
                                              (release/init.obj)
_imp__RegCloseKey                        H:\MyApp\htmlhelp.lib (/0             )
                                              (release/init.obj)
_imp__RegQueryValueExA                   H:\MyApp\htmlhelp.lib (/0             )
                                              (release/init.obj)
_imp__RegOpenKeyExA                      H:\MyApp\htmlhelp.lib (/0             )
                                              (release/init.obj)

I understand why it needs GetProcAddress etc, I can't figure out why the lib has references to imp_ versions which won't resolve. Using a hex editor I can see the htmlhelp.lib file has '!<arch>' as a header which I thought was a COFF archive, supposedly linkable.

I'm OK with C++ inside Visual Studio but I can't figure out how to get the Salford compiler (SCC) to compile and link this particular library.

What obvious thing am I missing?

Thanks in advance,

Ryan

I am guessing that the problem is that the library resides in an ocx (ActiveX) file rather than a DLL.

Which HTML functions are you accessing?

Hi Paul,

Yes, the lib does something with HHCTRL.OCX. I was hoping that the lib would be statically linked in and handle all of the OCX loading at runtime, but I'm not sure what I am doing.

The API call I am trying to execute is HtmlHelp as defined at https://msdn.microsoft.com/en-us/library/windows/desktop/ms670172(v=vs.85).aspx

My test code is;

  HWND return_code = HtmlHelp(GetDesktopWindow(), 'hlp.chm\::/copyright.htm', HH_DISPLAY_TOPIC, NULL);

I have been able to compile and run a console app launching help in Visual C using this code. So I'm a little lost.

Here is my test program...

#include <windows.h>
#define HH_DISPLAY_TOPIC 0x0000
HWND WINAPI HtmlHelpA(HWND hwndCaller,LPCSTR pszFile,UINT uCommand,DWORD dwData);
 
int main()
{
   HWND return_code = HtmlHelpA(GetDesktopWindow(), 'hlp.chm\::/copyright.htm', HH_DISPLAY_TOPIC, NULL); 
   return 0;
}

For SLINK you can load hhctrl.ocx but you will need to put hhctrl.ocx somewhere where SLINK can see it.

Thanks Paul,

That's moved me along somewhat. I can understand what's going on there.

I'm now getting a hang when calling the API but that's something I think I can troubleshoot. Probably down to bad parameters.

Regards

Ryan

You might need

extern 'C' HWND WINAPI HtmlHelpA....

Hi Paul,

I'm still stuck, I have attempted to use just your sample and replaced the .chm file too in case that is causing it.

I have also linked to both WOW64 and System32 versions of hhctrl.ocx but the app still hangs and never returns from the API call.

Do you have any more ideas? I have noticed that memory usage climbs dramatically for the process once in while so I have a leak or a bad calling convention.

Here is what I have;

helphang.cpp;

#include <windows.h> 
#define HH_DISPLAY_TOPIC 0x0000 

extern HWND WINAPI HtmlHelpA(HWND hwndCaller, LPCSTR pszFile, UINT uCommand, DWORD dwData);

int main()
{
	HWND return_code = HtmlHelpA(GetDesktopWindow(), 'hlp.chm\\::/copyright.htm', HH_DISPLAY_TOPIC, NULL);
	return 0;
}

I then compile and link it with;

scc helphang.cpp
slink helphang.dat

The linker command file is;

lo helphang
lo C:\Windows\System32\hhctrl.ocx
; lo C:\Windows\SysWOW64\hhctrl.ocx

file helphang

I've narrowed it down.

Part of the problem I was experiencing was that the first of my many test API calls failed and ran up a huge memory bill. During that time, it locked the CHM file.

So when I quit and retried another API approach, I just got a plain hang as the file was locked.

They both looked the same though.

I'll keep going and will post the answer, I suspect it is due to stack space as there is a note in the HTML API about that and a specific stack size is set in my original code.

I think that, on a 64 bit system, the ocx in System32 will be the 64 bit version. Not the one that you want.

It seems to be the location of the stack that is causing it, which is a worry as I don't really understand why the stack was set so high.

It works if I relocate (or shrink?) the stack, I'm not sure what the parameters do.

The slink command file and adjustments;

lo helphang
lo C:\Windows\System32\hhctrl.ocx
; lo C:\Windows\SysWOW64\hhctrl.ocx

; Takes about 40 seconds delay before launching and help app is corrupt.
; stack 0x21000000

; Does not come back.
; stack 0x40000000

; Launches immediately.
stack 0x01000000

file helphang

Obviously the stack was set that way for a reason so if I change it I may cause issues.