How to dynamically load DLL's, check if your app is manifested properly, track back Access Violations in your app and a brief foray into the windows dll using the clarion debugger disassembler window

[FedericoNavarro]

@anon23294430

I’m obviously doing something wrong. Likewise I’ve also looked at Larry Sand’s Clarionmag 3 part Loading Dll’s at Runtime cmag-2001-05.pdf and not been able to get that to work, using TYPE to sort of function overload.
And also Paul Attrydes post on his website for doing a DIY CALL instead of using the built in CALL which doesnt handle parameters.

So any idea’s what I’m doing wrong and which is the best method to use? I’m assuming the compiler still allows these things considering when these posts and articles were written.

Hi Richard, in the case of Larry Sand’s LoadLibrary, if you started a new hand coded project to test it, probably you missed the conditional compiler symbols in the project settings: ABCLinkMode=>1;ABCDllMode=>0

@anon23294430

I’ve not been able to get Larry’s example on dynamically loading dlls at runtime https://clarionmag.jira.com/wiki/download/attachments/399455/cmag-2001-05.zip?api=v2 but it looks similar to PaulA’s using the api prototype as a Type definition and then using the api type definition as a datatype like a group in the procedure parameter.

It doesn’t need the Type definition nor the Group in the procedure parameter, probably you infered that from the example in that link, but that is another wrapper class not needed to call loadlibrary (DiskInfo.clw vs being the call directly on FreDskSp.clw). In fact the technique is easy to implement as you keep the function prototypes the same as with statically linked, with just another function name to prevent name clashing and don’t using the NAME attribute.

I made an example modifying another previous simple example here:

How to check the hard disc space - Clarion9

<* > pointer based parameters have no problem, as Clarion assumes the absense of a parameter can be represented with a 0 pointer, but with simple value parameters, extra data is needed to support OMITTED. Here there is an example app based on both prototypes. With <> on simple value parameters it crashes, with = 0 it works. Also there is an screen capture of Clarion Debugger where it can be seen the extra PUSH 1’s to the stack when using <> [DebugCalls] TestOmitParam.clw (1,4 KB)

That example had the function GetDiskFreeSpaceExA statically linked and the one attached here incorporates the extra code for loadlibrary like the one used on Larry’s example, and by the way, what are the chances, was about GetDiskFreeSpaceExA, although on his example he didn’t make the paremeters omittable or with default value. As a side note, the function ULIntToDec in DiskInfo.clw also confirms the conversion needed the high value to be multiplied by 2^32 and not by 2^32-1, but as stated i64toDecimal should be optimal, probably it not existed in 2001. A last note the Kernel LoadLibrary object could be without & / NEW. LlcFreeLibrary and DISPOSE omitted.

Attached modified TestOmitParam.clw (needs LoadLib.inc and LoadLib.clw) from ClarionMag’s link…TestOmitParam.clw (2,3 KB)