Code safety.

[Miguel Pando]

Hello everyone.
I am a long time visitor to these forums, first time post.
Also, long time programmer(Cobol, Business Basic).
I know this program works, But, Is this code safe? Any memory leaks?
The DLL part is simulating what a C language program might be doing.

 
#COMPILE DLL "TEST.DLL"
DECLARE FUNCTION SysAllocStringByteLen LIB "OLEAUT32.DLL" ALIAS "SysAllocStringByteLen" (psz AS ASCIIZ, BYVAL ulen AS DWORD) AS DWORD
SUB TEST(ix AS LONG) EXPORT
    ix=SysAllocStringByteLen("Testing......", 16)
END SUB

#COMPILE EXE
DECLARE SUB TEST LIB "TEST.DLL"(s AS STRING)
FUNCTION PBMAIN() AS LONG
LOCAL z AS STRING
    TEST z
    MSGBOX z
END FUNCTION

Thanks for your comments.

[Edwin Knoppert]

I don't think so.
The caller should handle the return value but not a byref value.
If your caller can handle it, simply use As String for return value.
This will be a BSTR and destroyed by the caller (should be)

[Michael Mattias]

Forget copying the "C" code. Just figure out what the "C" code is doing and do it in BASIC.

In PB it's easy:

#COMPILE EXE
...
 LOCAL Z AS STRING
 CALL   test(Z) 
...
#COMPILE DLL
SUB TEST (X AS STRING) EXPORT 
  X = LSET$("Testing....", 16 USING $NUL)
END SUB

(LSET$ function not in alpha-button page of help file, but it is in the index)

MCM

[Rodney Hicks]

Or put the cursor on LSET$ and click the help icon.

[Michael Mattias]

>Or put the cursor on LSET$ and click the help icon

Um, that works for the detail ..but it means you aready know LSET$ is the function you want to use.....which I suspect is not the case here.

Just FWIW, another example here of why I believe verb-for-verb, statement-for-statement, function-for-function ports from one language to another are stone losers.

[Rodney Hicks]

Um, that works for the detail ..but it means you aready know LSET$ is the function you want to use.....which I suspect is not the case here.

And here I was thinking that it might have been already in some sample code he had at hand and didn't know the significance thereof and therefore didn't realize how significant it was. I would have thought that he investigated on his own before posting, and passed it by.
You are not wrong, so I think I'll quit thinking!!

[Michael Mattias]

That's the problem with everyone's documentation... it's only easy to use if you know what statement/function you want to use... but what you usually want to know is exactly that: which statement or function you want to use!

About all you can do is think of string (or array, or arithmetic) function in the same 'family' as your current problem, go to the help for that and hope "see also" gives you a steer in the right direction.

MCM

[Michael Mattias]

Eg this case... Best guess from the help file index would be "String Formatting."

That takes you to the page for USING$.

Does "See Also" for USING$ suggest RSET$, LSET$ or CSET$? Nope.

[Rodney Hicks]

There is also the 'Command Summary' with the section 'String Operations' that lists all String functions/statements. Command Summary is right on the Home page of the help file, easier to find than in the printed manual, and while it(LSET$/LSET) might be made to show up a few more places, it is there. Here again, you have to know what you're looking for, and be able to recognize it when you see it.
And while now a tad off topic, I'll go a little further afield and state that I noticed today that the two items in the "FILE" dropdown menu that were added with PB9, referring to Project files, do not show up in the Help file under the "File Menu", either electronically or printed. With tongue in cheek, I wonder whether I should leave this for someone else to find and report?!

[Michael Mattias]

>There is also the 'Command Summary' ...

Cool. I had never found that one before. Not too bad, not bad at all.

I think I might have found it sooner had the home page had the sub-links right there, eg ....

Command Summary 
 Array Operations
 COM Commands
 Communication Control
 Compiler Operations
 Debugging and Error Control
 File Commands
 Flow Control
 Graphic Commands
 Input Commands
 Memory Management
 Metastatements
 Numeric Operations
 Operating System
 Printing Commands
 String Operations
 Thread Control
 Time Commands
  Misc Operations

... but I don't think that would have fit on the page too well.

[Rodney Hicks]

I think I might have found it sooner had the home page had the sub-links right there,

One would think it would be a good place for a mouse hover - tool tip type of display of sub-links, if that's possible in the current 'Help' file scheme of things.
Didn't look too long, but I never found any tooltips anywhere in the help file.

[Gösta H. Lovgren-2]

Didn't look too long, but I never found any tooltips anywhere in the help file.

That's nothing. I can't even find "Command Summart". Is it in on the web page (somewhere)? Or in the Help file (somewhere else)?

[Rodney Hicks]

If you aren't sure you're on the Home Page of the Help file, click the Home Icon and there will be the buttons with each starting character of the KEYWORDS and under them the following list:

Introducing PowerBASIC For Windows
New Statements and Functions
Command Summary
Data Types
Programming Reference
Built-in numeric equates
Built-in string equates
Glossary
Register
Technical Support
Downloads
Peer Support Forums

Third item.

[Gösta H. Lovgren-2]

If you aren't sure you're on the Home Page of the Help file, click the Home Icon and there will be the buttons...

There are none so blind as those who do not see.

Thx Rod.

==========================================
"No problem can be solved
until it is reduced to some simple form.
The changing of a vague difficulty
into a specific, concrete form
is a very essential element in thinking."
J.P. Morgan
==========================================

[Miguel Pando]

Thank you all for responding.

>This will be a BSTR and destroyed by the caller (should be).

I think this is the main question. Is the caller De-Allocating the buffer
created by SysAllocStringByteLen.

>Forget copying the "C" code. Just figure out what the "C" code is doing
and do it in BASIC.

The caller(EXE) has no control on the language used to write the DLL. It will specify to use a buffer created with SysAllocStringByteLen.

Thanks again.