strptr problem with variable

[S.ean]

I am using STRPTR in a dll function that I created to pass a string value back to a program of mine.

All works well when I use a literal value in STRPTR eg STRPTR("HELLO"),
but when I try using a variable i.e

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DIM stVar AS STRING
stVar = "HELLO"
RETURN STRPTR(stVar)  'RETURN STRPTR("HELLO") does work though!!


then it does'nt work. Any ideas of why it is not.

Here is the function

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PUBLIC FUNCTION REPEAT CDECL ALIAS "REPEAT" (numTimes AS INTEGER,stRepeat AS ZSTRING PTR) AS ZSTRING PTR EXPORT
        DIM AS STRING stTemp
        stTemp = *stRepeat
        DIM AS INTEGER counter,repeatLen
        counter = 1
        DO
            stTemp = stTemp & stTemp
            counter *= 2
        LOOP WHILE (counter < numTimes)
        repeatLen = numTimes * LEN(*stRepeat)
        stTemp = LEFT(stTemp,repeatLen)
        RETURN STRPTR(stTemp)
END FUNCTION 


I use this dll in a liberty basic program like this :-

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CALLDLL #lib2,"REPEAT", n AS long, b$ AS PTR, result as long
print winstring(result)


I would really appreciate any help!

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[jevans4949]

When you exit a function, any variables declared within the function disappear.

A constant would not disappear.

The best thing is either to return a string from the function, in which case it would be passed back to the caller's variable, or else pass the target string as a parameter BYREF and set the target within the function.

If you HAVE to pass back a pointer, then you could declare a STATIC variable in the function, but I wouldn't recommend it.

[counting_pine]

The string, and its data, cease to exist after the function exits. So the pointer you return will no longer be valid.

If you use Static instead of Dim, the string and data will remain in memory between function calls, and the pointer will be safe to use until next time you modify the string.

Can I assume that Liberty Basic doesn't deallocate the pointer it receives? If it does, you will run into trouble next time you try to use the string.

[S.ean]

Thank you both.

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STATIC AS STRING stTemp 'instead of DIM


did the trick.

I have a similar BCX function which worked as expected without the STATIC keyword. I guess the compiler there must have static built in there somehow.

I am very pleased, thanks again.