going mad with DLLs and returning strings. bug???

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skyser

22

Years of Service

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Joined: 11th Sep 2003

Location: New York, NY

Posted: 6th Oct 2003 00:36

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so i'm writing a DLL and generally have the hang of things, but there is a quirk which is driving me crazy and i can't figure it out. it's one of those "how can this one thing possibly affect the other?" bugs.

so here goes...

* i've got lots of working functions that take multiple int parms and spit back int values. they all work fine. typical string table entries might be: INT FUNC[%LL%?myIntFunc@@YAHHH@Z or INT FUNC2[%LLL%?myIntFunc2@@YAHHH@Z

* i've got a working test function that takes no args and spits out a string. it's string entry looks kind of like: STR FUNC[%S%?myStrFunc@@YAKXZ

so far so good.

now all of these functions make use of a global map collection that is referred to by an index. so a typical function looks like:

+ Code Snippet

int getInfoInt(int mapIndex) {
   // no intervening code
   MAP_PTR_TYPE mp = globalCollectonOfMaps[mapIndex];
   if( ! mp ) {
       // freak out and report error
   }
   // do stuff
   return retVal;
}

this works fine for a million little functions returning ints. however it consistently reports a bad map index any time i try to return a string. so, for instance:

+ Code Snippet

DWORD getInfoString(int mapIndex) {
   // no intervening code
   // this next line will report bad index
   MAP_PTR_TYPE mp = globalCollectonOfMaps[mapIndex];
   if( ! mp ) {
       // freak out and report error
   }
   // do stuff
   return (DWORD) retVal;
}

this might have the string table entry: STR FUNC[%SL%?myStrFunc@@YAKXZ

so, to try and put it all together and explain... within DB i can have the following lines:

+ Code Snippet

index = 1

a = INT FUNC(index)    // won't complain 
s$ = STR FUNC(index)   // claims bad index, but it hasn't changed!!!

any tests i do where i set the index internally, make the problem go away. so for example:

+ Code Snippet

index = 1

a = INT FUNC(index)    // won't complain 
s$ = TEST STR FUNC()   // won't complain

argh! this is driving me nuts. does any one have some insight or sample code to share?

yours in madness,

--skyser

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Shadow Robert

23

Years of Service

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Joined: 22nd Sep 2002

Location: Hertfordshire, England

Posted: 6th Oct 2003 00:48

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its because your trying to link a value which isn't there, when you return strings if it isn't NULL then you must declare a blank string by creating a DeleteString first - then you can pass back the string value you wanted to, which is just a DWORD pointer.

checkout the TestCommands2 example in the SDK documentation as well as the readme on this as it explains it far better than i can.

simply fact is that you're creating a string, but what dbp need is a string instance pointer value - you can't simply pass back a string like

return (*DWORD) strMyString[index];
dbp has its own way of doing things internally.