Waldek Hebisch wrote:

Ken G. Brown wrote:

...

Thx a lot for your long explanation of Strings.

Here is another one that has me baffled.

My code in a procedure:

procedure doHeader (pageNum, numPages : Integer);

var pageNumStr, numPagesStr : Str255;

the call: NumToString(pageNum,pageNumStr);

I get compile error: error: type mismatch in argument 2 of `NumToString'

In NumberFormatting.p procedure NumToString(theNum: SInt32; var theString: Str255); external name '_NumToString';

You're using the wrong set of Mac OS X Pascal Interfaces here. Your cite is from FPC's FPCPInterfaces Mac OS X Pascal Interfaces. Only GPC's GPCPInterfaces Mac OS X Pascal Interfaces work correctly for GPC compiling.

...

What do I need to do in this case?

First, when you ask for help you should post a complete example.

Since this is really a Mac OS X Pascal Interfaces type problem, it would probably be better to seek help for questions like this on the MacPascal mailing list instead of this mailing list. You have a much better chance of getting faster help with Mac OS X interfacing problems and the reponders will be tailoring their help to a Mac OS X Pascal context. You'll also avoid creating additional problems for yourself when a non-Mac OS X GPC mailing list responder responds with a correct generic GPC answer which may not necessarily answer the real GPC and Mac OS X Pascal interfacing problem you're having difficulties with.

Secondly, the following "works" for me:

program foo; type Str255 = string(255); SInt32 = integer; var pageNum : SInt32; pageNumStr, numPagesStr : Str255; procedure NumToString(theNum: SInt32; var theString: Str255); external name '_NumToString';

begin NumToString(pageNum,pageNumStr); end .

"Works" here means that the linker complains about undefined function _NumToString (which is expected since I did not provide that function). I use a newer gpc version which fixed some parameter passing problems, but I doubt that gpc version matters for your problem

Third, if you want to call Pascal functions defined in different files, then read about units and modules in gpc documentation (external is for interfacing with other languages). OTOH if you want to call foreign function then you need correct definition of Str255 (Pascal string is probably wrong).

It is a foriegn interface to a Mac OS X exported C routine that expects a UCSD Pascal string format for the Str255 typed parameter. The only place one can find a GPC Str255 compatible type for the parameter is in the Mac OS X GPCPInterfaces' MacTypes.pas interface file. In that interface file Str255 is declared as a record type and is declared specificly for GPC to give the exact memory footprint as the UCSD Pascal string[255] type that the Mac OS X routines expect to be passed as parameters. (Note: GPC will accept the USCD string syntax but what you get is a GPC native Extended Pascal string schema based type that is the same as string(UCSD Pascal string size).)

Since GPC doesn't yet support UCSD Pascal string types, to call Mac OS X rountines you have to use the fake "string" record types predefined in the GPCPInterfaces' MacTypes.pas unit. To assist with working with the fake "string" record types and GPC's native Extended Pascal string schema types, a GPCStrings.pas unit is also provided in the GPCPInterfaces. GPCStrings provides things like operator overloading for the relational operators and the string concatenation operator (i.e., +) and conversion routines to deal with the worst of the pains involved in working with GPC's native string type and the MacTypes' fake "string" record types. GPCStrings isn't a perfect solution and it doesn't try to handle every possible UCSD Pascal string size - just the ones declared in MacTypes.pas that are needed in interfacing with Mac OS X routines.

I'll also mention that when you're code is interfacing with Mac OS X routines it is best to adopt a naming scheme to help in keeping track of what type of string thing - GPC's native schema based string or fake "string" record based string - your working with. In the GPCPInterfaces, the naming convention uses is: StrXX is a fake "string" record type and StringXX is the corresponding native GPC string with the same maximum character capacity as the fake "string" record type has. The StringXX types are declared in the GPCStrings unit's interface.

Gale Paeper gpaeper@empirenet.com