I am porting a Delphi application to Linux and as a stop I am first doing it from Delphi to Lazarus/Fpc on Windows.

Now when I try to compile it throws an error inside a unit I did not even know it used. And to further complicate the issue I cannot find a reference to the unit in question when doing a search in the project dir inside all pas files. This unit is not mentioned anywhere and still causes a compile error due to a missing reference.

I tried Lazarus Find In Files and set it to search "all files in project" and also search the project directory, but it comes up empty-handed...

So now I wonder:
Is there a Lazarus tool to trace why the unit is referenced in the first place? Is there such things as "chain of uses"?

The application I am porting is a client communications app that talks to a service over TCP/IP.
That service app uses the unit that pos up as erroneous now, but it should not be used by the client comm I need to find out why it does.

Perhaps it can be find in Projects properties?

View / Unit Dependencies

Mattias

Well, that only shows the units specifc to the application itself...

I figured out that the reason this unit was brought in was via another unit that *is* used since it contains declarations of the different data records and classes handled by the server and the client.

In this unit that extra unit is listed in uses since it contains stuff needed by functions inside this unit itself (but not needed by the client application).

So there seems to be a chain reaction concerning units involved in the application....

Bo Berglund via lazarus schrieb am Mi., 23.
Sep. 2020, 21:13:

So there seems to be a chain reaction concerning units involved in the application....

If course there is. That's how the unit system is supposed to work after all.

Regards,
Sven

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Yes, I realize that now.

It means that the client even though it will not interface to the hardware will have all of the code used to do that included in the app, right?

The reason this was brought in is that the client app needs to know the structure of the data on the server but not really the implementatiuon on the server side inmcluding hardware interfacing details...

Is it possible to have declaration of classes in one file and implementation in another?

For example one file holding the declarations and another implementations and then the client just uses the first whereas the server uses both?

Maybe this is where you can use inc files?

Or I should just accept it and move on...

Bo Berglund via lazarus schrieb am Do., 24.
Sep. 2020, 08:08:

The compiler (and linker) only includes code that is used. Thus as long as you don't call the hardware functions anywhere in your program (this includes indirectly or through initialization/finalization sections) then the code won't be in the final binary either.

Regards,
Sven
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Sven, I believe Bo's problem is that even though he won't need the Code (which the linker/compiler will surely cleverly disregard), he also do not even wish to "need" the physical Unit files to be in view of the compiler - at least not the secondary-dependency units - when he references a unit file in which he only needs a few declarations visible.

Sadly Bo, the entire premise of the Unit system is that every dependency will be in view, the compiler cannot decide BEFORE compiling that it would or wouldn't need a unit which appears in a "unit" clause lower down the dependency tree. Consider that a used unit may well declare a global variable that overrides one from a higher-up unit, for instance. So even though the program has all the participating symbols at hand without looking at this depended unit with the override, it will produce a different program (than when that override IS considered) and so cannot simply decide to ignore/not require a unit preemptively before actually parsing the physical file.

All units you use, pluse every dependent unit they use, must be available and visible to the compiler. That rule is absolute.

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R.Smith via lazarus schrieb am Do., 24.
Sep. 2020, 12:19:

Well, Bo could always split the data type declarations into a separate unit.

Regards,
Sven
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Sven Barth wrote

Well, Bo could always split the data type declarations into a separate unit.

But I cannot wrap my head around this (constructed example):

interface
type
 TMyRecord = packed record
   Item1: word;
   Item2: Cardinal;
  end;
TMyController = class
  private
    FGPIO_driver: TIoDriver;
    FGpF: TIoPort;
    function CheckValidRelay(Relay: byte): boolean;
  public
    constructor Create;
    destructor Destroy; override;
    procedure ClearRelays;
    function PulseRelay(Relay: byte; PulseTime: LongWord): boolean;
    function RelayOff(Relay: byte): boolean;
    function RelayOn(Relay: byte): boolean;
    function RelayState(Relay: byte): boolean;
    procedure Delay(T: LongWord);
  end;
implementation
  ...All of the methods here...

AFAIK the records could be declared elsewhere but the objects not since their methods, constructor, destructor etc reside in the same file below implementation, right?

Just specifying a uses file with everything above the implementation will not cut it, right?

But as I indicated I have just moved on and I am leaving this because it seems to do more harm than good and is a lot of work too.

Bo Berglund via lazarus schrieb am Do., 24.
Sep. 2020, 15:22:

Would your code require the hypothetical TMyController or only the TMyRecord? If it only requires the later then you could indeed solve this by moving the record into a separate unit. If your code requires TMyController as well, then it can't be left out anyway (though the compiler will leave out any non-virtual method of that class which isn't used).

Just specifying a uses file with everything above the implementation will not cut it, right?

No, that will not help.

Regards,
Sven
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