Difference between revisions of "Unit not found - How to find units"

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== Overview ==
 
== Overview ==
  
This page is about one of the most prominent errors of pascal: '''unit not found'''.
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This page is about one of the most prominent errors of pascal: '''unit not found''' or '''can't find unit'''.
 
This error has a lot of reasons and this page tries to gather most of the reasons, how to find out, which problem it is, and how to solve it.
 
This error has a lot of reasons and this page tries to gather most of the reasons, how to find out, which problem it is, and how to solve it.
  

Revision as of 12:25, 28 November 2006

Overview

This page is about one of the most prominent errors of pascal: unit not found or can't find unit. This error has a lot of reasons and this page tries to gather most of the reasons, how to find out, which problem it is, and how to solve it.

Notations, terms

  • .pas file: This is a place holder for any pascal unit source. For example unit1.pas or unit1.pp. Both extensions are allowed and there is no difference. There are other compilers, which ignore .pp files, but this page is about the Free Pascal compiler.
  • .pp file: Same as .pas. Just another extension for the same thing.
  • .p file: Same as .pas. Just another extension for the same thing. Commonly utilized on Macintosh.
  • .ppu file: This is place holder for any compiled pascal unit, created by the Free Pascal compiler.

Step 1: Compiler or IDE or both

The first step is to find out, if the IDE can not find the unit, or the compiler can not find it or both.

Although the compiler and the IDE are using quite similar search algorithms to find a unit, there are some differences. That's why sometimes the IDE can find a unit, which the compiler can not and vice versus. If the compiler can not find it, the compilation fails (Build, Ctrl+F9) with the error 'unit not found'. If the IDE can not find, the code tools will fail. For example Find Declaration (Alt+Up or Ctrl+Left mouse button) or Identifier completion (Ctrl+Space) will fail with the same error 'unit not found'.

Common:

  • Both search units in the search path.
  • Both search first for pascal sources (.pas, .pp) files. Under MacPAS mode: search for .p files too.
  • Both search for several cases: normal case, lower case, upper case. For example: if the uses section contains 'Unit1', then it searches:
 1. Unit1.pp
 2. unit1.pp
 3. UNIT1.PP
 4. Unit1.pas
 5. unit1.pas
 6. UNIT1.PAS

They are searched in every directory of the search path.

Differences:

  • FPC uses the fpc.cfg for additional search paths. The IDE uses them only to find files of the FPC sources. So adding a search path to the fpc.cfg is ignored by Lazarus.
  • FPC always starts in one directory and every relative filename is relative to this directory. For the Lazarus IDE each project and each package has its own base directory. So the search path of a package is relative to the package directory. The package directory is the directory of the .lpk file. The base directory of a project is the projects main source file (e.g. the .lpr file). If there is no main source file, the directory of the .lpi file is taken. Normally both are the same and the IDE has no graphical frontend to split. But by editing the .lpi file manually you can split them. At the moment there is only one prominent example for this case: the ppxxx.lpi files of the Free Pascal compiler.
  • FPC and Lazarus have different macros.
  • You can define additional source search paths for the IDE, which are not given to the compiler. (Compiler options -> Other source files)

Case 1: Both can not find a unit

  • Check if the unit exists: If not, then see chapter Searching packages, projects of a unit (ToDo: write me).
  • Check if the unit is readable: (You can open it in the IDE). A unit source does not need to be writable. If not, then fix the permissions or get a readable copy.
  • Check if the unit has a valid pascal name: (identifier plus extension). Valid examples: unit1.pas, Bogus2.pp, _1.pas, LAZ.PAS. Wrong examples: 1.pas (starts with number), a%.pas (contains special character), unit.PAS (extension uppercase, but filename lowercase).
  • Check if directory name contains special characters
  1. slashes / and backslashes \ are used as directory delimiter and should never be used for directory names
  2. dollar $ are used for macros and many scripting languages
  • Check for right case: If your unit name is all lowercase or all uppercase you don't need to worry. If not, then you must make sure, that every uses section in every source code uses exactly this case. For example: if your unit is named Unit1.pas, then every uses section must use Unit1. This is not so important under windows, but under any other platform (Linux, MacOSX). The IDE gives warnings when saving files with mixed case.
  • Check if the unit is in the search path. ToDo: write me

Case 2: Compiler finds a unit, but IDE does not

The next sub cases assumes, that Project -> Build (Ctrl+F9) in the Lazarus IDE works, but Find Declaration fails with the error: unit not found. If unsure, check Case 1 as well.

  • Check if the unit source exists: The IDE searches for pascal source (.pas, .pp) and ignores the .ppu files. The compiler can use a .ppu, but the Lazarus IDE not. This feature is planned, but there is no time frame.
  • Check if unit directory was added to your fpc.cfg: The compiler uses all paths defined in the fpc.cfg file. The IDE does not read this file. Add the search path to the compiler options of your projects and/or packages.
  • Check for macros and special compiler flags: The compiler understands the asterisk * character in search paths. The IDE treats this character as normal character. You can add the -Fu, -FU, -FE flags manually to the custom compiler flags in the lazarus IDE, but they are not parsed. Always use the right fields for options. The custom options are only for flags like the -D flag or uncommon compiler options, like new features of the unstable developer compiler.

Case 3: IDE finds a unit, but compiler does not

This is the case, when Find Declaration finds the unit, but building (Ctrl+F9) fails.

There are two cases: Either the compiler didn't find anything, or it does not like, what it found. In both cases it returns the same error: unit xyz not found.

Case 3.1: The compiler finds the .ppu file, but does not like it

This can happen, when the found .ppu file is older than a required unit (.pas, .pp or .ppu). For example if unit1 uses unit2 and unit2 was changed, then unit1 needs to be recompiled as well.

It can also happen, if you installed newer files without deleting the old ones. The compiler stops at the first found.

You can see, what the compiler finds and what is missing by giving the -vt command line switch. But this gives a lot of output and it is hard to read for newbies.

The easiest way is often to first recompile the packages and project clean (Build all). In case of the Lazarus sources itself: The configure build lazarus dialog has a button to setup all options for a clean build.

Case 3.2: The compiler does not find neither source (.pas, .pp) nor .ppu file

In this case you have to extend the search path. The question is: Adding the .ppu directory or the source directory?

WARNING: If you add the wrong search path, it can happen, that the compiler will create multiple copies of files and you will later get the 'unit not found' error of Case 3.1.

Many projects and packages have distinct source directories (.pas, .pp) and output directories (.ppu). If a package has an output directory, then only this directory should be added to the search path of any depending project and/or package. The IDE will do this automatically. For example: Adding the LCL as dependency to your project adds two output directories to your unit search path. You can see this in Compiler Options -> Inherited. Never add any other LCL directory to your search paths or you will get Case 3.1 errors.

  • Check if the unit is in the compiler search path: The search path given to the compiler are the -Fu options of the command line parameters. You can see the options given to the compiler in Compiler Options -> Show Options.