3.1.2 Unit les

When you compile a unit or program that needs other units, the compiler will look for compiled versions of these units in the following way:

1. It will look in the current directory.
2. It will look in the directory where the source le is being compiled.
3. It will look in the directory where the compiler binary is.
4. It will look in all the directories specied in the unit search path.

You can add a directory to the unit search path with the (-Fu (see page 5.1.3)) option. Every occurrence of one of this options will insert a directory to the unit search path. i.e. the last path on the command line will be searched rst.

The compiler adds several paths to the unit search path:

1. The contents of the environment variable XXUNITS, where XX must be replaced with one of the supported targets: GO32V2, LINUX,WIN32, OS2, BEOS, FREEBSD, NETBSD.
2. The standard unit directory. This directory is determined from the FPCDIR environment variable. If this variable is not set, then it is defaulted to the following:
   • On linux:

     /usr/local/lib/fpc/FPCVERSION   or     /usr/lib/fpc/FPCVERSION

     whichever is found rst.

   • On other OSes: the compiler binary directory, with '../' appended to it, if it exists. For instance, on Windows, this would mean

     C:\FPC\1.9.6\units\i386-win32

     This is assuming the compiler was installed in the directory

     C:\FPC\1.9.6

   After this directory is determined , the following paths are added to the search path:

   1. FPCDIR/units/FPCTARGET
   2. FPCDIR/units/FPCTARGET/rtl

   Here target must be replaced by the name of the target you are compiling for: this is a combination of CPU and OS, so for instance

   /usr/local/lib/fpc/1.9.6/units/i386-linux/

   or, when cross-compiling

   /usr/local/lib/fpc/1.9.6/units/i386-win32/

Note that (for optimization) the compiler will drop any non-existing paths from the search path, i.e. the existence of the path will be tested.

You can see what paths the compiler will search by giving the compiler the -vu option.

On systems where lenames are case sensitive (such as unix and linux), the compiler will :

1. Search for the original le name, i.e. preserves case.
2. Search for the lename all lowercased.
3. Search for the lename all uppercased.

This is necessary, since Pascal is case-independent, and the statements Uses Unit1; or uses unit1; should have the same eect.

It will do this rst with the extension .pp and then with the extension .pas.

For instance, suppose that the le foo.pp needs the unit bar. Then the command

will tell the compiler to look for the unit bar in the following places:

1. In the current directory.
2. In the directory where the compile binary is (not under linux).
3. In the parent directory of the current directory.
4. In the subdirectory units of the current directory
5. In the standard unit directory.

Also, unit names that are longer than 8 characters will rst be looked for with their full length. If the unit is not found with this name, the name will be truncated to 8 characters, and the compiler will look again in the same directories, but with the truncated name.

If the compiler nds the unit it needs, it will look for the source le of this unit in the same directory where it found the unit. If it nds the source of the unit, then it will compare the le times. If the source le was modied more recent than the unit le, the compiler will attempt to recompile the unit with this source le.

If the compiler doesn't nd a compiled version of the unit, or when the -B option is specied, then the compiler will look in the same manner for the unit source le, and attempt to recompile it.

It is recommended to set the unit search path in the conguration le fpc.cfg. If you do this, you don't need to specify the unit search path on the command-line every time you want to compile something.