FPC IDE: Can't find unit system - freepascal

Question

I just installed FPC 3.2.0 (on Linux Mint 19.3) and trying to use FPC IDE. I launched the IDE from the bin installation subfolder as ./fp, written a simplest program in IDE
program hello;
begin
writeln('hello');
end.
saved the program as hello.pas and when I compile it I get
(3,1) Fatal: Can't find unit system used by hello
(0) Fatal: Compilation aborted
This is strange because system is the compiler's unit, not a user's unit.
I tried to google the issue, found several posts in different forums, one question was dated back to 2007 year, and none of the questions was answered.
Is where a way to solve the issue or FPC IDE is dead for about 15 years?

Answer 1

Check the unit directories in options->directories -> unit directories.
The package configuration should have put a line like
/usr/lib/fpc/$FPCVERSION/units/$FPCTARGET/*
The dollar values are builtins (respectively 3.2.0 and i386-linux or x86_64-linux). Please verify that the directories with prebuilt .ppu .o are there.

Answer 2

Try to fix your installation of FPC or you can fix it manually by calling fpcmkcfg
fpcmkcfg -d "basepath=path/to/fpc/3.3" -o path/to/fpc.cfg
For instance, if the compiler is in /usr/local/bin, it will look in
/usr/local/etc.

Answer 3

Had the same problem on Ubuntu 20.04. To solve it, I had to create the file fp.cfg in my project's folder with the following content:
-Fu/usr/lib/x86_64-linux-gnu/fpc/$fpcversion/units/$fpctarget
-Fu/usr/lib/x86_64-linux-gnu/fpc/$fpcversion/units/$fpctarget/*
If this will not work, it means unit path on your system is different. You may use something like
dpkg -L fp-units-base-3.0.4 | grep .ppu
to find out where units are actually stored. Replace 3.0.4 with your actual Free Pascal version. If you do not know exact version, use
sudo apt install apt-show-versions
apt-show-versions fpc
It will show something like
fpc:all/focal 3.0.4+dfsg-23 uptodate
3.0.4 is the version number you need.
Another way of getting needed paths is running this command:
cat /etc/fpc.cfg | grep -- -Fu | head -2
So you may just run
cat /etc/fpc.cfg | grep -- -Fu | head -2 > fp.cfg
in your project's folder to have the problem solved.

Answer 4

How to use Free Pascal (Lazarus) on Linux - no install solution:
If not already installed, install "GNU binutils" (sudo apt-get install binutils)
Dowload the latest version of Free Pascal (Lazarus): from the Downloads section of the Lazarus Home page (Lazarus is a professional open-source cross platform IDE powered by Free Pascal):
2.1. In case of a Debian based Linux system (such as Ubuntu): the .deb package could be downloaded ("fpc-laz_<version> ... .deb" (replace <version> with an actual version number))
2.2. In case of a RPM based Linux system (such as Fedora): the .rpm package could be downloaded ("fpc-<version> ... .rpm" (replace <version> with an actual version number))
Extract the downloaded package:
3.1. Place the downloaded .deb / .rpm package in the folder where you are going to extract it
3.2. Extract the downloaded .deb / .rpm package by Right-Click-ing it and then choosing Extract Here
3.3. Rename the extracted folder, as you desire, for example "fpc"; Further we denote this folder as "<BASEFOLDER>" and its path as - "<BASEFOLDER_PATH>"
In the case of a .deb package: Open the extracted <BASEFOLDER> and then, extract "data.tar.xz" - by Right-Click-ing it and then choosing Extract Here
Launch the Free Pascal window by typing the next command in the terminal - this command may vary according to the terminal used - replace <terminal> with the terminal used (by default: for Gnome based Desktop Environments -> gnome-terminal; for KDE based Desktop Environments -> konsole; for Xfce based Desktop Environments -> xfce4-terminal; for the MATE Desktop Environment -> mate-terminal; ...):
<terminal> -e '<BASEFOLDER_PATH>/usr/bin/fp'
OR:
<terminal> -- '<BASEFOLDER_PATH>/usr/bin/fp'
To add the units folders: From the Free Pascal Menu, access: Options -> Directories -> and copy (CTRL + C to Copy from outside the IDE, and (FN + )SHIFT + Insert to Paste inside the IDE) to the "Units" tab, the next three lines, each on a new line (replace <BASEFOLDER_PATH> with its corresponding value, and replace <LIB_FOLDER> with: lib in case of a .deb package or lib64 in case of a .rpm package):
<BASEFOLDER_PATH>/usr/<LIB_FOLDER>/fpc/$fpcversion\units\$fpctarget
<BASEFOLDER_PATH>/usr/<LIB_FOLDER>/fpc/$fpcversion\units\$fpctarget\*
<BASEFOLDER_PATH>/usr/<LIB_FOLDER>/fpc/$fpcversion\units\$fpctarget\rtl
Please note that by moving the files from the <BASEFOLDER> directory to other <BASEFOLDER_PATH>, you'll have to update the above three lines so that they contain the new <BASEFOLDER_PATH>, otherwise you might get errors like:
"Fatal: Can't find unit ..."
For navigation inside the IDE using keyboard - the following shortcuts can be used: Alt + Highlighted-letter, Highlighted-letter(s), Tab / Shift + Tab, Arrows, Enter, Esc
For Official Online Documentation see:
Online Documentation