FPC Version Switcher

About

The FPC version switcher package integrates with the Lazarus IDE in order to allow easy switching of fpc versions.

Pre-requisites

Having multiple fpc versions installed
Having a homogeneous directory structure (path for different fpc versions should differ only by version number)
Having "fpc" as compiler executable in the IDE's Tools/Options/Files

Background

Actual compiler naming convention

The actual FPC compiler / cross-compiler is usually ppcxxx or ppcrossxxx where xxx denotes the cpu target.

For an i386 (32 bit) system:

ppc386 is the actual compiler
ppcrossx64 is the actual x86_64 cross compiler (produces 64 bit binaries)
ppcrossarm is the actual arm cross compiler (produces arm binaries)

etc...

For an x86_64 (64 bit) system:

ppcx64 is the actual compiler
ppcross386 is the actual i386 cross compiler (produces 32 bit binaries)
ppcrossarm is the actual arm cross compiler (produces arm binaries)

etc...

The fpc frontend executable

Rather than letting one guess the actual compiler name for a certain target cpu and call it directly, FPC provides the fpc front end executable, which takes care of calling the right actual compiler for the required target cpu. To do that, 3 things are needed:

The OS should be able to locate the fpc executable by either:
- adding the fpc executable path to the environment PATH variable (eg export PATH=/usr/bin;$PATH) and just calling "fpc".
- providing a fully qualified path (eg /usr/bin/fpc).

The fpc executable should be told what the target cpu is by using the -P<target_cpu> switch so that it can deduce by itself the actual compiler name.

The fpc executable should be able to locate the actual compiler by either:
- adding the actual compiler (ppcxxx) path to the environment PATH variable (eg export PATH=/usr/lib/fpc;$PATH)
- calling fpc with the -Xp<ppcxxx_path> switch to inform it about the location of the actual compiler (eg: fpc -Xp/usr/lib/fpc)

Some users opt to create in one folder symlinks with the fpc version suffixed (eg ppc386-3.1.1), and pointing to the actual compilers. The -V<version> switch lets the fpc executable append <version> to the actual compiler name (eg fpc -V3.1.1 on a 386 system will look for ppc386-3.1.1).

To sum up, calling fpc can take different forms:

fpc -P<cpu_target>
/usr/bin/fpc -Xp/usr/lib/fpc -P<cpu_target>
/usr/bin/fpc -Xp/usr/lib/fpc -V3.1.1 -P<cpu_target>

etc...

Checking fpc's mechanism

The -PP switch just displays the processor name.

On an i386 system (32 bit), the output of fpc -PP is i386
On an x86_64 system (64 bit), the output of fpc -PP is x86_64

The -PB switch will make fpc just display the actual compiler name for a target cpu.

On an i386 system (32 bit):

fpc -PB will output ppc386 (default cpu target)
fpc -Pi386 -PB will output ppc386
fpc -Px86_64 -PB will output ppcrossx64
fpc -Parm -PB will output ppcrossarm

etc...

On an x86_64 system (64 bit):

fpc -PB will output ppcx64 (default cpu target)
fpc -Px86_64 -PB will output ppcx64
fpc -Pi386 -PB will output ppcross386
fpc -Parm -PB will output ppcrossarm

etc...

One can even use it as follows:

<path_to_fpc_bin>/fpc -Xp<<path_to_fpc_lib> -V<fpc_version> -P<cpu_target> -PB

FPC tools

The actual compiler, once called, may need to locate some fpc utilities or tool. The path can be specified by either:

Adding the fpc tools path to the environment PATH variable (eg export PATH=/usr/local/bin/fpctools;$PATH)
Adding the -FD<fpc_tools_path> switch to fpc.cfg (eg: -FD/usr/local/bin/fpctools)
Calling fpc with the -FD<fpc_tools_path> switch (eg: fpc -FD/usr/local/bin/fpctools)

Cross binutils

For cross compiling, the cross binutils (cross assembler, cross linker, ...) folder should be in the environment PATH variable.