Platform Requirements

ThreadPool-FP is a dependency-free Free Pascal library. Its platform contract is deliberately small but must be respected.

Supported toolchains#

Tool	Minimum	Notes
Free Pascal	3.2.2 or later	Uses only the RTL and FCL (`Classes`, `SysUtils`, `SyncObjs`, `Math`)
Lazarus	4.0 or later	Only required for the package and project files; FPC-only users do not need it

The library has no external dependencies. ThreadPool.Tasks requires 3.2.2+; earlier FPC versions cannot compile the task unit.

Operating systems#

CI tests the full suite and all examples on Windows and Linux.
macOS follows the same Free Pascal thread model as Linux: it requires cthreads and is expected to work, but it is not part of the CI matrix.
Unit files obey the {$IFDEF WINDOWS}stdcall{$ELSE}cdecl{$ENDIF} interface calling-convention rule so IWorkerThread compiles on non-Windows targets.

cthreads is mandatory on Unix-like systems#

On Linux and macOS, cthreads must be the first unit in your program's uses clause. Without it a program can compile, then crash at run time with an access violation (exit code 217) when the first worker thread initializes.

uses
  {$IFDEF UNIX}
  cthreads, // must be first on Linux and macOS
  {$ENDIF}
  ThreadPool.Simple;

Windows does not need cthreads.

ProcessorCount caveats#

TThread.ProcessorCount is the default worker count and is read once at program start.
It counts logical CPUs (including hyper-threads) on most systems, not physical cores.
It does not reflect later changes (CPU affinity, power states, containers).
Treat the computed worker count as approximate guidance.

Worker-count rules#

Argument	Result
`AThreadCount <= 0`	`TThread.ProcessorCount`
`< 4`	raised to 4
`> 2 × ProcessorCount`	capped at `2 × ProcessorCount`

Building from source#

Compile a program with just the source path:

fpc -Fu./src MyProgram.pas

Build the package, tests, benchmark, and examples with Lazarus; the repository README describes the commands and the CI pipeline runs the same steps on both operating systems.

Concurrency runtime notes#

Objects created per callback on the worker thread need no extra setup.
Any shared object the callbacks touch must use Free Pascal's usual thread helpers (TCriticalSection, TThreadList, atomic operations from the RTL).
Never assume the Unix or Windows scheduler measures are identical; workers map to OS threads, and thread count fixes the parallelism independent of how many cores are busy right now.