FastMM4 FullDebugMode Setup Guide

  1. Download the latest FastMM4 release; currently it is version 4.992
  2. Copy the precompiled FullDebugMode dll’s from the downloaded archive to the folders where Windows can find them. I recommend to do the following:
    • Manually create ‘c:\Software’ folder (or name the folder as you like);
    • Create ‘c:\Software\DLL’ subfolder (for 32-bit dll’s) and ‘c:\Software\DLL64’ subfolder (for 64-bit dll’s);
    • Add the paths ‘c:\Software\DLL’ and ‘c:\Software\DLL64’ to the system PATH variable (open Start menu, begin typing ‘environment …’ and choose ‘Edit the system environment variables’)
    • Copy ‘FastMM_FullDebugMode.dll’ to ‘c:\Software\DLL’
    • Copy ‘FastMM_FullDebugMode64.dll’ to ‘c:\Software\DLL64’
  3. Create FastMM4 folder; let it be ‘c:\Software\FastMM4’
  4. Copy ‘*.pas’ files and ‘’ from the main folder of the downloaded archive to ‘c:\Software\FastMM4’; do not copy the subfolders of the archive, they are just not needed here
  5. Enable FullDebugMode (open ‘’, find {.$define FullDebugMode} entry and remove the dot, {.$define FullDebugMode} –> {$define FullDebugMode})

Now the system-wide setup is completed, and we can test apps.

Delphi 10.2 Tokyo:

  • Create new console project and open ‘Project Options’ dialog;
  • Select ‘All configurations’ target;
  • Add ‘c:\Software\FastMM4’ to the search path and click ‘OK’.
  • Add ‘FastMM4’ as the first item in the ‘uses’ clause and add a simple memory leak
program Project1;

{$R *.res}


procedure MemLeak;
var P: PByte;

  GetMem(P, 10);

    on E: Exception do
      Writeln(E.ClassName, ': ', E.Message);
//  Readln;

If you run the app you get FastMM4 error message

Lazarus 1.8.4:

  • Unfortunately FastMM4 does not support FPC on Windows and even a simplest code example does not compile.

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