Win64 for AMD64

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This article applies to Windows only.

See also: Multiplatform Programming Guide



Warning: November 2013: this page is obsolete; Windows x64 support has been implemented. This page is kept for historical reference only...


Compiling and building

Compiling a program

Win64 requires the usage of the internal linker of FPC so all programs must be compiled with -Xi.

Debugging and Profiling

There is currently no full debugger support available, we're working on improving this situation. Basic debugging can be done so far with WinDBG, the missing dwarf support of WinDBG makes things a little bit difficult though.

GDB for Win64 (beta version) is already available at


  • add compiler target
  • adapt rtl units
  • adapt api units
  • adapt fcl
  • get lazarus working
  • get integrated debugger working

Technical information

We're using our own assembler and linker to overcome the problem of the missing GNU Tools.

Information about the API etc. can be found at Win64/AMD64 API