developer-delphi-assembly-conventions

Delphi calling conventions for Windows x64 assembly interop follow the Microsoft x64 ABI, passing the first four parameters in registers and requiring specific callee-saved registers to be preserved across calls.

To pass parameters in Free Pascal inline assembly, you must follow the specific calling convention declared, such as using registers for the register convention or pushing onto the stack for stdcall and cdecl.

The register convention passes parameters via CPU registers for speed within Delphi, while stdcall pushes parameters onto the stack right-to-left and is the standard for Windows API and cross-language DLL exports.

When debugging mixed Pascal and assembly code, you must preserve callee-saved registers across function calls, while caller-saved registers can be freely modified by the called routine without restoration.

Yes, you can use the cdecl calling convention in Delphi to interface with external C code on Win32, as it matches the default C parameter passing rules by pushing arguments right-to-left with caller stack cleanup.

Your Delphi assembly routine corrupts the stack when calling Windows x64 APIs if it violates the x64 ABI by misaligning the stack pointer or failing to allocate the 32-byte shadow space before making the call.