Chris Wellons • 12/12/2025

Closures as Win32 window procedures

This article details an advanced C programming technique using JIT-compiled wrappers to create closures, specifically to enhance Win32 window procedures with a fifth argument for passing context. It discusses the limitations of the standard WNDPROC prototype, the common workarounds (global variables or GWLP_USERDATA), and presents a practical solution involving a custom trampoline for the x64 calling convention.

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#closures #c #callbacks