Patches

Changes to the reconstructed 1992 sources in vendor/cosmore, applied at configure time by cmake/PrepareCosmoreSources.cmake. The submodule itself is never modified, so the difference between the original and what is compiled is exactly this directory plus three mechanical transformations.

Everything the transformations can express is done there rather than here: dropping Borland headers with no modern equivalent, commenting out the 16-bit inline assembly, and pinning the base types to their original widths. A patch exists only where that is not enough.

Each patch carries a preamble explaining the defect and why the change is correct. Six restore behaviour the port would otherwise have lost; one is a deliberate change and says so.

Patch	What it addresses
0001	Two places store through a far pointer into video memory, which cannot be intercepted, so they are routed through the emulated adapter
0002	Globals shared with interrupt handlers become volatile; without it a modern compiler hoists the game clock out of its wait loop and the game hangs
0003	pushf/popf around critical sections, and the OPL2 register writes that lived inside the assembly. Without this game2.c has three disable() calls and no enable()
0004	A null sound pointer that real mode made harmless by aiming it at the interrupt vector table
0005	The calibrated busy-wait pair that AdLib detection depends on, replaced by a real microsecond wait
0006	The music chunk split, without which every note is written to register 0, and the BIOS timer chaining
0007	Not a fix. Changes the default jump key from ctrl to space

docs/porting-notes.md has the longer story of how each was found.

Regenerating a patch

Patches apply to the generated sources, after the transformations, not to the submodule. To revise one, configure a build, edit a copy of the file in build/<preset>/gen/, and diff it against the unmodified generated version.

The build fingerprints every generated file before and after each patch, so a patch that applies cleanly while changing nothing fails the configure step rather than silently doing nothing.