compat.pixman

// compat.pixman — behavioral test.
//
// The interesting thing about this package is not that it links; it is that
// pixman dispatches on the CPU at runtime, and this index compiles the SSE2
// and SSSE3 implementations with per-file `-msse2` / `-mssse3` so that the
// compiler may emit those instructions THERE and nowhere else. If the flags
// had been package-wide, code running before pixman's own CPUID check could
// carry SSSE3 — an illegal instruction on an older machine, from a library
// whose entire design is to avoid exactly that.
//
// So the test does two things a "does it link" check would not:
//
//   * asks pixman which implementation it CHOSE, through a real composite;
//   * composites actual pixels and reads them back, because the SIMD paths
//     are only reached with enough work to be worth dispatching to.
//
// No display, no GPU, no threads.

#ifdef __linux__

#include <pixman.h>

// …