Overview of Target Availability

Quxlang provides INCLUDE_IF for declarations that are available only on specific configured targets. The following system-call wrapper is present on Linux targets and absent from other targets:

::process_identifier INCLUDE_IF(OS_LINUX) FUNCTION(): I32
{
  RETURN linux_getpid();
}

The compiler evaluates the condition for each target. An excluded declaration is unavailable to name lookup and overload resolution and occupies no storage. This makes INCLUDE_IF appropriate for declarations whose types, instructions, libraries, or layouts are unavailable on another target.

Common predicates describe the architecture, backend, operating system, binary format, environment, and unwind format:

::native_word_size INCLUDE_IF(ARCH_IS_LAYOUTLESS == FALSE) FUNCTION(): SZ
{
  RETURN BYTES(SZ);
}

STATIC_IF provides statement-level target selection when the enclosing declaration remains available on every target.

Runtime selection of CPU-specific code

HAVE_* expressions report whether the current machine supports a configured CPU capability.

::use_vector_path FUNCTION(): BOOL
{
  RETURN HAVE_X64_FEATURE_AVX2;
}

These queries allow one executable to select among compiled CPU steppings at startup. When a stepping specifies a capability, the backend can replace an individual query with a constant; otherwise the query reads the detected capability state. Runtime detection and additional compiled steppings increase startup work and binary size, so configure capabilities that the program uses.

The Target Availability Reference lists every predicate family and the exact inclusion and runtime-query rules.