Target Availability

Target availability is expressed through compile-time target predicates, declaration-level INCLUDE_IF, and runtime HAVE_* CPU queries.

INCLUDE_IF

::name INCLUDE_IF(constant-expression) declaration
.name INCLUDE_IF(constant-expression) member-declaration

The condition must produce a compile-time BOOL for the active target. When it is FALSE, the compiler omits the declaration for that target.

::word_size INCLUDE_IF(ARCH_IS_X64) FUNCTION(): I32
{
  RETURN 64;
}

::conditional_fields STRUCT
{
  .compact INCLUDE_IF(TRUE) VAR BYTE;
  .wide INCLUDE_IF(FALSE) VAR U64;
}

An excluded declaration does not participate in name lookup, overload resolution, field layout, interface discovery, test discovery, or other compiler operations. Code cannot refer to it for that target.

INCLUDE_IF controls declarations. STATIC_IF selects statements inside an existing declaration; an unselected STATIC_IF branch is discarded during semantic generation.

Compile-time target predicates

The compiler provides these predicate families as compile-time BOOL values:

Category	Predicates
Architecture	ARCH_IS_X64, ARCH_IS_X86, ARCH_IS_ARM32, ARCH_IS_ARM64, ARCH_IS_RISCV64, ARCH_IS_Z_ARCH, ARCH_IS_JVM, ARCH_IS_LAYOUTLESS
Backend	BACKEND_LLVM, BACKEND_CORTADO
Operating system	OS_LINUX, OS_WINDOWS, OS_MACOS
Binary format	BINARY_ELF, BINARY_MACHO, BINARY_PE, BINARY_WASM
Environment	ENVIRONMENT_IS_GLIBC, ENVIRONMENT_IS_MUSL, ENVIRONMENT_IS_BIONIC, ENVIRONMENT_IS_MSVC, ENVIRONMENT_IS_UCRT, ENVIRONMENT_IS_CYGWIN, ENVIRONMENT_IS_STATIC, ENVIRONMENT_IS_LIBSYSTEM, ENVIRONMENT_IS_FREESTANDING
Unwind format	UNWIND_FORMAT_IS_NONE, UNWIND_FORMAT_IS_DWARF_EH_FRAME, UNWIND_FORMAT_IS_ARM_EHABI, UNWIND_FORMAT_IS_WINDOWS_SEH, UNWIND_FORMAT_IS_SJLJ, UNWIND_FORMAT_IS_WASM

Predicates may be combined with ordinary compile-time Boolean operators:

::hosted_linux_operation INCLUDE_IF(
  OS_LINUX && ENVIRONMENT_IS_FREESTANDING == FALSE
) FUNCTION()
{
}

Each concrete ARCH_IS_* predicate identifies the configured target architecture. ARCH_IS_LAYOUTLESS is TRUE when the managed runtime controls type representations and those types have no fixed byte layout visible to Quxlang code.

The capability registry reserves ARCH_IS_RISCV64 and RISC-V capability names. The current public qxcbuild.yml target loader does not yet accept a RISC-V target.

Runtime CPU capability queries

A source expression named HAVE_<CAPABILITY> returns a runtime BOOL:

::avx2_available FUNCTION(): BOOL
{
  RETURN HAVE_X64_FEATURE_AVX2;
}

The capability name uses the stable identifiers configured in target steppings, such as X64_FEATURE_AVX2 or X64_FEATURE_SSE4_1. Aggregate queries such as HAVE_X64_FEATURES_V3 require every constituent capability.

Query context	Result generation
Matching CPU family, capability fixed by the current stepping	LLVM emits the known Boolean value
Matching CPU family, capability detected at startup	The expression reads the compiler-owned _ENABLED state
Different CPU family	FALSE
Aggregate capability	Conjunction of its constituent capability results

The target's stepping sequence must contain each queried capability whose detection routine is required. Startup selects the highest compatible stepping and uses code compiled for that same stepping. The complete configuration and constant-folding contract is in CPU Capabilities and Steppings.

HAVE_* is a runtime expression. It is not accepted as the constant condition of INCLUDE_IF or STATIC_IF.

Availability examples

An architecture-specific assembly body normally combines architecture and operating-system availability:

::linux_exit INCLUDE_IF(OS_LINUX) ASM_PROCEDURE X64
{
  MOV RAX, 60
  SYSCALL
  RET
}

Inheritance is available during constant evaluation and on native targets. The current JVM backend does not implement it. A declaration that exercises native inheritance can be excluded with:

::native_hierarchy_test INCLUDE_IF(ARCH_IS_JVM!!) DUAL_TEST
{
  // Exercise the hierarchy here.
}

Unsupported expressions

TARGET("name"), kernel predicates, and OS_BSD are not implemented. Target selection remains part of bundle configuration; source declarations can use the predicate families listed above.

Backends and Layout specifies layout-dependent language features. qxcbuild.yml specifies target configuration.