The wlc command

wlc (White Language Compiler) is both the White compiler frontend and the native build driver. Its general command form is:

wlc <source.wl> [native files...] [options]

The first positional argument is the White entry file. Other White source files normally enter the program through import; native source, object, and library inputs may be supplied to the link step as additional files.

Run wlc --help to see the options supported by the installed compiler. This page describes the options used most often with White.

Output names

Without -o, the output name is derived from the entry file:

Build	Windows	Linux	macOS
executable	hello.exe	hello	hello
shared library	hello.dll	libhello.so	libhello.dylib
object	hello.obj	hello.o	hello.o
assembly	hello.s	hello.s	hello.s

-o <path> overrides the complete output path. The driver does not append an extension to an explicit name.

wlc src/main.wl -o build/app

Create the destination directory before compiling; wlc does not create missing parent directories for -o.

Optimization and debug information

The default optimization level is -O2.

-O0    disable optimization; useful while inspecting generated code
-O1    enable light optimization
-O2    normal optimized build
-O3    enable more aggressive speed optimization
-Os    optimize for size
-Oz    optimize more aggressively for size

-g asks Clang to include source-level debug information. It may be combined with any optimization level:

wlc main.wl -O0 -g

Stop before linking

-c produces an object file without linking:

wlc library.wl -c

-S produces textual assembly:

wlc main.wl -S

Use --emit-llvm with -S for textual LLVM IR, or with -c for LLVM bitcode:

wlc main.wl -S --emit-llvm
wlc main.wl -c --emit-llvm

The default names are main.ll and main.bc respectively.

Inspect the frontend

--dump-ast prints the parsed abstract syntax tree. --dump-ir prints the generated LLVM IR. These are compiler-development options; their output format is not a stable interface.

--keep-temps keeps the temporary .ll file used for an ordinary native build. -v prints the build stages, selected backend program, and each argument passed to it.

wlc main.wl -v --keep-temps

Shared libraries

--shared builds a library instead of an executable:

wlc exports.wl --shared

On Windows, the driver also creates the matching import library beside the DLL. An explicit output such as -o math.dll produces math.lib. Linux and macOS use the usual lib prefix only when the output name is left to the driver.

Exported White entry points use @ExportLib. Native interoperability and ABI rules are covered separately in the Language Guide.

Native libraries

-L <directory> and --library-path <directory> add a directory to the linker's library search path. The joined form is also accepted:

wlc app.wl -L ./native/lib
wlc app.wl -L./native/lib

An extern declaration with in "name" adds the corresponding -lname linker argument. --ldflags passes additional linker arguments when the regular library declarations and search paths are not enough:

wlc app.wl --ldflags "-pthread -lcustom"

Treat --ldflags as a native toolchain escape hatch. Flags accepted on one linker may not exist on another platform.

Targets and system roots

--target <triple> selects a supported target. Both forms below are valid:

wlc main.wl --target x86_64-unknown-linux-gnu
wlc main.wl --target=x86_64-unknown-linux-gnu

wlc --target-help prints the exact triples known by that compiler. --sysroot <directory> supplies the headers and libraries of the selected target to Clang. Selecting a triple is enough for LLVM IR, assembly, or object generation; linking for another operating system also needs its SDK or system root.

Cross-compilation is documented under Compiler and Tools because its setup depends on the host and target pair.

Exit status

wlc returns zero after a successful build and a non-zero status after a frontend, backend, or linking failure. A normal successful build ends with:

Build success: <output>

Scripts should use the process exit status rather than matching this text.