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Revision 1 of 2, by Trev on 9-8-2022. The page as it is now.

WebAssembly/Compiler

Prerequisites

The linker wasm-ld from the LLVM project. LLVM 11.0 and 12.0.1 are known to work.

Fedora

Development was done, using the Fedora packages llvm-11.0.0-1.fc33.x86_64 and lld-11.0.0-1.fc33.x86_64.

Ubuntu

Tested on Ubuntu 20.04. wasm-ld is part of package lld-12. Install it and set necessary symlinks:

% sudo apt install lld-12
% ln -sf /usr/lib/llvm-12/bin/wasm-ld ~/bin/wasm32-wasi-wasm-ld
% ln -sf /usr/lib/llvm-12/bin/wasm-ld ~/bin/wasm32-embedded-wasm-ld

Note: This assumes you have a $HOME/bin directory and it is in PATH.

macOS

Catalina

Tested on macOS Catalina with LLVM 11. For MacPorts wasm-ld is part of package llvm-11; upon installation it exists as wasm-ld-mp-11. Install the package and set necessary symlinks:

% sudo port install llvm-11
% ln -sf /opt/local/bin/wasm-ld-mp-11 ~/bin/wasm32-wasi-wasm-ld
% ln -sf /opt/local/bin/wasm-ld-mp-11 ~/bin/wasm32-embedded-wasm-ld

Note: This assumes you have a $HOME/bin directory and it is in PATH.

Monterey

Tested on macOS Monterey 12.5.1: wasm-ld is part of the official clang release for macOS: https://releases.llvm.org/download.html#11.1.0

Unpack it. When running wasm-ld, macOS might warn, that ldd cannot be verified. Open the System Preferences / Security / General. There should be ldd, unlock, then click Open Anyway.

Windows 10

Tested on Windows 10 Home 21H2. Download the LLVM 12.0.1 64-bit Windows installer. You are encouraged to verify the GPG signature on the installer. As administrator, run the installer. Let's say you installed into C:\llvm. Enable Windows 'developer mode' if you have not done so. Then set necessary symlinks:

 C:\> cd llvm\bin
 C:\llvm\bin> mklink wasm32-wasi-wasm-ld.exe wasm-ld.exe
 C:\llvm\bin> mklink wasm32-embedded-wasm-ld.exe wasm-ld.exe

Add C:\llvm\bin to your PATH.

Obtaining the compiler sources

Linux and macOS

The WebAssembly compiler target is part of the 'main' branch of the GitLab FPC source repo. Get the source:

% git clone https://gitlab.com/freepascal.org/fpc/source.git fpc

Enter the sources directory:

% cd fpc

Windows

The WebAssembly compiler target is part of the 'main' branch of the GitLab FPC source repo. Get the source:

C:\Users\OnlyMe> git clone https://gitlab.com/freepascal.org/fpc/source.git fpc

Enter the sources directory:

C:\Users\OnlyMe> cd fpc

Building and installing

If you are new to building the compiler, see Installing the Free Pascal Compiler and Cross compiling.

FPC supports two WebAssembly compilation targets: WASI and embedded.

Compilation target: WASI

Linux and macOS

Build the compiler and FPC units for the WASI target:

% make clean all OS_TARGET=wasi CPU_TARGET=wasm32 BINUTILSPREFIX= OPT="-O-" PP=fpc

Then, install, using INSTALL_PREFIX to specify a destination within your home directory:

% make crossinstall OS_TARGET=wasi CPU_TARGET=wasm32 INSTALL_PREFIX=$HOME/fpcwasm

Note: On macOS you might have to add -XR/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk to OPT.

Make a link to the cross compiler executable ppcrosswasm32:

% ln -sf ~/fpcwasm/lib/fpc/3.3.1/ppcrosswasm32 ~/bin/ppcrosswasm32

Note: This assumes you have a $HOME/bin directory and it is in PATH.

Windows

Make sure the Windows native compiler fpc.exe and the FPC-bundled make.exe are in your PATH. Especially ensure that the FPC make.exe comes first in your PATH; using another make.exe (such as the one installed by Delphi) that happens to be ahead in PATH may not work.

Build the compiler and FPC units for the WASI target:

C:\Users\OnlyMe\fpc> make clean all OS_TARGET=wasi CPU_TARGET=wasm32 BINUTILSPREFIX= OPT="-O-" PP=fpc

Then, install, using INSTALL_PREFIX to specify a destination folder:

C:\Users\OnlyMe\fpc> make crossinstall OS_TARGET=wasi CPU_TARGET=wasm32 INSTALL_PREFIX=c:\fpcwasm PP=fpc

Add C:\fpcwasm\bin\x86_64-win64 to your PATH to easily run the compiler ppcrosswasm32.exe.

Compilation target: Embedded

Linux and macOS

Build the compiler and FPC units for the 'embedded' target:

% make clean all OS_TARGET=embedded CPU_TARGET=wasm32 BINUTILSPREFIX= OPT="-O-" PP=fpc

Then, install, using INSTALL_PREFIX to specify a destination within your home directory:

% make crossinstall OS_TARGET=embedded CPU_TARGET=wasm32 INSTALL_PREFIX=$HOME/fpcwasm

If you have not built and installed the WASI cross compiler, then make a link to the cross compiler executable ppcrosswasm32;

% ln -sf ~/fpcwasm/lib/fpc/3.3.1/ppcrosswasm32 ~/bin/ppcrosswasm32

Note: This assumes you have a $HOME/bin directory and it is in PATH.

Windows

Make sure the Windows native compiler fpc.exe and the FPC-bundled make.exe are in your PATH. Especially ensure that the FPC make.exe comes first in your PATH; using another make.exe (such as the one installed by Delphi) that happens to be ahead in PATH may not work.

Build the compiler and FPC units for the 'embedded' target:

C:\Users\OnlyMe\fpc> make clean all OS_TARGET=embedded CPU_TARGET=wasm32 BINUTILSPREFIX= OPT="-O-" PP=fpc

Then, install, using INSTALL_PREFIX to specify a destination folder:

C:\Users\OnlyMe\fpc> make crossinstall OS_TARGET=embedded CPU_TARGET=wasm32 INSTALL_PREFIX=c:\fpcwasm PP=fpc

Add C:\fpcwasm\bin\x86_64-win64 to your PATH if you have not already done so.

Using the compiler

For Linux and macOS, if you have installed the cross compiler and units into $HOME/fpcwasm (as per the commands used above), then you need to configure $HOME/.fpc.cfg so that the cross compiler can locate its units.

For Ubuntu, add these lines:

pascal
#ifdef cpuwasm32
-Fu/home/yourusername/fpcwasm/lib/fpc/$fpcversion/units/$fpctarget/*
-Fu/home/yourusername/fpcwasm/lib/fpc/$fpcversion/units/$fpctarget/rtl
#endif

For macOS, add these lines:

pascal
#ifdef cpuwasm32
-Fu/Users/yourusername/fpcwasm/lib/fpc/$fpcversion/units/$fpctarget/*
-Fu/Users/yourusername/fpcwasm/lib/fpc/$fpcversion/units/$fpctarget/rtl
#endif

On Windows, if you have set C:\fpcwasm\bin\x86_64-win64 directory in your PATH, then ppcrosswasm32.exe will be able to find its units.

Using the compiler with Lazarus

When you create a new Lazarus project for a wasm program you can use the Simple Program template and then adjust the Project / Project Options / Compiler Options:

See Also

From the Free Pascal wiki, page "WebAssembly/Compiler", as it stood on 2022-09-08 after a change by Trev, out of the wiki's dump of 2024-05-26. Copyright stays with the author who wrote it, according to the old wiki's Licensing page. If you have concerns about this material, message the admin.