Tutorial: Meson Package

Tutorial: Meson Package#

Many scientific Python packages use Meson via meson-python as their build system. pyodide-build supports Meson out of the box.

Basic usage#

For most Meson packages, just run:

pyodide build .

pyodide-build automatically intercepts meson setup calls and injects the Meson cross file, which tells Meson the build is targeting Emscripten. No manual configuration is needed.

Passing Meson options#

Use -Csetup-args= to pass options to Meson:

pyodide build . \
    -Csetup-args=-Dsome-option=value \
    -Csetup-args=-Danother-option=false

Each Meson option needs its own -Csetup-args= prefix.

Real-world example: NumPy#

NumPy uses meson-python. Here’s how to build it for WebAssembly:

pyodide build . -Csetup-args=-Dallow-noblas=true

The -Dallow-noblas=true disables BLAS/LAPACK (which aren’t available as Emscripten libraries by default). This pattern — disabling optional native dependencies — is common when cross-compiling.

What the cross file provides#

The Meson cross file that pyodide-build injects tells Meson:

  • The host machine is emscripten / wasm32

  • Use node as the executable wrapper

  • Skip the compiler sanity check (Emscripten’s output can’t run natively)

Tip

If automatic cross file injection doesn’t work for your setup, you can pass it explicitly:

MESON_CROSS_FILE=$(pyodide config get meson_cross_file)
pyodide build . -Csetup-args=--cross-file="$MESON_CROSS_FILE"

Or via the MESON_CROSS_FILE environment variable:

export MESON_CROSS_FILE=$(pyodide config get meson_cross_file)
pyodide build .

What’s next?#