mimoo · April 10, 2025 14:49 · Apr 10, 2025 · Apr 10, 2025 · Apr 10, 2025
diff --git a/README.md b/README.md
@@ -1,4 +1,6 @@
-create this Dockerfile:
+Need to test some Rust program in a 32-bit environment? You're on MacOS? Looks like you're going to have to use Docker. Not only that, but you'll have to use Docker with a 64-bit linux environment, that can support building and running 32-bit binaries.
+
+Create this Dockerfile:
 
 ```
 FROM rust:latest

diff --git a/gistfile1.txt → README.md b/gistfile1.txt → README.md
diff --git a/gistfile1.txt b/gistfile1.txt
@@ -0,0 +1,37 @@
+create this Dockerfile:
+
+```
+FROM rust:latest
+
+# Ensure we don't use our local build folder
+ENV CARGO_TARGET_DIR=/tmp/target32
+
+# Install 32-bit compilation support
+RUN dpkg --add-architecture i386 && \
+    apt-get update && \
+    apt-get install -y gcc-multilib libc6-dev:i386
+
+# Install 32-bit Rust target
+RUN rustup target add i686-unknown-linux-gnu
+
+# Create app directory
+WORKDIR /usr/src/app
+
+# Set up local config for 32-bit default
+RUN mkdir -p .cargo && \
+    echo '[build]\ntarget = "i686-unknown-linux-gnu"' > .cargo/config.toml
+```
+
+then build it / run it:
+
+```
+docker build --platform=linux/amd64 -t rust-32 .
+
+docker run --platform=linux/amd64 -it --rm \
+  -v "$PWD":/usr/src/app \
+  -w /usr/src/app \
+  rust-32 \
+  bash
+```
+
+this will mount your local directory (which should contain your rust project) and any cargo command should automatically pick up on the 32-bit target that's set as default in `.cargo/config.toml`