Packaging/32bit Applications: Difference between revisions

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Nixpkgs provides <code>multiStdenv.mkDerivation</code> that should be used instead <code>stdenv.mkDerivation</code>.

This is equivalent to using <code>gcc-multilib</code> in debian derivatives.

=== Rust ===

env = {

# Use multilib clang as linker for i686 target.

# Required because Rust's bundled LLD doesn't know about Nix's multilib sysroot paths.

# clang_multi has the correct 32-bit library paths (glibc_multi) baked into its driver.

CARGO_TARGET_I686_UNKNOWN_LINUX_GNU_LINKER = "${pkgs.clang_multi}/bin/clang";

};

packages = with pkgs; [

# clang with multilib support (both 32-bit and 64-bit)

# This properly handles -m32 compilation with correct headers/libs

clang_multi

];

</syntaxhighlight>An example that will let you build with <code>cargo test --target i686-unknown-linux-gnu</code> from an x86_64 machine.

You will want something similar to the following in your <code>flake.nix</code>, <code>devenv.sh</code> , or whatever you're using as your entry point.

==== Rust LTO & cargo bench ====

If you are using LTO and are having trouble building benchmarks (<code>cargo bench</code>) you may need to disable it at the build step until someone documents a better workaround here.<syntaxhighlight lang="nix">

env = {

# Disable LTO for C/C++ code compiled by the `cc` crate for i686.

# Some crates (like `alloca`) add -flto when CC=clang, but binutils ld can't

# process LLVM IR bitcode. Using -fno-lto ensures native object files.

CFLAGS_i686_unknown_linux_gnu = "-fno-lto";

CXXFLAGS_i686_unknown_linux_gnu = "-fno-lto";

};

</syntaxhighlight>

[[Category:Development]]

@@ Line 9: / Line 9: @@
 Nixpkgs provides <code>multiStdenv.mkDerivation</code> that should be used instead <code>stdenv.mkDerivation</code>.
 This is equivalent to using <code>gcc-multilib</code> in debian derivatives.
+=== Rust ===
+<syntaxhighlight lang="nix">
+env = {
+  # Use multilib clang as linker for i686 target.
+  # Required because Rust's bundled LLD doesn't know about Nix's multilib sysroot paths.
+  # clang_multi has the correct 32-bit library paths (glibc_multi) baked into its driver.
+  CARGO_TARGET_I686_UNKNOWN_LINUX_GNU_LINKER = "${pkgs.clang_multi}/bin/clang";
+};
+packages = with pkgs; [
+  # clang with multilib support (both 32-bit and 64-bit)
+  # This properly handles -m32 compilation with correct headers/libs
+  clang_multi
+];
+</syntaxhighlight>An example that will let you build with <code>cargo test --target i686-unknown-linux-gnu</code> from an x86_64 machine.
+You will want something similar to the following in your <code>flake.nix</code>, <code>devenv.sh</code> , or whatever you're using as your entry point.
+==== Rust LTO & cargo bench ====
+If you are using LTO and are having trouble building benchmarks (<code>cargo bench</code>) you may need to disable it at the build step until someone documents a better workaround here.<syntaxhighlight lang="nix">
+env = {
+  # Disable LTO for C/C++ code compiled by the `cc` crate for i686.
+  # Some crates (like `alloca`) add -flto when CC=clang, but binutils ld can't
+  # process LLVM IR bitcode. Using -fno-lto ensures native object files.
+  CFLAGS_i686_unknown_linux_gnu = "-fno-lto";
+  CXXFLAGS_i686_unknown_linux_gnu = "-fno-lto";
+};
+</syntaxhighlight>
 [[Category:Development]]