From a588b1dfbc83c0915f2b4cf097d4892730b03482 Mon Sep 17 00:00:00 2001
From: exfalso <0slemi0@gmail.com>
Date: Thu, 24 Oct 2019 11:39:08 +0100
Subject: [PATCH 1/2] build-support/rust: Add target option

---
 pkgs/build-support/rust/default.nix | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/pkgs/build-support/rust/default.nix b/pkgs/build-support/rust/default.nix
index 27601e481c68..4f7c842ca483 100644
--- a/pkgs/build-support/rust/default.nix
+++ b/pkgs/build-support/rust/default.nix
@@ -18,6 +18,7 @@
   verifyCargoDeps ? false
 , buildType ? "release"
 , meta ? {}
+, target ? null
 
 , cargoVendorDir ? null
 , ... } @ args:
@@ -50,12 +51,13 @@ let
   rustHostConfig = {
     x86_64-pc-mingw32 = "x86_64-pc-windows-gnu";
   }.${hostConfig} or hostConfig;
+  rustTarget = if target == null then rustHostConfig else target;
 
   ccForBuild="${buildPackages.stdenv.cc}/bin/${buildPackages.stdenv.cc.targetPrefix}cc";
   cxxForBuild="${buildPackages.stdenv.cc}/bin/${buildPackages.stdenv.cc.targetPrefix}c++";
   ccForHost="${stdenv.cc}/bin/${stdenv.cc.targetPrefix}cc";
   cxxForHost="${stdenv.cc}/bin/${stdenv.cc.targetPrefix}c++";
-  releaseDir = "target/${rustHostConfig}/${buildType}";
+  releaseDir = "target/${rustTarget}/${buildType}";
 in
 
 stdenv.mkDerivation (args // {
@@ -88,7 +90,7 @@ stdenv.mkDerivation (args // {
     [target."${stdenv.buildPlatform.config}"]
     "linker" = "${ccForBuild}"
     ${stdenv.lib.optionalString (stdenv.buildPlatform.config != stdenv.hostPlatform.config) ''
-    [target."${rustHostConfig}"]
+    [target."${rustTarget}"]
     "linker" = "${ccForHost}"
     ${# https://github.com/rust-lang/rust/issues/46651#issuecomment-433611633
       stdenv.lib.optionalString (stdenv.hostPlatform.isMusl && stdenv.hostPlatform.isAarch64) ''
@@ -133,7 +135,7 @@ stdenv.mkDerivation (args // {
       "CXX_${stdenv.hostPlatform.config}"="${cxxForHost}" \
       cargo build \
         ${stdenv.lib.optionalString (buildType == "release") "--release"} \
-        --target ${rustHostConfig} \
+        --target ${rustTarget} \
         --frozen ${concatStringsSep " " cargoBuildFlags}
     )
 

From bb7184d6a62f3eefdadb069091f8985871279b15 Mon Sep 17 00:00:00 2001
From: exfalso <0slemi0@gmail.com>
Date: Fri, 1 Nov 2019 14:19:39 +0000
Subject: [PATCH 2/2] buildRustPackage: Add readme comment on target option

---
 doc/languages-frameworks/rust.section.md | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/doc/languages-frameworks/rust.section.md b/doc/languages-frameworks/rust.section.md
index 83b7b159bd63..5fb5d380d8b2 100644
--- a/doc/languages-frameworks/rust.section.md
+++ b/doc/languages-frameworks/rust.section.md
@@ -68,6 +68,17 @@ build-time.
 When `verifyCargoDeps` is set to `true`, the build will also verify that the
 `cargoSha256` is not out of date by comparing the `Cargo.lock` file in both the `cargoDeps` and `src`. Note that this option changes the value of `cargoSha256` since it also copies the `Cargo.lock` in it. To avoid breaking backward-compatibility this option is not enabled by default but hopefully will be in the future.
 
+### Building a crate for a different target
+
+To build your crate with a different cargo `--target` simply specify the `target` attribute:
+
+```nix
+pkgs.rustPlatform.buildRustPackage {
+  (...)
+  target = "x86_64-fortanix-unknown-sgx";
+}
+```
+
 ## Compiling Rust crates using Nix instead of Cargo
 
 ### Simple operation