From 760ebff16408c803ed4848c3355e78d20f9e092b Mon Sep 17 00:00:00 2001
From: Michael Mueller <mich@elmueller.net>
Date: Thu, 11 Sep 2025 21:25:32 +0200
Subject: [PATCH 1/2] Handle Rust >= 1.91 change to `target-pointer-width` JSON
 type

https://github.com/rust-lang/rust/pull/144443
---
 Cargo.lock               |  1 +
 crates/build/Cargo.toml  |  1 +
 crates/build/src/args.rs | 27 +++++++++++++++++++++++++--
 3 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index 11749731a..c30cf2617 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1869,6 +1869,7 @@ dependencies = [
  "pretty_assertions",
  "regex",
  "rustc_version 0.4.1",
+ "rustversion",
  "semver 1.0.26",
  "serde",
  "serde_json",
diff --git a/crates/build/Cargo.toml b/crates/build/Cargo.toml
index 05dddcaed..13db0a023 100644
--- a/crates/build/Cargo.toml
+++ b/crates/build/Cargo.toml
@@ -46,6 +46,7 @@ itertools = "0.14.0"
 alloy-json-abi = "1.3.1"
 
 polkavm-linker = { git = "https://github.com/paritytech/polkavm.git" }
+rustversion = "1"
 
 contract-metadata = { version = "6.0.0-alpha.3", path = "../metadata" }
 ink_metadata = { workspace = true }
diff --git a/crates/build/src/args.rs b/crates/build/src/args.rs
index 13fa38f7e..97a784579 100644
--- a/crates/build/src/args.rs
+++ b/crates/build/src/args.rs
@@ -26,6 +26,10 @@ use std::{
 use anyhow::Result;
 use clap::Args;
 use polkavm_linker::TARGET_JSON_64_BIT as POLKAVM_TARGET_JSON_64_BIT;
+use rustversion::{
+    before,
+    since,
+};
 
 use crate::CrateMetadata;
 
@@ -147,6 +151,26 @@ pub struct Target;
 impl Target {
     /// The target string to be passed to rustc in order to build for this target.
     pub fn llvm_target(crate_metadata: &CrateMetadata) -> String {
+        // With Rust 1.91, the `target-pointer-width` field became an Integer
+        // instead of a String. Depending on the toolchain this crate is compiled
+        // with, we transform the value in the PolkaVM JSON into the correct format.
+        //
+        // See <https://github.com/rust-lang/rust/pull/144443> for more details.
+        #[since(1.91)]
+        fn target_spec() -> String {
+            POLKAVM_TARGET_JSON_64_BIT.to_string().replace(
+                r#"target-pointer-width": "64""#,
+                r#"target-pointer-width": 64"#,
+            )
+        }
+        #[before(1.91)]
+        fn target_spec() -> String {
+            POLKAVM_TARGET_JSON_64_BIT.to_string().replace(
+                r#"target-pointer-width": 64"#,
+                r#"target-pointer-width": "64""#,
+            )
+        }
+
         // Instead of a target literal we use a JSON file with a more complex
         // target configuration here. The path to the file is passed for the
         // `rustc --target` argument. We write this file to the `target/` folder.
@@ -157,8 +181,7 @@ impl Target {
                 panic!("unable to create target dir {target_dir:?}: {e:?}")
             });
             let mut file = File::create(&path).unwrap();
-            file.write_all(POLKAVM_TARGET_JSON_64_BIT.as_bytes())
-                .unwrap();
+            file.write_all(target_spec().as_bytes()).unwrap();
         }
         path
     }

From 56e3a826370dde0eda62d5bfbdbead754dd23a35 Mon Sep 17 00:00:00 2001
From: Michael Mueller <mich@elmueller.net>
Date: Thu, 11 Sep 2025 21:32:08 +0200
Subject: [PATCH 2/2] Update changelog

---
 CHANGELOG.md | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8b45729df..51d72f038 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 [Unreleased]
 
+### Changed
+- Handle Rust >= 1.91 change of `target-pointer-width` JSON type ‒ [2131](https://github.com/use-ink/cargo-contract/pull/2131)
+
 ## [6.0.0-alpha.3]
 
 Compatibility of this release: