From 050b5022fad9581e33819e2e90492b82ce28276c Mon Sep 17 00:00:00 2001
From: Mads Marquart <mads@marquart.dk>
Date: Tue, 9 Aug 2022 21:49:28 +0200
Subject: [PATCH 1/2] Add static encoding strings

---
 crates/objc2-encode/CHANGELOG.md              |  3 +
 crates/objc2-encode/src/encoding.rs           | 11 +++
 crates/objc2-encode/src/lib.rs                |  3 -
 crates/objc2/src/encode/mod.rs                | 75 +++++++++++++++++++
 crates/test-ui/src/main.rs                    |  6 ++
 crates/tests/src/test_encode_utils.rs         | 24 +++++-
 .../crates/test_encoding_cstr/Cargo.toml      | 26 +++++++
 .../expected/apple-aarch64.s                  | 13 ++++
 .../test_encoding_cstr/expected/apple-armv7.s | 14 ++++
 .../expected/apple-armv7s.s                   | 14 ++++
 .../test_encoding_cstr/expected/apple-x86.s   | 14 ++++
 .../expected/apple-x86_64.s                   | 14 ++++
 .../test_encoding_cstr/expected/gnustep-x86.s | 18 +++++
 .../expected/gnustep-x86_64.s                 | 18 +++++
 .../crates/test_encoding_cstr/lib.rs          |  7 ++
 test-ui/ui-ignore/encode_cstr_not_ident.rs    | 15 ++++
 test-ui/ui-ignore/encode_cstr_too_long.rs     | 17 +++++
 17 files changed, 285 insertions(+), 7 deletions(-)
 create mode 100644 test-assembly/crates/test_encoding_cstr/Cargo.toml
 create mode 100644 test-assembly/crates/test_encoding_cstr/expected/apple-aarch64.s
 create mode 100644 test-assembly/crates/test_encoding_cstr/expected/apple-armv7.s
 create mode 100644 test-assembly/crates/test_encoding_cstr/expected/apple-armv7s.s
 create mode 100644 test-assembly/crates/test_encoding_cstr/expected/apple-x86.s
 create mode 100644 test-assembly/crates/test_encoding_cstr/expected/apple-x86_64.s
 create mode 100644 test-assembly/crates/test_encoding_cstr/expected/gnustep-x86.s
 create mode 100644 test-assembly/crates/test_encoding_cstr/expected/gnustep-x86_64.s
 create mode 100644 test-assembly/crates/test_encoding_cstr/lib.rs
 create mode 100644 test-ui/ui-ignore/encode_cstr_not_ident.rs
 create mode 100644 test-ui/ui-ignore/encode_cstr_too_long.rs

diff --git a/crates/objc2-encode/CHANGELOG.md b/crates/objc2-encode/CHANGELOG.md
index d1c6d6f11..16adb218f 100644
--- a/crates/objc2-encode/CHANGELOG.md
+++ b/crates/objc2-encode/CHANGELOG.md
@@ -6,6 +6,9 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 ## Unreleased - YYYY-MM-DD
 
+### Added
+* Added `Encode::ENCODING_CSTR` for statically generating an encoding string.
+
 
 ## 3.0.0 - 2023-07-31
 
diff --git a/crates/objc2-encode/src/encoding.rs b/crates/objc2-encode/src/encoding.rs
index 0404f5b61..17e556d29 100644
--- a/crates/objc2-encode/src/encoding.rs
+++ b/crates/objc2-encode/src/encoding.rs
@@ -2,6 +2,7 @@ use core::fmt;
 
 use crate::helper::{compare_encodings, Helper, NestingLevel};
 use crate::parse::Parser;
+use crate::static_str::{static_encoding_str_array, static_encoding_str_len};
 use crate::EncodingBox;
 
 /// An Objective-C type-encoding.
@@ -181,6 +182,16 @@ impl Encoding {
         }
     };
 
+    /// TODO
+    pub const fn static_encoding_str_len(&self) -> usize {
+        static_encoding_str_len(self, NestingLevel::new())
+    }
+
+    /// TODO
+    pub const fn static_encoding_str_array<const LEN: usize>(&self) -> [u8; LEN] {
+        static_encoding_str_array(self, NestingLevel::new())
+    }
+
     /// Check if one encoding is equivalent to another.
     ///
     /// Currently, equivalence testing mostly requires that the encodings are
diff --git a/crates/objc2-encode/src/lib.rs b/crates/objc2-encode/src/lib.rs
index 1bb1f564e..2c7d5b7ef 100644
--- a/crates/objc2-encode/src/lib.rs
+++ b/crates/objc2-encode/src/lib.rs
@@ -68,9 +68,6 @@ mod encoding;
 mod encoding_box;
 mod helper;
 mod parse;
-
-// Will be used at some point when generic constants are available
-#[allow(dead_code)]
 mod static_str;
 
 pub use self::encoding::Encoding;
diff --git a/crates/objc2/src/encode/mod.rs b/crates/objc2/src/encode/mod.rs
index 4cdf1d46c..a935bf10f 100644
--- a/crates/objc2/src/encode/mod.rs
+++ b/crates/objc2/src/encode/mod.rs
@@ -80,6 +80,7 @@ use core::num::{
 };
 use core::ptr::NonNull;
 use core::sync::atomic;
+use std::ffi::CStr;
 
 // Intentionally not `#[doc(hidden)]`
 pub mod __unstable;
@@ -112,6 +113,8 @@ pub use objc2_encode::{Encoding, EncodingBox, ParseError};
 /// passed to Objective-C via. `objc2::msg_send!` their destructor will not be
 /// called!
 ///
+/// Finally, you must not override [`ENCODING_CSTR`][Self::ENCODING_CSTR].
+///
 ///
 /// # Examples
 ///
@@ -149,6 +152,43 @@ pub use objc2_encode::{Encoding, EncodingBox, ParseError};
 pub unsafe trait Encode {
     /// The Objective-C type-encoding for this type.
     const ENCODING: Encoding;
+
+    #[doc(hidden)]
+    const __ENCODING_CSTR_LEN: usize = Self::ENCODING.static_encoding_str_len();
+
+    #[doc(hidden)]
+    const __ENCODING_CSTR_ARRAY: [u8; 128] = {
+        if Self::__ENCODING_CSTR_LEN >= 127 {
+            panic!("encoding string was too long! The maximum supported length is 1023.");
+        }
+
+        Self::ENCODING.static_encoding_str_array()
+    };
+
+    /// The encoding as a static [`CStr`].
+    ///
+    /// This has the same output as `Encoding::to_string`, but it is created
+    /// at compile-time instead.
+    ///
+    /// The encoding is guaranteed to be a pure ASCII string.
+    #[cfg(feature = "std")]
+    const ENCODING_CSTR: &'static CStr = {
+        let mut slice: &[u8] = &Self::__ENCODING_CSTR_ARRAY;
+        // Cut down to desired size (length + 1 for NUL byte)
+        // Equivalent to:
+        // slice[0..Self::__ENCODING_CSTR_LEN + 1]
+        while slice.len() > Self::__ENCODING_CSTR_LEN + 1 {
+            if let Some(res) = slice.split_last() {
+                slice = res.1;
+            } else {
+                unreachable!();
+            }
+        }
+        // SAFETY: `static_encoding_str_array` is guaranteed to not contain
+        // any NULL bytes (the only place those could appear would be in a
+        // struct or union name, and that case is checked).
+        unsafe { CStr::from_bytes_with_nul_unchecked(slice) }
+    };
 }
 
 /// Types whoose references has an Objective-C type-encoding.
@@ -768,4 +808,39 @@ mod tests {
         impls_encode(my_fn3 as extern "C" fn(_) -> _);
         impls_encode(my_fn4 as extern "C" fn(_, _) -> _);
     }
+
+    #[test]
+    #[cfg(feature = "std")]
+    fn test_cstr_simple() {
+        assert_eq!(i8::__ENCODING_CSTR_LEN, 1);
+
+        let mut array = [0; 128];
+        array[0] = b'c';
+        assert_eq!(i8::__ENCODING_CSTR_ARRAY, array);
+
+        let cstr = CStr::from_bytes_with_nul(b"c\0").unwrap();
+        assert_eq!(i8::ENCODING_CSTR, cstr);
+    }
+
+    #[test]
+    #[cfg(feature = "std")]
+    fn test_cstr() {
+        struct X;
+
+        unsafe impl Encode for X {
+            const ENCODING: Encoding = Encoding::Struct(
+                "abc",
+                &[
+                    Encoding::Union("def", &[Encoding::Char]),
+                    <*const *const i8>::ENCODING,
+                    <AtomicPtr<AtomicI16>>::ENCODING,
+                    <extern "C" fn()>::ENCODING,
+                ],
+            );
+        }
+
+        let s = b"{abc=(def=c)^*A^As^?}\0";
+
+        assert_eq!(X::ENCODING_CSTR.to_bytes_with_nul(), s);
+    }
 }
diff --git a/crates/test-ui/src/main.rs b/crates/test-ui/src/main.rs
index dcce08f5b..86760b2d8 100644
--- a/crates/test-ui/src/main.rs
+++ b/crates/test-ui/src/main.rs
@@ -13,8 +13,14 @@
 
 fn main() {
     let t = trybuild::TestCases::new();
+
     let path = std::path::Path::new(env!("CARGO_MANIFEST_DIR"))
         .join("ui")
         .join("*.rs");
     t.compile_fail(path);
+
+    let path = std::path::Path::new(env!("CARGO_MANIFEST_DIR"))
+        .join("ui-ignore")
+        .join("*.rs");
+    t.pass(path);
 }
diff --git a/crates/tests/src/test_encode_utils.rs b/crates/tests/src/test_encode_utils.rs
index 1892ca559..13a29be95 100644
--- a/crates/tests/src/test_encode_utils.rs
+++ b/crates/tests/src/test_encode_utils.rs
@@ -20,6 +20,12 @@ unsafe fn assert_encoding(s: *const c_char, e: Encoding) {
     assert_eq!(e.to_string(), s.trim_start_matches('r'));
 }
 
+unsafe fn assert_ty<T: Encode>(s: *const c_char) {
+    assert_encoding(s, T::ENCODING);
+    // To ensure ENCODING_CSTR is implemented correctly
+    assert_eq!(T::ENCODING_CSTR.to_str().unwrap(), T::ENCODING.to_string());
+}
+
 #[allow(unused)]
 unsafe fn assert_str<T: Display>(s: *const c_char, expected: T) {
     let s = CStr::from_ptr(s).to_str().unwrap();
@@ -38,6 +44,16 @@ macro_rules! assert_inner {
             unsafe { assert_encoding($stat, $expected) };
         }
     };
+    (ty $(#[$m:meta])* $stat:ident => $expected:ty) => {
+        $(#[$m])*
+        #[test]
+        fn $stat() {
+            extern "C" {
+                static $stat: *const c_char;
+            }
+            unsafe { assert_ty::<$expected>($stat) };
+        }
+    };
     (str $(#[$m:meta])* $stat:ident => $expected:expr) => {
         $(#[$m])*
         #[test]
@@ -77,10 +93,10 @@ macro_rules! assert_types {
         $stat:ident $($should_atomic:ident)? => $type:ident
     ) => {
         paste! {
-            assert_inner!(enc $(#[$m])* [<ENCODING_ $stat>] => <$type>::ENCODING);
-            assert_inner!(enc $(#[$m])* [<ENCODING_ $stat _POINTER>] => <*const $type>::ENCODING);
-            assert_inner!(enc $(#[$m])* [<ENCODING_ $stat _POINTER_POINTER>] => <*const *const $type>::ENCODING);
-            assert_inner!(enc $(#[$m])* [<ENCODING_ $stat _POINTER_POINTER_POINTER>] => <*const *const *const $type>::ENCODING);
+            assert_inner!(ty $(#[$m])* [<ENCODING_ $stat>] => $type);
+            assert_inner!(ty $(#[$m])* [<ENCODING_ $stat _POINTER>] => *const $type);
+            assert_inner!(ty $(#[$m])* [<ENCODING_ $stat _POINTER_POINTER>] => *const *const $type);
+            assert_inner!(ty $(#[$m])* [<ENCODING_ $stat _POINTER_POINTER_POINTER>] => *const *const *const $type);
             $(assert_types!(#$should_atomic);)?
             assert_inner!(enc $(#[$m])* $(#[cfg($should_atomic)])? [<ENCODING_ $stat _ATOMIC>] => Encoding::Atomic(&<$type>::ENCODING));
             assert_inner!(enc $(#[$m])* $(#[cfg($should_atomic)])? [<ENCODING_ $stat _ATOMIC_POINTER>] => Encoding::Pointer(&Encoding::Atomic(&<$type>::ENCODING)));
diff --git a/test-assembly/crates/test_encoding_cstr/Cargo.toml b/test-assembly/crates/test_encoding_cstr/Cargo.toml
new file mode 100644
index 000000000..7aaa9f726
--- /dev/null
+++ b/test-assembly/crates/test_encoding_cstr/Cargo.toml
@@ -0,0 +1,26 @@
+[package]
+name = "test_encoding_cstr"
+version = "0.1.0"
+edition = "2021"
+publish = false
+
+[lib]
+path = "lib.rs"
+
+[dependencies]
+objc2-encode = { path = "../../../objc2-encode", default-features = false }
+
+[features]
+default = ["apple", "std"]
+std = ["objc2-encode/std"]
+
+# Runtime
+apple = []
+gnustep-1-7 = []
+gnustep-1-8 = ["gnustep-1-7"]
+gnustep-1-9 = ["gnustep-1-8"]
+gnustep-2-0 = ["gnustep-1-9"]
+gnustep-2-1 = ["gnustep-2-0"]
+
+# Hack
+assembly-features = ["std"]
diff --git a/test-assembly/crates/test_encoding_cstr/expected/apple-aarch64.s b/test-assembly/crates/test_encoding_cstr/expected/apple-aarch64.s
new file mode 100644
index 000000000..987168def
--- /dev/null
+++ b/test-assembly/crates/test_encoding_cstr/expected/apple-aarch64.s
@@ -0,0 +1,13 @@
+	.section	__TEXT,__text,regular,pure_instructions
+	.section	__TEXT,__const
+l_anon.a88231c846af3b75605317c1ca346ede.0:
+	.asciz	"c\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"
+
+	.section	__DATA,__const
+	.globl	_ENC
+	.p2align	3
+_ENC:
+	.quad	l_anon.a88231c846af3b75605317c1ca346ede.0
+	.asciz	"\002\000\000\000\000\000\000"
+
+.subsections_via_symbols
diff --git a/test-assembly/crates/test_encoding_cstr/expected/apple-armv7.s b/test-assembly/crates/test_encoding_cstr/expected/apple-armv7.s
new file mode 100644
index 000000000..652d900da
--- /dev/null
+++ b/test-assembly/crates/test_encoding_cstr/expected/apple-armv7.s
@@ -0,0 +1,14 @@
+	.section	__TEXT,__text,regular,pure_instructions
+	.syntax unified
+	.section	__TEXT,__const
+l_anon.a88231c846af3b75605317c1ca346ede.0:
+	.asciz	"c\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"
+
+	.section	__DATA,__const
+	.globl	_ENC
+	.p2align	2
+_ENC:
+	.long	l_anon.a88231c846af3b75605317c1ca346ede.0
+	.asciz	"\002\000\000"
+
+.subsections_via_symbols
diff --git a/test-assembly/crates/test_encoding_cstr/expected/apple-armv7s.s b/test-assembly/crates/test_encoding_cstr/expected/apple-armv7s.s
new file mode 100644
index 000000000..652d900da
--- /dev/null
+++ b/test-assembly/crates/test_encoding_cstr/expected/apple-armv7s.s
@@ -0,0 +1,14 @@
+	.section	__TEXT,__text,regular,pure_instructions
+	.syntax unified
+	.section	__TEXT,__const
+l_anon.a88231c846af3b75605317c1ca346ede.0:
+	.asciz	"c\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"
+
+	.section	__DATA,__const
+	.globl	_ENC
+	.p2align	2
+_ENC:
+	.long	l_anon.a88231c846af3b75605317c1ca346ede.0
+	.asciz	"\002\000\000"
+
+.subsections_via_symbols
diff --git a/test-assembly/crates/test_encoding_cstr/expected/apple-x86.s b/test-assembly/crates/test_encoding_cstr/expected/apple-x86.s
new file mode 100644
index 000000000..ea253c6f6
--- /dev/null
+++ b/test-assembly/crates/test_encoding_cstr/expected/apple-x86.s
@@ -0,0 +1,14 @@
+	.section	__TEXT,__text,regular,pure_instructions
+	.intel_syntax noprefix
+	.section	__TEXT,__const
+l_anon.a88231c846af3b75605317c1ca346ede.0:
+	.asciz	"c\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"
+
+	.section	__DATA,__const
+	.globl	_ENC
+	.p2align	2
+_ENC:
+	.long	l_anon.a88231c846af3b75605317c1ca346ede.0
+	.asciz	"\002\000\000"
+
+.subsections_via_symbols
diff --git a/test-assembly/crates/test_encoding_cstr/expected/apple-x86_64.s b/test-assembly/crates/test_encoding_cstr/expected/apple-x86_64.s
new file mode 100644
index 000000000..a71ee045e
--- /dev/null
+++ b/test-assembly/crates/test_encoding_cstr/expected/apple-x86_64.s
@@ -0,0 +1,14 @@
+	.section	__TEXT,__text,regular,pure_instructions
+	.intel_syntax noprefix
+	.section	__TEXT,__const
+l_anon.a88231c846af3b75605317c1ca346ede.0:
+	.asciz	"c\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"
+
+	.section	__DATA,__const
+	.globl	_ENC
+	.p2align	3
+_ENC:
+	.quad	l_anon.a88231c846af3b75605317c1ca346ede.0
+	.asciz	"\002\000\000\000\000\000\000"
+
+.subsections_via_symbols
diff --git a/test-assembly/crates/test_encoding_cstr/expected/gnustep-x86.s b/test-assembly/crates/test_encoding_cstr/expected/gnustep-x86.s
new file mode 100644
index 000000000..1505e57a7
--- /dev/null
+++ b/test-assembly/crates/test_encoding_cstr/expected/gnustep-x86.s
@@ -0,0 +1,18 @@
+	.text
+	.intel_syntax noprefix
+	.type	.Lanon.a88231c846af3b75605317c1ca346ede.0,@object
+	.section	.rodata..Lanon.a88231c846af3b75605317c1ca346ede.0,"a",@progbits
+.Lanon.a88231c846af3b75605317c1ca346ede.0:
+	.asciz	"c\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"
+	.size	.Lanon.a88231c846af3b75605317c1ca346ede.0, 128
+
+	.type	ENC,@object
+	.section	.data.rel.ro.ENC,"aw",@progbits
+	.globl	ENC
+	.p2align	2
+ENC:
+	.long	.Lanon.a88231c846af3b75605317c1ca346ede.0
+	.asciz	"\002\000\000"
+	.size	ENC, 8
+
+	.section	".note.GNU-stack","",@progbits
diff --git a/test-assembly/crates/test_encoding_cstr/expected/gnustep-x86_64.s b/test-assembly/crates/test_encoding_cstr/expected/gnustep-x86_64.s
new file mode 100644
index 000000000..63ad4915d
--- /dev/null
+++ b/test-assembly/crates/test_encoding_cstr/expected/gnustep-x86_64.s
@@ -0,0 +1,18 @@
+	.text
+	.intel_syntax noprefix
+	.type	.Lanon.a88231c846af3b75605317c1ca346ede.0,@object
+	.section	.rodata..Lanon.a88231c846af3b75605317c1ca346ede.0,"a",@progbits
+.Lanon.a88231c846af3b75605317c1ca346ede.0:
+	.asciz	"c\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"
+	.size	.Lanon.a88231c846af3b75605317c1ca346ede.0, 128
+
+	.type	ENC,@object
+	.section	.data.rel.ro.ENC,"aw",@progbits
+	.globl	ENC
+	.p2align	3
+ENC:
+	.quad	.Lanon.a88231c846af3b75605317c1ca346ede.0
+	.asciz	"\002\000\000\000\000\000\000"
+	.size	ENC, 16
+
+	.section	".note.GNU-stack","",@progbits
diff --git a/test-assembly/crates/test_encoding_cstr/lib.rs b/test-assembly/crates/test_encoding_cstr/lib.rs
new file mode 100644
index 000000000..c74ede513
--- /dev/null
+++ b/test-assembly/crates/test_encoding_cstr/lib.rs
@@ -0,0 +1,7 @@
+//! Test that the encoding string that we output is not full length.
+use std::ffi::CStr;
+
+use objc2_encode::Encode;
+
+#[no_mangle]
+static ENC: &CStr = i8::ENCODING_CSTR;
diff --git a/test-ui/ui-ignore/encode_cstr_not_ident.rs b/test-ui/ui-ignore/encode_cstr_not_ident.rs
new file mode 100644
index 000000000..0ea52d93d
--- /dev/null
+++ b/test-ui/ui-ignore/encode_cstr_not_ident.rs
@@ -0,0 +1,15 @@
+//! Test that compilation fails when the struct name is invalid.
+//!
+//! Ideally, this should be tested by `trybuild`, but it doesn't work at the
+//! moment (`cargo check` doesn't catch the error).
+use objc2::{Encode, Encoding};
+
+struct X;
+
+unsafe impl Encode for X {
+    const ENCODING: Encoding<'static> = Encoding::Struct("-", &[]);
+}
+
+fn main() {
+    let _ = X::ENCODING_CSTR;
+}
diff --git a/test-ui/ui-ignore/encode_cstr_too_long.rs b/test-ui/ui-ignore/encode_cstr_too_long.rs
new file mode 100644
index 000000000..08b610fcb
--- /dev/null
+++ b/test-ui/ui-ignore/encode_cstr_too_long.rs
@@ -0,0 +1,17 @@
+//! Test that compilation fails when the encoding is too long.
+//!
+//! Ideally, this should be tested by `trybuild`, but it doesn't work at the
+//! moment (`cargo check` doesn't catch the error).
+use objc2::{Encode, Encoding};
+
+struct X;
+
+const S: &str = unsafe { std::str::from_utf8_unchecked(&[b'a'; 1020]) };
+
+unsafe impl Encode for X {
+    const ENCODING: Encoding<'static> = Encoding::Struct(S, &[]);
+}
+
+fn main() {
+    let _ = X::ENCODING_CSTR;
+}

From 9c31a419f9f0140f7ae2694d4924cdf76674930a Mon Sep 17 00:00:00 2001
From: Mads Marquart <mads@marquart.dk>
Date: Fri, 1 Sep 2023 19:39:01 +0200
Subject: [PATCH 2/2] Use static encoding strings

---
 crates/icrate/src/additions/Foundation/value.rs |  5 ++---
 crates/objc2/src/declare/mod.rs                 | 17 +++++------------
 2 files changed, 7 insertions(+), 15 deletions(-)

diff --git a/crates/icrate/src/additions/Foundation/value.rs b/crates/icrate/src/additions/Foundation/value.rs
index 78a69358d..f2af7c0b4 100644
--- a/crates/icrate/src/additions/Foundation/value.rs
+++ b/crates/icrate/src/additions/Foundation/value.rs
@@ -1,10 +1,9 @@
 #![cfg(feature = "Foundation_NSValue")]
-use alloc::string::ToString;
 use core::fmt;
 use core::hash;
 use core::mem::MaybeUninit;
 use core::str;
-use std::ffi::{CStr, CString};
+use std::ffi::CStr;
 
 use objc2::encode::Encode;
 
@@ -35,7 +34,7 @@ impl NSValue {
     /// [`NSPoint`]: crate::Foundation::NSPoint
     pub fn new<T: 'static + Copy + Encode>(value: T) -> Id<Self> {
         let bytes: NonNull<T> = NonNull::from(&value);
-        let encoding = CString::new(T::ENCODING.to_string()).unwrap();
+        let encoding = T::ENCODING_CSTR;
         unsafe {
             Self::initWithBytes_objCType(
                 Self::alloc(),
diff --git a/crates/objc2/src/declare/mod.rs b/crates/objc2/src/declare/mod.rs
index 97088959f..dba966091 100644
--- a/crates/objc2/src/declare/mod.rs
+++ b/crates/objc2/src/declare/mod.rs
@@ -124,7 +124,7 @@ mod ivar_encode;
 mod ivar_forwarding_impls;
 
 use alloc::format;
-use alloc::string::ToString;
+use core::ffi::CStr;
 use core::mem;
 use core::mem::ManuallyDrop;
 use core::ptr;
@@ -550,17 +550,11 @@ impl ClassBuilder {
     /// happens if there already was an ivar with that name.
     pub fn add_ivar<T: Encode>(&mut self, name: &str) {
         // SAFETY: The encoding is correct
-        unsafe { self.add_ivar_inner::<T>(name, &T::ENCODING) }
+        unsafe { self.add_ivar_inner::<T>(name, &T::ENCODING_CSTR) }
     }
 
     // Monomorphized version
-    unsafe fn add_ivar_inner_mono(
-        &mut self,
-        name: &str,
-        size: usize,
-        align: u8,
-        encoding: &Encoding,
-    ) {
+    unsafe fn add_ivar_inner_mono(&mut self, name: &str, size: usize, align: u8, encoding: &CStr) {
         // `class_addIvar` sadly doesn't check this for us.
         //
         // We must _always_ do the check, since there is no way for the user
@@ -575,7 +569,6 @@ impl ClassBuilder {
         }
 
         let c_name = CString::new(name).unwrap();
-        let encoding = CString::new(encoding.to_string()).unwrap();
         let success = Bool::from_raw(unsafe {
             ffi::class_addIvar(
                 self.as_mut_ptr(),
@@ -588,7 +581,7 @@ impl ClassBuilder {
         assert!(success.as_bool(), "failed to add ivar {name}");
     }
 
-    unsafe fn add_ivar_inner<T>(&mut self, name: &str, encoding: &Encoding) {
+    unsafe fn add_ivar_inner<T>(&mut self, name: &str, encoding: &CStr) {
         unsafe { self.add_ivar_inner_mono(name, mem::size_of::<T>(), T::LOG2_ALIGNMENT, encoding) }
     }
 
@@ -600,7 +593,7 @@ impl ClassBuilder {
     /// Same as [`ClassBuilder::add_ivar`].
     pub fn add_static_ivar<T: IvarType>(&mut self) {
         // SAFETY: The encoding is correct
-        unsafe { self.add_ivar_inner::<T::Type>(T::NAME, &T::Type::ENCODING) }
+        unsafe { self.add_ivar_inner::<T::Type>(T::NAME, &T::Type::ENCODING_CSTR) }
     }
 
     /// Adds the given protocol to self.