diff --git a/Cargo.lock b/Cargo.lock
index 00bfbadece3..30d1fe51af5 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -871,16 +871,6 @@ dependencies = [
  "typenum",
 ]
 
-[[package]]
-name = "cstr"
-version = "0.2.8"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c11a39d776a3b35896711da8a04dc1835169dcd36f710878187637314e47941b"
-dependencies = [
- "proc-macro2",
- "quote",
-]
-
 [[package]]
 name = "ctrlc"
 version = "3.3.1"
@@ -3179,7 +3169,6 @@ name = "rustc_codegen_llvm"
 version = "0.0.0"
 dependencies = [
  "bitflags",
- "cstr",
  "libc",
  "measureme",
  "object 0.31.1",
diff --git a/compiler/rustc_codegen_llvm/Cargo.toml b/compiler/rustc_codegen_llvm/Cargo.toml
index ad51f2d0958..39ff3a0ba2d 100644
--- a/compiler/rustc_codegen_llvm/Cargo.toml
+++ b/compiler/rustc_codegen_llvm/Cargo.toml
@@ -8,7 +8,6 @@ test = false
 
 [dependencies]
 bitflags = "1.0"
-cstr = "0.2"
 libc = "0.2"
 measureme = "10.0.0"
 object = { version = "0.31.1", default-features = false, features = [
diff --git a/compiler/rustc_codegen_llvm/src/allocator.rs b/compiler/rustc_codegen_llvm/src/allocator.rs
index a57508815d6..ad0636894b7 100644
--- a/compiler/rustc_codegen_llvm/src/allocator.rs
+++ b/compiler/rustc_codegen_llvm/src/allocator.rs
@@ -77,7 +77,7 @@ pub(crate) unsafe fn codegen(
                 llvm::LLVMRustGetOrInsertFunction(llmod, callee.as_ptr().cast(), callee.len(), ty);
             llvm::LLVMRustSetVisibility(callee, llvm::Visibility::Hidden);
 
-            let llbb = llvm::LLVMAppendBasicBlockInContext(llcx, llfn, "entry\0".as_ptr().cast());
+            let llbb = llvm::LLVMAppendBasicBlockInContext(llcx, llfn, c"entry".as_ptr().cast());
 
             let llbuilder = llvm::LLVMCreateBuilderInContext(llcx);
             llvm::LLVMPositionBuilderAtEnd(llbuilder, llbb);
@@ -129,7 +129,7 @@ pub(crate) unsafe fn codegen(
     attributes::apply_to_llfn(callee, llvm::AttributePlace::Function, &[no_return]);
     llvm::LLVMRustSetVisibility(callee, llvm::Visibility::Hidden);
 
-    let llbb = llvm::LLVMAppendBasicBlockInContext(llcx, llfn, "entry\0".as_ptr().cast());
+    let llbb = llvm::LLVMAppendBasicBlockInContext(llcx, llfn, c"entry".as_ptr().cast());
 
     let llbuilder = llvm::LLVMCreateBuilderInContext(llcx);
     llvm::LLVMPositionBuilderAtEnd(llbuilder, llbb);
diff --git a/compiler/rustc_codegen_llvm/src/back/lto.rs b/compiler/rustc_codegen_llvm/src/back/lto.rs
index 604f68eb6a4..8b05af7bed9 100644
--- a/compiler/rustc_codegen_llvm/src/back/lto.rs
+++ b/compiler/rustc_codegen_llvm/src/back/lto.rs
@@ -595,7 +595,7 @@ pub(crate) fn run_pass_manager(
             llvm::LLVMRustAddModuleFlag(
                 module.module_llvm.llmod(),
                 llvm::LLVMModFlagBehavior::Error,
-                "LTOPostLink\0".as_ptr().cast(),
+                c"LTOPostLink".as_ptr().cast(),
                 1,
             );
         }
diff --git a/compiler/rustc_codegen_llvm/src/back/write.rs b/compiler/rustc_codegen_llvm/src/back/write.rs
index ca2eab28f87..53b4296802e 100644
--- a/compiler/rustc_codegen_llvm/src/back/write.rs
+++ b/compiler/rustc_codegen_llvm/src/back/write.rs
@@ -891,11 +891,11 @@ unsafe fn embed_bitcode(
         let llglobal = llvm::LLVMAddGlobal(
             llmod,
             common::val_ty(llconst),
-            "rustc.embedded.module\0".as_ptr().cast(),
+            c"rustc.embedded.module".as_ptr().cast(),
         );
         llvm::LLVMSetInitializer(llglobal, llconst);
 
-        let section = if is_apple { "__LLVM,__bitcode\0" } else { ".llvmbc\0" };
+        let section = if is_apple { c"__LLVM,__bitcode" } else { c".llvmbc" };
         llvm::LLVMSetSection(llglobal, section.as_ptr().cast());
         llvm::LLVMRustSetLinkage(llglobal, llvm::Linkage::PrivateLinkage);
         llvm::LLVMSetGlobalConstant(llglobal, llvm::True);
@@ -904,10 +904,10 @@ unsafe fn embed_bitcode(
         let llglobal = llvm::LLVMAddGlobal(
             llmod,
             common::val_ty(llconst),
-            "rustc.embedded.cmdline\0".as_ptr().cast(),
+            c"rustc.embedded.cmdline".as_ptr().cast(),
         );
         llvm::LLVMSetInitializer(llglobal, llconst);
-        let section = if is_apple { "__LLVM,__cmdline\0" } else { ".llvmcmd\0" };
+        let section = if is_apple { c"__LLVM,__cmdline" } else { c".llvmcmd" };
         llvm::LLVMSetSection(llglobal, section.as_ptr().cast());
         llvm::LLVMRustSetLinkage(llglobal, llvm::Linkage::PrivateLinkage);
     } else {
diff --git a/compiler/rustc_codegen_llvm/src/base.rs b/compiler/rustc_codegen_llvm/src/base.rs
index 5b2bbdb4bde..2f7eb08ad3d 100644
--- a/compiler/rustc_codegen_llvm/src/base.rs
+++ b/compiler/rustc_codegen_llvm/src/base.rs
@@ -19,8 +19,6 @@
 use crate::llvm;
 use crate::value::Value;
 
-use cstr::cstr;
-
 use rustc_codegen_ssa::base::maybe_create_entry_wrapper;
 use rustc_codegen_ssa::mono_item::MonoItemExt;
 use rustc_codegen_ssa::traits::*;
@@ -110,11 +108,11 @@ fn module_codegen(tcx: TyCtxt<'_>, cgu_name: Symbol) -> ModuleCodegen<ModuleLlvm
 
             // Create the llvm.used and llvm.compiler.used variables.
             if !cx.used_statics.borrow().is_empty() {
-                cx.create_used_variable_impl(cstr!("llvm.used"), &*cx.used_statics.borrow());
+                cx.create_used_variable_impl(c"llvm.used", &*cx.used_statics.borrow());
             }
             if !cx.compiler_used_statics.borrow().is_empty() {
                 cx.create_used_variable_impl(
-                    cstr!("llvm.compiler.used"),
+                    c"llvm.compiler.used",
                     &*cx.compiler_used_statics.borrow(),
                 );
             }
diff --git a/compiler/rustc_codegen_llvm/src/builder.rs b/compiler/rustc_codegen_llvm/src/builder.rs
index 5968e70b1cc..b4aa001547c 100644
--- a/compiler/rustc_codegen_llvm/src/builder.rs
+++ b/compiler/rustc_codegen_llvm/src/builder.rs
@@ -6,7 +6,6 @@
 use crate::type_::Type;
 use crate::type_of::LayoutLlvmExt;
 use crate::value::Value;
-use cstr::cstr;
 use libc::{c_char, c_uint};
 use rustc_codegen_ssa::common::{IntPredicate, RealPredicate, SynchronizationScope, TypeKind};
 use rustc_codegen_ssa::mir::operand::{OperandRef, OperandValue};
@@ -25,7 +24,6 @@
 use rustc_target::abi::{self, call::FnAbi, Align, Size, WrappingRange};
 use rustc_target::spec::{HasTargetSpec, SanitizerSet, Target};
 use std::borrow::Cow;
-use std::ffi::CStr;
 use std::iter;
 use std::ops::Deref;
 use std::ptr;
@@ -45,13 +43,10 @@ fn drop(&mut self) {
     }
 }
 
-// FIXME(eddyb) use a checked constructor when they become `const fn`.
-const EMPTY_C_STR: &CStr = unsafe { CStr::from_bytes_with_nul_unchecked(b"\0") };
-
 /// Empty string, to be used where LLVM expects an instruction name, indicating
 /// that the instruction is to be left unnamed (i.e. numbered, in textual IR).
 // FIXME(eddyb) pass `&CStr` directly to FFI once it's a thin pointer.
-const UNNAMED: *const c_char = EMPTY_C_STR.as_ptr();
+const UNNAMED: *const c_char = c"".as_ptr();
 
 impl<'ll, 'tcx> BackendTypes for Builder<'_, 'll, 'tcx> {
     type Value = <CodegenCx<'ll, 'tcx> as BackendTypes>::Value;
@@ -1010,14 +1005,13 @@ fn resume(&mut self, exn0: &'ll Value, exn1: &'ll Value) {
     }
 
     fn cleanup_pad(&mut self, parent: Option<&'ll Value>, args: &[&'ll Value]) -> Funclet<'ll> {
-        let name = cstr!("cleanuppad");
         let ret = unsafe {
             llvm::LLVMBuildCleanupPad(
                 self.llbuilder,
                 parent,
                 args.as_ptr(),
                 args.len() as c_uint,
-                name.as_ptr(),
+                c"cleanuppad".as_ptr(),
             )
         };
         Funclet::new(ret.expect("LLVM does not have support for cleanuppad"))
@@ -1031,14 +1025,13 @@ fn cleanup_ret(&mut self, funclet: &Funclet<'ll>, unwind: Option<&'ll BasicBlock
     }
 
     fn catch_pad(&mut self, parent: &'ll Value, args: &[&'ll Value]) -> Funclet<'ll> {
-        let name = cstr!("catchpad");
         let ret = unsafe {
             llvm::LLVMBuildCatchPad(
                 self.llbuilder,
                 parent,
                 args.as_ptr(),
                 args.len() as c_uint,
-                name.as_ptr(),
+                c"catchpad".as_ptr(),
             )
         };
         Funclet::new(ret.expect("LLVM does not have support for catchpad"))
@@ -1050,14 +1043,13 @@ fn catch_switch(
         unwind: Option<&'ll BasicBlock>,
         handlers: &[&'ll BasicBlock],
     ) -> &'ll Value {
-        let name = cstr!("catchswitch");
         let ret = unsafe {
             llvm::LLVMBuildCatchSwitch(
                 self.llbuilder,
                 parent,
                 unwind,
                 handlers.len() as c_uint,
-                name.as_ptr(),
+                c"catchswitch".as_ptr(),
             )
         };
         let ret = ret.expect("LLVM does not have support for catchswitch");
diff --git a/compiler/rustc_codegen_llvm/src/consts.rs b/compiler/rustc_codegen_llvm/src/consts.rs
index df52f50f86f..2087754c66b 100644
--- a/compiler/rustc_codegen_llvm/src/consts.rs
+++ b/compiler/rustc_codegen_llvm/src/consts.rs
@@ -8,7 +8,6 @@
 use crate::type_::Type;
 use crate::type_of::LayoutLlvmExt;
 use crate::value::Value;
-use cstr::cstr;
 use rustc_codegen_ssa::traits::*;
 use rustc_hir::def_id::DefId;
 use rustc_middle::middle::codegen_fn_attrs::{CodegenFnAttrFlags, CodegenFnAttrs};
@@ -482,9 +481,9 @@ fn codegen_static(&self, def_id: DefId, is_mutable: bool) {
                             .all(|&byte| byte == 0);
 
                     let sect_name = if all_bytes_are_zero {
-                        cstr!("__DATA,__thread_bss")
+                        c"__DATA,__thread_bss"
                     } else {
-                        cstr!("__DATA,__thread_data")
+                        c"__DATA,__thread_data"
                     };
                     llvm::LLVMSetSection(g, sect_name.as_ptr());
                 }
@@ -513,7 +512,7 @@ fn codegen_static(&self, def_id: DefId, is_mutable: bool) {
                     let val = llvm::LLVMMetadataAsValue(self.llcx, meta);
                     llvm::LLVMAddNamedMetadataOperand(
                         self.llmod,
-                        "wasm.custom_sections\0".as_ptr().cast(),
+                        c"wasm.custom_sections".as_ptr().cast(),
                         val,
                     );
                 }
diff --git a/compiler/rustc_codegen_llvm/src/context.rs b/compiler/rustc_codegen_llvm/src/context.rs
index ca0f771f5b9..e8a7afcc632 100644
--- a/compiler/rustc_codegen_llvm/src/context.rs
+++ b/compiler/rustc_codegen_llvm/src/context.rs
@@ -8,7 +8,6 @@
 use crate::type_::Type;
 use crate::value::Value;
 
-use cstr::cstr;
 use rustc_codegen_ssa::base::wants_msvc_seh;
 use rustc_codegen_ssa::traits::*;
 use rustc_data_structures::base_n;
@@ -224,36 +223,42 @@ pub unsafe fn create_module<'ll>(
     // If skipping the PLT is enabled, we need to add some module metadata
     // to ensure intrinsic calls don't use it.
     if !sess.needs_plt() {
-        let avoid_plt = "RtLibUseGOT\0".as_ptr().cast();
-        llvm::LLVMRustAddModuleFlag(llmod, llvm::LLVMModFlagBehavior::Warning, avoid_plt, 1);
+        llvm::LLVMRustAddModuleFlag(
+            llmod,
+            llvm::LLVMModFlagBehavior::Warning,
+            c"RtLibUseGOT".as_ptr().cast(),
+            1,
+        );
     }
 
     // Enable canonical jump tables if CFI is enabled. (See https://reviews.llvm.org/D65629.)
     if sess.is_sanitizer_cfi_canonical_jump_tables_enabled() && sess.is_sanitizer_cfi_enabled() {
-        let canonical_jump_tables = "CFI Canonical Jump Tables\0".as_ptr().cast();
         llvm::LLVMRustAddModuleFlag(
             llmod,
             llvm::LLVMModFlagBehavior::Override,
-            canonical_jump_tables,
+            c"CFI Canonical Jump Tables".as_ptr().cast(),
             1,
         );
     }
 
     // Enable LTO unit splitting if specified or if CFI is enabled. (See https://reviews.llvm.org/D53891.)
     if sess.is_split_lto_unit_enabled() || sess.is_sanitizer_cfi_enabled() {
-        let enable_split_lto_unit = "EnableSplitLTOUnit\0".as_ptr().cast();
         llvm::LLVMRustAddModuleFlag(
             llmod,
             llvm::LLVMModFlagBehavior::Override,
-            enable_split_lto_unit,
+            c"EnableSplitLTOUnit".as_ptr().cast(),
             1,
         );
     }
 
     // Add "kcfi" module flag if KCFI is enabled. (See https://reviews.llvm.org/D119296.)
     if sess.is_sanitizer_kcfi_enabled() {
-        let kcfi = "kcfi\0".as_ptr().cast();
-        llvm::LLVMRustAddModuleFlag(llmod, llvm::LLVMModFlagBehavior::Override, kcfi, 1);
+        llvm::LLVMRustAddModuleFlag(
+            llmod,
+            llvm::LLVMModFlagBehavior::Override,
+            c"kcfi".as_ptr().cast(),
+            1,
+        );
     }
 
     // Control Flow Guard is currently only supported by the MSVC linker on Windows.
@@ -265,7 +270,7 @@ pub unsafe fn create_module<'ll>(
                 llvm::LLVMRustAddModuleFlag(
                     llmod,
                     llvm::LLVMModFlagBehavior::Warning,
-                    "cfguard\0".as_ptr() as *const _,
+                    c"cfguard".as_ptr() as *const _,
                     1,
                 )
             }
@@ -274,7 +279,7 @@ pub unsafe fn create_module<'ll>(
                 llvm::LLVMRustAddModuleFlag(
                     llmod,
                     llvm::LLVMModFlagBehavior::Warning,
-                    "cfguard\0".as_ptr() as *const _,
+                    c"cfguard".as_ptr() as *const _,
                     2,
                 )
             }
@@ -292,26 +297,26 @@ pub unsafe fn create_module<'ll>(
             llvm::LLVMRustAddModuleFlag(
                 llmod,
                 behavior,
-                "branch-target-enforcement\0".as_ptr().cast(),
+                c"branch-target-enforcement".as_ptr().cast(),
                 bti.into(),
             );
             llvm::LLVMRustAddModuleFlag(
                 llmod,
                 behavior,
-                "sign-return-address\0".as_ptr().cast(),
+                c"sign-return-address".as_ptr().cast(),
                 pac_ret.is_some().into(),
             );
             let pac_opts = pac_ret.unwrap_or(PacRet { leaf: false, key: PAuthKey::A });
             llvm::LLVMRustAddModuleFlag(
                 llmod,
                 behavior,
-                "sign-return-address-all\0".as_ptr().cast(),
+                c"sign-return-address-all".as_ptr().cast(),
                 pac_opts.leaf.into(),
             );
             llvm::LLVMRustAddModuleFlag(
                 llmod,
                 behavior,
-                "sign-return-address-with-bkey\0".as_ptr().cast(),
+                c"sign-return-address-with-bkey".as_ptr().cast(),
                 u32::from(pac_opts.key == PAuthKey::B),
             );
         } else {
@@ -327,7 +332,7 @@ pub unsafe fn create_module<'ll>(
         llvm::LLVMRustAddModuleFlag(
             llmod,
             llvm::LLVMModFlagBehavior::Override,
-            "cf-protection-branch\0".as_ptr().cast(),
+            c"cf-protection-branch".as_ptr().cast(),
             1,
         )
     }
@@ -335,7 +340,7 @@ pub unsafe fn create_module<'ll>(
         llvm::LLVMRustAddModuleFlag(
             llmod,
             llvm::LLVMModFlagBehavior::Override,
-            "cf-protection-return\0".as_ptr().cast(),
+            c"cf-protection-return".as_ptr().cast(),
             1,
         )
     }
@@ -344,7 +349,7 @@ pub unsafe fn create_module<'ll>(
         llvm::LLVMRustAddModuleFlag(
             llmod,
             llvm::LLVMModFlagBehavior::Error,
-            "Virtual Function Elim\0".as_ptr().cast(),
+            c"Virtual Function Elim".as_ptr().cast(),
             1,
         );
     }
@@ -476,14 +481,13 @@ pub fn coverage_context(&self) -> Option<&coverageinfo::CrateCoverageContext<'ll
     }
 
     pub(crate) fn create_used_variable_impl(&self, name: &'static CStr, values: &[&'ll Value]) {
-        let section = cstr!("llvm.metadata");
         let array = self.const_array(self.type_ptr_to(self.type_i8()), values);
 
         unsafe {
             let g = llvm::LLVMAddGlobal(self.llmod, self.val_ty(array), name.as_ptr());
             llvm::LLVMSetInitializer(g, array);
             llvm::LLVMRustSetLinkage(g, llvm::Linkage::AppendingLinkage);
-            llvm::LLVMSetSection(g, section.as_ptr());
+            llvm::LLVMSetSection(g, c"llvm.metadata".as_ptr());
         }
     }
 }
diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/gdb.rs b/compiler/rustc_codegen_llvm/src/debuginfo/gdb.rs
index 37f30917609..8be54b7eb71 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/gdb.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/gdb.rs
@@ -38,7 +38,6 @@ pub fn get_or_insert_gdb_debug_scripts_section_global<'ll>(cx: &CodegenCx<'ll, '
         unsafe { llvm::LLVMGetNamedGlobal(cx.llmod, c_section_var_name.as_ptr().cast()) };
 
     section_var.unwrap_or_else(|| {
-        let section_name = b".debug_gdb_scripts\0";
         let mut section_contents = Vec::new();
 
         // Add the pretty printers for the standard library first.
@@ -71,7 +70,7 @@ pub fn get_or_insert_gdb_debug_scripts_section_global<'ll>(cx: &CodegenCx<'ll, '
             let section_var = cx
                 .define_global(section_var_name, llvm_type)
                 .unwrap_or_else(|| bug!("symbol `{}` is already defined", section_var_name));
-            llvm::LLVMSetSection(section_var, section_name.as_ptr().cast());
+            llvm::LLVMSetSection(section_var, c".debug_gdb_scripts".as_ptr().cast());
             llvm::LLVMSetInitializer(section_var, cx.const_bytes(section_contents));
             llvm::LLVMSetGlobalConstant(section_var, llvm::True);
             llvm::LLVMSetUnnamedAddress(section_var, llvm::UnnamedAddr::Global);
diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs b/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs
index bd2fba12602..166454d3ae7 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs
@@ -20,7 +20,6 @@
 };
 use crate::value::Value;
 
-use cstr::cstr;
 use rustc_codegen_ssa::debuginfo::type_names::cpp_like_debuginfo;
 use rustc_codegen_ssa::debuginfo::type_names::VTableNameKind;
 use rustc_codegen_ssa::traits::*;
@@ -812,7 +811,6 @@ pub fn build_compile_unit_di_node<'ll, 'tcx>(
 
     let name_in_debuginfo = name_in_debuginfo.to_string_lossy();
     let work_dir = tcx.sess.opts.working_dir.to_string_lossy(FileNameDisplayPreference::Remapped);
-    let flags = "\0";
     let output_filenames = tcx.output_filenames(());
     let split_name = if tcx.sess.target_can_use_split_dwarf() {
         output_filenames
@@ -849,7 +847,7 @@ pub fn build_compile_unit_di_node<'ll, 'tcx>(
             producer.as_ptr().cast(),
             producer.len(),
             tcx.sess.opts.optimize != config::OptLevel::No,
-            flags.as_ptr().cast(),
+            c"".as_ptr().cast(),
             0,
             // NB: this doesn't actually have any perceptible effect, it seems. LLVM will instead
             // put the path supplied to `MCSplitDwarfFile` into the debug info of the final
@@ -878,8 +876,7 @@ pub fn build_compile_unit_di_node<'ll, 'tcx>(
             );
             let val = llvm::LLVMMetadataAsValue(debug_context.llcontext, gcov_metadata);
 
-            let llvm_gcov_ident = cstr!("llvm.gcov");
-            llvm::LLVMAddNamedMetadataOperand(debug_context.llmod, llvm_gcov_ident.as_ptr(), val);
+            llvm::LLVMAddNamedMetadataOperand(debug_context.llmod, c"llvm.gcov".as_ptr(), val);
         }
 
         // Insert `llvm.ident` metadata on the wasm targets since that will
@@ -892,7 +889,7 @@ pub fn build_compile_unit_di_node<'ll, 'tcx>(
             );
             llvm::LLVMAddNamedMetadataOperand(
                 debug_context.llmod,
-                cstr!("llvm.ident").as_ptr(),
+                c"llvm.ident".as_ptr(),
                 llvm::LLVMMDNodeInContext(debug_context.llcontext, &name_metadata, 1),
             );
         }
diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/mod.rs b/compiler/rustc_codegen_llvm/src/debuginfo/mod.rs
index c3f0a0033b0..aa7ae9355bc 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/mod.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/mod.rs
@@ -113,7 +113,7 @@ pub fn finalize(&self, sess: &Session) {
                 llvm::LLVMRustAddModuleFlag(
                     self.llmod,
                     llvm::LLVMModFlagBehavior::Warning,
-                    "Dwarf Version\0".as_ptr().cast(),
+                    c"Dwarf Version".as_ptr().cast(),
                     dwarf_version,
                 );
             } else {
@@ -121,17 +121,16 @@ pub fn finalize(&self, sess: &Session) {
                 llvm::LLVMRustAddModuleFlag(
                     self.llmod,
                     llvm::LLVMModFlagBehavior::Warning,
-                    "CodeView\0".as_ptr().cast(),
+                    c"CodeView".as_ptr().cast(),
                     1,
                 )
             }
 
             // Prevent bitcode readers from deleting the debug info.
-            let ptr = "Debug Info Version\0".as_ptr();
             llvm::LLVMRustAddModuleFlag(
                 self.llmod,
                 llvm::LLVMModFlagBehavior::Warning,
-                ptr.cast(),
+                c"Debug Info Version".as_ptr().cast(),
                 llvm::LLVMRustDebugMetadataVersion(),
             );
         }
diff --git a/compiler/rustc_codegen_llvm/src/lib.rs b/compiler/rustc_codegen_llvm/src/lib.rs
index 805843e5863..ff9909c720e 100644
--- a/compiler/rustc_codegen_llvm/src/lib.rs
+++ b/compiler/rustc_codegen_llvm/src/lib.rs
@@ -11,6 +11,7 @@
 #![feature(let_chains)]
 #![feature(never_type)]
 #![feature(impl_trait_in_assoc_type)]
+#![feature(c_str_literals)]
 #![recursion_limit = "256"]
 #![allow(rustc::potential_query_instability)]
 #![deny(rustc::untranslatable_diagnostic)]
diff --git a/compiler/rustc_hir_analysis/src/check/check.rs b/compiler/rustc_hir_analysis/src/check/check.rs
index 89f96695a2f..4a1f8ece7b2 100644
--- a/compiler/rustc_hir_analysis/src/check/check.rs
+++ b/compiler/rustc_hir_analysis/src/check/check.rs
@@ -704,7 +704,7 @@ pub(super) fn check_specialization_validity<'tcx>(
             // grandparent. In that case, if parent is a `default impl`, inherited items use the
             // "defaultness" from the grandparent, else they are final.
             None => {
-                if tcx.impl_defaultness(parent_impl.def_id()).is_default() {
+                if tcx.defaultness(parent_impl.def_id()).is_default() {
                     None
                 } else {
                     Some(Err(parent_impl.def_id()))
@@ -803,7 +803,7 @@ fn check_impl_items_against_trait<'tcx>(
                 .as_ref()
                 .is_some_and(|node_item| node_item.item.defaultness(tcx).has_value());
 
-            if !is_implemented && tcx.impl_defaultness(impl_id).is_final() {
+            if !is_implemented && tcx.defaultness(impl_id).is_final() {
                 missing_items.push(tcx.associated_item(trait_item_id));
             }
 
diff --git a/compiler/rustc_hir_analysis/src/collect.rs b/compiler/rustc_hir_analysis/src/collect.rs
index 2f7d465839c..c7b9fc9a697 100644
--- a/compiler/rustc_hir_analysis/src/collect.rs
+++ b/compiler/rustc_hir_analysis/src/collect.rs
@@ -941,7 +941,7 @@ fn trait_def(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::TraitDef {
 
                 match item {
                     Some(item) if matches!(item.kind, hir::AssocItemKind::Fn { .. }) => {
-                        if !tcx.impl_defaultness(item.id.owner_id).has_value() {
+                        if !tcx.defaultness(item.id.owner_id).has_value() {
                             tcx.sess.emit_err(errors::FunctionNotHaveDefaultImplementation {
                                 span: item.span,
                                 note_span: attr_span,
diff --git a/compiler/rustc_hir_analysis/src/collect/type_of.rs b/compiler/rustc_hir_analysis/src/collect/type_of.rs
index 65ab00fda81..e6fadd6cf4a 100644
--- a/compiler/rustc_hir_analysis/src/collect/type_of.rs
+++ b/compiler/rustc_hir_analysis/src/collect/type_of.rs
@@ -435,7 +435,7 @@ pub(super) fn type_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::EarlyBinder<Ty
                     in_trait,
                     ..
                 }) => {
-                    if in_trait && !tcx.impl_defaultness(owner).has_value() {
+                    if in_trait && !tcx.defaultness(owner).has_value() {
                         span_bug!(
                             tcx.def_span(def_id),
                             "tried to get type of this RPITIT with no definition"
diff --git a/compiler/rustc_infer/src/infer/error_reporting/note_and_explain.rs b/compiler/rustc_infer/src/infer/error_reporting/note_and_explain.rs
index d1f110472c9..9a8fac0fc1b 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/note_and_explain.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/note_and_explain.rs
@@ -586,7 +586,7 @@ fn point_at_associated_type(
                             // FIXME: account for returning some type in a trait fn impl that has
                             // an assoc type as a return type (#72076).
                             if let hir::Defaultness::Default { has_value: true } =
-                                tcx.impl_defaultness(item.id.owner_id)
+                                tcx.defaultness(item.id.owner_id)
                             {
                                 let assoc_ty = tcx.type_of(item.id.owner_id).subst_identity();
                                 if self.infcx.can_eq(param_env, assoc_ty, found) {
diff --git a/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs b/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs
index a15307e4345..243e4f5b659 100644
--- a/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs
+++ b/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs
@@ -231,7 +231,7 @@ fn into_args(self) -> (DefId, SimplifiedType) {
     opt_def_kind => { table_direct }
     impl_parent => { table }
     impl_polarity => { table_direct }
-    impl_defaultness => { table_direct }
+    defaultness => { table_direct }
     constness => { table_direct }
     coerce_unsized_info => { table }
     mir_const_qualif => { table }
diff --git a/compiler/rustc_metadata/src/rmeta/encoder.rs b/compiler/rustc_metadata/src/rmeta/encoder.rs
index 6ceb61e793e..05c9f154574 100644
--- a/compiler/rustc_metadata/src/rmeta/encoder.rs
+++ b/compiler/rustc_metadata/src/rmeta/encoder.rs
@@ -1437,8 +1437,8 @@ fn encode_info_for_trait_item(&mut self, def_id: DefId) {
         debug!("EncodeContext::encode_info_for_trait_item({:?})", def_id);
         let tcx = self.tcx;
 
-        let impl_defaultness = tcx.impl_defaultness(def_id.expect_local());
-        self.tables.impl_defaultness.set_some(def_id.index, impl_defaultness);
+        let defaultness = tcx.defaultness(def_id.expect_local());
+        self.tables.defaultness.set_some(def_id.index, defaultness);
         let trait_item = tcx.associated_item(def_id);
         self.tables.assoc_container.set_some(def_id.index, trait_item.container);
 
@@ -1466,8 +1466,8 @@ fn encode_info_for_impl_item(&mut self, def_id: DefId) {
         debug!("EncodeContext::encode_info_for_impl_item({:?})", def_id);
         let tcx = self.tcx;
 
-        let defaultness = self.tcx.impl_defaultness(def_id.expect_local());
-        self.tables.impl_defaultness.set_some(def_id.index, defaultness);
+        let defaultness = self.tcx.defaultness(def_id.expect_local());
+        self.tables.defaultness.set_some(def_id.index, defaultness);
         let impl_item = self.tcx.associated_item(def_id);
         self.tables.assoc_container.set_some(def_id.index, impl_item.container);
 
@@ -1653,7 +1653,7 @@ fn encode_info_for_item(&mut self, item: &'tcx hir::Item<'tcx>) {
                 );
             }
             hir::ItemKind::Impl(hir::Impl { defaultness, constness, .. }) => {
-                self.tables.impl_defaultness.set_some(def_id.index, *defaultness);
+                self.tables.defaultness.set_some(def_id.index, *defaultness);
                 self.tables.constness.set_some(def_id.index, *constness);
                 self.tables.impl_polarity.set_some(def_id.index, self.tcx.impl_polarity(def_id));
 
diff --git a/compiler/rustc_metadata/src/rmeta/mod.rs b/compiler/rustc_metadata/src/rmeta/mod.rs
index 2da888f4468..e9b67c70c47 100644
--- a/compiler/rustc_metadata/src/rmeta/mod.rs
+++ b/compiler/rustc_metadata/src/rmeta/mod.rs
@@ -420,7 +420,7 @@ fn encode(&self, buf: &mut FileEncoder) -> LazyTables {
     impl_parent: Table<DefIndex, RawDefId>,
     impl_polarity: Table<DefIndex, ty::ImplPolarity>,
     constness: Table<DefIndex, hir::Constness>,
-    impl_defaultness: Table<DefIndex, hir::Defaultness>,
+    defaultness: Table<DefIndex, hir::Defaultness>,
     // FIXME(eddyb) perhaps compute this on the fly if cheap enough?
     coerce_unsized_info: Table<DefIndex, LazyValue<ty::adjustment::CoerceUnsizedInfo>>,
     mir_const_qualif: Table<DefIndex, LazyValue<mir::ConstQualifs>>,
diff --git a/compiler/rustc_middle/src/query/mod.rs b/compiler/rustc_middle/src/query/mod.rs
index 0b31c9bbf81..45e0b498fac 100644
--- a/compiler/rustc_middle/src/query/mod.rs
+++ b/compiler/rustc_middle/src/query/mod.rs
@@ -1475,8 +1475,9 @@
         desc { "getting traits in scope at a block" }
     }
 
-    query impl_defaultness(def_id: DefId) -> hir::Defaultness {
-        desc { |tcx| "looking up whether `{}` is a default impl", tcx.def_path_str(def_id) }
+    /// Returns whether the impl or associated function has the `default` keyword.
+    query defaultness(def_id: DefId) -> hir::Defaultness {
+        desc { |tcx| "looking up whether `{}` has `default`", tcx.def_path_str(def_id) }
         separate_provide_extern
         feedable
     }
diff --git a/compiler/rustc_middle/src/traits/specialization_graph.rs b/compiler/rustc_middle/src/traits/specialization_graph.rs
index c016f722750..dc2cd203560 100644
--- a/compiler/rustc_middle/src/traits/specialization_graph.rs
+++ b/compiler/rustc_middle/src/traits/specialization_graph.rs
@@ -228,7 +228,7 @@ pub fn leaf_def(mut self, tcx: TyCtxt<'tcx>, trait_item_def_id: DefId) -> Option
             if let Some(item) = node.item(tcx, trait_item_def_id) {
                 if finalizing_node.is_none() {
                     let is_specializable = item.defaultness(tcx).is_default()
-                        || tcx.impl_defaultness(node.def_id()).is_default();
+                        || tcx.defaultness(node.def_id()).is_default();
 
                     if !is_specializable {
                         finalizing_node = Some(node);
diff --git a/compiler/rustc_middle/src/ty/assoc.rs b/compiler/rustc_middle/src/ty/assoc.rs
index 090b769323a..cce609c261e 100644
--- a/compiler/rustc_middle/src/ty/assoc.rs
+++ b/compiler/rustc_middle/src/ty/assoc.rs
@@ -48,7 +48,7 @@ pub fn ident(&self, tcx: TyCtxt<'_>) -> Ident {
     ///
     /// [`type_of`]: crate::ty::TyCtxt::type_of
     pub fn defaultness(&self, tcx: TyCtxt<'_>) -> hir::Defaultness {
-        tcx.impl_defaultness(self.def_id)
+        tcx.defaultness(self.def_id)
     }
 
     #[inline]
diff --git a/compiler/rustc_middle/src/ty/context.rs b/compiler/rustc_middle/src/ty/context.rs
index 673d09cddf4..e7335104e61 100644
--- a/compiler/rustc_middle/src/ty/context.rs
+++ b/compiler/rustc_middle/src/ty/context.rs
@@ -1884,18 +1884,28 @@ pub fn mk_projection(
     }
 
     #[inline]
-    pub fn mk_closure(self, closure_id: DefId, closure_substs: SubstsRef<'tcx>) -> Ty<'tcx> {
-        self.mk_ty_from_kind(Closure(closure_id, closure_substs))
+    pub fn mk_closure(self, def_id: DefId, closure_substs: SubstsRef<'tcx>) -> Ty<'tcx> {
+        debug_assert_eq!(
+            closure_substs.len(),
+            self.generics_of(self.typeck_root_def_id(def_id)).count() + 3,
+            "closure constructed with incorrect substitutions"
+        );
+        self.mk_ty_from_kind(Closure(def_id, closure_substs))
     }
 
     #[inline]
     pub fn mk_generator(
         self,
-        id: DefId,
+        def_id: DefId,
         generator_substs: SubstsRef<'tcx>,
         movability: hir::Movability,
     ) -> Ty<'tcx> {
-        self.mk_ty_from_kind(Generator(id, generator_substs, movability))
+        debug_assert_eq!(
+            generator_substs.len(),
+            self.generics_of(self.typeck_root_def_id(def_id)).count() + 5,
+            "generator constructed with incorrect number of substitutions"
+        );
+        self.mk_ty_from_kind(Generator(def_id, generator_substs, movability))
     }
 
     #[inline]
diff --git a/compiler/rustc_privacy/src/lib.rs b/compiler/rustc_privacy/src/lib.rs
index 65dfdf31e54..0197b99c7db 100644
--- a/compiler/rustc_privacy/src/lib.rs
+++ b/compiler/rustc_privacy/src/lib.rs
@@ -751,7 +751,7 @@ fn visit_item(&mut self, item: &'tcx hir::Item<'tcx>) {
                         reach.generics().predicates();
 
                         if trait_item_ref.kind == AssocItemKind::Type
-                            && !tcx.impl_defaultness(trait_item_ref.id.owner_id).has_value()
+                            && !tcx.defaultness(trait_item_ref.id.owner_id).has_value()
                         {
                             // No type to visit.
                         } else {
@@ -1927,7 +1927,7 @@ fn check_assoc_item(
 
         let (check_ty, is_assoc_ty) = match assoc_item_kind {
             AssocItemKind::Const | AssocItemKind::Fn { .. } => (true, false),
-            AssocItemKind::Type => (self.tcx.impl_defaultness(def_id).has_value(), true),
+            AssocItemKind::Type => (self.tcx.defaultness(def_id).has_value(), true),
         };
         check.in_assoc_ty = is_assoc_ty;
         check.generics().predicates();
diff --git a/compiler/rustc_symbol_mangling/src/typeid/typeid_itanium_cxx_abi.rs b/compiler/rustc_symbol_mangling/src/typeid/typeid_itanium_cxx_abi.rs
index 81af071eefd..85825513ce9 100644
--- a/compiler/rustc_symbol_mangling/src/typeid/typeid_itanium_cxx_abi.rs
+++ b/compiler/rustc_symbol_mangling/src/typeid/typeid_itanium_cxx_abi.rs
@@ -697,12 +697,12 @@ fn encode_ty<'tcx>(
         }
 
         // Unexpected types
-        ty::Bound(..)
+        ty::Alias(..)
+        | ty::Bound(..)
         | ty::Error(..)
         | ty::GeneratorWitness(..)
         | ty::GeneratorWitnessMIR(..)
         | ty::Infer(..)
-        | ty::Alias(..)
         | ty::Placeholder(..) => {
             bug!("encode_ty: unexpected `{:?}`", ty.kind());
         }
@@ -946,11 +946,18 @@ fn transform_ty<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>, options: TransformTyOptio
             );
         }
 
+        ty::Alias(..) => {
+            ty = transform_ty(
+                tcx,
+                tcx.normalize_erasing_regions(ty::ParamEnv::reveal_all(), ty),
+                options,
+            );
+        }
+
         ty::Bound(..)
         | ty::Error(..)
         | ty::GeneratorWitnessMIR(..)
         | ty::Infer(..)
-        | ty::Alias(..)
         | ty::Param(..)
         | ty::Placeholder(..) => {
             bug!("transform_ty: unexpected `{:?}`", ty.kind());
diff --git a/compiler/rustc_trait_selection/src/traits/util.rs b/compiler/rustc_trait_selection/src/traits/util.rs
index e2c9c62512e..537405b7eb9 100644
--- a/compiler/rustc_trait_selection/src/traits/util.rs
+++ b/compiler/rustc_trait_selection/src/traits/util.rs
@@ -295,7 +295,7 @@ pub fn future_trait_ref_and_outputs<'tcx>(
 
 pub fn impl_item_is_final(tcx: TyCtxt<'_>, assoc_item: &ty::AssocItem) -> bool {
     assoc_item.defaultness(tcx).is_final()
-        && tcx.impl_defaultness(assoc_item.container_id(tcx)).is_final()
+        && tcx.defaultness(assoc_item.container_id(tcx)).is_final()
 }
 
 pub enum TupleArgumentsFlag {
diff --git a/compiler/rustc_ty_utils/src/assoc.rs b/compiler/rustc_ty_utils/src/assoc.rs
index 57b4183d336..658ab03c0f4 100644
--- a/compiler/rustc_ty_utils/src/assoc.rs
+++ b/compiler/rustc_ty_utils/src/assoc.rs
@@ -297,8 +297,8 @@ fn associated_type_for_impl_trait_in_trait(
     // Copy visility of the containing function.
     trait_assoc_ty.visibility(tcx.visibility(fn_def_id));
 
-    // Copy impl_defaultness of the containing function.
-    trait_assoc_ty.impl_defaultness(tcx.impl_defaultness(fn_def_id));
+    // Copy defaultness of the containing function.
+    trait_assoc_ty.defaultness(tcx.defaultness(fn_def_id));
 
     // Copy type_of of the opaque.
     trait_assoc_ty.type_of(ty::EarlyBinder::bind(tcx.mk_opaque(
@@ -393,8 +393,8 @@ fn associated_type_for_impl_trait_in_impl(
     // Copy visility of the containing function.
     impl_assoc_ty.visibility(tcx.visibility(impl_fn_def_id));
 
-    // Copy impl_defaultness of the containing function.
-    impl_assoc_ty.impl_defaultness(tcx.impl_defaultness(impl_fn_def_id));
+    // Copy defaultness of the containing function.
+    impl_assoc_ty.defaultness(tcx.defaultness(impl_fn_def_id));
 
     // Copy generics_of the trait's associated item but the impl as the parent.
     // FIXME(-Zlower-impl-trait-in-trait-to-assoc-ty) resolves to the trait instead of the impl
diff --git a/compiler/rustc_ty_utils/src/instance.rs b/compiler/rustc_ty_utils/src/instance.rs
index 36a20c78fcc..dd911239ac4 100644
--- a/compiler/rustc_ty_utils/src/instance.rs
+++ b/compiler/rustc_ty_utils/src/instance.rs
@@ -204,7 +204,7 @@ fn resolve_associated_item<'tcx>(
             } else {
                 // All other methods are default methods of the `Future` trait.
                 // (this assumes that `ImplSource::Future` is only used for methods on `Future`)
-                debug_assert!(tcx.impl_defaultness(trait_item_id).has_value());
+                debug_assert!(tcx.defaultness(trait_item_id).has_value());
                 Some(Instance::new(trait_item_id, rcvr_substs))
             }
         }
diff --git a/compiler/rustc_ty_utils/src/ty.rs b/compiler/rustc_ty_utils/src/ty.rs
index 12ad8b0842f..b367d81a260 100644
--- a/compiler/rustc_ty_utils/src/ty.rs
+++ b/compiler/rustc_ty_utils/src/ty.rs
@@ -75,13 +75,13 @@ fn sized_constraint_for_ty<'tcx>(
     result
 }
 
-fn impl_defaultness(tcx: TyCtxt<'_>, def_id: LocalDefId) -> hir::Defaultness {
+fn defaultness(tcx: TyCtxt<'_>, def_id: LocalDefId) -> hir::Defaultness {
     match tcx.hir().get_by_def_id(def_id) {
         hir::Node::Item(hir::Item { kind: hir::ItemKind::Impl(impl_), .. }) => impl_.defaultness,
         hir::Node::ImplItem(hir::ImplItem { defaultness, .. })
         | hir::Node::TraitItem(hir::TraitItem { defaultness, .. }) => *defaultness,
         node => {
-            bug!("`impl_defaultness` called on {:?}", node);
+            bug!("`defaultness` called on {:?}", node);
         }
     }
 }
@@ -574,7 +574,7 @@ pub fn provide(providers: &mut Providers) {
         param_env_reveal_all_normalized,
         instance_def_size_estimate,
         issue33140_self_ty,
-        impl_defaultness,
+        defaultness,
         unsizing_params_for_adt,
         ..*providers
     };
diff --git a/library/core/src/cell.rs b/library/core/src/cell.rs
index 744767aae44..c1cc892eb86 100644
--- a/library/core/src/cell.rs
+++ b/library/core/src/cell.rs
@@ -59,7 +59,7 @@
 //! [`borrow`](`RefCell::borrow`), and a mutable borrow (`&mut T`) can be obtained with
 //! [`borrow_mut`](`RefCell::borrow_mut`). When these functions are called, they first verify that
 //! Rust's borrow rules will be satisfied: any number of immutable borrows are allowed or a
-//! single immutable borrow is allowed, but never both. If a borrow is attempted that would violate
+//! single mutable borrow is allowed, but never both. If a borrow is attempted that would violate
 //! these rules, the thread will panic.
 //!
 //! The corresponding [`Sync`] version of `RefCell<T>` is [`RwLock<T>`].
diff --git a/library/std/src/lib.rs b/library/std/src/lib.rs
index 318a46d1b63..d53f1a2b2ff 100644
--- a/library/std/src/lib.rs
+++ b/library/std/src/lib.rs
@@ -240,6 +240,7 @@
 #![feature(allocator_internals)]
 #![feature(allow_internal_unsafe)]
 #![feature(allow_internal_unstable)]
+#![feature(c_str_literals)]
 #![feature(c_unwind)]
 #![feature(cfg_target_thread_local)]
 #![feature(concat_idents)]
diff --git a/library/std/src/sys/unix/args.rs b/library/std/src/sys/unix/args.rs
index 9ed4d9c1e0d..0efe2570d67 100644
--- a/library/std/src/sys/unix/args.rs
+++ b/library/std/src/sys/unix/args.rs
@@ -242,13 +242,15 @@ pub fn args() -> Args {
         let mut res = Vec::new();
 
         unsafe {
-            let process_info_sel = sel_registerName("processInfo\0".as_ptr());
-            let arguments_sel = sel_registerName("arguments\0".as_ptr());
-            let utf8_sel = sel_registerName("UTF8String\0".as_ptr());
-            let count_sel = sel_registerName("count\0".as_ptr());
-            let object_at_sel = sel_registerName("objectAtIndex:\0".as_ptr());
+            let process_info_sel =
+                sel_registerName(c"processInfo".as_ptr() as *const libc::c_uchar);
+            let arguments_sel = sel_registerName(c"arguments".as_ptr() as *const libc::c_uchar);
+            let utf8_sel = sel_registerName(c"UTF8String".as_ptr() as *const libc::c_uchar);
+            let count_sel = sel_registerName(c"count".as_ptr() as *const libc::c_uchar);
+            let object_at_sel =
+                sel_registerName(c"objectAtIndex:".as_ptr() as *const libc::c_uchar);
 
-            let klass = objc_getClass("NSProcessInfo\0".as_ptr());
+            let klass = objc_getClass(c"NSProcessInfo".as_ptr() as *const libc::c_uchar);
             let info = objc_msgSend(klass, process_info_sel);
             let args = objc_msgSend(info, arguments_sel);
 
diff --git a/library/std/src/sys/unix/fs.rs b/library/std/src/sys/unix/fs.rs
index 09e9ae2720f..0e5691d40d1 100644
--- a/library/std/src/sys/unix/fs.rs
+++ b/library/std/src/sys/unix/fs.rs
@@ -1063,7 +1063,7 @@ pub fn file_attr(&self) -> io::Result<FileAttr> {
         cfg_has_statx! {
             if let Some(ret) = unsafe { try_statx(
                 fd,
-                b"\0" as *const _ as *const c_char,
+                c"".as_ptr() as *const c_char,
                 libc::AT_EMPTY_PATH | libc::AT_STATX_SYNC_AS_STAT,
                 libc::STATX_ALL,
             ) } {
diff --git a/library/std/src/sys/unix/mod.rs b/library/std/src/sys/unix/mod.rs
index bb9e65e68e5..54e2f20b317 100644
--- a/library/std/src/sys/unix/mod.rs
+++ b/library/std/src/sys/unix/mod.rs
@@ -1,6 +1,5 @@
 #![allow(missing_docs, nonstandard_style)]
 
-use crate::ffi::CStr;
 use crate::io::ErrorKind;
 
 pub use self::rand::hashmap_random_keys;
@@ -75,7 +74,7 @@ pub unsafe fn init(argc: isize, argv: *const *const u8, sigpipe: u8) {
     // thread-id for the main thread and so renaming the main thread will rename the
     // process and we only want to enable this on platforms we've tested.
     if cfg!(target_os = "macos") {
-        thread::Thread::set_name(&CStr::from_bytes_with_nul_unchecked(b"main\0"));
+        thread::Thread::set_name(&c"main");
     }
 
     unsafe fn sanitize_standard_fds() {
@@ -121,7 +120,7 @@ unsafe fn sanitize_standard_fds() {
                 if pfd.revents & libc::POLLNVAL == 0 {
                     continue;
                 }
-                if open64("/dev/null\0".as_ptr().cast(), libc::O_RDWR, 0) == -1 {
+                if open64(c"/dev/null".as_ptr().cast(), libc::O_RDWR, 0) == -1 {
                     // If the stream is closed but we failed to reopen it, abort the
                     // process. Otherwise we wouldn't preserve the safety of
                     // operations on the corresponding Rust object Stdin, Stdout, or
@@ -151,7 +150,7 @@ unsafe fn sanitize_standard_fds() {
             use libc::open64;
             for fd in 0..3 {
                 if libc::fcntl(fd, libc::F_GETFD) == -1 && errno() == libc::EBADF {
-                    if open64("/dev/null\0".as_ptr().cast(), libc::O_RDWR, 0) == -1 {
+                    if open64(c"/dev/null".as_ptr().cast(), libc::O_RDWR, 0) == -1 {
                         // If the stream is closed but we failed to reopen it, abort the
                         // process. Otherwise we wouldn't preserve the safety of
                         // operations on the corresponding Rust object Stdin, Stdout, or
diff --git a/library/std/src/sys/unix/process/process_common.rs b/library/std/src/sys/unix/process/process_common.rs
index 640648e8707..5f316b12b62 100644
--- a/library/std/src/sys/unix/process/process_common.rs
+++ b/library/std/src/sys/unix/process/process_common.rs
@@ -24,11 +24,11 @@
     if #[cfg(target_os = "fuchsia")] {
         // fuchsia doesn't have /dev/null
     } else if #[cfg(target_os = "redox")] {
-        const DEV_NULL: &str = "null:\0";
+        const DEV_NULL: &CStr = c"null:";
     } else if #[cfg(target_os = "vxworks")] {
-        const DEV_NULL: &str = "/null\0";
+        const DEV_NULL: &CStr = c"/null";
     } else {
-        const DEV_NULL: &str = "/dev/null\0";
+        const DEV_NULL: &CStr = c"/dev/null";
     }
 }
 
@@ -474,8 +474,7 @@ pub fn to_child_stdio(&self, readable: bool) -> io::Result<(ChildStdio, Option<A
                 let mut opts = OpenOptions::new();
                 opts.read(readable);
                 opts.write(!readable);
-                let path = unsafe { CStr::from_ptr(DEV_NULL.as_ptr() as *const _) };
-                let fd = File::open_c(&path, &opts)?;
+                let fd = File::open_c(DEV_NULL, &opts)?;
                 Ok((ChildStdio::Owned(fd.into_inner()), None))
             }
 
diff --git a/library/std/src/sys/unix/thread.rs b/library/std/src/sys/unix/thread.rs
index 7307d9b2c86..878af5088d9 100644
--- a/library/std/src/sys/unix/thread.rs
+++ b/library/std/src/sys/unix/thread.rs
@@ -163,10 +163,9 @@ pub fn set_name(name: &CStr) {
     #[cfg(target_os = "netbsd")]
     pub fn set_name(name: &CStr) {
         unsafe {
-            let cname = CStr::from_bytes_with_nul_unchecked(b"%s\0".as_slice());
             let res = libc::pthread_setname_np(
                 libc::pthread_self(),
-                cname.as_ptr(),
+                c"%s".as_ptr(),
                 name.as_ptr() as *mut libc::c_void,
             );
             debug_assert_eq!(res, 0);
diff --git a/library/std/src/sys/windows/c.rs b/library/std/src/sys/windows/c.rs
index 2bc40c4748a..07b0610d463 100644
--- a/library/std/src/sys/windows/c.rs
+++ b/library/std/src/sys/windows/c.rs
@@ -317,7 +317,7 @@ pub unsafe fn NtWriteFile(
 // Functions that aren't available on every version of Windows that we support,
 // but we still use them and just provide some form of a fallback implementation.
 compat_fn_with_fallback! {
-    pub static KERNEL32: &CStr = ansi_str!("kernel32");
+    pub static KERNEL32: &CStr = c"kernel32";
 
     // >= Win10 1607
     // https://docs.microsoft.com/en-us/windows/win32/api/processthreadsapi/nf-processthreadsapi-setthreaddescription
@@ -350,7 +350,7 @@ pub fn WaitOnAddress(
 }
 
 compat_fn_with_fallback! {
-    pub static NTDLL: &CStr = ansi_str!("ntdll");
+    pub static NTDLL: &CStr = c"ntdll";
 
     pub fn NtCreateKeyedEvent(
         KeyedEventHandle: LPHANDLE,
diff --git a/library/std/src/sys/windows/compat.rs b/library/std/src/sys/windows/compat.rs
index 4fe95d41116..649cc4bfdbf 100644
--- a/library/std/src/sys/windows/compat.rs
+++ b/library/std/src/sys/windows/compat.rs
@@ -228,9 +228,9 @@ pub fn option() -> Option<F> {
 /// Load all needed functions from "api-ms-win-core-synch-l1-2-0".
 pub(super) fn load_synch_functions() {
     fn try_load() -> Option<()> {
-        const MODULE_NAME: &CStr = ansi_str!("api-ms-win-core-synch-l1-2-0");
-        const WAIT_ON_ADDRESS: &CStr = ansi_str!("WaitOnAddress");
-        const WAKE_BY_ADDRESS_SINGLE: &CStr = ansi_str!("WakeByAddressSingle");
+        const MODULE_NAME: &CStr = c"api-ms-win-core-synch-l1-2-0";
+        const WAIT_ON_ADDRESS: &CStr = c"WaitOnAddress";
+        const WAKE_BY_ADDRESS_SINGLE: &CStr = c"WakeByAddressSingle";
 
         // Try loading the library and all the required functions.
         // If any step fails, then they all fail.
diff --git a/library/std/src/sys/windows/mod.rs b/library/std/src/sys/windows/mod.rs
index bcc172b0fae..b11c8962203 100644
--- a/library/std/src/sys/windows/mod.rs
+++ b/library/std/src/sys/windows/mod.rs
@@ -1,6 +1,6 @@
 #![allow(missing_docs, nonstandard_style)]
 
-use crate::ffi::{CStr, OsStr, OsString};
+use crate::ffi::{OsStr, OsString};
 use crate::io::ErrorKind;
 use crate::mem::MaybeUninit;
 use crate::os::windows::ffi::{OsStrExt, OsStringExt};
@@ -51,7 +51,7 @@ pub unsafe fn init(_argc: isize, _argv: *const *const u8, _sigpipe: u8) {
 
     // Normally, `thread::spawn` will call `Thread::set_name` but since this thread already
     // exists, we have to call it ourselves.
-    thread::Thread::set_name(&CStr::from_bytes_with_nul_unchecked(b"main\0"));
+    thread::Thread::set_name(&c"main");
 }
 
 // SAFETY: must be called only once during runtime cleanup.
diff --git a/src/librustdoc/clean/mod.rs b/src/librustdoc/clean/mod.rs
index 5fd867189fd..b84a9cf369c 100644
--- a/src/librustdoc/clean/mod.rs
+++ b/src/librustdoc/clean/mod.rs
@@ -1224,7 +1224,7 @@ pub(crate) fn clean_impl_item<'tcx>(
             }
             hir::ImplItemKind::Fn(ref sig, body) => {
                 let m = clean_function(cx, sig, impl_.generics, FunctionArgs::Body(body));
-                let defaultness = cx.tcx.impl_defaultness(impl_.owner_id);
+                let defaultness = cx.tcx.defaultness(impl_.owner_id);
                 MethodItem(m, Some(defaultness))
             }
             hir::ImplItemKind::Type(hir_ty) => {
@@ -1258,7 +1258,7 @@ pub(crate) fn clean_middle_assoc_item<'tcx>(
 
             let provided = match assoc_item.container {
                 ty::ImplContainer => true,
-                ty::TraitContainer => tcx.impl_defaultness(assoc_item.def_id).has_value(),
+                ty::TraitContainer => tcx.defaultness(assoc_item.def_id).has_value(),
             };
             if provided {
                 AssocConstItem(ty, ConstantKind::Extern { def_id: assoc_item.def_id })
@@ -1440,7 +1440,7 @@ fn param_eq_arg(param: &GenericParamDef, arg: &GenericArg) -> bool {
                 }
                 generics.where_predicates = where_predicates;
 
-                if tcx.impl_defaultness(assoc_item.def_id).has_value() {
+                if tcx.defaultness(assoc_item.def_id).has_value() {
                     AssocTypeItem(
                         Box::new(Typedef {
                             type_: clean_middle_ty(
diff --git a/src/librustdoc/passes/collect_intra_doc_links.rs b/src/librustdoc/passes/collect_intra_doc_links.rs
index 2b0fef267e9..c31ba3304b0 100644
--- a/src/librustdoc/passes/collect_intra_doc_links.rs
+++ b/src/librustdoc/passes/collect_intra_doc_links.rs
@@ -205,7 +205,7 @@ pub(crate) fn render(&self, s: &mut String, tcx: TyCtxt<'_>) {
             &UrlFragment::Item(def_id) => {
                 let kind = match tcx.def_kind(def_id) {
                     DefKind::AssocFn => {
-                        if tcx.impl_defaultness(def_id).has_value() {
+                        if tcx.defaultness(def_id).has_value() {
                             "method."
                         } else {
                             "tymethod."
diff --git a/src/tools/clippy/clippy_lints/src/missing_inline.rs b/src/tools/clippy/clippy_lints/src/missing_inline.rs
index 5a459548153..a41d5a9ce8d 100644
--- a/src/tools/clippy/clippy_lints/src/missing_inline.rs
+++ b/src/tools/clippy/clippy_lints/src/missing_inline.rs
@@ -105,7 +105,7 @@ fn check_item(&mut self, cx: &LateContext<'tcx>, it: &'tcx hir::Item<'_>) {
                     match tit_.kind {
                         hir::TraitItemKind::Const(..) | hir::TraitItemKind::Type(..) => {},
                         hir::TraitItemKind::Fn(..) => {
-                            if cx.tcx.impl_defaultness(tit.id.owner_id).has_value() {
+                            if cx.tcx.defaultness(tit.id.owner_id).has_value() {
                                 // trait method with default body needs inline in case
                                 // an impl is not provided
                                 let desc = "a default trait method";
diff --git a/src/tools/tidy/src/deps.rs b/src/tools/tidy/src/deps.rs
index db2b7910b71..abaed95a084 100644
--- a/src/tools/tidy/src/deps.rs
+++ b/src/tools/tidy/src/deps.rs
@@ -132,7 +132,6 @@
     "crossbeam-epoch",
     "crossbeam-utils",
     "crypto-common",
-    "cstr",
     "datafrog",
     "derive_more",
     "digest",
diff --git a/tests/codegen/sanitizer-cfi-emit-type-metadata-id-itanium-cxx-abi.rs b/tests/codegen/sanitizer-cfi-emit-type-metadata-id-itanium-cxx-abi.rs
index ebb26cd35c0..472d921ace0 100644
--- a/tests/codegen/sanitizer-cfi-emit-type-metadata-id-itanium-cxx-abi.rs
+++ b/tests/codegen/sanitizer-cfi-emit-type-metadata-id-itanium-cxx-abi.rs
@@ -587,6 +587,6 @@ pub fn foo149(_: Type14<Bar>, _: Type14<Bar>, _: Type14<Bar>) { }
 // CHECK: ![[TYPE144]] = !{i64 0, !"_ZTSFvu3refIvEE"}
 // CHECK: ![[TYPE145]] = !{i64 0, !"_ZTSFvu3refIvES_E"}
 // CHECK: ![[TYPE146]] = !{i64 0, !"_ZTSFvu3refIvES_S_E"}
-// CHECK: ![[TYPE147]] = !{i64 0, !"_ZTSFvu{{[0-9]+}}NtC{{[[:print:]]+}}_51sanitizer_cfi_emit_type_metadata_id_itanium_cxx_abi3BarE
-// CHECK: ![[TYPE148]] = !{i64 0, !"_ZTSFvu{{[0-9]+}}NtC{{[[:print:]]+}}_51sanitizer_cfi_emit_type_metadata_id_itanium_cxx_abi3BarS_E
-// CHECK: ![[TYPE149]] = !{i64 0, !"_ZTSFvu{{[0-9]+}}NtC{{[[:print:]]+}}_51sanitizer_cfi_emit_type_metadata_id_itanium_cxx_abi3BarS_S_E
+// CHECK: ![[TYPE147]] = !{i64 0, !"_ZTSFvu{{[0-9]+}}NtC{{[[:print:]]+}}_51sanitizer_cfi_emit_type_metadata_id_itanium_cxx_abi3BarE"}
+// CHECK: ![[TYPE148]] = !{i64 0, !"_ZTSFvu{{[0-9]+}}NtC{{[[:print:]]+}}_51sanitizer_cfi_emit_type_metadata_id_itanium_cxx_abi3BarS_E"}
+// CHECK: ![[TYPE149]] = !{i64 0, !"_ZTSFvu{{[0-9]+}}NtC{{[[:print:]]+}}_51sanitizer_cfi_emit_type_metadata_id_itanium_cxx_abi3BarS_S_E"}
diff --git a/tests/rustdoc/double-hyphen-to-dash.rs b/tests/rustdoc/double-hyphen-to-dash.rs
new file mode 100644
index 00000000000..66905f90cfc
--- /dev/null
+++ b/tests/rustdoc/double-hyphen-to-dash.rs
@@ -0,0 +1,9 @@
+// This test ensures that `--` (double-hyphen) is correctly converted into `–` (dash).
+
+#![crate_name = "foo"]
+
+// @has 'foo/index.html' '//*[@class="desc docblock-short"]' '–'
+// @has 'foo/struct.Bar.html' '//*[@class="docblock"]' '–'
+
+/// --
+pub struct Bar;