Rollup merge of #113334 - fmease:revert-lexing-c-str-lits, r=compiler-errors

Revert the lexing of `c"…"` string literals

Fixes \[after beta-backport\] #113235.
Further progress is tracked in #113333.

This PR *manually* reverts parts of #108801 (since a git-revert would've been too coarse-grained & messy)
and git-reverts #111647.

CC `@fee1-dead` (#108801) `@klensy` (#111647)
r? `@compiler-errors`

`@rustbot` label F-c_str_literals beta-nominated

33 files changed, 222 insertions, 101 deletions

diff --git a/Cargo.lock b/Cargo.lock
index b28eb4faa5b..edee662ab64 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -767,6 +767,16 @@ dependencies = [
 ]
 
 [[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 = "3.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -3016,6 +3026,7 @@ name = "rustc_codegen_llvm"
 version = "0.0.0"
 dependencies = [
  "bitflags 1.3.2",
+ "cstr",
  "libc",
  "measureme",
  "object",
diff --git a/compiler/rustc_codegen_llvm/Cargo.toml b/compiler/rustc_codegen_llvm/Cargo.toml
index 39ff3a0ba2d..ad51f2d0958 100644
--- a/compiler/rustc_codegen_llvm/Cargo.toml
+++ b/compiler/rustc_codegen_llvm/Cargo.toml
@@ -8,6 +8,7 @@ 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 ad0636894b7..a57508815d6 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, c"entry".as_ptr().cast());
+            let llbb = llvm::LLVMAppendBasicBlockInContext(llcx, llfn, "entry\0".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, c"entry".as_ptr().cast());
+    let llbb = llvm::LLVMAppendBasicBlockInContext(llcx, llfn, "entry\0".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 94885b40cc1..d7dd98d7938 100644
--- a/compiler/rustc_codegen_llvm/src/back/lto.rs
+++ b/compiler/rustc_codegen_llvm/src/back/lto.rs
@@ -601,7 +601,7 @@ pub(crate) fn run_pass_manager(
             llvm::LLVMRustAddModuleFlag(
                 module.module_llvm.llmod(),
                 llvm::LLVMModFlagBehavior::Error,
-                c"LTOPostLink".as_ptr().cast(),
+                "LTOPostLink\0".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 998e3b300da..0f5e975445f 100644
--- a/compiler/rustc_codegen_llvm/src/back/write.rs
+++ b/compiler/rustc_codegen_llvm/src/back/write.rs
@@ -931,16 +931,16 @@ unsafe fn embed_bitcode(
         let llglobal = llvm::LLVMAddGlobal(
             llmod,
             common::val_ty(llconst),
-            c"rustc.embedded.module".as_ptr().cast(),
+            "rustc.embedded.module\0".as_ptr().cast(),
         );
         llvm::LLVMSetInitializer(llglobal, llconst);
 
         let section = if is_apple {
-            c"__LLVM,__bitcode"
+            "__LLVM,__bitcode\0"
         } else if is_aix {
-            c".ipa"
+            ".ipa\0"
         } else {
-            c".llvmbc"
+            ".llvmbc\0"
         };
         llvm::LLVMSetSection(llglobal, section.as_ptr().cast());
         llvm::LLVMRustSetLinkage(llglobal, llvm::Linkage::PrivateLinkage);
@@ -950,15 +950,15 @@ unsafe fn embed_bitcode(
         let llglobal = llvm::LLVMAddGlobal(
             llmod,
             common::val_ty(llconst),
-            c"rustc.embedded.cmdline".as_ptr().cast(),
+            "rustc.embedded.cmdline\0".as_ptr().cast(),
         );
         llvm::LLVMSetInitializer(llglobal, llconst);
         let section = if is_apple {
-            c"__LLVM,__cmdline"
+            "__LLVM,__cmdline\0"
         } else if is_aix {
-            c".info"
+            ".info\0"
         } else {
-            c".llvmcmd"
+            ".llvmcmd\0"
         };
         llvm::LLVMSetSection(llglobal, section.as_ptr().cast());
         llvm::LLVMRustSetLinkage(llglobal, llvm::Linkage::PrivateLinkage);
diff --git a/compiler/rustc_codegen_llvm/src/base.rs b/compiler/rustc_codegen_llvm/src/base.rs
index 2f7eb08ad3d..5b2bbdb4bde 100644
--- a/compiler/rustc_codegen_llvm/src/base.rs
+++ b/compiler/rustc_codegen_llvm/src/base.rs
@@ -19,6 +19,8 @@ use crate::context::CodegenCx;
 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::*;
@@ -108,11 +110,11 @@ pub fn compile_codegen_unit(tcx: TyCtxt<'_>, cgu_name: Symbol) -> (ModuleCodegen
 
             // Create the llvm.used and llvm.compiler.used variables.
             if !cx.used_statics.borrow().is_empty() {
-                cx.create_used_variable_impl(c"llvm.used", &*cx.used_statics.borrow());
+                cx.create_used_variable_impl(cstr!("llvm.used"), &*cx.used_statics.borrow());
             }
             if !cx.compiler_used_statics.borrow().is_empty() {
                 cx.create_used_variable_impl(
-                    c"llvm.compiler.used",
+                    cstr!("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 9863ca35202..d55992bf092 100644
--- a/compiler/rustc_codegen_llvm/src/builder.rs
+++ b/compiler/rustc_codegen_llvm/src/builder.rs
@@ -6,6 +6,7 @@ use crate::llvm::{self, AtomicOrdering, AtomicRmwBinOp, BasicBlock, False, True}
 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};
@@ -25,6 +26,7 @@ use rustc_target::abi::{self, call::FnAbi, Align, Size, WrappingRange};
 use rustc_target::spec::{HasTargetSpec, SanitizerSet, Target};
 use smallvec::SmallVec;
 use std::borrow::Cow;
+use std::ffi::CStr;
 use std::iter;
 use std::ops::Deref;
 use std::ptr;
@@ -44,10 +46,13 @@ impl Drop for Builder<'_, '_, '_> {
     }
 }
 
+// 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 = c"".as_ptr();
+const UNNAMED: *const c_char = EMPTY_C_STR.as_ptr();
 
 impl<'ll, 'tcx> BackendTypes for Builder<'_, 'll, 'tcx> {
     type Value = <CodegenCx<'ll, 'tcx> as BackendTypes>::Value;
@@ -1002,13 +1007,14 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
     }
 
     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,
-                c"cleanuppad".as_ptr(),
+                name.as_ptr(),
             )
         };
         Funclet::new(ret.expect("LLVM does not have support for cleanuppad"))
@@ -1022,13 +1028,14 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
     }
 
     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,
-                c"catchpad".as_ptr(),
+                name.as_ptr(),
             )
         };
         Funclet::new(ret.expect("LLVM does not have support for catchpad"))
@@ -1040,13 +1047,14 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
         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,
-                c"catchswitch".as_ptr(),
+                name.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 2087754c66b..df52f50f86f 100644
--- a/compiler/rustc_codegen_llvm/src/consts.rs
+++ b/compiler/rustc_codegen_llvm/src/consts.rs
@@ -8,6 +8,7 @@ use crate::llvm::{self, True};
 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};
@@ -481,9 +482,9 @@ impl<'ll> StaticMethods for CodegenCx<'ll, '_> {
                             .all(|&byte| byte == 0);
 
                     let sect_name = if all_bytes_are_zero {
-                        c"__DATA,__thread_bss"
+                        cstr!("__DATA,__thread_bss")
                     } else {
-                        c"__DATA,__thread_data"
+                        cstr!("__DATA,__thread_data")
                     };
                     llvm::LLVMSetSection(g, sect_name.as_ptr());
                 }
@@ -512,7 +513,7 @@ impl<'ll> StaticMethods for CodegenCx<'ll, '_> {
                     let val = llvm::LLVMMetadataAsValue(self.llcx, meta);
                     llvm::LLVMAddNamedMetadataOperand(
                         self.llmod,
-                        c"wasm.custom_sections".as_ptr().cast(),
+                        "wasm.custom_sections\0".as_ptr().cast(),
                         val,
                     );
                 }
diff --git a/compiler/rustc_codegen_llvm/src/context.rs b/compiler/rustc_codegen_llvm/src/context.rs
index 287a22bc9a6..e1e0a442845 100644
--- a/compiler/rustc_codegen_llvm/src/context.rs
+++ b/compiler/rustc_codegen_llvm/src/context.rs
@@ -8,6 +8,7 @@ use crate::llvm_util;
 use crate::type_::Type;
 use crate::value::Value;
 
+use cstr::cstr;
 use rustc_codegen_ssa::base::{wants_msvc_seh, wants_wasm_eh};
 use rustc_codegen_ssa::traits::*;
 use rustc_data_structures::base_n;
@@ -223,42 +224,36 @@ 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() {
-        llvm::LLVMRustAddModuleFlag(
-            llmod,
-            llvm::LLVMModFlagBehavior::Warning,
-            c"RtLibUseGOT".as_ptr().cast(),
-            1,
-        );
+        let avoid_plt = "RtLibUseGOT\0".as_ptr().cast();
+        llvm::LLVMRustAddModuleFlag(llmod, llvm::LLVMModFlagBehavior::Warning, avoid_plt, 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,
-            c"CFI Canonical Jump Tables".as_ptr().cast(),
+            canonical_jump_tables,
             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,
-            c"EnableSplitLTOUnit".as_ptr().cast(),
+            enable_split_lto_unit,
             1,
         );
     }
 
     // Add "kcfi" module flag if KCFI is enabled. (See https://reviews.llvm.org/D119296.)
     if sess.is_sanitizer_kcfi_enabled() {
-        llvm::LLVMRustAddModuleFlag(
-            llmod,
-            llvm::LLVMModFlagBehavior::Override,
-            c"kcfi".as_ptr().cast(),
-            1,
-        );
+        let kcfi = "kcfi\0".as_ptr().cast();
+        llvm::LLVMRustAddModuleFlag(llmod, llvm::LLVMModFlagBehavior::Override, kcfi, 1);
     }
 
     // Control Flow Guard is currently only supported by the MSVC linker on Windows.
@@ -270,7 +265,7 @@ pub unsafe fn create_module<'ll>(
                 llvm::LLVMRustAddModuleFlag(
                     llmod,
                     llvm::LLVMModFlagBehavior::Warning,
-                    c"cfguard".as_ptr() as *const _,
+                    "cfguard\0".as_ptr() as *const _,
                     1,
                 )
             }
@@ -279,7 +274,7 @@ pub unsafe fn create_module<'ll>(
                 llvm::LLVMRustAddModuleFlag(
                     llmod,
                     llvm::LLVMModFlagBehavior::Warning,
-                    c"cfguard".as_ptr() as *const _,
+                    "cfguard\0".as_ptr() as *const _,
                     2,
                 )
             }
@@ -297,26 +292,26 @@ pub unsafe fn create_module<'ll>(
             llvm::LLVMRustAddModuleFlag(
                 llmod,
                 behavior,
-                c"branch-target-enforcement".as_ptr().cast(),
+                "branch-target-enforcement\0".as_ptr().cast(),
                 bti.into(),
             );
             llvm::LLVMRustAddModuleFlag(
                 llmod,
                 behavior,
-                c"sign-return-address".as_ptr().cast(),
+                "sign-return-address\0".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,
-                c"sign-return-address-all".as_ptr().cast(),
+                "sign-return-address-all\0".as_ptr().cast(),
                 pac_opts.leaf.into(),
             );
             llvm::LLVMRustAddModuleFlag(
                 llmod,
                 behavior,
-                c"sign-return-address-with-bkey".as_ptr().cast(),
+                "sign-return-address-with-bkey\0".as_ptr().cast(),
                 u32::from(pac_opts.key == PAuthKey::B),
             );
         } else {
@@ -332,7 +327,7 @@ pub unsafe fn create_module<'ll>(
         llvm::LLVMRustAddModuleFlag(
             llmod,
             llvm::LLVMModFlagBehavior::Override,
-            c"cf-protection-branch".as_ptr().cast(),
+            "cf-protection-branch\0".as_ptr().cast(),
             1,
         )
     }
@@ -340,7 +335,7 @@ pub unsafe fn create_module<'ll>(
         llvm::LLVMRustAddModuleFlag(
             llmod,
             llvm::LLVMModFlagBehavior::Override,
-            c"cf-protection-return".as_ptr().cast(),
+            "cf-protection-return\0".as_ptr().cast(),
             1,
         )
     }
@@ -349,7 +344,7 @@ pub unsafe fn create_module<'ll>(
         llvm::LLVMRustAddModuleFlag(
             llmod,
             llvm::LLVMModFlagBehavior::Error,
-            c"Virtual Function Elim".as_ptr().cast(),
+            "Virtual Function Elim\0".as_ptr().cast(),
             1,
         );
     }
@@ -481,13 +476,14 @@ impl<'ll, 'tcx> CodegenCx<'ll, 'tcx> {
     }
 
     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, c"llvm.metadata".as_ptr());
+            llvm::LLVMSetSection(g, section.as_ptr());
         }
     }
 }
diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/gdb.rs b/compiler/rustc_codegen_llvm/src/debuginfo/gdb.rs
index 8be54b7eb71..37f30917609 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/gdb.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/gdb.rs
@@ -38,6 +38,7 @@ 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.
@@ -70,7 +71,7 @@ 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, c".debug_gdb_scripts".as_ptr().cast());
+            llvm::LLVMSetSection(section_var, section_name.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 4b88ab8a97a..ad07d637106 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs
@@ -20,6 +20,7 @@ use crate::llvm::debuginfo::{
 };
 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::*;
@@ -811,6 +812,7 @@ 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
@@ -847,7 +849,7 @@ pub fn build_compile_unit_di_node<'ll, 'tcx>(
             producer.as_ptr().cast(),
             producer.len(),
             tcx.sess.opts.optimize != config::OptLevel::No,
-            c"".as_ptr().cast(),
+            flags.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
@@ -876,7 +878,8 @@ pub fn build_compile_unit_di_node<'ll, 'tcx>(
             );
             let val = llvm::LLVMMetadataAsValue(debug_context.llcontext, gcov_metadata);
 
-            llvm::LLVMAddNamedMetadataOperand(debug_context.llmod, c"llvm.gcov".as_ptr(), val);
+            let llvm_gcov_ident = cstr!("llvm.gcov");
+            llvm::LLVMAddNamedMetadataOperand(debug_context.llmod, llvm_gcov_ident.as_ptr(), val);
         }
 
         // Insert `llvm.ident` metadata on the wasm targets since that will
@@ -889,7 +892,7 @@ pub fn build_compile_unit_di_node<'ll, 'tcx>(
             );
             llvm::LLVMAddNamedMetadataOperand(
                 debug_context.llmod,
-                c"llvm.ident".as_ptr(),
+                cstr!("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 c2f16cad3fc..0858f6b5f8e 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/mod.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/mod.rs
@@ -113,7 +113,7 @@ impl<'ll, 'tcx> CodegenUnitDebugContext<'ll, 'tcx> {
                 llvm::LLVMRustAddModuleFlag(
                     self.llmod,
                     llvm::LLVMModFlagBehavior::Warning,
-                    c"Dwarf Version".as_ptr().cast(),
+                    "Dwarf Version\0".as_ptr().cast(),
                     dwarf_version,
                 );
             } else {
@@ -121,16 +121,17 @@ impl<'ll, 'tcx> CodegenUnitDebugContext<'ll, 'tcx> {
                 llvm::LLVMRustAddModuleFlag(
                     self.llmod,
                     llvm::LLVMModFlagBehavior::Warning,
-                    c"CodeView".as_ptr().cast(),
+                    "CodeView\0".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,
-                c"Debug Info Version".as_ptr().cast(),
+                ptr.cast(),
                 llvm::LLVMRustDebugMetadataVersion(),
             );
         }
diff --git a/compiler/rustc_codegen_llvm/src/lib.rs b/compiler/rustc_codegen_llvm/src/lib.rs
index 24968e00cc8..24ba28bbc82 100644
--- a/compiler/rustc_codegen_llvm/src/lib.rs
+++ b/compiler/rustc_codegen_llvm/src/lib.rs
@@ -11,7 +11,6 @@
 #![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_lexer/src/lib.rs b/compiler/rustc_lexer/src/lib.rs
index d511d2b1280..29335a8c0f4 100644
--- a/compiler/rustc_lexer/src/lib.rs
+++ b/compiler/rustc_lexer/src/lib.rs
@@ -367,13 +367,6 @@ impl Cursor<'_> {
                 Some(|terminated| Byte { terminated }),
             ),
 
-            // c-string literal, raw c-string literal or identifier.
-            'c' => self.c_or_byte_string(
-                |terminated| CStr { terminated },
-                |n_hashes| RawCStr { n_hashes },
-                None,
-            ),
-
             // Identifier (this should be checked after other variant that can
             // start as identifier).
             c if is_id_start(c) => self.ident_or_unknown_prefix(),
diff --git a/library/std/src/lib.rs b/library/std/src/lib.rs
index da08c018d0e..72b9ad3480b 100644
--- a/library/std/src/lib.rs
+++ b/library/std/src/lib.rs
@@ -241,7 +241,6 @@
 #![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 f8fa81e6ef1..eafd6821f54 100644
--- a/library/std/src/sys/unix/args.rs
+++ b/library/std/src/sys/unix/args.rs
@@ -242,15 +242,13 @@ mod imp {
         let mut res = Vec::new();
 
         unsafe {
-            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(c"NSProcessInfo".as_ptr() as *const libc::c_uchar);
+            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 klass = objc_getClass("NSProcessInfo\0".as_ptr());
             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 9cf5cfcc8d5..fbc7f04ce9a 100644
--- a/library/std/src/sys/unix/fs.rs
+++ b/library/std/src/sys/unix/fs.rs
@@ -1097,7 +1097,7 @@ impl File {
         cfg_has_statx! {
             if let Some(ret) = unsafe { try_statx(
                 fd,
-                c"".as_ptr() as *const c_char,
+                b"\0" as *const _ 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 1b72e21a832..326f1481e19 100644
--- a/library/std/src/sys/unix/mod.rs
+++ b/library/std/src/sys/unix/mod.rs
@@ -1,5 +1,6 @@
 #![allow(missing_docs, nonstandard_style)]
 
+use crate::ffi::CStr;
 use crate::io::ErrorKind;
 
 pub use self::rand::hashmap_random_keys;
@@ -74,7 +75,7 @@ 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(&c"main");
+        thread::Thread::set_name(&CStr::from_bytes_with_nul_unchecked(b"main\0"));
     }
 
     unsafe fn sanitize_standard_fds() {
@@ -121,7 +122,7 @@ pub unsafe fn init(argc: isize, argv: *const *const u8, sigpipe: u8) {
                 if pfd.revents & libc::POLLNVAL == 0 {
                     continue;
                 }
-                if open64(c"/dev/null".as_ptr().cast(), libc::O_RDWR, 0) == -1 {
+                if open64("/dev/null\0".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 +152,7 @@ pub unsafe fn init(argc: isize, argv: *const *const u8, sigpipe: u8) {
             use libc::open64;
             for fd in 0..3 {
                 if libc::fcntl(fd, libc::F_GETFD) == -1 && errno() == libc::EBADF {
-                    if open64(c"/dev/null".as_ptr().cast(), libc::O_RDWR, 0) == -1 {
+                    if open64("/dev/null\0".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 5f316b12b62..640648e8707 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 @@ cfg_if::cfg_if! {
     if #[cfg(target_os = "fuchsia")] {
         // fuchsia doesn't have /dev/null
     } else if #[cfg(target_os = "redox")] {
-        const DEV_NULL: &CStr = c"null:";
+        const DEV_NULL: &str = "null:\0";
     } else if #[cfg(target_os = "vxworks")] {
-        const DEV_NULL: &CStr = c"/null";
+        const DEV_NULL: &str = "/null\0";
     } else {
-        const DEV_NULL: &CStr = c"/dev/null";
+        const DEV_NULL: &str = "/dev/null\0";
     }
 }
 
@@ -474,7 +474,8 @@ impl Stdio {
                 let mut opts = OpenOptions::new();
                 opts.read(readable);
                 opts.write(!readable);
-                let fd = File::open_c(DEV_NULL, &opts)?;
+                let path = unsafe { CStr::from_ptr(DEV_NULL.as_ptr() as *const _) };
+                let fd = File::open_c(&path, &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 893f8b8df3f..4f2d9cf3655 100644
--- a/library/std/src/sys/unix/thread.rs
+++ b/library/std/src/sys/unix/thread.rs
@@ -163,9 +163,10 @@ impl Thread {
     #[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(),
-                c"%s".as_ptr(),
+                cname.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 b1b9e84fce9..d9ccba0e9da 100644
--- a/library/std/src/sys/windows/c.rs
+++ b/library/std/src/sys/windows/c.rs
@@ -321,7 +321,7 @@ 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 = c"kernel32";
+    pub static KERNEL32: &CStr = ansi_str!("kernel32");
 
     // >= Win10 1607
     // https://docs.microsoft.com/en-us/windows/win32/api/processthreadsapi/nf-processthreadsapi-setthreaddescription
@@ -354,7 +354,7 @@ compat_fn_optional! {
 }
 
 compat_fn_with_fallback! {
-    pub static NTDLL: &CStr = c"ntdll";
+    pub static NTDLL: &CStr = ansi_str!("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 649cc4bfdbf..4fe95d41116 100644
--- a/library/std/src/sys/windows/compat.rs
+++ b/library/std/src/sys/windows/compat.rs
@@ -228,9 +228,9 @@ macro_rules! compat_fn_optional {
 /// 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 = c"api-ms-win-core-synch-l1-2-0";
-        const WAIT_ON_ADDRESS: &CStr = c"WaitOnAddress";
-        const WAKE_BY_ADDRESS_SINGLE: &CStr = c"WakeByAddressSingle";
+        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");
 
         // 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 b11c8962203..bcc172b0fae 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::{OsStr, OsString};
+use crate::ffi::{CStr, 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(&c"main");
+    thread::Thread::set_name(&CStr::from_bytes_with_nul_unchecked(b"main\0"));
 }
 
 // SAFETY: must be called only once during runtime cleanup.
diff --git a/src/tools/tidy/src/deps.rs b/src/tools/tidy/src/deps.rs
index 1f6c0b75a09..ecc84c1618c 100644
--- a/src/tools/tidy/src/deps.rs
+++ b/src/tools/tidy/src/deps.rs
@@ -131,6 +131,7 @@ const PERMITTED_RUSTC_DEPENDENCIES: &[&str] = &[
     "crossbeam-epoch",
     "crossbeam-utils",
     "crypto-common",
+    "cstr",
     "datafrog",
     "derive_more",
     "digest",
diff --git a/tests/ui/rfcs/rfc-3348-c-string-literals/basic.rs b/tests/ui/rfcs/rfc-3348-c-string-literals/basic.rs
index e4b07ab8108..3fc5fd481ea 100644
--- a/tests/ui/rfcs/rfc-3348-c-string-literals/basic.rs
+++ b/tests/ui/rfcs/rfc-3348-c-string-literals/basic.rs
@@ -1,4 +1,6 @@
-// run-pass
+// FIXME(c_str_literals): This should be `run-pass`
+// known-bug: #113333
+// edition: 2021
 
 #![feature(c_str_literals)]
 
diff --git a/tests/ui/rfcs/rfc-3348-c-string-literals/basic.stderr b/tests/ui/rfcs/rfc-3348-c-string-literals/basic.stderr
new file mode 100644
index 00000000000..571c319d8c5
--- /dev/null
+++ b/tests/ui/rfcs/rfc-3348-c-string-literals/basic.stderr
@@ -0,0 +1,25 @@
+error: prefix `c` is unknown
+  --> $DIR/basic.rs:8:27
+   |
+LL |     assert_eq!(b"test\0", c"test".to_bytes_with_nul());
+   |                           ^ unknown prefix
+   |
+   = note: prefixed identifiers and literals are reserved since Rust 2021
+help: consider inserting whitespace here
+   |
+LL |     assert_eq!(b"test\0", c "test".to_bytes_with_nul());
+   |                            +
+
+error: no rules expected the token `"test"`
+  --> $DIR/basic.rs:8:28
+   |
+LL |     assert_eq!(b"test\0", c"test".to_bytes_with_nul());
+   |                            -^^^^^
+   |                            |
+   |                            no rules expected this token in macro call
+   |                            help: missing comma here
+   |
+   = note: while trying to match sequence start
+
+error: aborting due to 2 previous errors
+
diff --git a/tests/ui/rfcs/rfc-3348-c-string-literals/edition-2015-2018-lexing.rs b/tests/ui/rfcs/rfc-3348-c-string-literals/edition-2015-2018-lexing.rs
new file mode 100644
index 00000000000..2a4cd600426
--- /dev/null
+++ b/tests/ui/rfcs/rfc-3348-c-string-literals/edition-2015-2018-lexing.rs
@@ -0,0 +1,24 @@
+// Regression test for issue #113235.
+
+// check-pass
+// revisions: edition2015 edition2018
+//[edition2015] edition: 2015
+//[edition2018] edition: 2018
+
+// Make sure that in pre-2021 editions we continue to parse the snippet
+// `c"hello"` as an identifier followed by a (normal) string literal and
+// allow the code below to compile.
+// Prefixes including `c` as used by C string literals are only reserved
+// in edition 2021 and onward.
+//
+// Consider checking out rust-2021/reserved-prefixes-migration.rs as well.
+
+macro_rules! parse {
+    (c $e:expr) => {
+        $e
+    };
+}
+
+fn main() {
+    let _: &'static str = parse!(c"hello");
+}
diff --git a/tests/ui/rfcs/rfc-3348-c-string-literals/gate.rs b/tests/ui/rfcs/rfc-3348-c-string-literals/gate.rs
index b27da26ed23..ddd6d9a25da 100644
--- a/tests/ui/rfcs/rfc-3348-c-string-literals/gate.rs
+++ b/tests/ui/rfcs/rfc-3348-c-string-literals/gate.rs
@@ -1,4 +1,6 @@
 // gate-test-c_str_literals
+// known-bug: #113333
+// edition: 2021
 
 macro_rules! m {
     ($t:tt) => {}
@@ -6,8 +8,8 @@ macro_rules! m {
 
 fn main() {
     c"foo";
-    //~^ ERROR: `c".."` literals are experimental
+    // FIXME(c_str_literals): This should be ``c".."` literals are experimental`
 
     m!(c"test");
-    //~^ ERROR: `c".."` literals are experimental
+    // FIXME(c_str_literals): This should be ``c".."` literals are experimental`
 }
diff --git a/tests/ui/rfcs/rfc-3348-c-string-literals/gate.stderr b/tests/ui/rfcs/rfc-3348-c-string-literals/gate.stderr
index bc0c537aada..8de36ca4a6e 100644
--- a/tests/ui/rfcs/rfc-3348-c-string-literals/gate.stderr
+++ b/tests/ui/rfcs/rfc-3348-c-string-literals/gate.stderr
@@ -1,21 +1,32 @@
-error[E0658]: `c".."` literals are experimental
-  --> $DIR/gate.rs:8:5
+error: prefix `c` is unknown
+  --> $DIR/gate.rs:10:5
    |
 LL |     c"foo";
-   |     ^^^^^^
+   |     ^ unknown prefix
    |
-   = note: see issue #105723 <https://github.com/rust-lang/rust/issues/105723> for more information
-   = help: add `#![feature(c_str_literals)]` to the crate attributes to enable
+   = note: prefixed identifiers and literals are reserved since Rust 2021
+help: consider inserting whitespace here
+   |
+LL |     c "foo";
+   |      +
 
-error[E0658]: `c".."` literals are experimental
-  --> $DIR/gate.rs:11:8
+error: prefix `c` is unknown
+  --> $DIR/gate.rs:13:8
    |
 LL |     m!(c"test");
-   |        ^^^^^^^
+   |        ^ unknown prefix
+   |
+   = note: prefixed identifiers and literals are reserved since Rust 2021
+help: consider inserting whitespace here
    |
-   = note: see issue #105723 <https://github.com/rust-lang/rust/issues/105723> for more information
-   = help: add `#![feature(c_str_literals)]` to the crate attributes to enable
+LL |     m!(c "test");
+   |         +
+
+error: expected one of `!`, `.`, `::`, `;`, `?`, `{`, `}`, or an operator, found `"foo"`
+  --> $DIR/gate.rs:10:6
+   |
+LL |     c"foo";
+   |      ^^^^^ expected one of 8 possible tokens
 
-error: aborting due to 2 previous errors
+error: aborting due to 3 previous errors
 
-For more information about this error, try `rustc --explain E0658`.
diff --git a/tests/ui/rfcs/rfc-3348-c-string-literals/no-nuls.rs b/tests/ui/rfcs/rfc-3348-c-string-literals/no-nuls.rs
index 7bc6097f124..96945f125da 100644
--- a/tests/ui/rfcs/rfc-3348-c-string-literals/no-nuls.rs
+++ b/tests/ui/rfcs/rfc-3348-c-string-literals/no-nuls.rs
Binary files differdiff --git a/tests/ui/rfcs/rfc-3348-c-string-literals/no-nuls.stderr b/tests/ui/rfcs/rfc-3348-c-string-literals/no-nuls.stderr
index ff9006f6f97..2226c7aa6a9 100644
--- a/tests/ui/rfcs/rfc-3348-c-string-literals/no-nuls.stderr
+++ b/tests/ui/rfcs/rfc-3348-c-string-literals/no-nuls.stderr
Binary files differdiff --git a/tests/ui/rfcs/rfc-3348-c-string-literals/non-ascii.rs b/tests/ui/rfcs/rfc-3348-c-string-literals/non-ascii.rs
index 82e8e2090d7..066505c23df 100644
--- a/tests/ui/rfcs/rfc-3348-c-string-literals/non-ascii.rs
+++ b/tests/ui/rfcs/rfc-3348-c-string-literals/non-ascii.rs
@@ -1,4 +1,6 @@
-// run-pass
+// FIXME(c_str_literals): This should be `run-pass`
+// known-bug: #113333
+// edition: 2021
 
 #![feature(c_str_literals)]
 
diff --git a/tests/ui/rfcs/rfc-3348-c-string-literals/non-ascii.stderr b/tests/ui/rfcs/rfc-3348-c-string-literals/non-ascii.stderr
new file mode 100644
index 00000000000..47361fb61d2
--- /dev/null
+++ b/tests/ui/rfcs/rfc-3348-c-string-literals/non-ascii.stderr
@@ -0,0 +1,38 @@
+error: prefix `c` is unknown
+  --> $DIR/non-ascii.rs:9:9
+   |
+LL |         c"\xEF\x80🦀\u{1F980}".to_bytes_with_nul(),
+   |         ^ unknown prefix
+   |
+   = note: prefixed identifiers and literals are reserved since Rust 2021
+help: consider inserting whitespace here
+   |
+LL |         c "\xEF\x80🦀\u{1F980}".to_bytes_with_nul(),
+   |          +
+
+error: out of range hex escape
+  --> $DIR/non-ascii.rs:9:11
+   |
+LL |         c"\xEF\x80🦀\u{1F980}".to_bytes_with_nul(),
+   |           ^^^^ must be a character in the range [\x00-\x7f]
+
+error: out of range hex escape
+  --> $DIR/non-ascii.rs:9:15
+   |
+LL |         c"\xEF\x80🦀\u{1F980}".to_bytes_with_nul(),
+   |               ^^^^ must be a character in the range [\x00-\x7f]
+
+error: no rules expected the token `"\xEF\x80🦀\u{1F980}"`
+  --> $DIR/non-ascii.rs:9:10
+   |
+LL |         c"\xEF\x80🦀\u{1F980}".to_bytes_with_nul(),
+   |          -^^^^^^^^^^^^^^^^^^^^
+   |          |
+   |          no rules expected this token in macro call
+   |          help: missing comma here
+   |
+note: while trying to match `,`
+  --> $SRC_DIR/core/src/macros/mod.rs:LL:COL
+
+error: aborting due to 4 previous errors
+