Rollup merge of #132260 - Zalathar:type-safe-cast, r=compiler-errors

cg_llvm: Use a type-safe helper to cast `&str` and `&[u8]` to `*const c_char`

In `rustc_codegen_llvm` there are many uses of `.as_ptr().cast()` to convert a string or byte-slice to `*const c_char`, which then gets passed through FFI.

This works, but is fragile, because there's nothing constraining the pointer cast to actually be from `u8` to `c_char`. If the original value changes to something else that has an `as_ptr` method, or the context changes to expect something other than `c_char`, the cast will silently do the wrong thing.

By making the cast more explicit via a helper method, we can be sure that it will either perform the intended cast, or fail at compile time.

17 files changed, 110 insertions, 87 deletions

diff --git a/compiler/rustc_codegen_llvm/src/allocator.rs b/compiler/rustc_codegen_llvm/src/allocator.rs
index 55ee6dcdf87..a2e6c7eb856 100644
--- a/compiler/rustc_codegen_llvm/src/allocator.rs
+++ b/compiler/rustc_codegen_llvm/src/allocator.rs
@@ -7,6 +7,7 @@ use rustc_middle::bug;
 use rustc_middle::ty::TyCtxt;
 use rustc_session::config::{DebugInfo, OomStrategy};
 
+use crate::common::AsCCharPtr;
 use crate::llvm::{self, Context, False, Module, True, Type};
 use crate::{ModuleLlvm, attributes, debuginfo};
 
@@ -76,14 +77,14 @@ pub(crate) unsafe fn codegen(
     unsafe {
         // __rust_alloc_error_handler_should_panic
         let name = OomStrategy::SYMBOL;
-        let ll_g = llvm::LLVMRustGetOrInsertGlobal(llmod, name.as_ptr().cast(), name.len(), i8);
+        let ll_g = llvm::LLVMRustGetOrInsertGlobal(llmod, name.as_c_char_ptr(), name.len(), i8);
         llvm::set_visibility(ll_g, llvm::Visibility::from_generic(tcx.sess.default_visibility()));
         let val = tcx.sess.opts.unstable_opts.oom.should_panic();
         let llval = llvm::LLVMConstInt(i8, val as u64, False);
         llvm::LLVMSetInitializer(ll_g, llval);
 
         let name = NO_ALLOC_SHIM_IS_UNSTABLE;
-        let ll_g = llvm::LLVMRustGetOrInsertGlobal(llmod, name.as_ptr().cast(), name.len(), i8);
+        let ll_g = llvm::LLVMRustGetOrInsertGlobal(llmod, name.as_c_char_ptr(), name.len(), i8);
         llvm::set_visibility(ll_g, llvm::Visibility::from_generic(tcx.sess.default_visibility()));
         let llval = llvm::LLVMConstInt(i8, 0, False);
         llvm::LLVMSetInitializer(ll_g, llval);
@@ -115,7 +116,7 @@ fn create_wrapper_function(
         );
         let llfn = llvm::LLVMRustGetOrInsertFunction(
             llmod,
-            from_name.as_ptr().cast(),
+            from_name.as_c_char_ptr(),
             from_name.len(),
             ty,
         );
@@ -137,7 +138,7 @@ fn create_wrapper_function(
         }
 
         let callee =
-            llvm::LLVMRustGetOrInsertFunction(llmod, to_name.as_ptr().cast(), to_name.len(), ty);
+            llvm::LLVMRustGetOrInsertFunction(llmod, to_name.as_c_char_ptr(), to_name.len(), ty);
         if let Some(no_return) = no_return {
             // -> ! DIFlagNoReturn
             attributes::apply_to_llfn(callee, llvm::AttributePlace::Function, &[no_return]);
diff --git a/compiler/rustc_codegen_llvm/src/asm.rs b/compiler/rustc_codegen_llvm/src/asm.rs
index d1d7d0cf4ce..3c30822a2e2 100644
--- a/compiler/rustc_codegen_llvm/src/asm.rs
+++ b/compiler/rustc_codegen_llvm/src/asm.rs
@@ -15,7 +15,7 @@ use smallvec::SmallVec;
 use tracing::debug;
 
 use crate::builder::Builder;
-use crate::common::Funclet;
+use crate::common::{AsCCharPtr, Funclet};
 use crate::context::CodegenCx;
 use crate::type_::Type;
 use crate::type_of::LayoutLlvmExt;
@@ -420,7 +420,7 @@ impl<'tcx> AsmCodegenMethods<'tcx> for CodegenCx<'_, 'tcx> {
         unsafe {
             llvm::LLVMAppendModuleInlineAsm(
                 self.llmod,
-                template_str.as_ptr().cast(),
+                template_str.as_c_char_ptr(),
                 template_str.len(),
             );
         }
@@ -458,14 +458,14 @@ pub(crate) fn inline_asm_call<'ll>(
     let fty = bx.cx.type_func(&argtys, output);
     unsafe {
         // Ask LLVM to verify that the constraints are well-formed.
-        let constraints_ok = llvm::LLVMRustInlineAsmVerify(fty, cons.as_ptr().cast(), cons.len());
+        let constraints_ok = llvm::LLVMRustInlineAsmVerify(fty, cons.as_c_char_ptr(), cons.len());
         debug!("constraint verification result: {:?}", constraints_ok);
         if constraints_ok {
             let v = llvm::LLVMRustInlineAsm(
                 fty,
-                asm.as_ptr().cast(),
+                asm.as_c_char_ptr(),
                 asm.len(),
-                cons.as_ptr().cast(),
+                cons.as_c_char_ptr(),
                 cons.len(),
                 volatile,
                 alignstack,
diff --git a/compiler/rustc_codegen_llvm/src/back/lto.rs b/compiler/rustc_codegen_llvm/src/back/lto.rs
index 1f7a923dd2c..79527d1beb3 100644
--- a/compiler/rustc_codegen_llvm/src/back/lto.rs
+++ b/compiler/rustc_codegen_llvm/src/back/lto.rs
@@ -25,6 +25,7 @@ use tracing::{debug, info};
 use crate::back::write::{
     self, CodegenDiagnosticsStage, DiagnosticHandlers, bitcode_section_name, save_temp_bitcode,
 };
+use crate::common::AsCCharPtr;
 use crate::errors::{
     DynamicLinkingWithLTO, LlvmError, LtoBitcodeFromRlib, LtoDisallowed, LtoDylib, LtoProcMacro,
 };
@@ -604,7 +605,7 @@ pub(crate) fn run_pass_manager(
     unsafe {
         if !llvm::LLVMRustHasModuleFlag(
             module.module_llvm.llmod(),
-            "LTOPostLink".as_ptr().cast(),
+            "LTOPostLink".as_c_char_ptr(),
             11,
         ) {
             llvm::LLVMRustAddModuleFlagU32(
diff --git a/compiler/rustc_codegen_llvm/src/back/write.rs b/compiler/rustc_codegen_llvm/src/back/write.rs
index bf77fc56d08..e68ba96f14f 100644
--- a/compiler/rustc_codegen_llvm/src/back/write.rs
+++ b/compiler/rustc_codegen_llvm/src/back/write.rs
@@ -34,6 +34,7 @@ use crate::back::owned_target_machine::OwnedTargetMachine;
 use crate::back::profiling::{
     LlvmSelfProfiler, selfprofile_after_pass_callback, selfprofile_before_pass_callback,
 };
+use crate::common::AsCCharPtr;
 use crate::errors::{
     CopyBitcode, FromLlvmDiag, FromLlvmOptimizationDiag, LlvmError, UnknownCompression,
     WithLlvmError, WriteBytecode,
@@ -596,9 +597,9 @@ pub(crate) unsafe fn llvm_optimize(
             llvm_selfprofiler,
             selfprofile_before_pass_callback,
             selfprofile_after_pass_callback,
-            extra_passes.as_ptr().cast(),
+            extra_passes.as_c_char_ptr(),
             extra_passes.len(),
-            llvm_plugins.as_ptr().cast(),
+            llvm_plugins.as_c_char_ptr(),
             llvm_plugins.len(),
         )
     };
@@ -1042,7 +1043,7 @@ unsafe fn embed_bitcode(
             llvm::LLVMSetInitializer(llglobal, llconst);
 
             let section = bitcode_section_name(cgcx);
-            llvm::LLVMSetSection(llglobal, section.as_ptr().cast());
+            llvm::LLVMSetSection(llglobal, section.as_c_char_ptr());
             llvm::set_linkage(llglobal, llvm::Linkage::PrivateLinkage);
             llvm::LLVMSetGlobalConstant(llglobal, llvm::True);
 
@@ -1066,9 +1067,9 @@ unsafe fn embed_bitcode(
             // We need custom section flags, so emit module-level inline assembly.
             let section_flags = if cgcx.is_pe_coff { "n" } else { "e" };
             let asm = create_section_with_flags_asm(".llvmbc", section_flags, bitcode);
-            llvm::LLVMAppendModuleInlineAsm(llmod, asm.as_ptr().cast(), asm.len());
+            llvm::LLVMAppendModuleInlineAsm(llmod, asm.as_c_char_ptr(), asm.len());
             let asm = create_section_with_flags_asm(".llvmcmd", section_flags, cmdline.as_bytes());
-            llvm::LLVMAppendModuleInlineAsm(llmod, asm.as_ptr().cast(), asm.len());
+            llvm::LLVMAppendModuleInlineAsm(llmod, asm.as_c_char_ptr(), asm.len());
         }
     }
 }
diff --git a/compiler/rustc_codegen_llvm/src/common.rs b/compiler/rustc_codegen_llvm/src/common.rs
index ff47eb944dd..29adc616ee2 100644
--- a/compiler/rustc_codegen_llvm/src/common.rs
+++ b/compiler/rustc_codegen_llvm/src/common.rs
@@ -392,3 +392,21 @@ pub(crate) fn get_dllimport<'tcx>(
     tcx.native_library(id)
         .and_then(|lib| lib.dll_imports.iter().find(|di| di.name.as_str() == name))
 }
+
+/// Extension trait for explicit casts to `*const c_char`.
+pub(crate) trait AsCCharPtr {
+    /// Equivalent to `self.as_ptr().cast()`, but only casts to `*const c_char`.
+    fn as_c_char_ptr(&self) -> *const c_char;
+}
+
+impl AsCCharPtr for str {
+    fn as_c_char_ptr(&self) -> *const c_char {
+        self.as_ptr().cast()
+    }
+}
+
+impl AsCCharPtr for [u8] {
+    fn as_c_char_ptr(&self) -> *const c_char {
+        self.as_ptr().cast()
+    }
+}
diff --git a/compiler/rustc_codegen_llvm/src/consts.rs b/compiler/rustc_codegen_llvm/src/consts.rs
index 1e3abcfd1af..21d996ef460 100644
--- a/compiler/rustc_codegen_llvm/src/consts.rs
+++ b/compiler/rustc_codegen_llvm/src/consts.rs
@@ -19,7 +19,7 @@ use rustc_target::abi::{
 };
 use tracing::{debug, instrument, trace};
 
-use crate::common::CodegenCx;
+use crate::common::{AsCCharPtr, CodegenCx};
 use crate::errors::{
     InvalidMinimumAlignmentNotPowerOfTwo, InvalidMinimumAlignmentTooLarge, SymbolAlreadyDefined,
 };
@@ -400,7 +400,7 @@ impl<'ll> CodegenCx<'ll, '_> {
 
                 let new_g = llvm::LLVMRustGetOrInsertGlobal(
                     self.llmod,
-                    name.as_ptr().cast(),
+                    name.as_c_char_ptr(),
                     name.len(),
                     val_llty,
                 );
@@ -451,7 +451,7 @@ impl<'ll> CodegenCx<'ll, '_> {
                 if let Some(section) = attrs.link_section {
                     let section = llvm::LLVMMDStringInContext2(
                         self.llcx,
-                        section.as_str().as_ptr().cast(),
+                        section.as_str().as_c_char_ptr(),
                         section.as_str().len(),
                     );
                     assert!(alloc.provenance().ptrs().is_empty());
@@ -462,7 +462,7 @@ impl<'ll> CodegenCx<'ll, '_> {
                     let bytes =
                         alloc.inspect_with_uninit_and_ptr_outside_interpreter(0..alloc.len());
                     let alloc =
-                        llvm::LLVMMDStringInContext2(self.llcx, bytes.as_ptr().cast(), bytes.len());
+                        llvm::LLVMMDStringInContext2(self.llcx, bytes.as_c_char_ptr(), bytes.len());
                     let data = [section, alloc];
                     let meta = llvm::LLVMMDNodeInContext2(self.llcx, data.as_ptr(), data.len());
                     let val = llvm::LLVMMetadataAsValue(self.llcx, meta);
diff --git a/compiler/rustc_codegen_llvm/src/context.rs b/compiler/rustc_codegen_llvm/src/context.rs
index 067028a16ff..1a2197248b1 100644
--- a/compiler/rustc_codegen_llvm/src/context.rs
+++ b/compiler/rustc_codegen_llvm/src/context.rs
@@ -29,6 +29,7 @@ use smallvec::SmallVec;
 
 use crate::back::write::to_llvm_code_model;
 use crate::callee::get_fn;
+use crate::common::AsCCharPtr;
 use crate::debuginfo::metadata::apply_vcall_visibility_metadata;
 use crate::llvm::{Metadata, MetadataType};
 use crate::type_::Type;
@@ -231,7 +232,7 @@ pub(crate) unsafe fn create_module<'ll>(
     // If we're normalizing integers with CFI, ensure LLVM generated functions do the same.
     // See https://github.com/llvm/llvm-project/pull/104826
     if sess.is_sanitizer_cfi_normalize_integers_enabled() {
-        let cfi_normalize_integers = c"cfi-normalize-integers".as_ptr().cast();
+        let cfi_normalize_integers = c"cfi-normalize-integers".as_ptr();
         unsafe {
             llvm::LLVMRustAddModuleFlagU32(
                 llmod,
@@ -268,7 +269,7 @@ pub(crate) unsafe fn create_module<'ll>(
         let pfe =
             PatchableFunctionEntry::from_config(sess.opts.unstable_opts.patchable_function_entry);
         if pfe.prefix() > 0 {
-            let kcfi_offset = c"kcfi-offset".as_ptr().cast();
+            let kcfi_offset = c"kcfi-offset".as_ptr();
             unsafe {
                 llvm::LLVMRustAddModuleFlagU32(
                     llmod,
@@ -429,7 +430,7 @@ pub(crate) unsafe fn create_module<'ll>(
     let name_metadata = unsafe {
         llvm::LLVMMDStringInContext2(
             llcx,
-            rustc_producer.as_ptr().cast(),
+            rustc_producer.as_c_char_ptr(),
             rustc_producer.as_bytes().len(),
         )
     };
@@ -453,7 +454,7 @@ pub(crate) unsafe fn create_module<'ll>(
                 llmod,
                 llvm::LLVMModFlagBehavior::Error,
                 c"target-abi".as_ptr(),
-                llvm_abiname.as_ptr().cast(),
+                llvm_abiname.as_c_char_ptr(),
                 llvm_abiname.len(),
             );
         }
@@ -474,7 +475,7 @@ pub(crate) unsafe fn create_module<'ll>(
             // We already checked this during option parsing
             _ => unreachable!(),
         };
-        unsafe { llvm::LLVMRustAddModuleFlagU32(llmod, behavior, key.as_ptr().cast(), *value) }
+        unsafe { llvm::LLVMRustAddModuleFlagU32(llmod, behavior, key.as_c_char_ptr(), *value) }
     }
 
     llmod
diff --git a/compiler/rustc_codegen_llvm/src/coverageinfo/mod.rs b/compiler/rustc_codegen_llvm/src/coverageinfo/mod.rs
index c6b2a623ea6..a298ed86276 100644
--- a/compiler/rustc_codegen_llvm/src/coverageinfo/mod.rs
+++ b/compiler/rustc_codegen_llvm/src/coverageinfo/mod.rs
@@ -14,7 +14,7 @@ use rustc_target::abi::Size;
 use tracing::{debug, instrument};
 
 use crate::builder::Builder;
-use crate::common::CodegenCx;
+use crate::common::{AsCCharPtr, CodegenCx};
 use crate::coverageinfo::map_data::FunctionCoverageCollector;
 use crate::llvm;
 
@@ -236,7 +236,7 @@ fn create_pgo_func_name_var<'ll, 'tcx>(
     unsafe {
         llvm::LLVMRustCoverageCreatePGOFuncNameVar(
             llfn,
-            mangled_fn_name.as_ptr().cast(),
+            mangled_fn_name.as_c_char_ptr(),
             mangled_fn_name.len(),
         )
     }
@@ -248,7 +248,7 @@ pub(crate) fn write_filenames_section_to_buffer<'a>(
 ) {
     let (pointers, lengths) = filenames
         .into_iter()
-        .map(|s: &str| (s.as_ptr().cast(), s.len()))
+        .map(|s: &str| (s.as_c_char_ptr(), s.len()))
         .unzip::<_, _, Vec<_>, Vec<_>>();
 
     unsafe {
@@ -291,7 +291,7 @@ pub(crate) fn write_mapping_to_buffer(
 }
 
 pub(crate) fn hash_bytes(bytes: &[u8]) -> u64 {
-    unsafe { llvm::LLVMRustCoverageHashByteArray(bytes.as_ptr().cast(), bytes.len()) }
+    unsafe { llvm::LLVMRustCoverageHashByteArray(bytes.as_c_char_ptr(), bytes.len()) }
 }
 
 pub(crate) fn mapping_version() -> u32 {
diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs b/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs
index 15d441a986d..9064cfaeb29 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs
@@ -32,7 +32,7 @@ use super::type_names::{compute_debuginfo_type_name, compute_debuginfo_vtable_na
 use super::utils::{
     DIB, create_DIArray, debug_context, get_namespace_for_item, is_node_local_to_unit,
 };
-use crate::common::CodegenCx;
+use crate::common::{AsCCharPtr, CodegenCx};
 use crate::debuginfo::metadata::type_map::build_type_with_children;
 use crate::debuginfo::utils::{WidePtrKind, wide_pointer_kind};
 use crate::llvm::debuginfo::{
@@ -190,7 +190,7 @@ fn build_pointer_or_reference_di_node<'ll, 'tcx>(
                     data_layout.pointer_size.bits(),
                     data_layout.pointer_align.abi.bits() as u32,
                     0, // Ignore DWARF address space.
-                    ptr_type_debuginfo_name.as_ptr().cast(),
+                    ptr_type_debuginfo_name.as_c_char_ptr(),
                     ptr_type_debuginfo_name.len(),
                 )
             };
@@ -348,7 +348,7 @@ fn build_subroutine_type_di_node<'ll, 'tcx>(
             size,
             align,
             0, // Ignore DWARF address space.
-            name.as_ptr().cast(),
+            name.as_c_char_ptr(),
             name.len(),
         )
     };
@@ -518,7 +518,7 @@ fn recursion_marker_type_di_node<'ll, 'tcx>(cx: &CodegenCx<'ll, 'tcx>) -> &'ll D
             let name = "<recur_type>";
             llvm::LLVMRustDIBuilderCreateBasicType(
                 DIB(cx),
-                name.as_ptr().cast(),
+                name.as_c_char_ptr(),
                 name.len(),
                 cx.tcx.data_layout.pointer_size.bits(),
                 DW_ATE_unsigned,
@@ -640,14 +640,14 @@ pub(crate) fn file_metadata<'ll>(cx: &CodegenCx<'ll, '_>, source_file: &SourceFi
         unsafe {
             llvm::LLVMRustDIBuilderCreateFile(
                 DIB(cx),
-                file_name.as_ptr().cast(),
+                file_name.as_c_char_ptr(),
                 file_name.len(),
-                directory.as_ptr().cast(),
+                directory.as_c_char_ptr(),
                 directory.len(),
                 hash_kind,
-                hash_value.as_ptr().cast(),
+                hash_value.as_c_char_ptr(),
                 hash_value.len(),
-                source.map_or(ptr::null(), |x| x.as_ptr().cast()),
+                source.map_or(ptr::null(), |x| x.as_c_char_ptr()),
                 source.map_or(0, |x| x.len()),
             )
         }
@@ -662,12 +662,12 @@ fn unknown_file_metadata<'ll>(cx: &CodegenCx<'ll, '_>) -> &'ll DIFile {
 
         llvm::LLVMRustDIBuilderCreateFile(
             DIB(cx),
-            file_name.as_ptr().cast(),
+            file_name.as_c_char_ptr(),
             file_name.len(),
-            directory.as_ptr().cast(),
+            directory.as_c_char_ptr(),
             directory.len(),
             llvm::ChecksumKind::None,
-            hash_value.as_ptr().cast(),
+            hash_value.as_c_char_ptr(),
             hash_value.len(),
             ptr::null(),
             0,
@@ -788,7 +788,7 @@ fn build_basic_type_di_node<'ll, 'tcx>(
     let ty_di_node = unsafe {
         llvm::LLVMRustDIBuilderCreateBasicType(
             DIB(cx),
-            name.as_ptr().cast(),
+            name.as_c_char_ptr(),
             name.len(),
             cx.size_of(t).bits(),
             encoding,
@@ -810,7 +810,7 @@ fn build_basic_type_di_node<'ll, 'tcx>(
         llvm::LLVMRustDIBuilderCreateTypedef(
             DIB(cx),
             ty_di_node,
-            typedef_name.as_ptr().cast(),
+            typedef_name.as_c_char_ptr(),
             typedef_name.len(),
             unknown_file_metadata(cx),
             0,
@@ -861,7 +861,7 @@ fn build_param_type_di_node<'ll, 'tcx>(
         di_node: unsafe {
             llvm::LLVMRustDIBuilderCreateBasicType(
                 DIB(cx),
-                name.as_ptr().cast(),
+                name.as_c_char_ptr(),
                 name.len(),
                 Size::ZERO.bits(),
                 DW_ATE_unsigned,
@@ -948,9 +948,9 @@ pub(crate) fn build_compile_unit_di_node<'ll, 'tcx>(
     unsafe {
         let compile_unit_file = llvm::LLVMRustDIBuilderCreateFile(
             debug_context.builder,
-            name_in_debuginfo.as_ptr().cast(),
+            name_in_debuginfo.as_c_char_ptr(),
             name_in_debuginfo.len(),
-            work_dir.as_ptr().cast(),
+            work_dir.as_c_char_ptr(),
             work_dir.len(),
             llvm::ChecksumKind::None,
             ptr::null(),
@@ -963,7 +963,7 @@ pub(crate) fn build_compile_unit_di_node<'ll, 'tcx>(
             debug_context.builder,
             DW_LANG_RUST,
             compile_unit_file,
-            producer.as_ptr().cast(),
+            producer.as_c_char_ptr(),
             producer.len(),
             tcx.sess.opts.optimize != config::OptLevel::No,
             c"".as_ptr(),
@@ -971,7 +971,7 @@ pub(crate) fn build_compile_unit_di_node<'ll, 'tcx>(
             // 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
             // output(s).
-            split_name.as_ptr().cast(),
+            split_name.as_c_char_ptr(),
             split_name.len(),
             kind,
             0,
@@ -1022,7 +1022,7 @@ fn build_field_di_node<'ll, 'tcx>(
         llvm::LLVMRustDIBuilderCreateMemberType(
             DIB(cx),
             owner,
-            name.as_ptr().cast(),
+            name.as_c_char_ptr(),
             name.len(),
             unknown_file_metadata(cx),
             UNKNOWN_LINE_NUMBER,
@@ -1306,7 +1306,7 @@ fn build_generic_type_param_di_nodes<'ll, 'tcx>(
                             llvm::LLVMRustDIBuilderCreateTemplateTypeParameter(
                                 DIB(cx),
                                 None,
-                                name.as_ptr().cast(),
+                                name.as_c_char_ptr(),
                                 name.len(),
                                 actual_type_di_node,
                             )
@@ -1382,9 +1382,9 @@ pub(crate) fn build_global_var_di_node<'ll>(
         llvm::LLVMRustDIBuilderCreateStaticVariable(
             DIB(cx),
             Some(var_scope),
-            var_name.as_ptr().cast(),
+            var_name.as_c_char_ptr(),
             var_name.len(),
-            linkage_name.as_ptr().cast(),
+            linkage_name.as_c_char_ptr(),
             linkage_name.len(),
             file_metadata,
             line_number,
@@ -1602,9 +1602,9 @@ pub(crate) fn create_vtable_di_node<'ll, 'tcx>(
         llvm::LLVMRustDIBuilderCreateStaticVariable(
             DIB(cx),
             NO_SCOPE_METADATA,
-            vtable_name.as_ptr().cast(),
+            vtable_name.as_c_char_ptr(),
             vtable_name.len(),
-            linkage_name.as_ptr().cast(),
+            linkage_name.as_c_char_ptr(),
             linkage_name.len(),
             unknown_file_metadata(cx),
             UNKNOWN_LINE_NUMBER,
diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/metadata/enums/cpp_like.rs b/compiler/rustc_codegen_llvm/src/debuginfo/metadata/enums/cpp_like.rs
index 966788cf32f..5385d3a9212 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/metadata/enums/cpp_like.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/metadata/enums/cpp_like.rs
@@ -11,7 +11,7 @@ use rustc_middle::ty::{self, AdtDef, CoroutineArgs, CoroutineArgsExt, Ty};
 use rustc_target::abi::{Align, Endian, Size, TagEncoding, VariantIdx, Variants};
 use smallvec::smallvec;
 
-use crate::common::CodegenCx;
+use crate::common::{AsCCharPtr, CodegenCx};
 use crate::debuginfo::metadata::enums::DiscrResult;
 use crate::debuginfo::metadata::type_map::{self, Stub, UniqueTypeId};
 use crate::debuginfo::metadata::{
@@ -359,7 +359,7 @@ fn build_single_variant_union_fields<'ll, 'tcx>(
             llvm::LLVMRustDIBuilderCreateStaticMemberType(
                 DIB(cx),
                 enum_type_di_node,
-                TAG_FIELD_NAME.as_ptr().cast(),
+                TAG_FIELD_NAME.as_c_char_ptr(),
                 TAG_FIELD_NAME.len(),
                 unknown_file_metadata(cx),
                 UNKNOWN_LINE_NUMBER,
@@ -537,7 +537,7 @@ fn build_variant_struct_wrapper_type_di_node<'ll, 'tcx>(
                     llvm::LLVMRustDIBuilderCreateStaticMemberType(
                         DIB(cx),
                         wrapper_struct_type_di_node,
-                        name.as_ptr().cast(),
+                        name.as_c_char_ptr(),
                         name.len(),
                         unknown_file_metadata(cx),
                         UNKNOWN_LINE_NUMBER,
@@ -785,7 +785,7 @@ fn build_union_fields_for_direct_tag_enum_or_coroutine<'ll, 'tcx>(
             llvm::LLVMRustDIBuilderCreateMemberType(
                 DIB(cx),
                 enum_type_di_node,
-                field_name.as_ptr().cast(),
+                field_name.as_c_char_ptr(),
                 field_name.len(),
                 file_di_node,
                 line_number,
diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/metadata/enums/mod.rs b/compiler/rustc_codegen_llvm/src/debuginfo/metadata/enums/mod.rs
index fe1634146ff..4c848027b55 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/metadata/enums/mod.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/metadata/enums/mod.rs
@@ -13,7 +13,7 @@ use rustc_target::abi::{FieldIdx, TagEncoding, VariantIdx, Variants};
 
 use super::type_map::{DINodeCreationResult, UniqueTypeId};
 use super::{SmallVec, size_and_align_of};
-use crate::common::CodegenCx;
+use crate::common::{AsCCharPtr, CodegenCx};
 use crate::debuginfo::metadata::type_map::{self, Stub};
 use crate::debuginfo::metadata::{
     UNKNOWN_LINE_NUMBER, build_field_di_node, build_generic_type_param_di_nodes, type_di_node,
@@ -106,7 +106,7 @@ fn build_enumeration_type_di_node<'ll, 'tcx>(
             let value = [value as u64, (value >> 64) as u64];
             Some(llvm::LLVMRustDIBuilderCreateEnumerator(
                 DIB(cx),
-                name.as_ptr().cast(),
+                name.as_c_char_ptr(),
                 name.len(),
                 value.as_ptr(),
                 size.bits() as libc::c_uint,
@@ -119,7 +119,7 @@ fn build_enumeration_type_di_node<'ll, 'tcx>(
         llvm::LLVMRustDIBuilderCreateEnumerationType(
             DIB(cx),
             containing_scope,
-            type_name.as_ptr().cast(),
+            type_name.as_c_char_ptr(),
             type_name.len(),
             unknown_file_metadata(cx),
             UNKNOWN_LINE_NUMBER,
diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/metadata/enums/native.rs b/compiler/rustc_codegen_llvm/src/debuginfo/metadata/enums/native.rs
index 5e7dbdd921a..b7400c5aeb2 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/metadata/enums/native.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/metadata/enums/native.rs
@@ -10,7 +10,7 @@ use rustc_middle::ty::{self};
 use rustc_target::abi::{Size, TagEncoding, VariantIdx, Variants};
 use smallvec::smallvec;
 
-use crate::common::CodegenCx;
+use crate::common::{AsCCharPtr, CodegenCx};
 use crate::debuginfo::metadata::type_map::{self, Stub, StubInfo, UniqueTypeId};
 use crate::debuginfo::metadata::{
     DINodeCreationResult, NO_GENERICS, SmallVec, UNKNOWN_LINE_NUMBER, file_metadata,
@@ -244,7 +244,7 @@ fn build_enum_variant_part_di_node<'ll, 'tcx>(
             llvm::LLVMRustDIBuilderCreateVariantPart(
                 DIB(cx),
                 enum_type_di_node,
-                variant_part_name.as_ptr().cast(),
+                variant_part_name.as_c_char_ptr(),
                 variant_part_name.len(),
                 unknown_file_metadata(cx),
                 UNKNOWN_LINE_NUMBER,
@@ -253,7 +253,7 @@ fn build_enum_variant_part_di_node<'ll, 'tcx>(
                 DIFlags::FlagZero,
                 tag_member_di_node,
                 create_DIArray(DIB(cx), &[]),
-                variant_part_unique_type_id_str.as_ptr().cast(),
+                variant_part_unique_type_id_str.as_c_char_ptr(),
                 variant_part_unique_type_id_str.len(),
             )
         },
@@ -327,7 +327,7 @@ fn build_discr_member_di_node<'ll, 'tcx>(
                 Some(llvm::LLVMRustDIBuilderCreateMemberType(
                     DIB(cx),
                     containing_scope,
-                    tag_name.as_ptr().cast(),
+                    tag_name.as_c_char_ptr(),
                     tag_name.len(),
                     unknown_file_metadata(cx),
                     UNKNOWN_LINE_NUMBER,
@@ -399,7 +399,7 @@ fn build_enum_variant_member_di_node<'ll, 'tcx>(
         llvm::LLVMRustDIBuilderCreateVariantMemberType(
             DIB(cx),
             variant_part_di_node,
-            variant_member_info.variant_name.as_ptr().cast(),
+            variant_member_info.variant_name.as_c_char_ptr(),
             variant_member_info.variant_name.len(),
             file_di_node,
             line_number,
diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/metadata/type_map.rs b/compiler/rustc_codegen_llvm/src/debuginfo/metadata/type_map.rs
index 714e3c0b145..d050dc9b406 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/metadata/type_map.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/metadata/type_map.rs
@@ -9,7 +9,7 @@ use rustc_middle::ty::{ParamEnv, PolyExistentialTraitRef, Ty, TyCtxt};
 use rustc_target::abi::{Align, Size, VariantIdx};
 
 use super::{SmallVec, UNKNOWN_LINE_NUMBER, unknown_file_metadata};
-use crate::common::CodegenCx;
+use crate::common::{AsCCharPtr, CodegenCx};
 use crate::debuginfo::utils::{DIB, create_DIArray, debug_context};
 use crate::llvm::debuginfo::{DIFlags, DIScope, DIType};
 use crate::llvm::{self};
@@ -191,7 +191,7 @@ pub(super) fn stub<'ll, 'tcx>(
                 llvm::LLVMRustDIBuilderCreateStructType(
                     DIB(cx),
                     containing_scope,
-                    name.as_ptr().cast(),
+                    name.as_c_char_ptr(),
                     name.len(),
                     unknown_file_metadata(cx),
                     UNKNOWN_LINE_NUMBER,
@@ -202,7 +202,7 @@ pub(super) fn stub<'ll, 'tcx>(
                     empty_array,
                     0,
                     vtable_holder,
-                    unique_type_id_str.as_ptr().cast(),
+                    unique_type_id_str.as_c_char_ptr(),
                     unique_type_id_str.len(),
                 )
             }
@@ -211,7 +211,7 @@ pub(super) fn stub<'ll, 'tcx>(
             llvm::LLVMRustDIBuilderCreateUnionType(
                 DIB(cx),
                 containing_scope,
-                name.as_ptr().cast(),
+                name.as_c_char_ptr(),
                 name.len(),
                 unknown_file_metadata(cx),
                 UNKNOWN_LINE_NUMBER,
@@ -220,7 +220,7 @@ pub(super) fn stub<'ll, 'tcx>(
                 flags,
                 Some(empty_array),
                 0,
-                unique_type_id_str.as_ptr().cast(),
+                unique_type_id_str.as_c_char_ptr(),
                 unique_type_id_str.len(),
             )
         },
diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/mod.rs b/compiler/rustc_codegen_llvm/src/debuginfo/mod.rs
index 5b32a542750..85eb1c8509d 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/mod.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/mod.rs
@@ -31,7 +31,7 @@ use self::namespace::mangled_name_of_instance;
 use self::utils::{DIB, create_DIArray, is_node_local_to_unit};
 use crate::abi::FnAbi;
 use crate::builder::Builder;
-use crate::common::CodegenCx;
+use crate::common::{AsCCharPtr, CodegenCx};
 use crate::llvm;
 use crate::llvm::debuginfo::{
     DIArray, DIBuilder, DIFile, DIFlags, DILexicalBlock, DILocation, DISPFlags, DIScope, DIType,
@@ -389,9 +389,9 @@ impl<'ll, 'tcx> DebugInfoCodegenMethods<'tcx> for CodegenCx<'ll, 'tcx> {
             llvm::LLVMRustDIBuilderCreateMethod(
                 DIB(self),
                 containing_scope,
-                name.as_ptr().cast(),
+                name.as_c_char_ptr(),
                 name.len(),
-                linkage_name.as_ptr().cast(),
+                linkage_name.as_c_char_ptr(),
                 linkage_name.len(),
                 file_metadata,
                 loc.line,
@@ -406,9 +406,9 @@ impl<'ll, 'tcx> DebugInfoCodegenMethods<'tcx> for CodegenCx<'ll, 'tcx> {
             llvm::LLVMRustDIBuilderCreateFunction(
                 DIB(self),
                 containing_scope,
-                name.as_ptr().cast(),
+                name.as_c_char_ptr(),
                 name.len(),
-                linkage_name.as_ptr().cast(),
+                linkage_name.as_c_char_ptr(),
                 linkage_name.len(),
                 file_metadata,
                 loc.line,
@@ -494,7 +494,7 @@ impl<'ll, 'tcx> DebugInfoCodegenMethods<'tcx> for CodegenCx<'ll, 'tcx> {
                                 Some(llvm::LLVMRustDIBuilderCreateTemplateTypeParameter(
                                     DIB(cx),
                                     None,
-                                    name.as_ptr().cast(),
+                                    name.as_c_char_ptr(),
                                     name.len(),
                                     actual_type_metadata,
                                 ))
@@ -635,7 +635,7 @@ impl<'ll, 'tcx> DebugInfoCodegenMethods<'tcx> for CodegenCx<'ll, 'tcx> {
                 DIB(self),
                 dwarf_tag,
                 scope_metadata,
-                name.as_ptr().cast(),
+                name.as_c_char_ptr(),
                 name.len(),
                 file_metadata,
                 loc.line,
diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/namespace.rs b/compiler/rustc_codegen_llvm/src/debuginfo/namespace.rs
index 3578755aae0..33d9bc23890 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/namespace.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/namespace.rs
@@ -5,7 +5,7 @@ use rustc_hir::def_id::DefId;
 use rustc_middle::ty::{self, Instance};
 
 use super::utils::{DIB, debug_context};
-use crate::common::CodegenCx;
+use crate::common::{AsCCharPtr, CodegenCx};
 use crate::llvm;
 use crate::llvm::debuginfo::DIScope;
 
@@ -36,7 +36,7 @@ pub(crate) fn item_namespace<'ll>(cx: &CodegenCx<'ll, '_>, def_id: DefId) -> &'l
         llvm::LLVMRustDIBuilderCreateNameSpace(
             DIB(cx),
             parent_scope,
-            namespace_name_string.as_ptr().cast(),
+            namespace_name_string.as_c_char_ptr(),
             namespace_name_string.len(),
             false, // ExportSymbols (only relevant for C++ anonymous namespaces)
         )
diff --git a/compiler/rustc_codegen_llvm/src/declare.rs b/compiler/rustc_codegen_llvm/src/declare.rs
index 33258cb46fa..d338c848754 100644
--- a/compiler/rustc_codegen_llvm/src/declare.rs
+++ b/compiler/rustc_codegen_llvm/src/declare.rs
@@ -20,6 +20,7 @@ use smallvec::SmallVec;
 use tracing::debug;
 
 use crate::abi::{FnAbi, FnAbiLlvmExt};
+use crate::common::AsCCharPtr;
 use crate::context::CodegenCx;
 use crate::llvm::AttributePlace::Function;
 use crate::llvm::Visibility;
@@ -41,7 +42,7 @@ fn declare_raw_fn<'ll>(
 ) -> &'ll Value {
     debug!("declare_raw_fn(name={:?}, ty={:?})", name, ty);
     let llfn = unsafe {
-        llvm::LLVMRustGetOrInsertFunction(cx.llmod, name.as_ptr().cast(), name.len(), ty)
+        llvm::LLVMRustGetOrInsertFunction(cx.llmod, name.as_c_char_ptr(), name.len(), ty)
     };
 
     llvm::SetFunctionCallConv(llfn, callconv);
@@ -68,7 +69,7 @@ impl<'ll, 'tcx> CodegenCx<'ll, 'tcx> {
     /// return its Value instead.
     pub(crate) fn declare_global(&self, name: &str, ty: &'ll Type) -> &'ll Value {
         debug!("declare_global(name={:?})", name);
-        unsafe { llvm::LLVMRustGetOrInsertGlobal(self.llmod, name.as_ptr().cast(), name.len(), ty) }
+        unsafe { llvm::LLVMRustGetOrInsertGlobal(self.llmod, name.as_c_char_ptr(), name.len(), ty) }
     }
 
     /// Declare a C ABI function.
@@ -209,7 +210,7 @@ impl<'ll, 'tcx> CodegenCx<'ll, 'tcx> {
     /// Gets declared value by name.
     pub(crate) fn get_declared_value(&self, name: &str) -> Option<&'ll Value> {
         debug!("get_declared_value(name={:?})", name);
-        unsafe { llvm::LLVMRustGetNamedValue(self.llmod, name.as_ptr().cast(), name.len()) }
+        unsafe { llvm::LLVMRustGetNamedValue(self.llmod, name.as_c_char_ptr(), name.len()) }
     }
 
     /// Gets defined or externally defined (AvailableExternally linkage) value by
diff --git a/compiler/rustc_codegen_llvm/src/llvm/mod.rs b/compiler/rustc_codegen_llvm/src/llvm/mod.rs
index 6aac2eea81d..cabe6c031d3 100644
--- a/compiler/rustc_codegen_llvm/src/llvm/mod.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm/mod.rs
@@ -17,13 +17,13 @@ pub use self::IntPredicate::*;
 pub use self::Linkage::*;
 pub use self::MetadataType::*;
 pub use self::RealPredicate::*;
+pub use self::ffi::*;
+use crate::common::AsCCharPtr;
 
 pub mod archive_ro;
 pub mod diagnostic;
 mod ffi;
 
-pub use self::ffi::*;
-
 impl LLVMRustResult {
     pub fn into_result(self) -> Result<(), ()> {
         match self {
@@ -53,9 +53,9 @@ pub fn CreateAttrStringValue<'ll>(llcx: &'ll Context, attr: &str, value: &str) -
     unsafe {
         LLVMCreateStringAttribute(
             llcx,
-            attr.as_ptr().cast(),
+            attr.as_c_char_ptr(),
             attr.len().try_into().unwrap(),
-            value.as_ptr().cast(),
+            value.as_c_char_ptr(),
             value.len().try_into().unwrap(),
         )
     }
@@ -65,7 +65,7 @@ pub fn CreateAttrString<'ll>(llcx: &'ll Context, attr: &str) -> &'ll Attribute {
     unsafe {
         LLVMCreateStringAttribute(
             llcx,
-            attr.as_ptr().cast(),
+            attr.as_c_char_ptr(),
             attr.len().try_into().unwrap(),
             std::ptr::null(),
             0,
@@ -294,7 +294,7 @@ pub fn get_value_name(value: &Value) -> &[u8] {
 /// Safe wrapper for `LLVMSetValueName2` from a byte slice
 pub fn set_value_name(value: &Value, name: &[u8]) {
     unsafe {
-        let data = name.as_ptr().cast();
+        let data = name.as_c_char_ptr();
         LLVMSetValueName2(value, data, name.len());
     }
 }