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.

7 files changed, 50 insertions, 50 deletions

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)
         )