Introduce DIBuilderBox, an owning pointer to DIBuilder

Author: Zalathar

compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs

@@ -944,7 +944,7 @@ pub(crate) fn build_compile_unit_di_node<'ll, 'tcx>(
 
     unsafe {
         let compile_unit_file = llvm::LLVMRustDIBuilderCreateFile(
-            debug_context.builder,
+            debug_context.builder.as_ref(),
             name_in_debuginfo.as_c_char_ptr(),
             name_in_debuginfo.len(),
             work_dir.as_c_char_ptr(),
@@ -957,7 +957,7 @@ pub(crate) fn build_compile_unit_di_node<'ll, 'tcx>(
         );
 
         let unit_metadata = llvm::LLVMRustDIBuilderCreateCompileUnit(
-            debug_context.builder,
+            debug_context.builder.as_ref(),
             DW_LANG_RUST,
             compile_unit_file,
             producer.as_c_char_ptr(),

compiler/rustc_codegen_llvm/src/debuginfo/mod.rs

@@ -33,7 +33,7 @@ use crate::builder::Builder;
 use crate::common::{AsCCharPtr, CodegenCx};
 use crate::llvm;
 use crate::llvm::debuginfo::{
-    DIArray, DIBuilder, DIFile, DIFlags, DILexicalBlock, DILocation, DISPFlags, DIScope, DIType,
+    DIArray, DIBuilderBox, DIFile, DIFlags, DILexicalBlock, DILocation, DISPFlags, DIScope, DIType,
     DIVariable,
 };
 use crate::value::Value;
@@ -55,26 +55,18 @@ const DW_TAG_arg_variable: c_uint = 0x101;
 /// A context object for maintaining all state needed by the debuginfo module.
 pub(crate) struct CodegenUnitDebugContext<'ll, 'tcx> {
     llmod: &'ll llvm::Module,
-    builder: &'ll mut DIBuilder<'ll>,
+    builder: DIBuilderBox<'ll>,
     created_files: RefCell<UnordMap<Option<(StableSourceFileId, SourceFileHash)>, &'ll DIFile>>,
 
     type_map: metadata::TypeMap<'ll, 'tcx>,
     namespace_map: RefCell<DefIdMap<&'ll DIScope>>,
     recursion_marker_type: OnceCell<&'ll DIType>,
 }
 
-impl Drop for CodegenUnitDebugContext<'_, '_> {
-    fn drop(&mut self) {
-        unsafe {
-            llvm::LLVMRustDIBuilderDispose(&mut *(self.builder as *mut _));
-        }
-    }
-}
-
 impl<'ll, 'tcx> CodegenUnitDebugContext<'ll, 'tcx> {
     pub(crate) fn new(llmod: &'ll llvm::Module) -> Self {
         debug!("CodegenUnitDebugContext::new");
-        let builder = unsafe { llvm::LLVMRustDIBuilderCreate(llmod) };
+        let builder = DIBuilderBox::new(llmod);
         // DIBuilder inherits context from the module, so we'd better use the same one
         CodegenUnitDebugContext {
             llmod,
@@ -87,7 +79,7 @@ impl<'ll, 'tcx> CodegenUnitDebugContext<'ll, 'tcx> {
     }
 
     pub(crate) fn finalize(&self, sess: &Session) {
-        unsafe { llvm::LLVMRustDIBuilderFinalize(self.builder) };
+        unsafe { llvm::LLVMRustDIBuilderFinalize(self.builder.as_ref()) };
         if !sess.target.is_like_msvc {
             // Debuginfo generation in LLVM by default uses a higher
             // version of dwarf than macOS currently understands. We can

compiler/rustc_codegen_llvm/src/debuginfo/utils.rs

@@ -41,7 +41,7 @@ pub(crate) fn debug_context<'a, 'll, 'tcx>(
 #[inline]
 #[allow(non_snake_case)]
 pub(crate) fn DIB<'a, 'll>(cx: &'a CodegenCx<'ll, '_>) -> &'a DIBuilder<'ll> {
-    cx.dbg_cx.as_ref().unwrap().builder
+    cx.dbg_cx.as_ref().unwrap().builder.as_ref()
 }
 
 pub(crate) fn get_namespace_for_item<'ll>(cx: &CodegenCx<'ll, '_>, def_id: DefId) -> &'ll DIScope {

compiler/rustc_codegen_llvm/src/llvm/ffi.rs

@@ -725,13 +725,40 @@ pub type DiagnosticHandlerTy = unsafe extern "C" fn(&DiagnosticInfo, *mut c_void
 pub type InlineAsmDiagHandlerTy = unsafe extern "C" fn(&SMDiagnostic, *const c_void, c_uint);
 
 pub mod debuginfo {
+    use std::ptr;
+
     use bitflags::bitflags;
 
     use super::{InvariantOpaque, Metadata};
+    use crate::llvm::{self, Module};
 
     #[repr(C)]
     pub struct DIBuilder<'a>(InvariantOpaque<'a>);
 
+    pub(crate) struct DIBuilderBox<'ll> {
+        raw: ptr::NonNull<DIBuilder<'ll>>,
+    }
+
+    impl<'ll> DIBuilderBox<'ll> {
+        pub(crate) fn new(llmod: &'ll Module) -> Self {
+            let raw = unsafe { llvm::LLVMCreateDIBuilder(llmod) };
+            let raw = ptr::NonNull::new(raw).unwrap();
+            Self { raw }
+        }
+
+        pub(crate) fn as_ref(&self) -> &DIBuilder<'ll> {
+            // SAFETY: This is an owning pointer, so `&DIBuilder` is valid
+            // for as long as `&self` is.
+            unsafe { self.raw.as_ref() }
+        }
+    }
+
+    impl<'ll> Drop for DIBuilderBox<'ll> {
+        fn drop(&mut self) {
+            unsafe { llvm::LLVMDisposeDIBuilder(self.raw) };
+        }
+    }
+
     pub type DIDescriptor = Metadata;
     pub type DILocation = Metadata;
     pub type DIScope = DIDescriptor;
@@ -1599,6 +1626,13 @@ unsafe extern "C" {
     ) -> &'a Value;
 }
 
+// FFI bindings for `DIBuilder` functions in the LLVM-C API.
+// Try to keep these in the same order as in `llvm/include/llvm-c/DebugInfo.h`.
+unsafe extern "C" {
+    pub(crate) fn LLVMCreateDIBuilder<'ll>(M: &'ll Module) -> *mut DIBuilder<'ll>;
+    pub(crate) fn LLVMDisposeDIBuilder<'ll>(Builder: ptr::NonNull<DIBuilder<'ll>>);
+}
+
 #[link(name = "llvm-wrapper", kind = "static")]
 unsafe extern "C" {
     pub fn LLVMRustInstallErrorHandlers();
@@ -1866,10 +1900,6 @@ unsafe extern "C" {
         ValueLen: size_t,
     );
 
-    pub fn LLVMRustDIBuilderCreate(M: &Module) -> &mut DIBuilder<'_>;
-
-    pub fn LLVMRustDIBuilderDispose<'a>(Builder: &'a mut DIBuilder<'a>);
-
     pub fn LLVMRustDIBuilderFinalize(Builder: &DIBuilder<'_>);
 
     pub fn LLVMRustDIBuilderCreateCompileUnit<'a>(

compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp

@@ -909,14 +909,6 @@ extern "C" void LLVMRustGlobalAddMetadata(LLVMValueRef Global, unsigned Kind,
   unwrap<GlobalObject>(Global)->addMetadata(Kind, *unwrap<MDNode>(MD));
 }
 
-extern "C" LLVMRustDIBuilderRef LLVMRustDIBuilderCreate(LLVMModuleRef M) {
-  return new DIBuilder(*unwrap(M));
-}
-
-extern "C" void LLVMRustDIBuilderDispose(LLVMRustDIBuilderRef Builder) {
-  delete Builder;
-}
-
 extern "C" void LLVMRustDIBuilderFinalize(LLVMRustDIBuilderRef Builder) {
   Builder->finalize();
 }