Options to generate uncallable C++ functions.

Downstream code generators may need to know about the existence of certain C++
functions even if those functions can't be called. This is counterintuitive but:

* A type can't even be allocated if it contains pure virtual functions
  or if its constructor is private.
* A type may not be relocatable if it contains a deleted move constructor.

This PR provides command line options to reveal the existence of these
functions. Subsequent PRs will announce their special status using the
ParseCallbacks mechanism.

Part of google/autocxx#124.

Author: adetaylor

bindgen-tests/tests/expectations/tests/uncallable_functions.rs

@@ -0,0 +1,9 @@
+// bindgen-flags: --generate-deleted-functions --generate-private-functions --generate-pure-virtual-functions --generate-inline-functions -- -x c++ -std=c++14
+
+class Test {
+public:
+    virtual void a() = 0;
+    void b() = delete;
+private:
+    void c() {}
+};

bindgen-tests/tests/headers/uncallable_functions.hpp

@@ -4564,14 +4564,20 @@ impl CodeGenerator for Function {
             }
         }
 
-        // Pure virtual methods have no actual symbol, so we can't generate
-        // something meaningful for them.
-        let is_dynamic_function = match self.kind() {
-            FunctionKind::Method(ref method_kind)
-                if method_kind.is_pure_virtual() =>
-            {
-                return None;
+        let is_pure_virtual = match self.kind() {
+            FunctionKind::Method(ref method_kind) => {
+                method_kind.is_pure_virtual()
             }
+            _ => false,
+        };
+        if is_pure_virtual && !ctx.options().generate_pure_virtual_functions {
+            // Pure virtual methods have no actual symbol, so we can't generate
+            // something meaningful for them. Downstream code postprocessors
+            // might want to find out about them.
+            return None;
+        }
+
+        let is_dynamic_function = match self.kind() {
             FunctionKind::Function => {
                 ctx.options().dynamic_library_name.is_some()
             }

bindgen/codegen/mod.rs

@@ -734,8 +734,7 @@ impl ClangSubItemParser for Function {
         if visibility != CXVisibility_Default {
             return Err(ParseError::Continue);
         }
-
-        if cursor.access_specifier() == CX_CXXPrivate {
+        if cursor.access_specifier() == CX_CXXPrivate && !context.options().generate_private_functions {
             return Err(ParseError::Continue);
         }
 
@@ -755,7 +754,7 @@ impl ClangSubItemParser for Function {
                 return Err(ParseError::Continue);
             }
 
-            if cursor.is_deleted_function() {
+            if cursor.is_deleted_function() && !context.options().generate_deleted_functions {
                 return Err(ParseError::Continue);
             }
 

bindgen/ir/function.rs

@@ -510,6 +510,18 @@ struct BindgenCommand {
     /// bitfields. This flag is ignored if the `--respect-cxx-access-specs` flag is used.
     #[arg(long, value_name = "VISIBILITY")]
     default_visibility: Option<FieldVisibilityKind>,
+    /// Whether to generate C++ functions marked with "=delete" even though they
+    /// can't be called.
+    #[arg(long)]
+    generate_deleted_functions: bool,
+    /// Whether to generate C++ "pure virtual" functions even though they can't
+    /// be called.
+    #[arg(long)]
+    generate_pure_virtual_functions: bool,
+    /// Whether to generate C++ private functions even though they can't
+    /// be called.
+    #[arg(long)]
+    generate_private_functions: bool,
     /// Whether to emit diagnostics or not.
     #[cfg(feature = "experimental")]
     #[arg(long, requires = "experimental")]
@@ -657,6 +669,9 @@ where
         wrap_static_fns_path,
         wrap_static_fns_suffix,
         default_visibility,
+        generate_deleted_functions,
+        generate_pure_virtual_functions,
+        generate_private_functions,
         #[cfg(feature = "experimental")]
         emit_diagnostics,
         generate_shell_completions,
@@ -948,6 +963,9 @@ where
             wrap_static_fns_path,
             wrap_static_fns_suffix,
             default_visibility,
+            generate_deleted_functions,
+            generate_pure_virtual_functions,
+            generate_private_functions,
         }
     );
 

bindgen/options/cli.rs

@@ -2211,4 +2211,58 @@ options! {
         },
         as_args: "--clang-macro-fallback-build-dir",
     }
+    /// Whether to always report C++ "deleted" functions.
+    generate_deleted_functions: bool {
+        methods: {
+            /// Set whether to generate C++ functions even marked "=deleted"
+            ///
+            /// Although not useful to call these functions, downstream code
+            /// generators may need to know whether they've been deleted in
+            /// order to determine the relocatability of a C++ type
+            /// (specifically by virtue of which constructors exist.)
+            pub fn generate_deleted_functions(mut self, doit: bool) -> Self {
+                self.options.generate_deleted_functions = doit;
+                self
+            }
+
+        },
+        as_args: "--generate-deleted-functions",
+    },
+    /// Whether to always report C++ "pure virtual" functions.
+    generate_pure_virtual_functions: bool {
+        methods: {
+            /// Set whether to generate C++ functions that are pure virtual.
+            ///
+            /// These functions can't be called, so the only reason
+            /// to generate them is if downstream postprocessors
+            /// need to know of their existence. This is necessary,
+            /// for instance, to determine whether a type itself is
+            /// pure virtual and thus can't be allocated.
+            /// Downstream code generators may choose to make code to
+            /// allow types to be allocated but need to avoid doing so
+            /// if the type contains pure virtual functions.
+            pub fn generate_pure_virtual_functions(mut self, doit: bool) -> Self {
+                self.options.generate_pure_virtual_functions = doit;
+                self
+            }
+
+        },
+        as_args: "--generate-pure-virtual-functions",
+    },
+    /// Whether to always report C++ "private" functions.
+    generate_private_functions: bool {
+        methods: {
+            /// Set whether to generate C++ functions that are private.
+            ///
+            /// These functions can't be called, so the only reason
+            /// to generate them is if downstream postprocessors
+            /// need to know of their existence.
+            pub fn generate_private_functions(mut self, doit: bool) -> Self {
+                self.options.generate_private_functions = doit;
+                self
+            }
+
+        },
+        as_args: "--generate-private-functions",
+    },
 }