Add dynamic loading support

Co-authored-by: Michael-F-Bryan <michaelfbryan@gmail.com>

src/codegen/dyngen.rs

@@ -0,0 +1,306 @@
+use super::ToRustTyOrOpaque;
+use crate::codegen::utils;
+use crate::ir::context::{BindgenContext, ItemId};
+use crate::ir::function::{Abi, Function, FunctionKind};
+use crate::ir::item::{Item, ItemCanonicalName};
+use crate::ir::item_kind::ItemKind;
+use crate::ir::ty::TypeKind;
+use crate::HashSet;
+use proc_macro2::Ident;
+
+/// This trait is similar to the CodeGenerator trait in src/codegen/mod.rs, but is instead focused
+/// on the generation of dynamic bindings rather than static.
+pub trait DynamicBindingGenerator {
+    /// Extra information from the caller.
+    type Extra;
+
+    /// Generate dynamic bindings for a particular item type.
+    fn dyngen<'a>(
+        &self,
+        ctx: &BindgenContext,
+        result: &mut DynamicBindingCodegenResult,
+        extra: &Self::Extra,
+    );
+}
+
+/// Used to build the output tokens for dynamic bindings.
+pub struct DynamicBindingCodegenResult {
+    /// Tracks the tokens that will appears inside the library struct -- e.g.:
+    /// ```ignore
+    /// struct Lib {
+    ///    __library: ::libloading::Library,
+    ///    x: Result<unsafe extern ..., ::libloading::Error>, // <- tracks these
+    ///    ...
+    /// }
+    /// ```
+    struct_members: Vec<proc_macro2::TokenStream>,
+
+    /// Tracks the tokens that will appear inside the library struct's implementation, e.g.:
+    ///
+    /// ```ignore
+    /// impl Lib {
+    ///     ...
+    ///     pub unsafe fn foo(&self, ...) { // <- tracks these
+    ///         ...
+    ///     }
+    /// }
+    /// ```
+    struct_implementation: Vec<proc_macro2::TokenStream>,
+
+    /// Tracks the tokens that will appear inside the struct used for checking if a symbol is
+    /// usable, e.g.:
+    /// ```ignore
+    /// pub fn f(&self) -> Result<(), &'a ::libloading::Error> { // <- tracks these
+    ///     self.__library.f.as_ref().map(|_| ())
+    /// }
+    /// ```
+    runtime_checks: Vec<proc_macro2::TokenStream>,
+
+    /// Tracks the initialization of the fields inside the `::new` constructor of the library
+    /// struct, e.g.:
+    /// ```ignore
+    /// impl Lib {
+    ///
+    ///     pub unsafe fn new<P>(path: P) -> Result<Self, ::libloading::Error>
+    ///     where
+    ///         P: AsRef<::std::ffi::OsStr>,
+    ///     {
+    ///         ...
+    ///         let foo = __library.get(...) ...; // <- tracks these
+    ///         ...
+    ///     }
+    ///
+    ///     ...
+    /// }
+    /// ```
+    constructor_inits: Vec<proc_macro2::TokenStream>,
+
+    /// Tracks the information that is passed to the library struct at the end of the `::new`
+    /// constructor, e.g.:
+    /// ```ignore
+    /// impl LibFoo {
+    ///     pub unsafe fn new<P>(path: P) -> Result<Self, ::libloading::Error>
+    ///     where
+    ///         P: AsRef<::std::ffi::OsStr>,
+    ///     {
+    ///         ...
+    ///         Ok(LibFoo {
+    ///             __library: __library,
+    ///             foo,
+    ///             bar, // <- tracks these
+    ///             ...
+    ///         })
+    ///     }
+    /// }
+    /// ```
+    init_fields: Vec<proc_macro2::TokenStream>,
+
+    /// Keeps track of the items that we have seen.
+    items_seen: HashSet<ItemId>,
+}
+
+impl DynamicBindingCodegenResult {
+    pub fn new() -> Self {
+        DynamicBindingCodegenResult {
+            struct_members: vec![],
+            struct_implementation: vec![],
+            runtime_checks: vec![],
+            constructor_inits: vec![],
+            init_fields: vec![],
+            items_seen: Default::default(),
+        }
+    }
+
+    pub fn seen<Id: Into<ItemId>>(&self, item: Id) -> bool {
+        self.items_seen.contains(&item.into())
+    }
+
+    pub fn set_seen<Id: Into<ItemId>>(&mut self, item: Id) {
+        self.items_seen.insert(item.into());
+    }
+
+    pub fn get_tokens(
+        &self,
+        lib_ident: Ident,
+        check_struct_ident: Ident,
+    ) -> proc_macro2::TokenStream {
+        let struct_members = &self.struct_members;
+        let constructor_inits = &self.constructor_inits;
+        let init_fields = &self.init_fields;
+        let struct_implementation = &self.struct_implementation;
+        let runtime_checks = &self.runtime_checks;
+        quote! {
+            extern crate libloading;
+
+            pub struct #lib_ident {
+                __library: ::libloading::Library,
+                #(#struct_members)*
+            }
+
+            impl #lib_ident {
+                pub unsafe fn new<P>(
+                    path: P
+                ) -> Result<Self, ::libloading::Error>
+                where P: AsRef<::std::ffi::OsStr> {
+                    let __library = ::libloading::Library::new(path)?;
+                    #( #constructor_inits )*
+                    Ok(
+                        #lib_ident {
+                            __library: __library,
+                            #( #init_fields ),*
+                        }
+                    )
+                }
+
+                pub fn can_call(&self) -> #check_struct_ident {
+                    #check_struct_ident { __library: self }
+                }
+
+                #( #struct_implementation )*
+            }
+
+            pub struct #check_struct_ident<'a> {
+                __library: &'a #lib_ident,
+            }
+
+            impl<'a> #check_struct_ident<'a> {
+                #( #runtime_checks )*
+            }
+        }
+    }
+
+    pub fn add_function(
+        &mut self,
+        ident: Ident,
+        abi: Abi,
+        args: Vec<proc_macro2::TokenStream>,
+        args_identifiers: Vec<proc_macro2::TokenStream>,
+        ret: proc_macro2::TokenStream,
+        ret_ty: proc_macro2::TokenStream,
+    ) {
+        self.struct_members.push(quote!{
+            #ident: Result<unsafe extern #abi fn ( #( #args ),* ) #ret, ::libloading::Error>,
+        });
+
+        self.struct_implementation.push(quote! {
+            pub unsafe fn #ident ( &self, #( #args ),* ) -> #ret_ty {
+                let sym = self.#ident.as_ref().expect("Expected function, got error.");
+                (sym)(#( #args_identifiers ),*)
+            }
+        });
+
+        self.runtime_checks.push(quote! {
+            pub fn #ident (&self) -> Result<(), &'a::libloading::Error> {
+                self.__library.#ident.as_ref().map(|_| ())
+            }
+        });
+
+        let ident_str = ident.to_string();
+        self.constructor_inits.push(quote! {
+            let #ident = __library.get(#ident_str.as_bytes()).map(|sym| *sym);
+        });
+
+        self.init_fields.push(quote! {
+            #ident
+        });
+    }
+}
+
+impl DynamicBindingGenerator for Item {
+    type Extra = ();
+
+    fn dyngen<'a>(
+        &self,
+        ctx: &BindgenContext,
+        result: &mut DynamicBindingCodegenResult,
+        _extra: &(),
+    ) {
+        assert!(self.is_dynamic(ctx));
+        if !self.is_enabled_for_codegen(ctx) {
+            return;
+        }
+
+        // If this item is blacklisted, or we've already seen it, nothing to do.
+        if self.is_blacklisted(ctx) || result.seen(self.id()) {
+            debug!(
+                "<Item as DynamicBindingGenerator>::dyngen: Ignoring hidden or seen: \
+                 self = {:?}",
+                self
+            );
+            return;
+        }
+
+        debug!(
+            "<Item as DynamicBindingGenerator>::dyngen: self = {:?}",
+            self
+        );
+
+        if !ctx.codegen_items().contains(&self.id()) {
+            warn!("Found non-whitelisted item in dynamic binding generation: {:?}", self);
+        }
+
+        result.set_seen(self.id());
+
+        match *self.kind() {
+            ItemKind::Function(ref fun) => {
+                assert!(fun.kind() == FunctionKind::Function);
+                fun.dyngen(ctx, result, self);
+            }
+            _ => panic!(
+                "Unexpected item type when doing dynamic bindings generation."
+            ),
+        }
+    }
+}
+
+impl DynamicBindingGenerator for Function {
+    type Extra = Item;
+
+    fn dyngen<'a>(
+        &self,
+        ctx: &BindgenContext,
+        result: &mut DynamicBindingCodegenResult,
+        item: &Item,
+    ) {
+        let signature_item = ctx.resolve_item(self.signature());
+        let signature = signature_item.kind().expect_type().canonical_type(ctx);
+        let signature = match *signature.kind() {
+            TypeKind::Function(ref sig) => sig,
+            _ => panic!("Signature kind is not a Function: {:?}", signature),
+        };
+
+        let canonical_name = item.canonical_name(ctx);
+        let abi = match signature.abi() {
+            Abi::ThisCall if !ctx.options().rust_features().thiscall_abi => {
+                warn!("Skipping function with thiscall ABI that isn't supported by the configured Rust target");
+                return;
+            }
+            Abi::Win64 if signature.is_variadic() => {
+                warn!("Skipping variadic function with Win64 ABI that isn't supported");
+                return;
+            }
+            Abi::Unknown(unknown_abi) => {
+                panic!(
+                    "Invalid or unknown abi {:?} for function {:?} ({:?})",
+                    unknown_abi, canonical_name, self
+                );
+            }
+            abi => abi,
+        };
+
+        let args = utils::fnsig_arguments(ctx, signature);
+        let args_identifiers =
+            utils::fnsig_argument_identifiers(ctx, signature);
+        let ret = utils::fnsig_return_ty(ctx, signature);
+
+        let ident = ctx.rust_ident(&canonical_name);
+
+        let return_item = ctx.resolve_item(signature.return_type());
+        let ret_ty = match *return_item.kind().expect_type().kind() {
+            TypeKind::Void => quote! {()},
+            _ => return_item.to_rust_ty_or_opaque(ctx, &()),
+        };
+
+        result.add_function(ident, abi, args, args_identifiers, ret, ret_ty);
+    }
+}