Rewrite the core of the binding generator.

TL;DR: The binding generator is a mess as of right now. At first it was funny
(in a "this is challenging" sense) to improve on it, but this is not
sustainable.

The truth is that the current architecture of the binding generator is a huge
pile of hacks, so these few days I've been working on rewriting it with a few
goals.

 1) Have the hacks as contained and identified as possible. They're sometimes
    needed because how clang exposes the AST, but ideally those hacks are well
    identified and don't interact randomly with each others.

    As an example, in the current bindgen when scanning the parameters of a
    function that references a struct clones all the struct information, then if
    the struct name changes (because we mangle it), everything breaks.

 2) Support extending the bindgen output without having to deal with clang. The
    way I'm aiming to do this is separating completely the parsing stage from
    the code generation one, and providing a single id for each item the binding
    generator provides.

 3) No more random mutation of the internal representation from anywhere. That
    means no more Rc<RefCell<T>>, no more random circular references, no more
    borrow_state... nothing.

 4) No more deduplication of declarations before code generation.

    Current bindgen has a stage, called `tag_dup_decl`[1], that takes care of
    deduplicating declarations. That's completely buggy, and for C++ it's a
    complete mess, since we YOLO modify the world.

    I've managed to take rid of this using the clang canonical declaration, and
    the definition, to avoid scanning any type/item twice.

 5) Code generation should not modify any internal data structure. It can lookup
    things, traverse whatever it needs, but not modifying randomly.

 6) Each item should have a canonical name, and a single source of mangling
    logic, and that should be computed from the inmutable state, at code
    generation.

    I've put a few canonical_name stuff in the code generation phase, but it's
    still not complete, and should change if I implement namespaces.

Improvements pending until this can land:

 1) Add support for missing core stuff, mainly generating functions (note that
    we parse the signatures for types correctly though), bitfields, generating
    C++ methods.

 2) Add support for the necessary features that were added to work around some
    C++ pitfalls, like opaque types, etc...

 3) Add support for the sugar that Manish added recently.

 4) Optionally (and I guess this can land without it, because basically nobody
    uses it since it's so buggy), bring back namespace support.

These are not completely trivial, but I think I can do them quite easily with
the current architecture.

I'm putting the current state of affairs here as a request for comments... Any
thoughts? Note that there are still a few smells I want to eventually
re-redesign, like the ParseError::Recurse thing, but until that happens I'm
way happier with this kind of architecture.

I'm keeping the old `parser.rs` and `gen.rs` in tree just for reference while I
code, but they will go away.

[1]: https://github.com/Yamakaky/rust-bindgen/blob/master/src/gen.rs#L448

1 files changed, 220 insertions, 0 deletions

diff --git a/src/ir/function.rs b/src/ir/function.rs
new file mode 100644
index 00000000..b95ac57b
--- /dev/null
+++ b/src/ir/function.rs
@@ -0,0 +1,220 @@
+use super::item::{Item, ItemId};
+use super::ty::TypeKind;
+use super::context::BindgenContext;
+use syntax::abi;
+use clang;
+use clangll::Enum_CXCallingConv;
+use parse::{ClangItemParser, ClangSubItemParser, ParseError, ParseResult};
+
+/// A function declaration , with a signature, arguments, and argument names.
+///
+/// The argument names vector must be the same length as the ones in the
+/// signature.
+#[derive(Debug)]
+pub struct Function {
+    name: String,
+    /// The mangled name, that is, the symbol.
+    mangled_name: Option<String>,
+    /// The id pointing to the current function signature.
+    signature: ItemId,
+    /// The doc comment on the function, if any.
+    comment: Option<String>,
+}
+
+impl Function {
+    pub fn new(name: String,
+               mangled_name: Option<String>,
+               sig: ItemId,
+               comment: Option<String>) -> Self {
+        Function {
+            name: name,
+            mangled_name: mangled_name,
+            signature: sig,
+            comment: comment,
+        }
+    }
+
+    pub fn name(&self) -> &str {
+        &self.name
+    }
+
+    pub fn mangled_name(&self) -> Option<&str> {
+        self.mangled_name.as_ref().map(|n| &**n)
+    }
+
+    pub fn signature(&self) -> ItemId {
+        self.signature
+    }
+}
+
+/// A function signature.
+#[derive(Debug)]
+pub struct FunctionSig {
+    /// The return type of the function.
+    return_type: ItemId,
+    /// The type of the arguments, optionally with the name of the argument when
+    /// declared.
+    argument_types: Vec<(Option<String>, ItemId)>,
+    /// Whether this function is variadic.
+    is_variadic: bool,
+    /// The abi of this function.
+    abi: abi::Abi,
+}
+
+fn get_abi(cc: Enum_CXCallingConv) -> abi::Abi {
+    use clangll::*;
+    match cc {
+        CXCallingConv_Default => abi::Abi::C,
+        CXCallingConv_C => abi::Abi::C,
+        CXCallingConv_X86StdCall => abi::Abi::Stdcall,
+        CXCallingConv_X86FastCall => abi::Abi::Fastcall,
+        CXCallingConv_AAPCS => abi::Abi::Aapcs,
+        CXCallingConv_X86_64Win64 => abi::Abi::Win64,
+        other => panic!("unsupported calling convention: {}", other),
+    }
+}
+
+pub fn cursor_mangling(cursor: &clang::Cursor) -> Option<String> {
+    let mut mangling = cursor.mangling();
+
+    // Try to undo backend linkage munging (prepended _, generally)
+    if cfg!(target_os = "macos") {
+        mangling.remove(0);
+    }
+
+    if mangling.is_empty() { None } else { Some(mangling) }
+}
+
+impl FunctionSig {
+    pub fn new(return_type: ItemId,
+               arguments: Vec<(Option<String>, ItemId)>,
+               is_variadic: bool,
+               abi: abi::Abi) -> Self {
+        FunctionSig {
+            return_type: return_type,
+            argument_types: arguments,
+            is_variadic: is_variadic,
+            abi: abi,
+        }
+    }
+
+    pub fn from_ty(ty: &clang::Type,
+                   cursor: &clang::Cursor,
+                   ctx: &mut BindgenContext) -> Result<Self, ParseError> {
+        use clangll::*;
+        debug!("FunctionSig::from_ty {:?} {:?}", ty, cursor);
+
+        // Don't parse operatorxx functions in C++
+        let spelling = cursor.spelling();
+        if spelling.starts_with("operator") {
+            return Err(ParseError::Continue);
+        }
+
+        let cursor = if cursor.is_valid() {
+            *cursor
+        } else {
+            ty.declaration()
+        };
+        let mut args: Vec<_> = match cursor.kind() {
+            CXCursor_FunctionDecl |
+            CXCursor_CXXMethod => {
+                // For CXCursor_FunctionDecl, cursor.args() is the reliable way
+                // to get parameter names and types.
+                cursor.args().iter().map(|arg| {
+                    let arg_ty = arg.cur_type();
+                    let name = arg.spelling();
+                    let name = if name.is_empty() { None } else { Some(name) };
+                    let ty = Item::from_ty(&arg_ty, Some(*arg), None, ctx)
+                                    .expect("Argument?");
+                    (name, ty)
+                }).collect()
+            }
+            _ => {
+                // For non-CXCursor_FunctionDecl, visiting the cursor's children
+                // is the only reliable way to get parameter names.
+                let mut args = vec![];
+                cursor.visit(|c, _| {
+                    if c.kind() == CXCursor_ParmDecl {
+                        let ty = Item::from_ty(&c.cur_type(), Some(*c), None, ctx)
+                                    .expect("ParmDecl?");
+                        let name = c.spelling();
+                        let name = if name.is_empty() { None } else { Some(name) };
+                        args.push((name, ty));
+                    }
+                    CXChildVisit_Continue
+                });
+                args
+            }
+        };
+
+        if cursor.kind() == CXCursor_CXXMethod {
+            let is_const = cursor.method_is_const();
+            let is_virtual = cursor.method_is_virtual();
+            let is_static = cursor.method_is_static();
+            if !is_static && !is_virtual {
+                let class = Item::parse(cursor.semantic_parent(), None, ctx)
+                                .expect("Expected to parse the class");
+                let ptr = Item::builtin_type(TypeKind::Pointer(class), is_const, ctx);
+                args.insert(0, (Some("this".into()), ptr));
+            } else if is_virtual {
+                let void = Item::builtin_type(TypeKind::Void, false, ctx);
+                let ptr = Item::builtin_type(TypeKind::Pointer(void), false, ctx);
+                args.insert(0, (Some("this".into()), ptr));
+            }
+        }
+
+        let ret = try!(Item::from_ty(&ty.ret_type(), None, None, ctx));
+        let abi = get_abi(ty.call_conv());
+
+        Ok(Self::new(ret, args, ty.is_variadic(), abi))
+    }
+
+    pub fn return_type(&self) -> ItemId {
+        self.return_type
+    }
+
+    pub fn argument_types(&self) -> &[(Option<String>, ItemId)] {
+        &self.argument_types
+    }
+
+    pub fn abi(&self) -> abi::Abi {
+        self.abi
+    }
+
+    pub fn is_variadic(&self) -> bool {
+        // Clang reports some functions as variadic when they *might* be
+        // variadic. We do the argument check because rust doesn't codegen well
+        // variadic functions without an initial argument.
+        self.is_variadic && !self.argument_types.is_empty()
+    }
+}
+
+impl ClangSubItemParser for Function {
+    fn parse(cursor: clang::Cursor,
+             context: &mut BindgenContext) -> Result<ParseResult<Self>, ParseError> {
+        use clangll::*;
+        match cursor.kind() {
+            CXCursor_FunctionDecl |
+            CXCursor_CXXMethod => {},
+            _ => return Err(ParseError::Continue),
+        };
+
+        debug!("Function::parse({:?}, {:?})", cursor, cursor.cur_type());
+
+        // Grab the signature using Item::from_ty.
+        let sig = try!(Item::from_ty(&cursor.cur_type(), Some(cursor), None, context));
+
+        let name = cursor.spelling();
+        assert!(!name.is_empty(), "Empty function name?");
+
+        let mut mangled_name = cursor_mangling(&cursor);
+        if mangled_name.as_ref() == Some(&name) {
+            mangled_name = None;
+        }
+
+        let comment = cursor.raw_comment();
+
+        let function = Self::new(name, mangled_name, sig, comment);
+        Ok(ParseResult::New(function, Some(cursor)))
+    }
+}