Make the improper_ctypes lint more robust

It now checks extern fns in addition to foreign fns and checks `DefStruct`
defs as well.

There is room for improvement: for example, I believe that pointers
should be safe in extern fn signatures regardless of the pointee's
representation.

The `FIXME` on `rust_begin_unwind_fmt` is because I don't think it
should be, or needs to be, C ABI (cc @eddyb) and it takes a problematic
`fmt::Arguments` structure by value.

Fix rust-lang#20098, fix rust-lang#19834

Author: tomjakubowski

src/librustc/lint/builtin.rs

@@ -405,15 +405,17 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
         match self.cx.tcx.def_map.borrow()[path_id].clone() {
             def::DefPrimTy(ast::TyInt(ast::TyI)) => {
                 self.cx.span_lint(IMPROPER_CTYPES, sp,
-                                  "found rust type `int` in foreign module, while \
-                                   libc::c_int or libc::c_long should be used");
+                                  "found rust type `int` in foreign module or \
+                                  extern fn, while libc::c_int or libc::c_long \
+                                  should be used");
             }
             def::DefPrimTy(ast::TyUint(ast::TyU)) => {
                 self.cx.span_lint(IMPROPER_CTYPES, sp,
-                                  "found rust type `uint` in foreign module, while \
-                                   libc::c_uint or libc::c_ulong should be used");
+                                  "found rust type `uint` in foreign module or \
+                                  extern fn, while libc::c_uint or libc::c_ulong \
+                                  should be used");
             }
-            def::DefTy(..) => {
+            def::DefTy(..) | def::DefStruct(..) => {
                 let tty = match self.cx.tcx.ast_ty_to_ty_cache.borrow().get(&ty_id) {
                     Some(&ty::atttce_resolved(t)) => t,
                     _ => panic!("ast_ty_to_ty_cache was incomplete after typeck!")
@@ -422,8 +424,9 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
                 if !ty::is_ffi_safe(self.cx.tcx, tty) {
                     self.cx.span_lint(IMPROPER_CTYPES, sp,
                                       "found type without foreign-function-safe
-                                      representation annotation in foreign module, consider \
-                                      adding a #[repr(...)] attribute to the type");
+                                      representation annotation in foreign module or \
+                                      extern fn, consider adding a #[repr(...)] \
+                                      attribute to the type");
                 }
             }
             _ => ()
@@ -455,7 +458,7 @@ impl LintPass for ImproperCTypes {
             vis.visit_ty(ty);
         }
 
-        fn check_foreign_fn(cx: &Context, decl: &ast::FnDecl) {
+        fn check_fn(cx: &Context, decl: &ast::FnDecl) {
             for input in decl.inputs.iter() {
                 check_ty(cx, &*input.ty);
             }
@@ -468,11 +471,17 @@ impl LintPass for ImproperCTypes {
             ast::ItemForeignMod(ref nmod) if nmod.abi != abi::RustIntrinsic => {
                 for ni in nmod.items.iter() {
                     match ni.node {
-                        ast::ForeignItemFn(ref decl, _) => check_foreign_fn(cx, &**decl),
+                        ast::ForeignItemFn(ref decl, _) => check_fn(cx, &**decl),
                         ast::ForeignItemStatic(ref t, _) => check_ty(cx, &**t)
                     }
                 }
             }
+            ast::ItemFn(ref decl, _, abi, _, _) => {
+                match abi {
+                    abi::Rust | abi::RustIntrinsic | abi::RustCall => (),
+                    _ => check_fn(cx, &**decl)
+                }
+            }
             _ => (),
         }
     }

src/libstd/rt/unwind.rs

@@ -482,6 +482,7 @@ pub mod eabi {
 #[cfg(not(test))]
 /// Entry point of panic from the libcore crate.
 #[lang = "panic_fmt"]
+#[allow(improper_ctypes)] // FIXME(tomjakubowski)
 pub extern fn rust_begin_unwind(msg: fmt::Arguments,
                                 file: &'static str, line: uint) -> ! {
     begin_unwind_fmt(msg, &(file, line))
@@ -492,6 +493,7 @@ pub extern fn rust_begin_unwind(msg: fmt::Arguments,
 #[cfg(not(test))]
 /// Entry point of panic from the libcore crate.
 #[lang = "panic_fmt"]
+#[allow(improper_ctypes)] // FIXME(tomjakubowski)
 pub extern fn rust_begin_unwind(msg: &fmt::Arguments,
                                 file: &'static str, line: uint) -> ! {
     begin_unwind_fmt(msg, &(file, line))

src/test/compile-fail/lint-ctypes-xcrate-struct.rs

@@ -0,0 +1,23 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![deny(improper_ctypes)]
+
+#[repr(C)]
+pub struct Foo {
+    _x: String
+}
+
+extern {
+    pub fn bad(f: Foo); //~ ERROR found type without foreign-function-safe
+}
+
+fn main() {
+}

src/test/compile-fail/lint-ctypes.rs

@@ -1,4 +1,4 @@
-// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
 // file at the top-level directory of this distribution and at
 // http://rust-lang.org/COPYRIGHT.
 //
@@ -12,15 +12,38 @@
 
 extern crate libc;
 
+#[deriving(Copy)]
+pub struct Bad {
+    _x: u32
+}
+
+#[deriving(Copy)]
+#[repr(C)]
+pub struct Good {
+    _x: u32
+}
+
 extern {
     pub fn bare_type1(size: int); //~ ERROR: found rust type
     pub fn bare_type2(size: uint); //~ ERROR: found rust type
     pub fn ptr_type1(size: *const int); //~ ERROR: found rust type
     pub fn ptr_type2(size: *const uint); //~ ERROR: found rust type
+    pub fn non_c_repr_type(b: Bad); //~ ERROR: found type without foreign-function-safe
 
     pub fn good1(size: *const libc::c_int);
     pub fn good2(size: *const libc::c_uint);
+    pub fn good3(g: Good);
 }
 
+pub extern fn ex_bare_type1(_: int) {} //~ ERROR: found rust type
+pub extern fn ex_bare_type2(_: uint)  {} //~ ERROR: found rust type
+pub extern fn ex_ptr_type1(_: *const int) {} //~ ERROR: found rust type
+pub extern fn ex_ptr_type2(_: *const uint) {}  //~ ERROR: found rust type
+pub extern fn ex_non_c_repr_type(_: Bad) {} //~ ERROR: found type without foreign-function-safe
+
+pub extern fn ex_good1(_: *const libc::c_int) {}
+pub extern fn ex_good2(_: *const libc::c_uint) {}
+pub extern fn ex_good3(_: Good) {}
+
 fn main() {
 }