Auto merge of #43641 - oli-obk:truncating_for_fun_and___wait_what, r=<try>

Lint casting signed integers smaller than `isize` to raw pointers

cc #43291 (keeping open as tracking issue)

Author: bors

src/librustc_lint/builtin.rs

@@ -1261,3 +1261,54 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnionsWithDropFields {
         }
     }
 }
+
+
+/// Lint for casts from types other than `usize` or `isize` to raw pointers
+pub struct IntoToRawPtrCast;
+
+declare_lint! {
+    pub INT_TO_RAW_PTR_CAST,
+    Deny,
+    "cast from signed int other than `isize` to raw pointer"
+}
+
+impl LintPass for IntoToRawPtrCast {
+    fn get_lints(&self) -> LintArray {
+        lint_array!(INT_TO_RAW_PTR_CAST)
+    }
+}
+
+impl<'a, 'tcx> LateLintPass<'a, 'tcx> for IntoToRawPtrCast {
+    fn check_expr(&mut self, cx: &LateContext, expr: &hir::Expr) {
+        if let hir::ExprCast(ref base, _) = expr.node {
+            let base_ty = cx.tables.expr_ty(base);
+            let target_ty = cx.tables.expr_ty(expr);
+            if let ty::TyRawPtr(..) = target_ty.sty {
+                match base_ty.sty {
+                    ty::TyInt(ast::IntTy::Is) |
+                    ty::TyInt(ast::IntTy::I128) |
+                    ty::TyInt(ast::IntTy::I64) => return,
+                    ty::TyInt(ast::IntTy::I32) => {
+                        if cx.tcx.data_layout.pointer_size.bytes() <= 4 {
+                            return;
+                        }
+                    },
+                    ty::TyInt(ast::IntTy::I16) => {
+                        if cx.tcx.data_layout.pointer_size.bytes() <= 2 {
+                            return;
+                        }
+                    },
+                    // these we report
+                    ty::TyInt(_) => {},
+                    // only int casts are relevant
+                    _ => return,
+                }
+                cx.span_lint(
+                    INT_TO_RAW_PTR_CAST,
+                    expr.span,
+                    &format!("cast from `{}` to raw pointer", base_ty),
+                );
+            }
+        }
+    }
+}

src/librustc_lint/lib.rs

@@ -142,6 +142,7 @@ pub fn register_builtins(store: &mut lint::LintStore, sess: Option<&Session>) {
                  PluginAsLibrary,
                  MutableTransmutes,
                  UnionsWithDropFields,
+                 IntoToRawPtrCast,
                  );
 
     add_builtin_with_new!(sess,
@@ -241,6 +242,10 @@ pub fn register_builtins(store: &mut lint::LintStore, sess: Option<&Session>) {
             id: LintId::of(LATE_BOUND_LIFETIME_ARGUMENTS),
             reference: "issue #42868 <https://github.com/rust-lang/rust/issues/42868>",
         },
+        FutureIncompatibleInfo {
+            id: LintId::of(builtin::INT_TO_RAW_PTR_CAST),
+            reference: "issue #43291 <https://github.com/rust-lang/rust/issues/43291>",
+        },
         ]);
 
     // Register renamed and removed lints

src/libstd/sys_common/at_exit_imp.rs

@@ -48,7 +48,7 @@ pub fn cleanup() {
         unsafe {
             LOCK.lock();
             let queue = QUEUE;
-            QUEUE = if i == ITERS - 1 {1} else {0} as *mut _;
+            QUEUE = if i == ITERS - 1 {1usize} else {0usize} as *mut _;
             LOCK.unlock();
 
             // make sure we're not recursively cleaning up

src/test/run-pass/cast-to-infer-ty.rs

@@ -11,6 +11,8 @@
 // Check that we allow a cast to `_` so long as the target type can be
 // inferred elsewhere.
 
+#[allow(int_to_raw_ptr_cast)]
+
 pub fn main() {
     let i: *const i32 = 0 as _;
     assert!(i.is_null());

src/test/run-pass/mir_misc_casts.rs

@@ -9,6 +9,7 @@
 // except according to those terms.
 
 #![feature(libc)]
+#![allow(int_to_raw_ptr_cast)]
 
 extern crate libc;
 

src/test/run-pass/supported-cast.rs

@@ -9,6 +9,7 @@
 // except according to those terms.
 
 #![feature(libc)]
+#![allow(int_to_raw_ptr_cast)]
 
 extern crate libc;