disable size asserts in the compiler when randomizing layouts

Author: the8472

Cargo.lock

@@ -3816,6 +3816,7 @@ dependencies = [
  "rustc_feature",
  "rustc_hir",
  "rustc_hir_pretty",
+ "rustc_index",
  "rustc_interface",
  "rustc_lint",
  "rustc_log",

compiler/rustc/Cargo.toml

@@ -23,3 +23,4 @@ jemalloc = ['jemalloc-sys']
 llvm = ['rustc_driver/llvm']
 max_level_info = ['rustc_driver/max_level_info']
 rustc_use_parallel_compiler = ['rustc_driver/rustc_use_parallel_compiler']
+rustc_randomized_layouts = ['rustc_driver/rustc_randomized_layouts']

compiler/rustc_driver/Cargo.toml

@@ -30,6 +30,7 @@ rustc_interface = { path = "../rustc_interface" }
 rustc_ast = { path = "../rustc_ast" }
 rustc_span = { path = "../rustc_span" }
 rustc_typeck = { path = "../rustc_typeck" }
+rustc_index = { path = "../rustc_index" }
 
 [target.'cfg(unix)'.dependencies]
 libc = "0.2"
@@ -42,3 +43,4 @@ llvm = ['rustc_interface/llvm']
 max_level_info = ['rustc_log/max_level_info']
 rustc_use_parallel_compiler = ['rustc_data_structures/rustc_use_parallel_compiler', 'rustc_interface/rustc_use_parallel_compiler',
     'rustc_middle/rustc_use_parallel_compiler']
+rustc_randomized_layouts = ['rustc_index/rustc_randomized_layouts']

compiler/rustc_index/Cargo.toml

@@ -11,3 +11,6 @@ arrayvec = { version = "0.7", default-features = false }
 rustc_serialize = { path = "../rustc_serialize" }
 rustc_macros = { path = "../rustc_macros" }
 smallvec = "1.8.1"
+
+[features]
+rustc_randomized_layouts = []

compiler/rustc_index/src/lib.rs

@@ -18,8 +18,19 @@ pub use rustc_macros::newtype_index;
 
 /// Type size assertion. The first argument is a type and the second argument is its expected size.
 #[macro_export]
+#[cfg(not(feature = "rustc_randomized_layouts"))]
 macro_rules! static_assert_size {
     ($ty:ty, $size:expr) => {
         const _: [(); $size] = [(); ::std::mem::size_of::<$ty>()];
     };
 }
+
+#[macro_export]
+#[cfg(feature = "rustc_randomized_layouts")]
+macro_rules! static_assert_size {
+    ($ty:ty, $size:expr) => {
+        // no effect other than using the statements.
+        // struct sizes are not deterministic under randomized layouts
+        const _: (usize, usize) = ($size, ::std::mem::size_of::<$ty>());
+    };
+}

src/bootstrap/lib.rs

@@ -753,6 +753,9 @@ impl Build {
         if self.config.rustc_parallel {
             features.push("rustc_use_parallel_compiler");
         }
+        if self.config.rust_randomize_layout {
+            features.push("rustc_randomized_layouts");
+        }
 
         // If debug logging is on, then we want the default for tracing:
         // https://github.com/tokio-rs/tracing/blob/3dd5c03d907afdf2c39444a29931833335171554/tracing/src/level_filters.rs#L26