Prevent clobbering of data in Result's tail padding internally and externally

.github/workflows/ci.yml

@@ -12,22 +12,22 @@ jobs:
       fail-fast: false
       matrix:
         config:
-          #- {
-          #    name: "Windows MSVC",
-          #    artifact: "Windows-MSVC.tar.xz",
-          #    # MSVC 17.6.3 can no longer build Subspace. 16 doesn't work either.
-          #    # https://developercommunity.visualstudio.com/t/Update-to-1763-now-rejects-valid-C-i/10394500
-          #    os: windows-latest,
-          #    build_type: "Release",
-          #    cc: "cl",
-          #    cxx: "cl",
-          #    environment_script: "C:/Program Files/Microsoft Visual Studio/2022/Enterprise/VC/Auxiliary/Build/vcvars64.bat",
-          #  }
-          #- {
-          #    name: "Windows MinGW", artifact: "Windows-MinGW.tar.xz",
-          #    os: windows-latest,
-          #    build_type: "Release", cc: "gcc", cxx: "g++"
-          #  }
+        # MSVC is broken: https://github.com/chromium/subspace/issues/267
+        #- {
+        #    name: "Windows MSVC",
+        #    artifact: "Windows-MSVC.tar.xz",
+        #    os: windows-latest,
+        #    build_type: "Release",
+        #    cc: "cl",
+        #    cxx: "cl",
+        #    environment_script: "C:/Program Files/Microsoft Visual Studio/2022/Enterprise/VC/Auxiliary/Build/vcvars64.bat",
+        #  }
+
+        #- {
+        #    name: "Windows MinGW", artifact: "Windows-MinGW.tar.xz",
+        #    os: windows-latest,
+        #    build_type: "Release", cc: "gcc", cxx: "g++"
+        #  }
 
         - {
             name: "Ubuntu Clang-16 Debug",
@@ -75,7 +75,7 @@ jobs:
             build_type: "Release",
             cc: "gcc-13",
             cxx: "g++-13",
-            clang_version: 18,
+            clang_version: 17,
             installed_clang_version: 14
           }
 

.github/workflows/try.yml

@@ -15,83 +15,83 @@ jobs:
       fail-fast: false
       matrix:
         config:
-          #- {
-          #    name: "Windows MSVC",
-          #    artifact: "Windows-MSVC.tar.xz",
-          #    # MSVC 17.6.3 can no longer build Subspace. 16 doesn't work either.
-          #    # https://developercommunity.visualstudio.com/t/Update-to-1763-now-rejects-valid-C-i/10394500
-          #    os: windows-latest,
-          #    build_type: "Release",
-          #    cc: "cl",
-          #    cxx: "cl",
-          #    environment_script: "C:/Program Files/Microsoft Visual Studio/2022/Enterprise/VC/Auxiliary/Build/vcvars64.bat",
-          #  }
-          #- {
-          #    name: "Windows MinGW", artifact: "Windows-MinGW.tar.xz",
-          #    os: windows-latest,
-          #    build_type: "Release", cc: "gcc", cxx: "g++"
-          #  }
-
-          - {
-              name: "Ubuntu Clang-16 Debug",
-              os: ubuntu-latest,
-              build_type: "Debug",
-              cc: "clang-16",
-              cxx: "clang++-16",
-              clang_version: 16,
-              installed_clang_version: 14
-            }
-
-          - {
-              name: "Ubuntu Clang-17 Debug",
-              os: ubuntu-latest,
-              build_type: "Debug",
-              cc: "clang-17",
-              cxx: "clang++-17",
-              clang_version: 17,
-              installed_clang_version: 14
-            }
-
-          - {
-              name: "Ubuntu Clang-17 Sanitizer",
-              os: ubuntu-latest,
-              build_type: "Release",
-              cc: "clang-17",
-              cxx: "clang++-17",
-              clang_version: 17,
-              installed_clang_version: 14
-            }
-
-          - {
-              name: "Ubuntu Clang-18 Debug",
-              os: ubuntu-latest,
-              build_type: "Debug",
-              cc: "clang-18",
-              cxx: "clang++-18",
-              clang_version: 18,
-              installed_clang_version: 14
-            }
-
-          - {
-              name: "Ubuntu GCC",
-              os: ubuntu-latest,
-              build_type: "Release",
-              cc: "gcc-13",
-              cxx: "g++-13",
-              clang_version: 18,
-              installed_clang_version: 14
-            }
-
-          # Clang doesn't have good enough C++20 support to compile this library
-          # yet.
-          #- {
-          #    name: "macOS Latest Clang",
-          #    artifact: "macOS.tar.xz",
-          #    os: macos-latest,
-          #    build_type: "Release",
-          #    cc: "clang",
-          #    cxx: "clang++",
-          #  }
+        # MSVC is broken: https://github.com/chromium/subspace/issues/267
+        #- {
+        #    name: "Windows MSVC",
+        #    artifact: "Windows-MSVC.tar.xz",
+        #    os: windows-latest,
+        #    build_type: "Release",
+        #    cc: "cl",
+        #    cxx: "cl",
+        #    environment_script: "C:/Program Files/Microsoft Visual Studio/2022/Enterprise/VC/Auxiliary/Build/vcvars64.bat",
+        #  }
+
+        #- {
+        #    name: "Windows MinGW", artifact: "Windows-MinGW.tar.xz",
+        #    os: windows-latest,
+        #    build_type: "Release", cc: "gcc", cxx: "g++"
+        #  }
+
+        - {
+            name: "Ubuntu Clang-16 Debug",
+            os: ubuntu-latest,
+            build_type: "Debug",
+            cc: "clang-16",
+            cxx: "clang++-16",
+            clang_version: 16,
+            installed_clang_version: 14
+          }
+
+        - {
+            name: "Ubuntu Clang-17 Debug",
+            os: ubuntu-latest,
+            build_type: "Debug",
+            cc: "clang-17",
+            cxx: "clang++-17",
+            clang_version: 17,
+            installed_clang_version: 14
+          }
+
+        - {
+            name: "Ubuntu Clang-17 Sanitizer",
+            os: ubuntu-latest,
+            build_type: "Release",
+            cc: "clang-17",
+            cxx: "clang++-17",
+            clang_version: 17,
+            installed_clang_version: 14
+          }
+
+        - {
+            name: "Ubuntu Clang-18 Debug",
+            os: ubuntu-latest,
+            build_type: "Debug",
+            cc: "clang-18",
+            cxx: "clang++-18",
+            clang_version: 18,
+            installed_clang_version: 14
+          }
+
+        - {
+            name: "Ubuntu GCC",
+            os: ubuntu-latest,
+            build_type: "Release",
+            cc: "gcc-13",
+            cxx: "g++-13",
+            clang_version: 17,
+            installed_clang_version: 14
+          }
+
+        # Clang doesn't have good enough C++20 support to compile this library
+        # yet.
+        #- {
+        #    name: "macOS Latest Clang",
+        #    artifact: "macOS.tar.xz",
+        #    os: macos-latest,
+        #    build_type: "Release",
+        #    cc: "clang",
+        #    cxx: "clang++",
+        #  }
 
     steps:
       - uses: actions/checkout@v3

README.md

@@ -56,7 +56,7 @@ check out which compiler versions are used by the
 |------------|---------|
 | **Clang:** | 16 and up |
 | **GCC**:   | 13 and up |
-| **MSVC**:   | 17.4.2 (not [newer versions](https://github.com/chromium/subspace/issues/267)) |
+| **MSVC**:   | VS2022 17.8.1 (Build 17.8.34316.72) and up |
 
 We attempt to work around bugs when reasonable, to widen compiler version
 support. See [compiler_bugs.h](sus/macros/__private/compiler_bugs.h) for

subdoc/lib/path.cc

@@ -36,17 +36,28 @@ bool path_contains_namespace(clang::Decl* decl, Namespace n) noexcept {
 }
 
 bool path_is_private(clang::NamedDecl* decl) noexcept {
+  // clang::Linkage members were renamed in 18.
+#if CLANG_VERSION_MAJOR >= 18
+  constexpr auto ModuleLinkage = clang::Linkage::Module;
+  constexpr auto ExternalLinkage = clang::Linkage::External;
+  constexpr auto NoneLinkage = clang::Linkage::None;
+#else
+  constexpr auto ModuleLinkage = clang::Linkage::ModuleLinkage;
+  constexpr auto ExternalLinkage = clang::Linkage::ExternalLinkage;
+  constexpr auto NoneLinkage = clang::Linkage::NoLinkage;
+#endif
+
   clang::Linkage linkage = decl->getLinkageInternal();
-  if (linkage != clang::Linkage::ModuleLinkage &&
-      linkage != clang::Linkage::ExternalLinkage) {
-    // NoLinkage describes itself as "can only be referred to from within its
-    // scope".
+  if (linkage != ModuleLinkage &&
+      linkage != ExternalLinkage) {
+    // Linkage::None describes itself as "can only be referred to from within
+    // its scope".
     //
     // However `namespace a { using b::S; }` brings S into `a` in a way that is
-    // usable publicly from other scopes. So we accept `NoLinkage` for
+    // usable publicly from other scopes. So we accept `Linkage::None` for
     // `UsingDecl` and `UsingEnumDecl` (aka `BaseUsingDecl`). Similar for
     // type aliases.
-    if (!(linkage == clang::Linkage::NoLinkage &&
+    if (!(linkage == NoneLinkage &&
           (clang::isa<clang::BaseUsingDecl>(decl) ||
            clang::isa<clang::TypedefNameDecl>(decl)))) {
       return true;

sus/collections/array.h

@@ -54,9 +54,8 @@ namespace __private {
 
 template <class T, size_t N>
 struct Storage final {
-  sus_msvc_bug_10416202_else(
-      [[sus_no_unique_address]]) sus::iter::IterRefCounter iter_refs_;
-  T data_[N];
+  [[sus_no_unique_address]] sus::iter::IterRefCounter iter_refs_;
+  [[sus_no_unique_address]] T data_[N];
 };
 
 template <class T>

sus/collections/invalidation_off_size_unittest.cc

@@ -24,9 +24,7 @@ using sus::Slice;
 
 constexpr usize array_padding = 0u
     // No support for no_unique_address in clang-cl.
-    sus_clang_bug_49358(+sizeof(i32))
-    // MSVC bug with no_unique_address and arrays, so not used here.
-    sus_clang_bug_49358_else(sus_msvc_bug_10416202(+sizeof(i32)));
+    sus_clang_bug_49358(+sizeof(i32));
 
 static_assert(alignof(Array<i32, 5>) == alignof(i32));
 static_assert(sizeof(Array<i32, 5>) == sizeof(i32) * 5 + array_padding);

sus/env/var.h

@@ -31,7 +31,7 @@ struct VarError {
 
   /// This struct acts as a proxy for the Reason enum, so it can be implicitly
   /// constructed from the reason value.
-  VarError(Reason r) : reason(r) {}
+  constexpr VarError(Reason r) : reason(r) {}
 
   Reason reason;
 

sus/macros/__private/compiler_bugs.h

@@ -98,8 +98,7 @@
 // TODO: https://github.com/llvm/llvm-project/issues/49358
 // Clang-cl doesn't support either [[no_unique_address]] nor
 // [[msvc::no_unique_address]]
-#if _MSC_VER && defined(__clang__) && \
-    __clang_major__ > 0  // TODO: Update when the bug is fixed.
+#if _MSC_VER && defined(__clang__) && __clang_major__ <= 17
 #define sus_clang_bug_49358(...) __VA_ARGS__
 #define sus_clang_bug_49358_else(...)
 #else

sus/mem/copy.h

@@ -84,4 +84,10 @@ concept TrivialCopy =
 template <class T>
 concept CopyOrRef = Copy<T> || std::is_reference_v<T>;
 
+/// Matches types which are [`CopyOrRef`]($sus::mem::CopyOrRef) or are `void`.
+///
+/// A helper for genertic types which can hold void as a type.
+template <class T>
+concept CopyOrRefOrVoid = CopyOrRef<T> || std::is_void_v<T>;
+
 }  // namespace sus::mem

sus/mem/move.h

@@ -63,6 +63,12 @@ concept Move =
 template <class T>
 concept MoveOrRef = Move<T> || std::is_reference_v<T>;
 
+/// Matches types which are [`MoveOrRef`]($sus::mem::MoveOrRef) or are `void`.
+///
+/// A helper for genertic types which can hold void as a type.
+template <class T>
+concept MoveOrRefOrVoid = MoveOrRef<T> || std::is_void_v<T>;
+
 /// Cast `t` to an r-value reference so that it can be used to construct or be
 /// assigned to a (non-reference) object of type `T`.
 ///

sus/option/__private/storage.h

@@ -161,6 +161,11 @@ struct Storage<T, false> final {
 
  private:
   union {
+    // TODO: We can make this T [[no_unique_address]], however then
+    // we can not construct_at on it. Instead, we would need to only
+    // construct_at the Storage class, and have the ctor set them both.
+    //
+    // See also https://github.com/llvm/llvm-project/issues/70494
     T val_;
   };
   State state_ = None;

sus/option/option.h

@@ -1991,6 +1991,10 @@ class Option final {
   using StorageType =
       std::conditional_t<std::is_reference_v<U>, Storage<StoragePointer<U>>,
                          Storage<U>>;
+  // TODO: We can make this no_unique_address, however... if StorageType<T> has
+  // tail padding and Option was marked with no_unique_address, then
+  // constructing T may clobber stuff OUTSIDE the Option. So this can only be
+  // no_unique_address when StorageType<T> has no tail padding.
   StorageType<T> t_;
 
   sus_class_trivially_relocatable_if_types(::sus::marker::unsafe_fn,