Infer @PointerBounds macro from clang __counted_by parameters (#77387)

This results in an automatic wrapper function with safe pointer types
when the imported function has bounds attributes. This exercises similar
pathways as the recently added functionality for specifying macros from
swift_attr. The new functionality is guarded by the experimental
language feature SafeInteropWrappers.

rdar://97942270

Author: hnrklssn

include/swift/Basic/Features.def

@@ -406,6 +406,10 @@ EXPERIMENTAL_FEATURE(WarnUnsafe, true)
 /// Import unsafe C and C++ constructs as @unsafe.
 EXPERIMENTAL_FEATURE(SafeInterop, true)
 
+// Import bounds safety and lifetime attributes from interop headers to
+// generate Swift wrappers with safe pointer types.
+EXPERIMENTAL_FEATURE(SafeInteropWrappers, false)
+
 /// Ignore resilience errors due to C++ types.
 EXPERIMENTAL_FEATURE(AssumeResilientCxxTypes, true)
 

include/swift/Option/Options.td

@@ -792,6 +792,11 @@ def enable_experimental_concise_pound_file : Flag<["-"],
   Flags<[FrontendOption, ModuleInterfaceOption]>,
   HelpText<"Enable experimental concise '#file' identifier">;
 
+def enable_experimental_bounds_safety_interop :
+  Flag<["-"], "enable-experimental-bounds-safety-interop">,
+  Flags<[NoDriverOption, FrontendOption, HelpHidden, ModuleInterfaceOption]>,
+  HelpText<"Enable experimental C bounds safety interop code generation and config directives">;
+
 def enable_experimental_cxx_interop :
   Flag<["-"], "enable-experimental-cxx-interop">,
   Flags<[NoDriverOption, FrontendOption, HelpHidden]>,

lib/AST/FeatureSet.cpp

@@ -325,6 +325,7 @@ static bool usesFeatureAllowUnsafeAttribute(Decl *decl) {
 
 UNINTERESTING_FEATURE(WarnUnsafe)
 UNINTERESTING_FEATURE(SafeInterop)
+UNINTERESTING_FEATURE(SafeInteropWrappers)
 UNINTERESTING_FEATURE(AssumeResilientCxxTypes)
 UNINTERESTING_FEATURE(CoroutineAccessorsUnwindOnCallerError)
 UNINTERESTING_FEATURE(CoroutineAccessorsAllocateInCallee)

lib/ClangImporter/ClangImporter.cpp

@@ -579,6 +579,9 @@ void importer::getNormalInvocationArguments(
     }
   }
 
+  if (LangOpts.hasFeature(Feature::SafeInteropWrappers))
+    invocationArgStrs.push_back("-fexperimental-bounds-safety-attributes");
+
   // Set C language options.
   if (triple.isOSDarwin()) {
     invocationArgStrs.insert(invocationArgStrs.end(), {

lib/ClangImporter/ImportDecl.cpp

@@ -108,7 +108,8 @@ createFuncOrAccessor(ClangImporter::Implementation &impl, SourceLoc funcLoc,
                      std::optional<AccessorInfo> accessorInfo, DeclName name,
                      SourceLoc nameLoc, GenericParamList *genericParams,
                      ParameterList *bodyParams, Type resultTy, bool async,
-                     bool throws, DeclContext *dc, ClangNode clangNode) {
+                     bool throws, DeclContext *dc, ClangNode clangNode,
+                     bool hasBoundsAnnotation) {
   FuncDecl *decl;
   if (accessorInfo) {
     decl = AccessorDecl::create(
@@ -124,6 +125,9 @@ createFuncOrAccessor(ClangImporter::Implementation &impl, SourceLoc funcLoc,
                                     genericParams, dc, clangNode);
   }
   impl.importSwiftAttrAttributes(decl);
+  if (hasBoundsAnnotation)
+    impl.importBoundsAttributes(decl);
+
   return decl;
 }
 
@@ -3272,7 +3276,8 @@ namespace {
       }
       return Impl.importFunctionParameterList(
           dc, decl, nonSelfParams, decl->isVariadic(), allowNSUIntegerAsInt,
-          argNames, genericParams, /*resultType=*/nullptr);
+          argNames, genericParams, /*resultType=*/nullptr,
+          /*hasBoundsAnnotatedParam=*/nullptr);
     }
 
     Decl *
@@ -3690,6 +3695,7 @@ namespace {
 
       bool importFuncWithoutSignature =
           isa<clang::CXXMethodDecl>(decl) && Impl.importSymbolicCXXDecls;
+      bool hasBoundsAnnotation = false;
       if (!dc->isModuleScopeContext() && !isa<clang::CXXMethodDecl>(decl)) {
         // Handle initializers.
         if (name.getBaseName().isConstructor()) {
@@ -3786,7 +3792,7 @@ namespace {
           importedType = Impl.importFunctionParamsAndReturnType(
               dc, decl, {decl->param_begin(), decl->param_size()},
               decl->isVariadic(), isInSystemModule(dc), name, bodyParams,
-              templateParams);
+              templateParams, &hasBoundsAnnotation);
         }
 
         if (auto *mdecl = dyn_cast<clang::CXXMethodDecl>(decl)) {
@@ -3853,10 +3859,10 @@ namespace {
         auto resultTy = importedType.getType();
 
         FuncDecl *func =
-            createFuncOrAccessor(Impl, loc, accessorInfo, name,
-                                 nameLoc, genericParams, bodyParams, resultTy,
+            createFuncOrAccessor(Impl, loc, accessorInfo, name, nameLoc,
+                                 genericParams, bodyParams, resultTy,
                                  /*async=*/false, /*throws=*/false, dc,
-                                 clangNode);
+                                 clangNode, hasBoundsAnnotation);
         result = func;
 
         if (!dc->isModuleScopeContext()) {
@@ -4899,12 +4905,14 @@ namespace {
         }
       }
 
-      auto result = createFuncOrAccessor(Impl,
-                                         /*funcLoc*/ SourceLoc(), accessorInfo,
-                                         importedName.getDeclName(),
-                                         /*nameLoc*/ SourceLoc(),
-                                         /*genericParams=*/nullptr, bodyParams,
-                                         resultTy, async, throws, dc, decl);
+      bool hasBoundsAnnotation =
+          false; // currently only implemented for functions
+      auto result = createFuncOrAccessor(
+          Impl,
+          /*funcLoc*/ SourceLoc(), accessorInfo, importedName.getDeclName(),
+          /*nameLoc*/ SourceLoc(),
+          /*genericParams=*/nullptr, bodyParams, resultTy, async, throws, dc,
+          decl, hasBoundsAnnotation);
 
       result->setAccess(decl->isDirectMethod() ? AccessLevel::Public
                                                : getOverridableAccessLevel(dc));
@@ -6544,7 +6552,8 @@ Decl *SwiftDeclConverter::importGlobalAsInitializer(
   } else {
     parameterList = Impl.importFunctionParameterList(
         dc, decl, {decl->param_begin(), decl->param_end()}, decl->isVariadic(),
-        allowNSUIntegerAsInt, argNames, /*genericParams=*/{}, /*resultType=*/nullptr);
+        allowNSUIntegerAsInt, argNames, /*genericParams=*/{},
+        /*resultType=*/nullptr, /*hasBoundsAnnotatedParam=*/nullptr);
   }
   if (!parameterList)
     return nullptr;
@@ -8344,6 +8353,53 @@ static bool importAsUnsafe(ClangImporter::Implementation &impl,
   return false;
 }
 
+void ClangImporter::Implementation::importNontrivialAttribute(
+    Decl *MappedDecl, llvm::StringRef AttrString) {
+  bool cached = true;
+  while (true) {
+    // Dig out a source file we can use for parsing.
+    auto &sourceFile = getClangSwiftAttrSourceFile(
+        *MappedDecl->getDeclContext()->getParentModule(), AttrString, cached);
+
+    auto topLevelDecls = sourceFile.getTopLevelDecls();
+
+    // If we're using the cached version, check whether we can correctly
+    // clone the attribute.
+    if (cached) {
+      bool hasNonclonableAttribute = false;
+      for (auto decl : topLevelDecls) {
+        if (hasNonclonableAttribute)
+          break;
+
+        for (auto attr : decl->getAttrs()) {
+          if (!attr->canClone()) {
+            hasNonclonableAttribute = true;
+            break;
+          }
+        }
+      }
+
+      // We cannot clone one of the attributes. Go back and build a new
+      // source file without caching it.
+      if (hasNonclonableAttribute) {
+        cached = false;
+        continue;
+      }
+    }
+
+    // Collect the attributes from the synthesized top-level declaration in
+    // the source file. If we're using a cached copy, clone the attribute.
+    for (auto decl : topLevelDecls) {
+      SmallVector<DeclAttribute *, 2> attrs(decl->getAttrs().begin(),
+                                            decl->getAttrs().end());
+      for (auto attr : attrs) {
+        MappedDecl->getAttrs().add(cached ? attr->clone(SwiftContext) : attr);
+      }
+    }
+    break;
+  }
+}
+
 void
 ClangImporter::Implementation::importSwiftAttrAttributes(Decl *MappedDecl) {
   auto ClangDecl =
@@ -8481,53 +8537,7 @@ ClangImporter::Implementation::importSwiftAttrAttributes(Decl *MappedDecl) {
         continue;
       }
 
-      bool cached = true;
-      while (true) {
-        // Dig out a source file we can use for parsing.
-        auto &sourceFile = getClangSwiftAttrSourceFile(
-            *MappedDecl->getDeclContext()->getParentModule(),
-            swiftAttr->getAttribute(),
-            cached);
-
-        auto topLevelDecls = sourceFile.getTopLevelDecls();
-
-        // If we're using the cached version, check whether we can correctly
-        // clone the attribute.
-        if (cached) {
-          bool hasNonclonableAttribute = false;
-          for (auto decl : topLevelDecls) {
-            if (hasNonclonableAttribute)
-              break;
-
-            for (auto attr : decl->getAttrs()) {
-              if (!attr->canClone()) {
-                hasNonclonableAttribute = true;
-                break;
-              }
-            }
-          }
-
-          // We cannot clone one of the attributes. Go back and build a new
-          // source file without caching it.
-          if (hasNonclonableAttribute) {
-            cached = false;
-            continue;
-          }
-        }
-
-        // Collect the attributes from the synthesized top-level declaration in
-        // the source file. If we're using a cached copy, clone the attribute.
-        for (auto decl : topLevelDecls) {
-          SmallVector<DeclAttribute *, 2> attrs(decl->getAttrs().begin(),
-                                                decl->getAttrs().end());
-          for (auto attr : attrs) {
-            MappedDecl->getAttrs().add(cached ? attr->clone(SwiftContext)
-                                              : attr);
-          }
-        }
-
-        break;
-      }
+      importNontrivialAttribute(MappedDecl, swiftAttr->getAttribute());
     }
 
     if (seenUnsafe || importAsUnsafe(*this, ClangDecl, MappedDecl)) {
@@ -8613,6 +8623,70 @@ ClangImporter::Implementation::importSwiftAttrAttributes(Decl *MappedDecl) {
   }
 }
 
+namespace {
+class PointerParamInfoPrinter {
+public:
+  clang::ASTContext &ctx;
+  llvm::raw_ostream &out;
+  bool firstParam = true;
+  PointerParamInfoPrinter(clang::ASTContext &ctx, llvm::raw_ostream &out)
+      : ctx(ctx), out(out) {
+    out << "@PointerBounds(";
+  }
+  ~PointerParamInfoPrinter() { out << ")"; }
+
+  void printCountedBy(const clang::CountAttributedType *CAT,
+                      size_t pointerIndex) {
+    if (!firstParam) {
+      out << ", ";
+    } else {
+      firstParam = false;
+    }
+    clang::Expr *countExpr = CAT->getCountExpr();
+    bool isSizedBy = CAT->isCountInBytes();
+    out << ".";
+    if (isSizedBy)
+      out << "sizedBy";
+    else
+      out << "countedBy";
+    out << "(pointer: " << pointerIndex + 1 << ", ";
+    if (isSizedBy)
+      out << "size";
+    else
+      out << "count";
+    out << ": \"";
+    countExpr->printPretty(
+        out, {}, {ctx.getLangOpts()}); // TODO: map clang::Expr to Swift Expr
+    out << "\")";
+  }
+};
+} // namespace
+
+void ClangImporter::Implementation::importBoundsAttributes(
+    FuncDecl *MappedDecl) {
+  assert(SwiftContext.LangOpts.hasFeature(Feature::SafeInteropWrappers));
+  auto ClangDecl =
+      dyn_cast_or_null<clang::FunctionDecl>(MappedDecl->getClangDecl());
+  // any function with safe pointer imports should have a clang decl
+  assert(ClangDecl);
+  if (!ClangDecl)
+    return;
+
+  llvm::SmallString<128> MacroString;
+  {
+    llvm::raw_svector_ostream out(MacroString);
+
+    PointerParamInfoPrinter printer(getClangASTContext(), out);
+    for (auto [index, param] : llvm::enumerate(ClangDecl->parameters())) {
+      if (auto CAT = param->getType()->getAs<clang::CountAttributedType>()) {
+        printer.printCountedBy(CAT, index);
+      }
+    }
+  }
+
+  importNontrivialAttribute(MappedDecl, MacroString);
+}
+
 static bool isUsingMacroName(clang::SourceManager &SM,
                              clang::SourceLocation loc,
                              StringRef MacroName) {