[clang-tidy] Add portability-avoid-platform-specific-fundamental-types

clang-tools-extra/clang-tidy/portability/AvoidPlatformSpecificFundamentalTypesCheck.cpp

@@ -0,0 +1,121 @@
+//===--- AvoidPlatformSpecificFundamentalTypesCheck.cpp - clang-tidy
+//---------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "AvoidPlatformSpecificFundamentalTypesCheck.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/ASTMatchers/ASTMatchers.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::portability {
+
+AvoidPlatformSpecificFundamentalTypesCheck::
+    AvoidPlatformSpecificFundamentalTypesCheck(StringRef Name,
+                                               ClangTidyContext *Context)
+    : ClangTidyCheck(Name, Context) {}
+
+void AvoidPlatformSpecificFundamentalTypesCheck::registerMatchers(
+    MatchFinder *Finder) {
+  // Create a matcher for platform-specific fundamental integer types
+  // This should only match direct uses of builtin types, not typedefs
+  auto PlatformSpecificFundamentalType = qualType(allOf(
+      // Must be a builtin type directly (not through typedef)
+      builtinType(),
+      // Only match the specific fundamental integer types we care about
+      anyOf(asString("short"), asString("short int"), asString("signed short"),
+            asString("signed short int"), asString("unsigned short"),
+            asString("unsigned short int"), asString("int"), asString("signed"),
+            asString("signed int"), asString("unsigned"),
+            asString("unsigned int"), asString("long"), asString("long int"),
+            asString("signed long"), asString("signed long int"),
+            asString("unsigned long"), asString("unsigned long int"),
+            asString("long long"), asString("long long int"),
+            asString("signed long long"), asString("signed long long int"),
+            asString("unsigned long long"),
+            asString("unsigned long long int"))));
+
+  // Match variable declarations with platform-specific fundamental integer
+  // types
+  Finder->addMatcher(
+      varDecl(hasType(PlatformSpecificFundamentalType)).bind("var_decl"), this);
+
+  // Match function declarations with platform-specific fundamental integer
+  // return types
+  Finder->addMatcher(
+      functionDecl(returns(PlatformSpecificFundamentalType)).bind("func_decl"),
+      this);
+
+  // Match function parameters with platform-specific fundamental integer types
+  Finder->addMatcher(
+      parmVarDecl(hasType(PlatformSpecificFundamentalType)).bind("param_decl"),
+      this);
+
+  // Match field declarations with platform-specific fundamental integer types
+  Finder->addMatcher(
+      fieldDecl(hasType(PlatformSpecificFundamentalType)).bind("field_decl"),
+      this);
+
+  // Match typedef declarations with platform-specific fundamental underlying
+  // types
+  Finder->addMatcher(
+      typedefDecl(hasUnderlyingType(PlatformSpecificFundamentalType))
+          .bind("typedef_decl"),
+      this);
+
+  // Match type alias declarations with platform-specific fundamental underlying
+  // types
+  Finder->addMatcher(typeAliasDecl(hasType(PlatformSpecificFundamentalType))
+                         .bind("alias_decl"),
+                     this);
+}
+
+void AvoidPlatformSpecificFundamentalTypesCheck::check(
+    const MatchFinder::MatchResult &Result) {
+  SourceLocation Loc;
+  QualType QT;
+
+  if (const auto *VD = Result.Nodes.getNodeAs<VarDecl>("var_decl")) {
+    Loc = VD->getLocation();
+    QT = VD->getType();
+  } else if (const auto *FD =
+                 Result.Nodes.getNodeAs<FunctionDecl>("func_decl")) {
+    Loc = FD->getLocation();
+    QT = FD->getReturnType();
+  } else if (const auto *PD =
+                 Result.Nodes.getNodeAs<ParmVarDecl>("param_decl")) {
+    Loc = PD->getLocation();
+    QT = PD->getType();
+  } else if (const auto *FD = Result.Nodes.getNodeAs<FieldDecl>("field_decl")) {
+    Loc = FD->getLocation();
+    QT = FD->getType();
+  } else if (const auto *TD =
+                 Result.Nodes.getNodeAs<TypedefDecl>("typedef_decl")) {
+    Loc = TD->getLocation();
+    QT = TD->getUnderlyingType();
+  } else if (const auto *AD =
+                 Result.Nodes.getNodeAs<TypeAliasDecl>("alias_decl")) {
+    Loc = AD->getLocation();
+    QT = AD->getUnderlyingType();
+  } else {
+    return;
+  }
+
+  if (Loc.isInvalid() || QT.isNull())
+    return;
+
+  // Get the type name for the diagnostic
+  std::string TypeName = QT.getAsString();
+
+  diag(Loc, "avoid using platform-dependent fundamental integer type '%0'; "
+            "consider using a typedef or fixed-width type instead")
+      << TypeName;
+}
+
+} // namespace clang::tidy::portability

clang-tools-extra/clang-tidy/portability/AvoidPlatformSpecificFundamentalTypesCheck.h

@@ -0,0 +1,43 @@
+//===--- AvoidPlatformSpecificFundamentalTypesCheck.h - clang-tidy -------*- C++
+//-*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_PORTABILITY_AVOIDPLATFORMSPECIFICFUNDAMENTALTYPESCHECK_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_PORTABILITY_AVOIDPLATFORMSPECIFICFUNDAMENTALTYPESCHECK_H
+
+#include "../ClangTidyCheck.h"
+
+namespace clang::tidy::portability {
+
+/// Find fundamental integer types and recommend using typedefs or fixed-width
+/// types.
+///
+/// Detects fundamental integer types (int, short, long, long long, and their
+/// unsigned variants) and warns against their use due to platform-dependent
+/// behavior. Excludes semantic types like char, bool, wchar_t, char16_t,
+/// char32_t, size_t, and ptrdiff_t.
+///
+/// For the user-facing documentation see:
+/// http://clang.llvm.org/extra/clang-tidy/checks/portability/avoid-platform-specific-fundamental-types.html
+class AvoidPlatformSpecificFundamentalTypesCheck : public ClangTidyCheck {
+public:
+  AvoidPlatformSpecificFundamentalTypesCheck(StringRef Name,
+                                             ClangTidyContext *Context);
+  void registerMatchers(ast_matchers::MatchFinder *Finder) override;
+  void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
+  bool isLanguageVersionSupported(const LangOptions &LangOpts) const override {
+    return LangOpts.CPlusPlus11;
+  }
+  std::optional<TraversalKind> getCheckTraversalKind() const override {
+    return TK_IgnoreUnlessSpelledInSource;
+  }
+};
+
+} // namespace clang::tidy::portability
+
+#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_PORTABILITY_AVOIDPLATFORMSPECIFICFUNDAMENTALTYPESCHECK_H

clang-tools-extra/clang-tidy/portability/CMakeLists.txt

@@ -5,6 +5,7 @@ set(LLVM_LINK_COMPONENTS
   )
 
 add_clang_library(clangTidyPortabilityModule STATIC
+  AvoidPlatformSpecificFundamentalTypesCheck.cpp
   AvoidPragmaOnceCheck.cpp
   PortabilityTidyModule.cpp
   RestrictSystemIncludesCheck.cpp

clang-tools-extra/clang-tidy/portability/PortabilityTidyModule.cpp

@@ -9,6 +9,7 @@
 #include "../ClangTidy.h"
 #include "../ClangTidyModule.h"
 #include "../ClangTidyModuleRegistry.h"
+#include "AvoidPlatformSpecificFundamentalTypesCheck.h"
 #include "AvoidPragmaOnceCheck.h"
 #include "RestrictSystemIncludesCheck.h"
 #include "SIMDIntrinsicsCheck.h"
@@ -21,6 +22,8 @@ namespace portability {
 class PortabilityModule : public ClangTidyModule {
 public:
   void addCheckFactories(ClangTidyCheckFactories &CheckFactories) override {
+    CheckFactories.registerCheck<AvoidPlatformSpecificFundamentalTypesCheck>(
+        "portability-avoid-platform-specific-fundamental-types");
     CheckFactories.registerCheck<AvoidPragmaOnceCheck>(
         "portability-avoid-pragma-once");
     CheckFactories.registerCheck<RestrictSystemIncludesCheck>(

clang-tools-extra/docs/clang-tidy/checks/list.rst

@@ -353,6 +353,7 @@ Clang-Tidy Checks
    :doc:`performance-type-promotion-in-math-fn <performance/type-promotion-in-math-fn>`, "Yes"
    :doc:`performance-unnecessary-copy-initialization <performance/unnecessary-copy-initialization>`, "Yes"
    :doc:`performance-unnecessary-value-param <performance/unnecessary-value-param>`, "Yes"
+   :doc:`portability-avoid-platform-specific-fundamental-types <portability/avoid-platform-specific-fundamental-types>`,
    :doc:`portability-avoid-pragma-once <portability/avoid-pragma-once>`,
    :doc:`portability-restrict-system-includes <portability/restrict-system-includes>`, "Yes"
    :doc:`portability-simd-intrinsics <portability/simd-intrinsics>`,

clang-tools-extra/docs/clang-tidy/checks/portability/avoid-platform-specific-fundamental-types.rst

@@ -0,0 +1,111 @@
+.. title:: clang-tidy - portability-avoid-platform-specific-fundamental-types
+
+portability-avoid-platform-specific-fundamental-types
+=====================================================
+
+Finds fundamental types and recommends using typedefs or fixed-width types instead.
+
+This check detects fundamental integer types (``int``, ``short``, ``long``, ``long long``, and their
+``unsigned`` variants) and warns against their use due to non-standard platform-dependent behavior.
+For example, ``long`` is 64 bits on Linux but 32 bits on Windows. There is no standard rationale or
+intent for the sizes of these types.
+
+Instead of fundamental types, use fixed-width types such as ``int32_t`` or implementation-defined
+types with standard semantics, e.g. ``int_fast32_t`` for the fastest integer type greater than or
+equal to 32 bits.
+
+Examples
+--------
+
+.. code-block:: c++
+
+  // Bad: platform-dependent fundamental types
+  int global_int = 42;
+  short global_short = 10;
+  long global_long = 100L;
+  unsigned long global_unsigned_long = 100UL;
+
+  void function_with_int_param(int param) {
+    // ...
+  }
+
+  int function_returning_int() {
+    return 42;
+  }
+
+  struct MyStruct {
+    int member_int;
+    long member_long;
+  };
+
+.. code-block:: c++
+
+  // Good: use fixed-width types or typedefs
+  #include <cstdint>
+
+  int32_t global_int32 = 42;
+  int16_t global_int16 = 10;
+  int64_t global_int64 = 100L;
+  uint64_t global_uint64 = 100UL;
+
+  void function_with_int32_param(int32_t param) {
+    // ...
+  }
+
+  int32_t function_returning_int32() {
+    return 42;
+  }
+
+  struct MyStruct {
+    int32_t member_int32;
+    int64_t member_int64;
+  };
+
+The check will also warn about typedef declarations that use fundamental types as their underlying type:
+
+.. code-block:: c++
+
+  // Bad: typedef using fundamental type
+  typedef long long MyLongType;
+  using MyIntType = int;
+
+.. code-block:: c++
+
+  // Good: use descriptive names or fixed-width types
+  typedef int64_t TimestampType;
+  using CounterType = uint32_t;
+
+Rationale
+---------
+
+Fundamental integer types have platform-dependent sizes and behavior:
+
+- ``int`` is typically 32 bits on modern platforms but is only guaranteed to be 16 bits by the spec
+- ``long int`` is 32 bits on Windows but 64 bits on most Unix systems
+
+The C++ specification does not define these types beyond their minimum sizes. That means they can
+communicate intent in non-standard ways and are often needlessly incompatible. For example, ``int``
+was traditionally the word size of a given processor in 16-bit and 32-bit computing and was a
+reasonable default for performance. This is no longer true on modern 64-bit computers, but the size
+of ``int`` remains fixed at 32 bits for backwards compatibility with code that relied on a 32-bit
+implementation of ``int``.
+
+If code is explicitly relying on the size of an ``int`` being 32 bits, it is better to say so in
+the typename with ``int32_t``. Otherwise, use an appropriate implementation-defined type that
+communicates your intent.
+
+Types Not Flagged
+-----------------
+
+The following types are intentionally not flagged:
+
+- ``char``, ``signed char``, ``unsigned char`` (character types)
+- ``bool`` (boolean type)
+- Standard library typedefs like ``size_t``, ``ptrdiff_t``, or ``uint32_t``.
+- Already typedef'd types, though the check will flag the typedef itself
+
+``char`` is excluded because it is implementation-defined to always be 1 byte, regardless of the
+platform's definition of a byte.
+
+``bool`` is excluded because it can only be true or false, and is not vulnerable to overflow or
+narrowing issues that occur as a result of using implementation-defined types.