Prazek updated this revision to Diff 100216.
Prazek marked 8 inline comments as done.
Prazek added a comment.
- Thanks for the review Aaron, that is much better.
https://reviews.llvm.org/D33470
Files:
clang-tidy/misc/CMakeLists.txt
clang-tidy/misc/DefaultNumericsCheck.cpp
clang-tidy/misc/DefaultNumericsCheck.h
clang-tidy/misc/MiscTidyModule.cpp
docs/ReleaseNotes.rst
docs/clang-tidy/checks/list.rst
docs/clang-tidy/checks/misc-default-numerics.rst
test/clang-tidy/misc-default-numerics.cpp
Index: test/clang-tidy/misc-default-numerics.cpp
===================================================================
--- /dev/null
+++ test/clang-tidy/misc-default-numerics.cpp
@@ -0,0 +1,42 @@
+// RUN: %check_clang_tidy %s misc-default-numerics %t
+
+namespace std {
+
+template <typename T>
+struct numeric_limit {
+ static T min() { return T(); }
+ static T max() { return T(); }
+};
+
+template <>
+struct numeric_limit<int> {
+ static int min() { return -1; }
+ static int max() { return 1; }
+};
+
+} // namespace std
+
+class MyType {};
+template <typename T>
+class MyTemplate {};
+
+void test() {
+ auto x = std::numeric_limit<int>::min();
+
+ auto y = std::numeric_limit<MyType>::min();
+ // CHECK-MESSAGES: [[@LINE-1]]:12: warning: 'std::numeric_limits::min' called with type 'MyType'; no such specialization exists, so the default value for that type is returned
+
+ auto z = std::numeric_limit<MyTemplate<int>>::max();
+ // CHECK-MESSAGES: [[@LINE-1]]:12: warning: 'std::numeric_limits::max' called with type 'MyTemplate<int>';
+}
+
+template <typename T>
+void fun() {
+ auto x = std::numeric_limit<T>::min();
+}
+
+void testTemplate() {
+ fun<int>();
+ // FIXME: This should generate warning with backtrace.
+ fun<MyType>;
+}
Index: docs/clang-tidy/checks/misc-default-numerics.rst
===================================================================
--- /dev/null
+++ docs/clang-tidy/checks/misc-default-numerics.rst
@@ -0,0 +1,23 @@
+.. title:: clang-tidy - misc-default-numerics
+
+misc-default-numerics
+=====================
+
+This check flags usages of ``std::numeric_limits<T>::{min,max}()`` for
+unspecialized types. It is dangerous because the calls return ``T()``
+in this case, which is unlikely to represent the minimum or maximum value for
+the type.
+
+Consider scenario:
+.. code-block:: c++
+
+ // 1. Have a:
+ typedef long long BigInt
+
+ // 2. Use
+ std::numeric_limits<BigInt>::min()
+
+ // 3. Replace the BigInt typedef with class implementing BigIntegers
+ class BigInt { ;;; };
+
+ // 4. Your code continues to compile, but the call to min() returns BigInt{}
Index: docs/clang-tidy/checks/list.rst
===================================================================
--- docs/clang-tidy/checks/list.rst
+++ docs/clang-tidy/checks/list.rst
@@ -75,6 +75,7 @@
misc-assert-side-effect
misc-bool-pointer-implicit-conversion
misc-dangling-handle
+ misc-default-numerics
misc-definitions-in-headers
misc-fold-init-type
misc-forward-declaration-namespace
Index: docs/ReleaseNotes.rst
===================================================================
--- docs/ReleaseNotes.rst
+++ docs/ReleaseNotes.rst
@@ -71,7 +71,11 @@
<http://clang.llvm.org/extra/clang-tidy/checks/cppcoreguidelines-no-malloc.html>`_ check
Allow custom memory management functions to be considered as well.
-
+
+- New `misc-default-numerics
+ <http://clang.llvm.org/extra/clang-tidy/checks/misc-default-numerics.html>`_ check
+ Finds uses of ``std::numeric_limit<T>`` for unspecialized types
+
- New `misc-forwarding-reference-overload
<http://clang.llvm.org/extra/clang-tidy/checks/misc-forwarding-reference-overload.html>`_ check
Index: clang-tidy/misc/MiscTidyModule.cpp
===================================================================
--- clang-tidy/misc/MiscTidyModule.cpp
+++ clang-tidy/misc/MiscTidyModule.cpp
@@ -14,6 +14,7 @@
#include "AssertSideEffectCheck.h"
#include "BoolPointerImplicitConversionCheck.h"
#include "DanglingHandleCheck.h"
+#include "DefaultNumericsCheck.h"
#include "DefinitionsInHeadersCheck.h"
#include "FoldInitTypeCheck.h"
#include "ForwardDeclarationNamespaceCheck.h"
@@ -66,6 +67,7 @@
CheckFactories.registerCheck<ArgumentCommentCheck>("misc-argument-comment");
CheckFactories.registerCheck<AssertSideEffectCheck>(
"misc-assert-side-effect");
+ CheckFactories.registerCheck<DefaultNumericsCheck>("misc-default-numerics");
CheckFactories.registerCheck<ForwardingReferenceOverloadCheck>(
"misc-forwarding-reference-overload");
CheckFactories.registerCheck<MisplacedConstCheck>("misc-misplaced-const");
Index: clang-tidy/misc/DefaultNumericsCheck.h
===================================================================
--- /dev/null
+++ clang-tidy/misc/DefaultNumericsCheck.h
@@ -0,0 +1,37 @@
+//===--- DefaultNumericsCheck.h - clang-tidy---------------------*- C++ -*-===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MISC_DEFAULT_NUMERICS_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MISC_DEFAULT_NUMERICS_H
+
+#include "../ClangTidy.h"
+
+namespace clang {
+namespace tidy {
+namespace misc {
+
+/// This check flags usages of ``std::numeric_limits<T>::{min,max}()`` for
+/// unspecialized types. It is dangerous because it returns T(), which might is
+/// rarely minimum or maximum for this type.
+///
+/// For the user-facing documentation see:
+/// http://clang.llvm.org/extra/clang-tidy/checks/misc-default-numerics.html
+class DefaultNumericsCheck : public ClangTidyCheck {
+public:
+ DefaultNumericsCheck(StringRef Name, ClangTidyContext *Context)
+ : ClangTidyCheck(Name, Context) {}
+ void registerMatchers(ast_matchers::MatchFinder *Finder) override;
+ void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
+};
+
+} // namespace misc
+} // namespace tidy
+} // namespace clang
+
+#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MISC_DEFAULT_NUMERICS_H
Index: clang-tidy/misc/DefaultNumericsCheck.cpp
===================================================================
--- /dev/null
+++ clang-tidy/misc/DefaultNumericsCheck.cpp
@@ -0,0 +1,51 @@
+//===--- DefaultNumericsCheck.cpp - clang-tidy-----------------------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "DefaultNumericsCheck.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang {
+namespace tidy {
+namespace misc {
+
+void DefaultNumericsCheck::registerMatchers(MatchFinder *Finder) {
+ if (!getLangOpts().CPlusPlus)
+ return;
+ // FIXME: We should also warn in template intantiations, but it would require
+ // printing backtrace.
+ Finder->addMatcher(
+ callExpr(
+ callee(cxxMethodDecl(
+ hasAnyName("min", "max"),
+ ofClass(classTemplateSpecializationDecl(
+ hasName("::std::numeric_limit"),
+ unless(isExplicitTemplateSpecialization()),
+ hasTemplateArgument(0, templateArgument().bind("type")))))),
+ unless(isInTemplateInstantiation()))
+ .bind("call"),
+ this);
+}
+
+void DefaultNumericsCheck::check(const MatchFinder::MatchResult &Result) {
+ const auto &MatchedCall = *Result.Nodes.getNodeAs<CallExpr>("call");
+ const auto &NumericType = *Result.Nodes.getNodeAs<TemplateArgument>("type");
+ bool IsMax = MatchedCall.getCalleeDecl()->getAsFunction()->getName() == "max";
+
+ diag(MatchedCall.getLocStart(),
+ "'std::numeric_limits::%select{min|max}0' called with type %1; no such "
+ "specialization exists, so the default value for that type is returned")
+ << IsMax << NumericType;
+}
+
+} // namespace misc
+} // namespace tidy
+} // namespace clang
Index: clang-tidy/misc/CMakeLists.txt
===================================================================
--- clang-tidy/misc/CMakeLists.txt
+++ clang-tidy/misc/CMakeLists.txt
@@ -3,6 +3,7 @@
add_clang_library(clangTidyMiscModule
ArgumentCommentCheck.cpp
AssertSideEffectCheck.cpp
+ DefaultNumericsCheck.cpp
ForwardingReferenceOverloadCheck.cpp
MisplacedConstCheck.cpp
UnconventionalAssignOperatorCheck.cpp
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