Add bugprone-bool-to-integer-conversion

[Prazek]

Summary

Tested on llvm codebase.
It have found many places like:

• returning true/false in function returning int,
• assigning true/false to integer inside some classes.

[Prazek]

Maybe we should merge it with http://reviews.llvm.org/D18745 and name it 'modernize-wrong-literal-cast'. The other question is, will it be better to move it to readability?

[krystyna]

docs/clang-tidy/checks/modernize-bool-to-integer-conversion.rst

9

int a = false;

[mnbvmar]

This check throws a warning also on the conversion to floats (probably very rare ones):

double number = true;

Even though this behavior is correct, the code warns about the implicit conversion to integers.

docs/ReleaseNotes.rst

119

with int literals

[Prazek]

In D18821#393556, @mnbvmar wrote:

This check throws a warning also on the conversion to floats (probably very rare ones):

double number = true;

Even though this behavior is correct, the code warns about the implicit conversion to integers.

That case is extremaly rare. I will see what I can do

[Prazek]

Added new test cases

[alexfh]

Actually, did you think about adding this as a clang diagnostic?

Richard, what do you think about complaining in Clang about int i = true; kind of code?

clang-tidy/modernize/BoolToIntegerConversionCheck.cpp

50

s/. Use/; use/

Same below.

docs/ReleaseNotes.rst

119

The phrase is technically incorrect. The check does not replace implicit cast from bool literals. It replaces bool literals (which are being implicitly cast to integers) with integer literals.

docs/clang-tidy/checks/modernize-bool-to-integer-conversion.rst

10

There should be an empty line after .. code-block ....

[Prazek]

In D18821#394486, @alexfh wrote:

Actually, did you think about adding this as a clang diagnostic?

Richard, what do you think about complaining in Clang about int i = true; kind of code?

Glad to hear that :)

[alexfh]

clang-tidy/modernize/BoolToIntegerConversionCheck.cpp

48

I'd prefer an alternative with less code duplication:

auto Diag = diag("implicitly converting bool literal to %0%select{|inside a macro}1; use ...") << Type;
if (<should add fixes>)
  Diag << 1 << FixItHint::...;
else
  Diag << 0;

[Prazek]

Used isMacroID to determinate if it's macro

[alexfh]

BTW, why is the check in the 'modernize' module? It doesn't seem to make anything more modern. I would guess, the pattern it detects is most likely to result from a programming error. Also, the fix, though it retains the behavior, has a high chance to be incorrect. Can you share the results of running this check on LLVM? At least, how many problems it found and how many times the suggested fix was correct.

I'd suggest to move the check to misc or maybe it's time to create a separate directory for checks targeting various bug-prone patterns.

clang-tidy/modernize/BoolToIntegerConversionCheck.cpp

44

nit: Since both positive and negative branches are present, I'd prefer to make the condition slightly simple by removing the negation.

[Prazek]

In D18821#398843, @alexfh wrote:

BTW, why is the check in the 'modernize' module? It doesn't seem to make anything more modern. I would guess, the pattern it detects is most likely to result from a programming error. Also, the fix, though it retains the behavior, has a high chance to be incorrect. Can you share the results of running this check on LLVM? At least, how many problems it found and how many times the suggested fix was correct.

I'd suggest to move the check to misc or maybe it's time to create a separate directory for checks targeting various bug-prone patterns.

There were many places. Most of them where when assigning true/false to some member which was int.
The other place was inside some functions that were returning only true or false, but the return type of this function was int, so I guess what programmer meant there was to return bool.

[alexfh]

In D18821#399064, @Prazek wrote:

In D18821#398843, @alexfh wrote:

BTW, why is the check in the 'modernize' module? It doesn't seem to make anything more modern. I would guess, the pattern it detects is most likely to result from a programming error. Also, the fix, though it retains the behavior, has a high chance to be incorrect. Can you share the results of running this check on LLVM? At least, how many problems it found and how many times the suggested fix was correct.

I'd suggest to move the check to misc or maybe it's time to create a separate directory for checks targeting various bug-prone patterns.

There were many places.

Would be nice, if you could tell the number and provide a list of locations. Have any of these been fixed since then?

[Prazek]

In D18821#399079, @alexfh wrote:

In D18821#399064, @Prazek wrote:

In D18821#398843, @alexfh wrote:

BTW, why is the check in the 'modernize' module? It doesn't seem to make anything more modern. I would guess, the pattern it detects is most likely to result from a programming error. Also, the fix, though it retains the behavior, has a high chance to be incorrect. Can you share the results of running this check on LLVM? At least, how many problems it found and how many times the suggested fix was correct.

I'd suggest to move the check to misc or maybe it's time to create a separate directory for checks targeting various bug-prone patterns.

There were many places.

Would be nice, if you could tell the number and provide a list of locations. Have any of these been fixed since then?

No, I didn't know that I can do that - I always heard that I can't format code that I didn't change, so I though the same thing is here. I will try do post review of changes in clang/llvm soon.

[Prazek]

http://reviews.llvm.org/D19105
Here is a diff containing fixes for clang. What I see is that it would be nice to detect bitfields of 1 bit and treet it as bool, so it won't warn it such cases.

[Prazek]

I will think name for new module that would have all the checks like this.
I added ingnoring of bitfields of size 1

[Prazek]

In D18821#398843, @alexfh wrote:

BTW, why is the check in the 'modernize' module? It doesn't seem to make anything more modern. I would guess, the pattern it detects is most likely to result from a programming error. Also, the fix, though it retains the behavior, has a high chance to be incorrect. Can you share the results of running this check on LLVM? At least, how many problems it found and how many times the suggested fix was correct.

I'd suggest to move the check to misc or maybe it's time to create a separate directory for checks targeting various bug-prone patterns.

Do you have any thought about the name for such a module? I belive that misc is overloaded.

So for this we are looking for something that is probably not a bug, but it makes code a little bit inaccurate
Maybe something like:

• accuracy,
• correctness,
• certainity,
• safety,
• maybebugmaybenothardtosay

[• Quuxplusone]

I would like to see a new version of http://reviews.llvm.org/D19105 with all the "1-bit-bitfield" diffs removed.
Right now, it's hard to see that there's *anything* in D19105 that's not a miscorrection of a 1-bit bitfield.

Do you have an example of a large codebase where this check runs with few false positives and a non-zero number of true positives?

[Prazek]

In D18821#403103, @Quuxplusone wrote:

I would like to see a new version of http://reviews.llvm.org/D19105 with all the "1-bit-bitfield" diffs removed.
Right now, it's hard to see that there's *anything* in D19105 that's not a miscorrection of a 1-bit bitfield.

Do you have an example of a large codebase where this check runs with few false positives and a non-zero number of true positives?

I will post fixex tomorrow. I don't think there will be any false or true positives in warnings, but the main problems with fixes are that many times developer wants to use bools, but it decalres field/return type as int.

[Prazek]

In D18821#402686, @Prazek wrote:

In D18821#398843, @alexfh wrote:

BTW, why is the check in the 'modernize' module? It doesn't seem to make anything more modern. I would guess, the pattern it detects is most likely to result from a programming error. Also, the fix, though it retains the behavior, has a high chance to be incorrect. Can you share the results of running this check on LLVM? At least, how many problems it found and how many times the suggested fix was correct.

I'd suggest to move the check to misc or maybe it's time to create a separate directory for checks targeting various bug-prone patterns.

Do you have any thought about the name for such a module? I belive that misc is overloaded.

So for this we are looking for something that is probably not a bug, but it makes code a little bit inaccurate
Maybe something like:

• accuracy,
• correctness,
• certainity,
• safety,
• maybebugmaybenothardtosay

after a long though I think that "accuracy" is the best name here - we want to look for a code that is valid, but not accurate

[alexfh]

In D18821#403117, @Prazek wrote:

In D18821#402686, @Prazek wrote:

In D18821#398843, @alexfh wrote:

BTW, why is the check in the 'modernize' module? It doesn't seem to make anything more modern. I would guess, the pattern it detects is most likely to result from a programming error. Also, the fix, though it retains the behavior, has a high chance to be incorrect. Can you share the results of running this check on LLVM? At least, how many problems it found and how many times the suggested fix was correct.

I'd suggest to move the check to misc or maybe it's time to create a separate directory for checks targeting various bug-prone patterns.

Do you have any thought about the name for such a module? I belive that misc is overloaded.

So for this we are looking for something that is probably not a bug, but it makes code a little bit inaccurate
Maybe something like:

• accuracy,
• correctness,
• certainity,
• safety,
• maybebugmaybenothardtosay

after a long though I think that "accuracy" is the best name here - we want to look for a code that is valid, but not accurate

There are many possible reasons this pattern can appear in the code. Sometimes it's a bug, sometimes, it's an attempt to make the code look better than it is ;) It seems to me though, that having a type mismatch of this kind is a bug-prone pattern, so I would start a more generic "bugprone" category of checks (and move some misc- checks there later on).

Also, please re-upload D19105 after disabling matches on 1-bit bitfields in the check.

[Prazek]

It seems that it works right now.
The other funny thing that the check found is cases like

bool b;
if (b == true)

I will update the llvm/clang changes today.
Do you want to see only the changes that clang-tidy made, or do you want to see it after some changing that I will do?

[Prazek]

Updated the diff with changes
http://reviews.llvm.org/D19105

[alexfh]

docs/clang-tidy/checks/bugprone-bool-to-integer-conversion.rst

43 ↗

(On Diff #56138)

This is a false positive and should be fixed regardless of whether we disable fixits or not. Just documenting it doesn't help much.

[Prazek]

+Fixed bug with operators
+ added fixup for function return type

I will post changes on clang tomorrow

[Prazek]

Some small bugfixes afeter running it on llvm

[Prazek]

aborting with virtual functions

[Prazek]

ping

[alexfh]

docs/clang-tidy/checks/bugprone-bool-to-integer-conversion.rst

37 ↗

(On Diff #58961)

It may well not be a bug. It's definitely not a bug for extern "C" functions and functions in C code. We definitely don't need to change the function return type, since it's a rather involved change (and clang-tidy checks currently are simply not able to make such change correctly in case of a function with external linkage). So please remove this automated fix.

41 ↗

(On Diff #58961)

Please check that your documentation compiles.

test/clang-tidy/bugprone-bool-to-integer-conversion.cpp

191 ↗

(On Diff #58309)

That's a dangerous fix. It should either be removed or guarded by an option.

[Prazek]

docs/clang-tidy/checks/bugprone-bool-to-integer-conversion.rst

37 ↗

(On Diff #58961)

This check runs only on C++ functions. Maybe checking that the function isExternC() would be enough?

test/clang-tidy/bugprone-bool-to-integer-conversion.cpp

192 ↗

(On Diff #58961)

Why it is dangerous? What I see after runnign on llvm code base, that it is one of the most frequent case.
The only bug is the extern "C" thing.

[alexfh]

Sorry for the delay. Your patch was lost in my inbox. Feel free to ping me earlier.

docs/clang-tidy/checks/bugprone-bool-to-integer-conversion.rst

37 ↗

(On Diff #58961)

As I've said, extern "C" is not the only way to make a function a part of an API exposed to external users.

test/clang-tidy/bugprone-bool-to-integer-conversion.cpp

192 ↗

(On Diff #58961)

Well, extern "C" is not the only way to expose functions to some external code. This fix potentially changes ABI, which is generally not a safe thing to do. I think, we should make the fix optional.

clang-tidy/modernize/BoolToIntegerConversionCheck.h

+//===--- BoolToIntegerConversionCheck.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_MODERNIZE_BOOL_TO_INTEGER_CONVERSION_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_BOOL_TO_INTEGER_CONVERSION_H
+
+#include "../ClangTidy.h"
+
+namespace clang {
+namespace tidy {
+namespace modernize {
+
+/// Finds implicit casts of bool literal to integer types like int a = true,
+/// and replaces it with integer literals like int a = 1
+///
+/// For the user-facing documentation see:
+/// http://clang.llvm.org/extra/clang-tidy/checks/modernize-bool-to-integer-conversion.html
+class BoolToIntegerConversionCheck : public ClangTidyCheck {
+public:
+  BoolToIntegerConversionCheck(StringRef Name, ClangTidyContext *Context)
+      : ClangTidyCheck(Name, Context) {}
+  void registerMatchers(ast_matchers::MatchFinder *Finder) override;
+  void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
+};
+
+} // namespace modernize
+} // namespace tidy
+} // namespace clang
+
+#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_BOOL_TO_INTEGER_CONVERSION_H

clang-tidy/modernize/BoolToIntegerConversionCheck.cpp

+//===--- BoolToIntegerConversionCheck.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 "BoolToIntegerConversionCheck.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/Lex/Lexer.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang {
+namespace tidy {
+namespace modernize {
+
+/// Checks, if integer \p Literal is preprocessor dependent
+static bool isPreprocessorIndependent(const CXXBoolLiteralExpr *Literal,
+                                      const MatchFinder::MatchResult &Result) {
+  const LangOptions &Opts = Result.Context->getLangOpts();
+  auto LiteralSource = Lexer::getSourceText(
+      CharSourceRange::getTokenRange(Literal->getSourceRange()),
+      *Result.SourceManager, Opts);
+
+  // If it's not 'true' of 'false', that means that it must be inside macro.
+  return LiteralSource == "true" || LiteralSource == "false";
+}
+
+void BoolToIntegerConversionCheck::registerMatchers(MatchFinder *Finder) {
+  if (!getLangOpts().CPlusPlus)
+    return;
+  Finder->addMatcher(
+      implicitCastExpr(has(cxxBoolLiteral().bind("bool_literal"))), this);
+}
+
+void BoolToIntegerConversionCheck::check(
+    const MatchFinder::MatchResult &Result) {
+  const auto *BoolLiteral =
+      Result.Nodes.getNodeAs<CXXBoolLiteralExpr>("bool_literal");
+  if (isPreprocessorIndependent(BoolLiteral, Result)) {
+    diag(BoolLiteral->getLocation(), "implicitly converting bool literal to "
+                                     "integer. Use integer literal instead")
+        << FixItHint::CreateReplacement(BoolLiteral->getSourceRange(),
+                                        BoolLiteral->getValue() ? "1" : "0");
+  } else {
+    diag(BoolLiteral->getLocation(), "implicitly converting bool literal to "
+                                     "integer inside macro. Use integer "
+                                     "literal instead");
+  }
+}
+
+} // namespace modernize
+} // namespace tidy
+} // namespace clang

clang-tidy/modernize/CMakeLists.txt

 set(LLVM_LINK_COMPONENTS support)
 
 add_clang_library(clangTidyModernizeModule
+  BoolToIntegerConversionCheck.cpp
   DeprecatedHeadersCheck.cpp
   LoopConvertCheck.cpp
   LoopConvertUtils.cpp
   MakeUniqueCheck.cpp
   ModernizeTidyModule.cpp
   PassByValueCheck.cpp
   RawStringLiteralCheck.cpp
   RedundantVoidArgCheck.cpp

clang-tidy/modernize/ModernizeTidyModule.cpp

 //===--- ModernizeTidyModule.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 "../ClangTidy.h"
 #include "../ClangTidyModule.h"
 #include "../ClangTidyModuleRegistry.h"
+#include "BoolToIntegerConversionCheck.h"
 #include "DeprecatedHeadersCheck.h"
 #include "LoopConvertCheck.h"
 #include "MakeUniqueCheck.h"
 #include "PassByValueCheck.h"
 #include "RawStringLiteralCheck.h"
 #include "RedundantVoidArgCheck.h"
 #include "ReplaceAutoPtrCheck.h"
 #include "ShrinkToFitCheck.h"
 #include "UseAutoCheck.h"
 #include "UseDefaultCheck.h"
 #include "UseNullptrCheck.h"
 #include "UseOverrideCheck.h"
 
 using namespace clang::ast_matchers;
 
 namespace clang {
 namespace tidy {
 namespace modernize {
 
 class ModernizeModule : public ClangTidyModule {
 public:
   void addCheckFactories(ClangTidyCheckFactories &CheckFactories) override {
+    CheckFactories.registerCheck<BoolToIntegerConversionCheck>(
+        "modernize-bool-to-integer-conversion");
     CheckFactories.registerCheck<DeprecatedHeadersCheck>(
         "modernize-deprecated-headers");
     CheckFactories.registerCheck<LoopConvertCheck>("modernize-loop-convert");
     CheckFactories.registerCheck<MakeUniqueCheck>("modernize-make-unique");
     CheckFactories.registerCheck<PassByValueCheck>("modernize-pass-by-value");
     CheckFactories.registerCheck<RawStringLiteralCheck>(
         "modernize-raw-string-literal");
     CheckFactories.registerCheck<RedundantVoidArgCheck>(

docs/ReleaseNotes.rst

- New `misc-suspicious-semicolon
   Finds most instances of stray semicolons that unexpectedly alter the meaning
   of the code.
 
 - New `modernize-deprecated-headers
   <http://clang.llvm.org/extra/clang-tidy/checks/modernize-deprecated-headers.html>`_ check
 
   Replaces C standard library headers with their C++ alternatives.
 
+- New `modernize-bool-to-integer-conversion
+  <http://clang.llvm.org/extra/clang-tidy/checks/modernize-bool-to-integer-conversion.html>`_ check
+
+  Replaces implicit cast from bool literals to integers to int literals.
+
 - New `modernize-raw-string-literal
   <http://clang.llvm.org/extra/clang-tidy/checks/modernize-raw-string-literal.html>`_ check
 
   Selectively replaces string literals containing escaped characters with raw
   string literals.
 
 - New `performance-faster-string-find
   <http://clang.llvm.org/extra/clang-tidy/checks/performance-faster-string-find.html>`_ check

docs/clang-tidy/checks/list.rst

.. toctree::
    cppcoreguidelines-pro-type-static-cast-downcast
    cppcoreguidelines-pro-type-union-access
    cppcoreguidelines-pro-type-vararg
    google-build-explicit-make-pair
    google-build-namespaces
    google-build-using-namespace
    google-explicit-constructor
    google-global-names-in-headers
-   google-readability-braces-around-statements (redirects to readability-braces-around-statements) <readability-braces-around-statements>
+   google-readability-braces-around-statements (redirects to readability-braces-around-statements) <google-readability-braces-around-statements>
    google-readability-casting
-   google-readability-function-size (redirects to readability-function-size) <readability-function-size>
+   google-readability-function-size (redirects to readability-function-size) <google-readability-function-size>
    google-readability-namespace-comments
    google-readability-redundant-smartptr-get
    google-readability-todo
    google-runtime-int
    google-runtime-member-string-references
    google-runtime-memset
    google-runtime-operator
    google-runtime-references
.. toctree::
    misc-swapped-arguments
    misc-throw-by-value-catch-by-reference
    misc-undelegated-constructor
    misc-uniqueptr-reset-release
    misc-unused-alias-decls
    misc-unused-parameters
    misc-unused-raii
    misc-virtual-near-miss
+   modernize-bool-to-integer-conversion
    modernize-deprecated-headers
    modernize-loop-convert
    modernize-make-unique
    modernize-pass-by-value
    modernize-raw-string-literal
    modernize-redundant-void-arg
    modernize-replace-auto-ptr
    modernize-shrink-to-fit

docs/clang-tidy/checks/modernize-bool-to-integer-conversion.rst

+.. title:: clang-tidy - modernize-bool-to-integer-conversion
+
+modernize-bool-to-integer-conversion
+====================================
+
+This check looks for implicit conversion from bool literals to integer types
+
+.. code-block:: C++
+  int a = false
+  vector<bool> v(true); // Makes vector of one element
+
+  // Changes it to
+  int a = 0;
+  vector<bool> v(1); // Makes vector of one element
+
+

test/clang-tidy/modernize-bool-to-integer-conversion.cpp

+// RUN: %check_clang_tidy %s modernize-bool-to-integer-conversion %t
+
+int is42Answer = true;
+// CHECK-MESSAGES: :[[@LINE-1]]:18: warning: implicitly converting bool literal to integer. Use integer literal instead [modernize-bool-to-integer-conversion]
+// CHECK-FIXES: int is42Answer = 1;{{$}}
+
+int noItsNot = false;
+// CHECK-MESSAGES: :[[@LINE-1]]:16: warning: implicitly {{..}}
+// CHECK-FIXES: int noItsNot = 0;{{$}}
+int a = 42;
+int az = a;
+
+long long ll = true;
+// CHECK-MESSAGES: :[[@LINE-1]]:16: warning: implicitly {{..}}
+// CHECK-FIXES: long long ll = 1;{{$}}
+
+void fun(int) {}
+#define ONE true
+
+// No fixup for macros.
+int one = ONE;
+// CHECK-MESSAGES: :[[@LINE-1]]:11: warning: implicitly converting bool literal to integer inside macro. Use integer literal instead [modernize-bool-to-integer-conversion]
+
+void test() {
+    fun(ONE);
+    // CHECK-MESSAGES: :[[@LINE-1]]:9: warning: implicitly converting bool {{..}}
+
+    fun(42);
+    fun(true);
+// CHECK-MESSAGES: :[[@LINE-1]]:9: warning: implicitly {{..}}
+// CHECK-FIXES: fun(1);{{$}}
+}
+
+char c = true;
+// CHECK-MESSAGES: :[[@LINE-1]]:10: warning: implicitly {{..}}
+// CHECK-FIXES: char c = 1;
+
+char c2 = 1;
+char c3 = '0';
+bool b = true;