[PATCH] D158338: [clang-tidy] [bugprone-implicit-widenin g-of-multiplication-result]Improved check to ignore false positives with integer literals.

[Félix-Antoine Constantin via Phabricator via cfe-commits]

felix642 created this revision.
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The following code is safe and should not trigger the warning
constexpr std::size_t k1Mb = 1024 * 1024;

Fixes #64732


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D158338

Files:
  clang-tools-extra/clang-tidy/bugprone/ImplicitWideningOfMultiplicationResultCheck.cpp
  clang-tools-extra/docs/ReleaseNotes.rst
  clang-tools-extra/test/clang-tidy/checkers/bugprone/implicit-widening-of-multiplication-result-int.cpp


Index: clang-tools-extra/test/clang-tidy/checkers/bugprone/implicit-widening-of-multiplication-result-int.cpp
===================================================================
--- clang-tools-extra/test/clang-tidy/checkers/bugprone/implicit-widening-of-multiplication-result-int.cpp
+++ clang-tools-extra/test/clang-tidy/checkers/bugprone/implicit-widening-of-multiplication-result-int.cpp
@@ -107,10 +107,28 @@
 long n14(int a, int b, int c) {
   return a + b * c;
 }
+
 long n15(int a, int b, int c) {
   return a * b + c;
 }
 
+unsigned long n16()
+{
+  return (1024u) * 1024;
+}
+
+long n17(int a) {
+  return a + 1024 * 1024;
+}
+
+long n18(int a)
+{
+  return (a * 1024);
+  // CHECK-NOTES-ALL: :[[@LINE-1]]:11: warning: performing an implicit widening conversion to type 'long' of a multiplication performed in type 'int'
+  // CHECK-NOTES-ALL: :[[@LINE-2]]:11: note: make conversion explicit to silence this warning
+  // CHECK-NOTES-ALL: :[[@LINE-3]]:11: note: perform multiplication in a wider type
+}
+
 #ifdef __cplusplus
 template <typename T1, typename T2>
 T2 template_test(T1 a, T1 b) {
Index: clang-tools-extra/docs/ReleaseNotes.rst
===================================================================
--- clang-tools-extra/docs/ReleaseNotes.rst
+++ clang-tools-extra/docs/ReleaseNotes.rst
@@ -173,6 +173,10 @@
   <clang-tidy/checks/bugprone/reserved-identifier>`, so that it does not warn
   on macros starting with underscore and lowercase letter.
 
+- Improved :doc:`bugprone-implicit-widening-of-multiplication-result
+  <clang-tidy/checks/bugprone/bugprone-implicit-widening-of-multiplication-result>`
+  check to ignore false-positives with integer literals.
+
 - Improved :doc:`bugprone-lambda-function-name
   <clang-tidy/checks/bugprone/lambda-function-name>` check by adding option
   `IgnoreMacros` to ignore warnings in macros.
Index: clang-tools-extra/clang-tidy/bugprone/ImplicitWideningOfMultiplicationResultCheck.cpp
===================================================================
--- clang-tools-extra/clang-tidy/bugprone/ImplicitWideningOfMultiplicationResultCheck.cpp
+++ clang-tools-extra/clang-tidy/bugprone/ImplicitWideningOfMultiplicationResultCheck.cpp
@@ -34,6 +34,13 @@
   return BO->getLHS()->IgnoreParens();
 }
 
+static bool hasIntegerLiteralOperators(const Expr* E)
+{
+  const auto *BO = dyn_cast<BinaryOperator>(E);
+  return isa<IntegerLiteral>(BO->getLHS()->IgnoreParenImpCasts()) &&
+      isa<IntegerLiteral>(BO->getRHS()->IgnoreParenImpCasts());
+}
+
 ImplicitWideningOfMultiplicationResultCheck::
     ImplicitWideningOfMultiplicationResultCheck(StringRef Name,
                                                 ClangTidyContext *Context)
@@ -89,6 +96,10 @@
   if (!LHS)
     return;
 
+  // Widening multiplication on Integer Literals.
+  if(hasIntegerLiteralOperators(E))
+    return;
+
   // Ok, looks like we should diagnose this.
   diag(E->getBeginLoc(), "performing an implicit widening conversion to type "
                          "%0 of a multiplication performed in type %1")


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