[clang-tidy] misc-misplaced-widening-cast: Disable checking of implicit widening casts by default

[baloghadamsoftware]

Summary

Users reported some false positives using this check. This patch sets the default value of the option for checking implicit widening casts to false. We also suggest renaming the check to something like missing-or-misplaced-widening cast so the name also covers the implicit case. This patch supersedes D31097.

[alexfh]

LG

[lebedev.ri]

The doc wasn't updated :/

clang-tidy/misc/MisplacedWideningCastCheck.cpp

 
 namespace clang {
 namespace tidy {
 namespace misc {
 
 MisplacedWideningCastCheck::MisplacedWideningCastCheck(
     StringRef Name, ClangTidyContext *Context)
     : ClangTidyCheck(Name, Context),
-      CheckImplicitCasts(Options.get("CheckImplicitCasts", true)) {}
+      CheckImplicitCasts(Options.get("CheckImplicitCasts", false)) {}
 
 void MisplacedWideningCastCheck::storeOptions(
     ClangTidyOptions::OptionMap &Opts) {
   Options.store(Opts, "CheckImplicitCasts", CheckImplicitCasts);
 }
 
 void MisplacedWideningCastCheck::registerMatchers(MatchFinder *Finder) {
   const auto Calc =

test/clang-tidy/misc-misplaced-widening-cast-implicit-enabled.cpp

+// RUN: %check_clang_tidy %s misc-misplaced-widening-cast %t -- -config="{CheckOptions: [{key: misc-misplaced-widening-cast.CheckImplicitCasts, value: 1}]}" --
+
+void func(long arg) {}
+
+void assign(int a, int b) {
+  long l;
+
+  l = a * b;
+  // CHECK-MESSAGES: :[[@LINE-1]]:7: warning: either cast from 'int' to 'long' is ineffective, or there is loss of precision before the conversion [misc-misplaced-widening-cast]
+  l = (long)(a * b);
+  // CHECK-MESSAGES: :[[@LINE-1]]:7: warning: either cast from 'int' to 'long'
+  l = (long)a * b;
+
+  l = a << 8;
+  // CHECK-MESSAGES: :[[@LINE-1]]:7: warning: either cast from 'int' to 'long'
+  l = (long)(a << 8);
+  // CHECK-MESSAGES: :[[@LINE-1]]:7: warning: either cast from 'int' to 'long'
+  l = (long)b << 8;
+
+  l = static_cast<long>(a * b);
+  // CHECK-MESSAGES: :[[@LINE-1]]:7: warning: either cast from 'int' to 'long'
+}
+
+void compare(int a, int b, long c) {
+  bool l;
+
+  l = a * b == c;
+  // CHECK-MESSAGES: :[[@LINE-1]]:7: warning: either cast from 'int' to 'long'
+  l = c == a * b;
+  // CHECK-MESSAGES: :[[@LINE-1]]:12: warning: either cast from 'int' to 'long'
+  l = (long)(a * b) == c;
+  // CHECK-MESSAGES: :[[@LINE-1]]:7: warning: either cast from 'int' to 'long'
+  l = c == (long)(a * b);
+  // CHECK-MESSAGES: :[[@LINE-1]]:12: warning: either cast from 'int' to 'long'
+  l = (long)a * b == c;
+  l = c == (long)a * b;
+}
+
+void init(unsigned int n) {
+  long l1 = n << 8;
+  // CHECK-MESSAGES: :[[@LINE-1]]:13: warning: either cast from 'unsigned int' to 'long'
+  long l2 = (long)(n << 8);
+  // CHECK-MESSAGES: :[[@LINE-1]]:13: warning: either cast from 'unsigned int' to 'long'
+  long l3 = (long)n << 8;
+}
+
+void call(unsigned int n) {
+  func(n << 8);
+  // CHECK-MESSAGES: :[[@LINE-1]]:8: warning: either cast from 'unsigned int' to 'long'
+  func((long)(n << 8));
+  // CHECK-MESSAGES: :[[@LINE-1]]:8: warning: either cast from 'unsigned int' to 'long'
+  func((long)n << 8);
+}
+
+long ret(int a) {
+  if (a < 0) {
+    return a * 1000;
+    // CHECK-MESSAGES: :[[@LINE-1]]:12: warning: either cast from 'int' to 'long'
+  } else if (a > 0) {
+    return (long)(a * 1000);
+    // CHECK-MESSAGES: :[[@LINE-1]]:12: warning: either cast from 'int' to 'long'
+  } else {
+    return (long)a * 1000;
+  }
+}
+
+void dontwarn1(unsigned char a, int i, unsigned char *p) {
+  long l;
+  // The result is a 9 bit value, there is no truncation in the implicit cast.
+  l = (long)(a + 15);
+  // The result is a 12 bit value, there is no truncation in the implicit cast.
+  l = (long)(a << 4);
+  // The result is a 3 bit value, there is no truncation in the implicit cast.
+  l = (long)((i % 5) + 1);
+  // The result is a 16 bit value, there is no truncation in the implicit cast.
+  l = (long)(((*p) << 8) + *(p + 1));
+}
+
+template <class T> struct DontWarn2 {
+  void assign(T a, T b) {
+    long l;
+    l = (long)(a * b);
+  }
+};
+DontWarn2<int> DW2;
+
+// Cast is not suspicious when casting macro.
+#define A  (X<<2)
+long macro1(int X) {
+  return (long)A;
+}
+
+// Don't warn about cast in macro.
+#define B(X,Y)   (long)(X*Y)
+long macro2(int x, int y) {
+  return B(x,y);
+}
+
+void floatingpoint(float a, float b) {
+  double d = (double)(a * b); // Currently we don't warn for this.
+}

test/clang-tidy/misc-misplaced-widening-cast.cpp

-// RUN: %check_clang_tidy %s misc-misplaced-widening-cast %t -- -config="{CheckOptions: [{key: misc-misplaced-widening-cast.CheckImplicitCasts, value: 1}]}" --
-
-void func(long arg) {}
-
-void assign(int a, int b) {
-  long l;
-
-  l = a * b;
-  // CHECK-MESSAGES: :[[@LINE-1]]:7: warning: either cast from 'int' to 'long' is ineffective, or there is loss of precision before the conversion [misc-misplaced-widening-cast]
-  l = (long)(a * b);
-  // CHECK-MESSAGES: :[[@LINE-1]]:7: warning: either cast from 'int' to 'long'
-  l = (long)a * b;
-
-  l = a << 8;
-  // CHECK-MESSAGES: :[[@LINE-1]]:7: warning: either cast from 'int' to 'long'
-  l = (long)(a << 8);
-  // CHECK-MESSAGES: :[[@LINE-1]]:7: warning: either cast from 'int' to 'long'
-  l = (long)b << 8;
-
-  l = static_cast<long>(a * b);
-  // CHECK-MESSAGES: :[[@LINE-1]]:7: warning: either cast from 'int' to 'long'
-}
-
-void compare(int a, int b, long c) {
-  bool l;
-
-  l = a * b == c;
-  // CHECK-MESSAGES: :[[@LINE-1]]:7: warning: either cast from 'int' to 'long'
-  l = c == a * b;
-  // CHECK-MESSAGES: :[[@LINE-1]]:12: warning: either cast from 'int' to 'long'
-  l = (long)(a * b) == c;
-  // CHECK-MESSAGES: :[[@LINE-1]]:7: warning: either cast from 'int' to 'long'
-  l = c == (long)(a * b);
-  // CHECK-MESSAGES: :[[@LINE-1]]:12: warning: either cast from 'int' to 'long'
-  l = (long)a * b == c;
-  l = c == (long)a * b;
-}
-
-void init(unsigned int n) {
-  long l1 = n << 8;
-  // CHECK-MESSAGES: :[[@LINE-1]]:13: warning: either cast from 'unsigned int' to 'long'
-  long l2 = (long)(n << 8);
-  // CHECK-MESSAGES: :[[@LINE-1]]:13: warning: either cast from 'unsigned int' to 'long'
-  long l3 = (long)n << 8;
-}
-
-void call(unsigned int n) {
-  func(n << 8);
-  // CHECK-MESSAGES: :[[@LINE-1]]:8: warning: either cast from 'unsigned int' to 'long'
-  func((long)(n << 8));
-  // CHECK-MESSAGES: :[[@LINE-1]]:8: warning: either cast from 'unsigned int' to 'long'
-  func((long)n << 8);
-}
-
-long ret(int a) {
-  if (a < 0) {
-    return a * 1000;
-    // CHECK-MESSAGES: :[[@LINE-1]]:12: warning: either cast from 'int' to 'long'
-  } else if (a > 0) {
-    return (long)(a * 1000);
-    // CHECK-MESSAGES: :[[@LINE-1]]:12: warning: either cast from 'int' to 'long'
-  } else {
-    return (long)a * 1000;
-  }
-}
-
-void dontwarn1(unsigned char a, int i, unsigned char *p) {
-  long l;
-  // The result is a 9 bit value, there is no truncation in the implicit cast.
-  l = (long)(a + 15);
-  // The result is a 12 bit value, there is no truncation in the implicit cast.
-  l = (long)(a << 4);
-  // The result is a 3 bit value, there is no truncation in the implicit cast.
-  l = (long)((i % 5) + 1);
-  // The result is a 16 bit value, there is no truncation in the implicit cast.
-  l = (long)(((*p) << 8) + *(p + 1));
-}
-
-template <class T> struct DontWarn2 {
-  void assign(T a, T b) {
-    long l;
-    l = (long)(a * b);
-  }
-};
-DontWarn2<int> DW2;
-
-// Cast is not suspicious when casting macro.
-#define A  (X<<2)
-long macro1(int X) {
-  return (long)A;
-}
-
-// Don't warn about cast in macro.
-#define B(X,Y)   (long)(X*Y)
-long macro2(int x, int y) {
-  return B(x,y);
-}
-
-void floatingpoint(float a, float b) {
-  double d = (double)(a * b); // Currently we don't warn for this.
-}