[clang-tidy] new cppcoreguidelines-narrowing-conversions check.

Summary:
Checks for narrowing conversions, e.g.

int i = 0;
i += 0.1;

This has what some might consider false positives for:
i += ceil(d);

Reviewers: alexfh, hokein

Subscribers: srhines, nemanjai, mgorny, JDevlieghere, xazax.hun, kbarton

Differential Revision: https://reviews.llvm.org/D38455

llvm-svn: 333066

1 files changed, 103 insertions, 0 deletions

diff --git a/clang-tools-extra/test/clang-tidy/cppcoreguidelines-narrowing-conversions.cpp b/clang-tools-extra/test/clang-tidy/cppcoreguidelines-narrowing-conversions.cpp
new file mode 100644
index 00000000000..ecffba6b844
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/cppcoreguidelines-narrowing-conversions.cpp
@@ -0,0 +1,103 @@
+// RUN: %check_clang_tidy %s cppcoreguidelines-narrowing-conversions %t
+
+float ceil(float);
+namespace std {
+double ceil(double);
+long double floor(long double);
+} // namespace std
+
+namespace floats {
+
+struct ConvertsToFloat {
+  operator float() const { return 0.5; }
+};
+
+float operator "" _Pa(unsigned long long);
+
+void not_ok(double d) {
+  int i = 0;
+  i = d;
+  // CHECK-MESSAGES: :[[@LINE-1]]:7: warning: narrowing conversion from 'double' to 'int' [cppcoreguidelines-narrowing-conversions]
+  i = 0.5f;
+  // CHECK-MESSAGES: :[[@LINE-1]]:7: warning: narrowing conversion from 'float' to 'int' [cppcoreguidelines-narrowing-conversions]
+  i = static_cast<float>(d);
+  // CHECK-MESSAGES: :[[@LINE-1]]:7: warning: narrowing conversion from 'float' to 'int' [cppcoreguidelines-narrowing-conversions]
+  i = ConvertsToFloat();
+  // CHECK-MESSAGES: :[[@LINE-1]]:7: warning: narrowing conversion from 'float' to 'int' [cppcoreguidelines-narrowing-conversions]
+  i = 15_Pa;
+  // CHECK-MESSAGES: :[[@LINE-1]]:7: warning: narrowing conversion from 'float' to 'int' [cppcoreguidelines-narrowing-conversions]
+}
+
+void not_ok_binary_ops(double d) {
+  int i = 0;
+  i += 0.5;
+  // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: narrowing conversion from 'double' to 'int' [cppcoreguidelines-narrowing-conversions]
+  i += 0.5f;
+  // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: narrowing conversion from 'float' to 'int' [cppcoreguidelines-narrowing-conversions]
+  i += d;
+  // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: narrowing conversion from 'double' to 'int' [cppcoreguidelines-narrowing-conversions]
+  // We warn on the following even though it's not dangerous because there is no
+  // reason to use a double literal here.
+  // TODO(courbet): Provide an automatic fix.
+  i += 2.0;
+  // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: narrowing conversion from 'double' to 'int' [cppcoreguidelines-narrowing-conversions]
+  i += 2.0f;
+  // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: narrowing conversion from 'float' to 'int' [cppcoreguidelines-narrowing-conversions]
+
+  i *= 0.5f;
+  // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: narrowing conversion from 'float' to 'int' [cppcoreguidelines-narrowing-conversions]
+  i /= 0.5f;
+  // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: narrowing conversion from 'float' to 'int' [cppcoreguidelines-narrowing-conversions]
+  i += (double)0.5f;
+  // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: narrowing conversion from 'double' to 'int' [cppcoreguidelines-narrowing-conversions]
+}
+
+void ok(double d) {
+  int i = 0;
+  i = 1;
+  i = static_cast<int>(0.5);
+  i = static_cast<int>(d);
+  i = std::ceil(0.5);
+  i = ::std::floor(0.5);
+  {
+    using std::ceil;
+    i = ceil(0.5f);
+  }
+  i = ceil(0.5f);
+}
+
+void ok_binary_ops(double d) {
+  int i = 0;
+  i += 1;
+  i += static_cast<int>(0.5);
+  i += static_cast<int>(d);
+  i += (int)d;
+  i += std::ceil(0.5);
+  i += ::std::floor(0.5);
+  {
+    using std::ceil;
+    i += ceil(0.5f);
+  }
+  i += ceil(0.5f);
+}
+
+// We're bailing out in templates and macros.
+template <typename T1, typename T2>
+void f(T1 one, T2 two) {
+  one += two;
+}
+
+void template_context() {
+  f(1, 2);
+  f(1, .5);
+}
+
+#define DERP(i, j) (i += j)
+
+void macro_context() {
+  int i = 0;
+  DERP(i, 2);
+  DERP(i, .5);
+}
+
+}  // namespace floats