When performing an implicit from float to bool, the floating point value must be *exactly* zero in order for the conversion to result in 0. This does not involve a conversion through an integer value, and so truncation of the value is not performed.

This patch address PR25876.

llvm-svn: 256643

2 files changed, 12 insertions, 1 deletions

diff --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp
index 59d51f7e84c..cbdcb5e4839 100644
--- a/clang/lib/Sema/SemaChecking.cpp
+++ b/clang/lib/Sema/SemaChecking.cpp
@@ -6983,7 +6983,7 @@ void DiagnoseFloatingLiteralImpCast(Sema &S, FloatingLiteral *FL, QualType T,
 
   SmallString<16> PrettyTargetValue;
   if (T->isSpecificBuiltinType(BuiltinType::Bool))
-    PrettyTargetValue = IntegerValue == 0 ? "false" : "true";
+    PrettyTargetValue = Value.isZero() ? "false" : "true";
   else
     IntegerValue.toString(PrettyTargetValue);
 
diff --git a/clang/test/SemaCXX/warn-literal-conversion.cpp b/clang/test/SemaCXX/warn-literal-conversion.cpp
index d7bec4c73e5..5d4b6f7f5bf 100644
--- a/clang/test/SemaCXX/warn-literal-conversion.cpp
+++ b/clang/test/SemaCXX/warn-literal-conversion.cpp
@@ -38,3 +38,14 @@ void test0() {
   int y = (24*60*60) * 0.25;
   int pennies = 123.45 * 100;
 }
+
+// Similarly, test floating point conversion to bool. Only float values of zero
+// are converted to false; everything else is converted to true.
+void test1() {
+  bool b1 = 0.99f; // expected-warning {{implicit conversion from 'float' to 'bool' changes value from 0.99 to true}}
+  bool b2 = 0.99; // expected-warning {{implicit conversion from 'double' to 'bool' changes value from 0.99 to true}}
+  // These do not warn because they can be directly converted to integral
+  // values.
+  bool b3 = 0.0f;
+  bool b4 = 0.0;
+}