Added checking (during parsing) of comparison of floating point values using == or !=.

This is the same functionality gcc provides via --Wfloat-equal.

llvm-svn: 41574

clang/Sema/SemaExpr.cpp

@@ -1157,6 +1157,9 @@ inline QualType Sema::CheckCompareOperands( // C99 6.5.8
     if (lType->isRealType() && rType->isRealType())
       return Context.IntTy;
   } else {
+    if (lType->isRealType() && rType->isRealType()) 
+      Diag(loc, diag::warn_floatingpoint_eq);
+
     if (lType->isArithmeticType() && rType->isArithmeticType())
       return Context.IntTy;
   }

clang/include/clang/Basic/DiagnosticKinds.def

@@ -696,7 +696,7 @@ DIAG(err_typecheck_choose_expr_requires_constant, ERROR,
 DIAG(warn_unused_expr, WARNING,
      "expression result unused")
 
-// Extra checking for finding simple bugs.
+// CHECK: printf format string errors
 DIAG(warn_printf_not_string_constant, WARNING,
      "format string is not a string literal (potentially insecure)")
 DIAG(warn_printf_write_back, WARNING,
@@ -716,11 +716,16 @@ DIAG(warn_printf_format_string_is_wide_literal, WARNING,
 DIAG(warn_printf_format_string_contains_null_char, WARNING,
   "format string contains '\\0' within the string body")
 
+// CHECK: returning address/reference of stack memory
 DIAG(warn_ret_stack_addr, WARNING,
   "address of stack memory associated with local variable '%0' returned")
 DIAG(warn_ret_stack_ref, WARNING,
   "reference to stack memory associated with local variable '%0' returned")
 
+// CHECK: floating point values should not use "==" or "!="
+DIAG(warn_floatingpoint_eq, WARNING,
+  "comparing floating point with == or != is unsafe")
+
 // CFString checking
 DIAG(err_cfstring_literal_not_string_constant, ERROR,
   "CFString literal is not a string constant")

clang/test/Sema/floating-point-compare.c

@@ -0,0 +1,9 @@
+// RUN: clang -parse-ast-check %s
+
+int foo(float x, float y) {
+  return x == y; // expected-warning {{comparing floating point with ==}}
+} 
+
+int bar(float x, float y) {
+  return x != y; // expected-warning {{comparing floating point with ==}}
+}