Added warning for unary minus used with unsigned type
Summary:
Inspired by MSVC, which found some occurrences of this expression on our code base.
Fixes PR38950
Reviewers: rsmith, craig.topper, spatel, RKSimon, aaron.ballman, thakis
Reviewed By: rsmith
Subscribers: joerg, Quuxplusone, lebedev.ri, craig.topper, RKSimon, cfe-commits
Differential Revision: https://reviews.llvm.org/D52137
llvm-svn: 343560
diff --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp
index a258d34..d6183dd 100644
--- a/clang/lib/Sema/SemaChecking.cpp
+++ b/clang/lib/Sema/SemaChecking.cpp
@@ -10896,6 +10896,19 @@
return DiagnoseImpCast(S, E, T, CC, diag::warn_impcast_integer_precision);
}
+ if (TargetRange.Width > SourceRange.Width) {
+ if (auto *UO = dyn_cast<UnaryOperator>(E))
+ if (UO->getOpcode() == UO_Minus)
+ if (Source->isUnsignedIntegerType()) {
+ if (Target->isUnsignedIntegerType())
+ return DiagnoseImpCast(S, E, T, CC,
+ diag::warn_impcast_high_order_zero_bits);
+ if (Target->isSignedIntegerType())
+ return DiagnoseImpCast(S, E, T, CC,
+ diag::warn_impcast_nonnegative_result);
+ }
+ }
+
if (TargetRange.Width == SourceRange.Width && !TargetRange.NonNegative &&
SourceRange.NonNegative && Source->isSignedIntegerType()) {
// Warn when doing a signed to signed conversion, warn if the positive