PR3333: warn when shifting by invalid amount
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@78385 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/clang/Basic/DiagnosticSemaKinds.td b/include/clang/Basic/DiagnosticSemaKinds.td
index aac64ce..591cf0a 100644
--- a/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/include/clang/Basic/DiagnosticSemaKinds.td
@@ -1237,6 +1237,14 @@
"comparing floating point with == or != is unsafe">,
InGroup<DiagGroup<"float-equal">>, DefaultIgnore;
+def warn_shift_negative : Warning<
+ "shift count is negative">;
+def warn_shift_gt_typewidth : Warning<
+ "shift count >= width of type">;
+def warn_op_no_effect : Warning<
+ "operation has no effect">,
+ InGroup<DiagGroup<"all">>, DefaultIgnore;
+
def err_sizeof_nonfragile_interface : Error<
"invalid application of '%select{alignof|sizeof}1' to interface %0 in "
"non-fragile ABI">;
diff --git a/lib/Sema/SemaExpr.cpp b/lib/Sema/SemaExpr.cpp
index 7ef30d3..51ebd07 100644
--- a/lib/Sema/SemaExpr.cpp
+++ b/lib/Sema/SemaExpr.cpp
@@ -4124,6 +4124,29 @@
UsualUnaryConversions(rex);
+ // Sanity-check shift operands
+ llvm::APSInt Right;
+ // Check right/shifter operand
+ if (rex->isIntegerConstantExpr(Right, Context)) {
+ // Check left/shiftee operand
+ llvm::APSInt Left;
+ if (lex->isIntegerConstantExpr(Left, Context)) {
+ if (Left == 0 && Right != 0)
+ Diag(Loc, diag::warn_op_no_effect)
+ << lex->getSourceRange() << rex->getSourceRange();
+ }
+ if (isCompAssign && Right == 0)
+ Diag(Loc, diag::warn_op_no_effect) << rex->getSourceRange();
+ else if (Right.isNegative())
+ Diag(Loc, diag::warn_shift_negative) << rex->getSourceRange();
+ else {
+ llvm::APInt LeftBits(Right.getBitWidth(),
+ Context.getTypeSize(lex->getType()));
+ if (Right.uge(LeftBits))
+ Diag(Loc, diag::warn_shift_gt_typewidth) << rex->getSourceRange();
+ }
+ }
+
// "The type of the result is that of the promoted left operand."
return LHSTy;
}
diff --git a/test/Sema/shift.c b/test/Sema/shift.c
index 5acbe12..4c2b88a 100644
--- a/test/Sema/shift.c
+++ b/test/Sema/shift.c
@@ -1,6 +1,35 @@
-// RUN: clang-cc -fsyntax-only %s
+// RUN: clang-cc -Wall -fsyntax-only -verify %s
+
+#include <limits.h>
+
+enum {
+ X = 1 << 0,
+ Y = 1 << 1,
+ Z = 1 << 2
+};
void test() {
char c;
- c <<= 14;
+
+ c = 0 << 0;
+ c = 0 << 1; // expected-warning {{no effect}}
+ c = 1 << 0;
+ c = 1 << -0;
+ c = 1 >> -0;
+ c = 1 << -1; // expected-warning {{shift count is negative}}
+ c = 1 >> -1; // expected-warning {{shift count is negative}}
+ c = 1 << c;
+ c <<= 0; // expected-warning {{no effect}}
+ c >>= 0; // expected-warning {{no effect}}
+ c <<= 1;
+ c >>= 1;
+ c <<= -1; // expected-warning {{shift count is negative}}
+ c >>= -1; // expected-warning {{shift count is negative}}
+ c <<= 999999; // expected-warning {{shift count >= width of type}}
+ c >>= 999999; // expected-warning {{shift count >= width of type}}
+ c <<= CHAR_BIT; // expected-warning {{shift count >= width of type}}
+ c >>= CHAR_BIT; // expected-warning {{shift count >= width of type}}
+ c <<= CHAR_BIT+1; // expected-warning {{shift count >= width of type}}
+ c >>= CHAR_BIT+1; // expected-warning {{shift count >= width of type}}
+ (void)((long)c << CHAR_BIT);
}