replica
/
hanchenye-llvm-project
2
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

Implemented a warning when an input several bitwise operations are 

likely be implicitly truncated:

  * All forms of Bitwise-and, bitwise-or, and integer multiplication.
  * The assignment form of integer addition, subtraction, and exclusive-or
  * The RHS of the comma operator
  * The LHS of left shifts.

llvm-svn: 178273
This commit is contained in:
Sam Panzer 2013-03-28 19:07:11 +00:00
parent 4e55526737
commit 6fffec6fd4
3 changed files with 165 additions and 17 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
clang/include/clang/Basic/DiagnosticSemaKinds.td
View File

@ -2084,6 +2084,11 @@ def warn_impcast_integer_64_32 : Warning<
def warn_impcast_integer_precision_constant : Warning<
"implicit conversion from %2 to %3 changes value from %0 to %1">,
InGroup<ConstantConversion>;
def warn_impcast_integer_precision_binop_constant : Warning<
"implicit conversion of binary operation from %2 to %3 may change its value; "
"value of operand would be changed from %0 to %1 if converted before "
"operation">,
InGroup<ConstantConversion>;
def warn_impcast_bitfield_precision_constant : Warning<
"implicit truncation from %2 to bitfield changes value from %0 to %1">,
InGroup<ConstantConversion>;

135
clang/lib/Sema/SemaChecking.cpp
View File

@ -4686,7 +4686,8 @@ static void AnalyzeAssignment(Sema &S, BinaryOperator *E) {
// We want to recurse on the RHS as normal unless we're assigning to
// a bitfield.
if (FieldDecl *Bitfield = E->getLHS()->getBitField()) {
if (AnalyzeBitFieldAssignment(S, Bitfield, E->getRHS(),
if (E->getOpcode() != BO_AndAssign &&
AnalyzeBitFieldAssignment(S, Bitfield, E->getRHS(),
E->getOperatorLoc())) {
// Recurse, ignoring any implicit conversions on the RHS.
return AnalyzeImplicitConversions(S, E->getRHS()->IgnoreParenImpCasts(),
@ -4795,8 +4796,82 @@ void CheckImplicitArgumentConversions(Sema &S, CallExpr *TheCall,
}
}
// Try to evaluate E as an integer. If EvaluateAsInt succeeds, Value is set to
// the resulting value, ResultExpr is set to E.
// Otherwise, the output parameters are not modified.
static bool EvalAsInt(ASTContext &Ctx, llvm::APSInt &Value, Expr *E,
Expr **ResultExpr) {
if (E->EvaluateAsInt(Value, Ctx, Expr::SE_AllowSideEffects)) {
*ResultExpr = E;
return true;
}
return false;
}
// Returns true when Value's value would change when narrowed to TargetRange.
static bool TruncationChangesValue(const llvm::APSInt &Value,
const IntRange &TargetRange,
bool IsBitwiseAnd) {
// Checks if there are any active non-sign bits past the width of TargetRange.
if (IsBitwiseAnd)
return Value.getBitWidth() - Value.getNumSignBits() > TargetRange.Width;
llvm::APSInt UnsignedValue(Value);
unsigned BitWidth = TargetRange.NonNegative ?
UnsignedValue.getActiveBits() : Value.getMinSignedBits();
return BitWidth > TargetRange.Width;
}
// Determine if E is an expression containing or likely to contain an implicit
// narrowing bug involving a constant.
// If so, Value is set to the value of that constant. NarrowedExpr is set to the
// problematic sub-expression if it is a strict subset of E.
static bool OperandMightImplicitlyNarrow(ASTContext &Ctx, llvm::APSInt &Value,
Expr *E, IntRange TargetRange,
Expr **NarrowedExpr) {
BinaryOperator *BO = dyn_cast<BinaryOperator>(E);
if (!BO)
return false;
switch (BO->getOpcode()) {
case BO_And:
case BO_AndAssign:
return (EvalAsInt(Ctx, Value, BO->getLHS(), NarrowedExpr)
&& TruncationChangesValue(Value, TargetRange, true)) ||
(EvalAsInt(Ctx, Value, BO->getRHS(), NarrowedExpr)
&& TruncationChangesValue(Value, TargetRange, true));
case BO_Or:
case BO_OrAssign:
// FIXME: Include BO_Add, BO_Sub, and BO_Xor when we avoid false positives.
case BO_AddAssign:
case BO_SubAssign:
case BO_Mul:
case BO_MulAssign:
case BO_XorAssign:
return (EvalAsInt(Ctx, Value, BO->getLHS(), NarrowedExpr)
&& TruncationChangesValue(Value, TargetRange, false)) ||
(EvalAsInt(Ctx, Value, BO->getRHS(), NarrowedExpr)
&& TruncationChangesValue(Value, TargetRange, false));
// We can ignore the left side of the comma operator, since the value is
// explicitly ignored anyway.
case BO_Comma:
return EvalAsInt(Ctx, Value, BO->getRHS(), NarrowedExpr) &&
TruncationChangesValue(Value, TargetRange, false);
case BO_Shl:
return EvalAsInt(Ctx, Value, BO->getLHS(), NarrowedExpr) &&
TruncationChangesValue(Value, TargetRange, false);
default:
break;
}
return false;
}
void CheckImplicitConversion(Sema &S, Expr *E, QualType T,
SourceLocation CC, bool *ICContext = 0) {
SourceLocation CC, bool *ICContext = NULL) {
if (E->isTypeDependent() || E->isValueDependent()) return;
const Type *Source = S.Context.getCanonicalType(E->getType()).getTypePtr();
@ -4977,17 +5052,30 @@ void CheckImplicitConversion(Sema &S, Expr *E, QualType T,
IntRange SourceRange = GetExprRange(S.Context, E);
IntRange TargetRange = IntRange::forTargetOfCanonicalType(S.Context, Target);
if (SourceRange.Width > TargetRange.Width) {
// If the source is a constant, use a default-on diagnostic.
// TODO: this should happen for bitfield stores, too.
llvm::APSInt Value(32);
if (E->isIntegerConstantExpr(Value, S.Context)) {
if (S.SourceMgr.isInSystemMacro(CC))
return;
llvm::APSInt Value(32);
Expr *NarrowedExpr = NULL;
// Use a default-on diagnostic if the source is involved in a
// narrowing-prone binary operation with a constant.
if (OperandMightImplicitlyNarrow(S.Context, Value, E, TargetRange,
&NarrowedExpr)) {
std::string PrettySourceValue = Value.toString(10);
std::string PrettyTargetValue = PrettyPrintInRange(Value, TargetRange);
S.DiagRuntimeBehavior(E->getExprLoc(), NarrowedExpr,
S.PDiag(diag::warn_impcast_integer_precision_binop_constant)
<< PrettySourceValue << PrettyTargetValue
<< E->getType() << T << NarrowedExpr->getSourceRange()
<< clang::SourceRange(CC));
return;
} else if (SourceRange.Width > TargetRange.Width) {
// People want to build with -Wshorten-64-to-32 and not -Wconversion.
if (S.SourceMgr.isInSystemMacro(CC))
return;
// If the source is a constant, use a default-on diagnostic.
if (E->EvaluateAsInt(Value, S.Context, Expr::SE_AllowSideEffects)) {
std::string PrettySourceValue = Value.toString(10);
std::string PrettyTargetValue = PrettyPrintInRange(Value, TargetRange);
S.DiagRuntimeBehavior(E->getExprLoc(), E,
S.PDiag(diag::warn_impcast_integer_precision_constant)
<< PrettySourceValue << PrettyTargetValue
@ -4996,10 +5084,6 @@ void CheckImplicitConversion(Sema &S, Expr *E, QualType T,
return;
}
// People want to build with -Wshorten-64-to-32 and not -Wconversion.
if (S.SourceMgr.isInSystemMacro(CC))
return;
if (TargetRange.Width == 32 && S.Context.getIntWidth(E->getType()) == 64)
return DiagnoseImpCast(S, E, T, CC, diag::warn_impcast_integer_64_32,
/* pruneControlFlow */ true);
@ -5129,6 +5213,25 @@ void AnalyzeImplicitConversions(Sema &S, Expr *OrigE, SourceLocation CC) {
if (E->getType() != T)
CheckImplicitConversion(S, E, T, CC);
// For CompoundAssignmentOperators, check the conversion from the computed
// LHS type to the type of the assignee.
if (CompoundAssignOperator *CAO = dyn_cast<CompoundAssignOperator>(E)) {
QualType LHST = CAO->getComputationLHSType();
// This CheckImplicitConversion would trigger a warning in addition to the
// more serious problem of using NULLs in arithmetic.
// Let the call to CheckImplicitConversion on the child expressions at the
// bottom of this function handle them by filtering those out here.
// Similarly, disable the extra check for shift assignments, since any
// narrowing would be less serious than a too-large shift count.
if (LHST != T &&
T->isIntegralType(S.Context) && LHST->isIntegralType(S.Context) &&
!CAO->isShiftAssignOp() &&
CAO->getRHS()->isNullPointerConstant(S.Context,
Expr::NPC_ValueDependentIsNotNull)
!= Expr::NPCK_GNUNull)
CheckImplicitConversion(S, CAO->getRHS(), T, CC);
}
// Now continue drilling into this expression.
// Skip past explicit casts.
@ -5142,8 +5245,8 @@ void AnalyzeImplicitConversions(Sema &S, Expr *OrigE, SourceLocation CC) {
if (BO->isComparisonOp())
return AnalyzeComparison(S, BO);
// And with simple assignments.
if (BO->getOpcode() == BO_Assign)
// And with assignments.
if (BO->isAssignmentOp())
return AnalyzeAssignment(S, BO);
}

42
clang/test/Sema/constant-conversion.c
View File

@ -66,13 +66,18 @@ void test7() {
struct {
unsigned int twoBits1:2;
unsigned int twoBits2:2;
unsigned int reserved:28;
unsigned int twoBits3:2;
unsigned int reserved:26;
} f;
f.twoBits1 = ~1; // expected-warning {{implicit truncation from 'int' to bitfield changes value from -2 to 2}}
f.twoBits2 = ~2; // expected-warning {{implicit truncation from 'int' to bitfield changes value from -3 to 1}}
f.twoBits1 &= ~1; // no-warning
f.twoBits2 &= ~2; // no-warning
f.twoBits3 |= 4; // expected-warning {{implicit truncation from 'int' to bitfield changes value from 4 to 0}}
f.twoBits3 += 4; // expected-warning {{implicit truncation from 'int' to bitfield changes value from 4 to 0}}
f.twoBits3 *= 4; // expected-warning {{implicit truncation from 'int' to bitfield changes value from 4 to 0}}
f.twoBits3 |= 1; // no-warning
}
void test8() {
@ -80,3 +85,38 @@ void test8() {
struct { enum E x : 1; } f;
f.x = C; // expected-warning {{implicit truncation from 'int' to bitfield changes value from 2 to 0}}
}
int func(int);
void test9() {
unsigned char x = 0;
unsigned char y = 0;
x = y | 0x1ff; // expected-warning {{implicit conversion of binary operation from 'int' to 'unsigned char' may change its value; value of operand would be changed from 511 to 255 if converted before operation}}
x = y | 0xff; // no-warning
x = y & 0xdff; // expected-warning {{implicit conversion of binary operation from 'int' to 'unsigned char' may change its value; value of operand would be changed from 3583 to 255 if converted before operation}}
x = y & 0xff; // no-warning
x = y & ~1; // no-warning
x = 0x1ff | y; // expected-warning {{implicit conversion of binary operation from 'int' to 'unsigned char' may change its value; value of operand would be changed from 511 to 255 if converted before operation}}
x = 0xff | y; // no-warning
x = (y | 0x1ff); // expected-warning {{implicit conversion of binary operation from 'int' to 'unsigned char' may change its value; value of operand would be changed from 511 to 255 if converted before operation}}
x = (y | 0xff); // no-warning
x = 0xff + y; // no-warning
x += 0x1ff; // expected-warning {{implicit conversion from 'int' to 'unsigned char' changes value from 511 to 255}}
x = 0xff - y; // no-warning
x -= 0x1ff; // expected-warning {{implicit conversion from 'int' to 'unsigned char' changes value from 511 to 255}}
x = y * 0x1ff; // expected-warning {{implicit conversion of binary operation from 'int' to 'unsigned char' may change its value; value of operand would be changed from 511 to 255 if converted before operation}}
x = y * 0xff; // no-warning
x *= 0x1ff; // expected-warning {{implicit conversion from 'int' to 'unsigned char' changes value from 511 to 255}}
x = y ^ 0xff; // no-warning
x ^= 0x1ff; // expected-warning {{implicit conversion from 'int' to 'unsigned char' changes value from 511 to 255}}
x = (func(1), 0x1ff); // expected-warning {{implicit conversion of binary operation from 'int' to 'unsigned char' may change its value; value of operand would be changed from 511 to 255 if converted before operation}}
x = (func(1), 0xff); // no-warning
x = 0xff << y; // no-warning
x = 0x1ff << y; // expected-warning {{implicit conversion of binary operation from 'int' to 'unsigned char' may change its value; value of operand would be changed from 511 to 255 if converted before operation}}
// These next two tests make sure that both LHS and RHS are checked for
// narrowing operations.
x = 0x1ff | 0xff; // expected-warning {{implicit conversion of binary operation from 'int' to 'unsigned char' may change its value; value of operand would be changed from 511 to 255 if converted before operation}}
x = 0xff | 0x1ff; // expected-warning {{implicit conversion of binary operation from 'int' to 'unsigned char' may change its value; value of operand would be changed from 511 to 255 if converted before operation}}
}