r205069 - Improve -Wunreachable-code to provide a means to indicate code is intentionally marked dead via if((0)).
Ted Kremenek
kremenek at apple.com
Fri Mar 28 17:35:21 PDT 2014
Author: kremenek
Date: Fri Mar 28 19:35:20 2014
New Revision: 205069
URL: http://llvm.org/viewvc/llvm-project?rev=205069&view=rev
Log:
Improve -Wunreachable-code to provide a means to indicate code is intentionally marked dead via if((0)).
Taking a hint from -Wparentheses, use an extra '()' as a sigil that
a dead condition is intentionally dead. For example:
if ((0)) { dead }
When this sigil is found, do not emit a dead code warning. When the
analysis sees:
if (0)
it suggests inserting '()' as a Fix-It.
Modified:
cfe/trunk/include/clang/Analysis/Analyses/ReachableCode.h
cfe/trunk/include/clang/Analysis/CFG.h
cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
cfe/trunk/lib/Analysis/CFG.cpp
cfe/trunk/lib/Analysis/ReachableCode.cpp
cfe/trunk/lib/Sema/AnalysisBasedWarnings.cpp
cfe/trunk/test/Sema/warn-unreachable.c
Modified: cfe/trunk/include/clang/Analysis/Analyses/ReachableCode.h
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Analysis/Analyses/ReachableCode.h?rev=205069&r1=205068&r2=205069&view=diff
==============================================================================
--- cfe/trunk/include/clang/Analysis/Analyses/ReachableCode.h (original)
+++ cfe/trunk/include/clang/Analysis/Analyses/ReachableCode.h Fri Mar 28 19:35:20 2014
@@ -50,7 +50,9 @@ class Callback {
public:
virtual ~Callback() {}
virtual void HandleUnreachable(UnreachableKind UK,
- SourceLocation L, SourceRange R1,
+ SourceLocation L,
+ SourceRange ConditionVal,
+ SourceRange R1,
SourceRange R2) = 0;
};
Modified: cfe/trunk/include/clang/Analysis/CFG.h
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Analysis/CFG.h?rev=205069&r1=205068&r2=205069&view=diff
==============================================================================
--- cfe/trunk/include/clang/Analysis/CFG.h (original)
+++ cfe/trunk/include/clang/Analysis/CFG.h Fri Mar 28 19:35:20 2014
@@ -623,10 +623,10 @@ public:
CFGTerminator getTerminator() { return Terminator; }
const CFGTerminator getTerminator() const { return Terminator; }
- Stmt *getTerminatorCondition();
+ Stmt *getTerminatorCondition(bool StripParens = true);
- const Stmt *getTerminatorCondition() const {
- return const_cast<CFGBlock*>(this)->getTerminatorCondition();
+ const Stmt *getTerminatorCondition(bool StripParens = true) const {
+ return const_cast<CFGBlock*>(this)->getTerminatorCondition(StripParens);
}
const Stmt *getLoopTarget() const { return LoopTarget; }
Modified: cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td?rev=205069&r1=205068&r2=205069&view=diff
==============================================================================
--- cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td (original)
+++ cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td Fri Mar 28 19:35:20 2014
@@ -373,6 +373,8 @@ def warn_unreachable_return : Warning<
def warn_unreachable_loop_increment : Warning<
"loop will run at most once (loop increment never executed)">,
InGroup<UnreachableCodeLoopIncrement>, DefaultIgnore;
+def note_unreachable_silence : Note<
+ "silence by adding parentheses to mark code as explicitly dead">;
/// Built-in functions.
def ext_implicit_lib_function_decl : ExtWarn<
Modified: cfe/trunk/lib/Analysis/CFG.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Analysis/CFG.cpp?rev=205069&r1=205068&r2=205069&view=diff
==============================================================================
--- cfe/trunk/lib/Analysis/CFG.cpp (original)
+++ cfe/trunk/lib/Analysis/CFG.cpp Fri Mar 28 19:35:20 2014
@@ -4112,7 +4112,7 @@ void CFGBlock::printTerminator(raw_ostre
TPrinter.print(getTerminator());
}
-Stmt *CFGBlock::getTerminatorCondition() {
+Stmt *CFGBlock::getTerminatorCondition(bool StripParens) {
Stmt *Terminator = this->Terminator;
if (!Terminator)
return NULL;
@@ -4171,6 +4171,9 @@ Stmt *CFGBlock::getTerminatorCondition()
return Terminator;
}
+ if (!StripParens)
+ return E;
+
return E ? E->IgnoreParens() : NULL;
}
Modified: cfe/trunk/lib/Analysis/ReachableCode.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Analysis/ReachableCode.cpp?rev=205069&r1=205068&r2=205069&view=diff
==============================================================================
--- cfe/trunk/lib/Analysis/ReachableCode.cpp (original)
+++ cfe/trunk/lib/Analysis/ReachableCode.cpp Fri Mar 28 19:35:20 2014
@@ -133,10 +133,17 @@ static bool isConfigurationValue(const V
/// those blocks.
static bool isConfigurationValue(const Stmt *S,
Preprocessor &PP,
- bool IncludeIntegers = true) {
+ SourceRange *SilenceableCondVal = nullptr,
+ bool IncludeIntegers = true,
+ bool WrappedInParens = false) {
if (!S)
return false;
+ // Special case looking for the sigil '()' around an integer literal.
+ if (const ParenExpr *PE = dyn_cast<ParenExpr>(S))
+ return isConfigurationValue(PE->getSubExpr(), PP, SilenceableCondVal,
+ IncludeIntegers, true);
+
if (const Expr *Ex = dyn_cast<Expr>(S))
S = Ex->IgnoreParenCasts();
@@ -148,9 +155,15 @@ static bool isConfigurationValue(const S
}
case Stmt::DeclRefExprClass:
return isConfigurationValue(cast<DeclRefExpr>(S)->getDecl(), PP);
- case Stmt::IntegerLiteralClass:
- return IncludeIntegers ? isExpandedFromConfigurationMacro(S, PP)
- : false;
+ case Stmt::IntegerLiteralClass: {
+ const IntegerLiteral *E = cast<IntegerLiteral>(S);
+ if (IncludeIntegers) {
+ if (SilenceableCondVal && !SilenceableCondVal->getBegin().isValid())
+ *SilenceableCondVal = E->getSourceRange();
+ return WrappedInParens || isExpandedFromConfigurationMacro(E, PP);
+ }
+ return false;
+ }
case Stmt::MemberExprClass:
return isConfigurationValue(cast<MemberExpr>(S)->getMemberDecl(), PP);
case Stmt::ObjCBoolLiteralExprClass:
@@ -163,13 +176,18 @@ static bool isConfigurationValue(const S
// values if they are used in a logical or comparison operator
// (not arithmetic).
IncludeIntegers &= (B->isLogicalOp() || B->isComparisonOp());
- return isConfigurationValue(B->getLHS(), PP, IncludeIntegers) ||
- isConfigurationValue(B->getRHS(), PP, IncludeIntegers);
+ return isConfigurationValue(B->getLHS(), PP, SilenceableCondVal,
+ IncludeIntegers) ||
+ isConfigurationValue(B->getRHS(), PP, SilenceableCondVal,
+ IncludeIntegers);
}
case Stmt::UnaryOperatorClass: {
const UnaryOperator *UO = cast<UnaryOperator>(S);
+ if (SilenceableCondVal)
+ *SilenceableCondVal = UO->getSourceRange();
return UO->getOpcode() == UO_LNot &&
- isConfigurationValue(UO->getSubExpr(), PP);
+ isConfigurationValue(UO->getSubExpr(), PP, SilenceableCondVal,
+ IncludeIntegers, WrappedInParens);
}
default:
return false;
@@ -204,11 +222,13 @@ static bool shouldTreatSuccessorsAsReach
if (isa<SwitchStmt>(Term))
return true;
// Specially handle '||' and '&&'.
- if (isa<BinaryOperator>(Term))
+ if (isa<BinaryOperator>(Term)) {
return isConfigurationValue(Term, PP);
+ }
}
- return isConfigurationValue(B->getTerminatorCondition(), PP);
+ const Stmt *Cond = B->getTerminatorCondition(/* stripParens */ false);
+ return isConfigurationValue(Cond, PP);
}
static unsigned scanFromBlock(const CFGBlock *Start,
@@ -314,9 +334,9 @@ namespace {
const Stmt *findDeadCode(const CFGBlock *Block);
void reportDeadCode(const CFGBlock *B,
- const Stmt *S,
- clang::reachable_code::Callback &CB);
- };
+ const Stmt *S,
+ clang::reachable_code::Callback &CB);
+ };
}
void DeadCodeScan::enqueue(const CFGBlock *block) {
@@ -529,6 +549,8 @@ void DeadCodeScan::reportDeadCode(const
UK = reachable_code::UK_Return;
}
+ SourceRange SilenceableCondVal;
+
if (UK == reachable_code::UK_Other) {
// Check if the dead code is part of the "loop target" of
// a for/for-range loop. This is the block that contains
@@ -544,14 +566,26 @@ void DeadCodeScan::reportDeadCode(const
}
CB.HandleUnreachable(reachable_code::UK_Loop_Increment,
- Loc, SourceRange(Loc, Loc), R2);
+ Loc, SourceRange(), SourceRange(Loc, Loc), R2);
return;
}
+
+ // Check if the dead block has a predecessor whose branch has
+ // a configuration value that *could* be modified to
+ // silence the warning.
+ CFGBlock::const_pred_iterator PI = B->pred_begin();
+ if (PI != B->pred_end()) {
+ if (const CFGBlock *PredBlock = PI->getPossiblyUnreachableBlock()) {
+ const Stmt *TermCond =
+ PredBlock->getTerminatorCondition(/* strip parens */ false);
+ isConfigurationValue(TermCond, PP, &SilenceableCondVal);
+ }
+ }
}
SourceRange R1, R2;
SourceLocation Loc = GetUnreachableLoc(S, R1, R2);
- CB.HandleUnreachable(UK, Loc, R1, R2);
+ CB.HandleUnreachable(UK, Loc, SilenceableCondVal, R1, R2);
}
//===----------------------------------------------------------------------===//
Modified: cfe/trunk/lib/Sema/AnalysisBasedWarnings.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/AnalysisBasedWarnings.cpp?rev=205069&r1=205068&r2=205069&view=diff
==============================================================================
--- cfe/trunk/lib/Sema/AnalysisBasedWarnings.cpp (original)
+++ cfe/trunk/lib/Sema/AnalysisBasedWarnings.cpp Fri Mar 28 19:35:20 2014
@@ -66,7 +66,9 @@ namespace {
UnreachableCodeHandler(Sema &s) : S(s) {}
void HandleUnreachable(reachable_code::UnreachableKind UK,
- SourceLocation L, SourceRange R1,
+ SourceLocation L,
+ SourceRange SilenceableCondVal,
+ SourceRange R1,
SourceRange R2) override {
unsigned diag = diag::warn_unreachable;
switch (UK) {
@@ -84,6 +86,17 @@ namespace {
}
S.Diag(L, diag) << R1 << R2;
+
+ SourceLocation Open = SilenceableCondVal.getBegin();
+ if (Open.isValid()) {
+ SourceLocation Close = SilenceableCondVal.getEnd();
+ Close = S.PP.getLocForEndOfToken(Close);
+ if (Close.isValid()) {
+ S.Diag(Open, diag::note_unreachable_silence)
+ << FixItHint::CreateInsertion(Open, "/* DISABLES CODE */ (")
+ << FixItHint::CreateInsertion(Close, ")");
+ }
+ }
}
};
}
Modified: cfe/trunk/test/Sema/warn-unreachable.c
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Sema/warn-unreachable.c?rev=205069&r1=205068&r2=205069&view=diff
==============================================================================
--- cfe/trunk/test/Sema/warn-unreachable.c (original)
+++ cfe/trunk/test/Sema/warn-unreachable.c Fri Mar 28 19:35:20 2014
@@ -257,7 +257,7 @@ int test_config_constant(int x) {
calledFun(); // no-warning
return 1;
}
- if (!1) {
+ if (!1) { // expected-note {{silence by adding parentheses to mark code as explicitly dead}}
calledFun(); // expected-warning {{will never be executed}}
return 1;
}
@@ -268,7 +268,7 @@ int test_config_constant(int x) {
if (x > 10)
return CONFIG_CONSTANT ? calledFun() : calledFun(); // no-warning
else
- return 1 ?
+ return 1 ? // expected-note {{silence by adding parentheses to mark code as explicitly dead}}
calledFun() :
calledFun(); // expected-warning {{will never be executed}}
}
@@ -365,3 +365,34 @@ int test_break_preceded_by_noreturn_SUPP
}
#pragma clang diagnostic pop
+
+// Test "silencing" with parentheses.
+void test_with_paren_silencing(int x) {
+ if (0) calledFun(); // expected-warning {{will never be executed}} expected-note {{silence by adding parentheses to mark code as explicitly dead}}
+ if ((0)) calledFun(); // no-warning
+
+ if (1) // expected-note {{silence by adding parentheses to mark code as explicitly dead}}
+ calledFun();
+ else
+ calledFun(); // expected-warning {{will never be executed}}
+
+ if ((1))
+ calledFun();
+ else
+ calledFun(); // no-warning
+
+ if (!1) // expected-note {{silence by adding parentheses to mark code as explicitly dead}}
+ calledFun(); // expected-warning {{code will never be executed}}
+ else
+ calledFun();
+
+ if ((!1))
+ calledFun(); // no-warning
+ else
+ calledFun();
+
+ if (!(1))
+ calledFun(); // no-warning
+ else
+ calledFun();
+}
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