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//==- DeadStores.cpp - Check for stores to dead variables --------*- C++ -*-==//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines a DeadStores, a flow-sensitive checker that looks for
// stores to variables that are no longer live.
//
//===----------------------------------------------------------------------===//
#include "clang/Analysis/LocalCheckers.h"
#include "clang/Analysis/Analyses/LiveVariables.h"
#include "clang/Analysis/Visitors/CFGRecStmtVisitor.h"
#include "clang/Analysis/PathSensitive/BugReporter.h"
#include "clang/Analysis/PathSensitive/GRExprEngine.h"
#include "clang/Basic/Diagnostic.h"
#include "clang/AST/ASTContext.h"
#include "llvm/Support/Compiler.h"
using namespace clang;
namespace {
class VISIBILITY_HIDDEN DeadStoreObs : public LiveVariables::ObserverTy {
ASTContext &Ctx;
Diagnostic &Diags;
DiagnosticClient &Client;
public:
DeadStoreObs(ASTContext &ctx, Diagnostic &diags, DiagnosticClient &client)
: Ctx(ctx), Diags(diags), Client(client) {}
virtual ~DeadStoreObs() {}
void CheckDeclRef(DeclRefExpr* DR, Expr* Val,
const LiveVariables::AnalysisDataTy& AD,
const LiveVariables::ValTy& Live) {
if (VarDecl* VD = dyn_cast<VarDecl>(DR->getDecl()))
if (VD->hasLocalStorage() && !Live(VD, AD)) {
SourceRange R = Val->getSourceRange();
Diags.Report(&Client,
Ctx.getFullLoc(DR->getSourceRange().getBegin()),
diag::warn_dead_store, 0, 0, &R, 1);
}
}
virtual void ObserveStmt(Stmt* S,
const LiveVariables::AnalysisDataTy& AD,
const LiveVariables::ValTy& Live) {
// Skip statements in macros.
if (S->getLocStart().isMacroID())
return;
if (BinaryOperator* B = dyn_cast<BinaryOperator>(S)) {
if (!B->isAssignmentOp()) return; // Skip non-assignments.
if (DeclRefExpr* DR = dyn_cast<DeclRefExpr>(B->getLHS()))
CheckDeclRef(DR, B->getRHS(), AD, Live);
}
else if (UnaryOperator* U = dyn_cast<UnaryOperator>(S)) {
if (!U->isIncrementOp())
return;
Expr *Ex = U->getSubExpr()->IgnoreParenCasts();
if (DeclRefExpr* DR = dyn_cast<DeclRefExpr>(Ex))
CheckDeclRef(DR, U, AD, Live);
}
else if (DeclStmt* DS = dyn_cast<DeclStmt>(S))
// Iterate through the decls. Warn if any initializers are complex
// expressions that are not live (never used).
for (ScopedDecl* SD = DS->getDecl(); SD; SD = SD->getNextDeclarator()) {
VarDecl* V = dyn_cast<VarDecl>(SD);
if (!V) continue;
if (V->hasLocalStorage())
if (Expr* E = V->getInit()) {
if (!Live(V, AD)) {
// Special case: check for initializations with constants.
//
// e.g. : int x = 0;
//
// If x is EVER assigned a new value later, don't issue
// a warning. This is because such initialization can be
// due to defensive programming.
if (!E->isConstantExpr(Ctx,NULL)) {
// Flag a warning.
SourceRange R = E->getSourceRange();
Diags.Report(&Client,
Ctx.getFullLoc(V->getLocation()),
diag::warn_dead_store, 0, 0, &R, 1);
}
}
}
}
}
};
} // end anonymous namespace
//===----------------------------------------------------------------------===//
// Driver function to invoke the Dead-Stores checker on a CFG.
//===----------------------------------------------------------------------===//
void clang::CheckDeadStores(CFG& cfg, ASTContext &Ctx, Diagnostic &Diags) {
LiveVariables L(cfg);
L.runOnCFG(cfg);
DeadStoreObs A(Ctx, Diags, Diags.getClient());
L.runOnAllBlocks(cfg, &A);
}
//===----------------------------------------------------------------------===//
// BugReporter-based invocation of the Dead-Stores checker.
//===----------------------------------------------------------------------===//
namespace {
class VISIBILITY_HIDDEN DiagBugReport : public RangedBugReport {
std::list<std::string> Strs;
FullSourceLoc L;
public:
DiagBugReport(BugType& D, FullSourceLoc l) :
RangedBugReport(D, NULL), L(l) {}
virtual ~DiagBugReport() {}
virtual FullSourceLoc getLocation(SourceManager&) { return L; }
void addString(const std::string& s) { Strs.push_back(s); }
typedef std::list<std::string>::const_iterator str_iterator;
str_iterator str_begin() const { return Strs.begin(); }
str_iterator str_end() const { return Strs.end(); }
};
class VISIBILITY_HIDDEN DiagCollector : public DiagnosticClient {
std::list<DiagBugReport> Reports;
BugType& D;
public:
DiagCollector(BugType& d) : D(d) {}
virtual ~DiagCollector() {}
virtual void HandleDiagnostic(Diagnostic &Diags,
Diagnostic::Level DiagLevel,
FullSourceLoc Pos,
diag::kind ID,
const std::string *Strs,
unsigned NumStrs,
const SourceRange *Ranges,
unsigned NumRanges) {
// FIXME: Use a map from diag::kind to BugType, instead of having just
// one BugType.
Reports.push_back(DiagBugReport(D, Pos));
DiagBugReport& R = Reports.back();
for ( ; NumRanges ; --NumRanges, ++Ranges)
R.addRange(*Ranges);
for ( ; NumStrs ; --NumStrs, ++Strs)
R.addString(*Strs);
}
// Iterators.
typedef std::list<DiagBugReport>::iterator iterator;
iterator begin() { return Reports.begin(); }
iterator end() { return Reports.end(); }
};
class VISIBILITY_HIDDEN DeadStoresChecker : public BugTypeCacheLocation {
public:
virtual const char* getName() const {
return "dead store";
}
virtual const char* getDescription() const {
return "Value stored to variable is never subsequently read.";
}
virtual void EmitWarnings(BugReporter& BR) {
// Run the dead store checker and collect the diagnostics.
DiagCollector C(*this);
DeadStoreObs A(BR.getContext(), BR.getDiagnostic(), C);
GRExprEngine& Eng = BR.getEngine();
Eng.getLiveness().runOnAllBlocks(Eng.getCFG(), &A);
// Emit the bug reports.
for (DiagCollector::iterator I = C.begin(), E = C.end(); I != E; ++I)
BR.EmitWarning(*I);
}
};
} // end anonymous namespace
BugType* clang::MakeDeadStoresChecker() {
return new DeadStoresChecker();
}
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