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AnalysisBasedWarnings.cpp
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//=- AnalysisBasedWarnings.cpp - Sema warnings based on libAnalysis -*- 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 analysis_warnings::[Policy,Executor].
// Together they are used by Sema to issue warnings based on inexpensive
// static analysis algorithms in libAnalysis.
//
//===----------------------------------------------------------------------===//
#include "clang/Sema/AnalysisBasedWarnings.h"
#include "clang/AST/DeclCXX.h"
#include "clang/AST/DeclObjC.h"
#include "clang/AST/EvaluatedExprVisitor.h"
#include "clang/AST/ExprCXX.h"
#include "clang/AST/ExprObjC.h"
#include "clang/AST/ParentMap.h"
#include "clang/AST/RecursiveASTVisitor.h"
#include "clang/AST/StmtCXX.h"
#include "clang/AST/StmtObjC.h"
#include "clang/AST/StmtVisitor.h"
#include "clang/Analysis/Analyses/CFGReachabilityAnalysis.h"
#include "clang/Analysis/Analyses/Consumed.h"
#include "clang/Analysis/Analyses/ReachableCode.h"
#include "clang/Analysis/Analyses/ThreadSafety.h"
#include "clang/Analysis/Analyses/UninitializedValues.h"
#include "clang/Analysis/AnalysisDeclContext.h"
#include "clang/Analysis/CFG.h"
#include "clang/Analysis/CFGStmtMap.h"
#include "clang/Basic/SourceLocation.h"
#include "clang/Basic/SourceManager.h"
#include "clang/Lex/Preprocessor.h"
#include "clang/Sema/ScopeInfo.h"
#include "clang/Sema/SemaInternal.h"
#include "llvm/ADT/BitVector.h"
#include "llvm/ADT/MapVector.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/Support/Casting.h"
#include <algorithm>
#include <deque>
#include <iterator>
using namespace clang;
//===----------------------------------------------------------------------===//
// Unreachable code analysis.
//===----------------------------------------------------------------------===//
namespace {
class UnreachableCodeHandler : public reachable_code::Callback {
Sema &S;
SourceRange PreviousSilenceableCondVal;
public:
UnreachableCodeHandler(Sema &s) : S(s) {}
void HandleUnreachable(reachable_code::UnreachableKind UK,
SourceLocation L,
SourceRange SilenceableCondVal,
SourceRange R1,
SourceRange R2) override {
// Avoid reporting multiple unreachable code diagnostics that are
// triggered by the same conditional value.
if (PreviousSilenceableCondVal.isValid() &&
SilenceableCondVal.isValid() &&
PreviousSilenceableCondVal == SilenceableCondVal)
return;
PreviousSilenceableCondVal = SilenceableCondVal;
unsigned diag = diag::warn_unreachable;
switch (UK) {
case reachable_code::UK_Break:
diag = diag::warn_unreachable_break;
break;
case reachable_code::UK_Return:
diag = diag::warn_unreachable_return;
break;
case reachable_code::UK_Loop_Increment:
diag = diag::warn_unreachable_loop_increment;
break;
case reachable_code::UK_Other:
break;
}
S.Diag(L, diag) << R1 << R2;
SourceLocation Open = SilenceableCondVal.getBegin();
if (Open.isValid()) {
SourceLocation Close = SilenceableCondVal.getEnd();
Close = S.getLocForEndOfToken(Close);
if (Close.isValid()) {
S.Diag(Open, diag::note_unreachable_silence)
<< FixItHint::CreateInsertion(Open, "/* DISABLES CODE */ (")
<< FixItHint::CreateInsertion(Close, ")");
}
}
}
};
} // anonymous namespace
/// CheckUnreachable - Check for unreachable code.
static void CheckUnreachable(Sema &S, AnalysisDeclContext &AC) {
// As a heuristic prune all diagnostics not in the main file. Currently
// the majority of warnings in headers are false positives. These
// are largely caused by configuration state, e.g. preprocessor
// defined code, etc.
//
// Note that this is also a performance optimization. Analyzing
// headers many times can be expensive.
if (!S.getSourceManager().isInMainFile(AC.getDecl()->getLocStart()))
return;
UnreachableCodeHandler UC(S);
reachable_code::FindUnreachableCode(AC, S.getPreprocessor(), UC);
}
namespace {
/// \brief Warn on logical operator errors in CFGBuilder
class LogicalErrorHandler : public CFGCallback {
Sema &S;
public:
LogicalErrorHandler(Sema &S) : CFGCallback(), S(S) {}
static bool HasMacroID(const Expr *E) {
if (E->getExprLoc().isMacroID())
return true;
// Recurse to children.
for (const Stmt *SubStmt : E->children())
if (const Expr *SubExpr = dyn_cast_or_null<Expr>(SubStmt))
if (HasMacroID(SubExpr))
return true;
return false;
}
void compareAlwaysTrue(const BinaryOperator *B, bool isAlwaysTrue) override {
if (HasMacroID(B))
return;
SourceRange DiagRange = B->getSourceRange();
S.Diag(B->getExprLoc(), diag::warn_tautological_overlap_comparison)
<< DiagRange << isAlwaysTrue;
}
void compareBitwiseEquality(const BinaryOperator *B,
bool isAlwaysTrue) override {
if (HasMacroID(B))
return;
SourceRange DiagRange = B->getSourceRange();
S.Diag(B->getExprLoc(), diag::warn_comparison_bitwise_always)
<< DiagRange << isAlwaysTrue;
}
};
} // anonymous namespace
//===----------------------------------------------------------------------===//
// Check for infinite self-recursion in functions
//===----------------------------------------------------------------------===//
// Returns true if the function is called anywhere within the CFGBlock.
// For member functions, the additional condition of being call from the
// this pointer is required.
static bool hasRecursiveCallInPath(const FunctionDecl *FD, CFGBlock &Block) {
// Process all the Stmt's in this block to find any calls to FD.
for (const auto &B : Block) {
if (B.getKind() != CFGElement::Statement)
continue;
const CallExpr *CE = dyn_cast<CallExpr>(B.getAs<CFGStmt>()->getStmt());
if (!CE || !CE->getCalleeDecl() ||
CE->getCalleeDecl()->getCanonicalDecl() != FD)
continue;
// Skip function calls which are qualified with a templated class.
if (const DeclRefExpr *DRE =
dyn_cast<DeclRefExpr>(CE->getCallee()->IgnoreParenImpCasts())) {
if (NestedNameSpecifier *NNS = DRE->getQualifier()) {
if (NNS->getKind() == NestedNameSpecifier::TypeSpec &&
isa<TemplateSpecializationType>(NNS->getAsType())) {
continue;
}
}
}
const CXXMemberCallExpr *MCE = dyn_cast<CXXMemberCallExpr>(CE);
if (!MCE || isa<CXXThisExpr>(MCE->getImplicitObjectArgument()) ||
!MCE->getMethodDecl()->isVirtual())
return true;
}
return false;
}
// Returns true if every path from the entry block passes through a call to FD.
static bool checkForRecursiveFunctionCall(const FunctionDecl *FD, CFG *cfg) {
llvm::SmallPtrSet<CFGBlock *, 16> Visited;
llvm::SmallVector<CFGBlock *, 16> WorkList;
// Keep track of whether we found at least one recursive path.
bool foundRecursion = false;
const unsigned ExitID = cfg->getExit().getBlockID();
// Seed the work list with the entry block.
WorkList.push_back(&cfg->getEntry());
while (!WorkList.empty()) {
CFGBlock *Block = WorkList.pop_back_val();
for (auto I = Block->succ_begin(), E = Block->succ_end(); I != E; ++I) {
if (CFGBlock *SuccBlock = *I) {
if (!Visited.insert(SuccBlock).second)
continue;
// Found a path to the exit node without a recursive call.
if (ExitID == SuccBlock->getBlockID())
return false;
// If the successor block contains a recursive call, end analysis there.
if (hasRecursiveCallInPath(FD, *SuccBlock)) {
foundRecursion = true;
continue;
}
WorkList.push_back(SuccBlock);
}
}
}
return foundRecursion;
}
static void checkRecursiveFunction(Sema &S, const FunctionDecl *FD,
const Stmt *Body, AnalysisDeclContext &AC) {
FD = FD->getCanonicalDecl();
// Only run on non-templated functions and non-templated members of
// templated classes.
if (FD->getTemplatedKind() != FunctionDecl::TK_NonTemplate &&
FD->getTemplatedKind() != FunctionDecl::TK_MemberSpecialization)
return;
CFG *cfg = AC.getCFG();
if (!cfg) return;
// Emit diagnostic if a recursive function call is detected for all paths.
if (checkForRecursiveFunctionCall(FD, cfg))
S.Diag(Body->getLocStart(), diag::warn_infinite_recursive_function);
}
//===----------------------------------------------------------------------===//
// Check for throw in a non-throwing function.
//===----------------------------------------------------------------------===//
/// Determine whether an exception thrown by E, unwinding from ThrowBlock,
/// can reach ExitBlock.
static bool throwEscapes(Sema &S, const CXXThrowExpr *E, CFGBlock &ThrowBlock,
CFG *Body) {
SmallVector<CFGBlock *, 16> Stack;
llvm::BitVector Queued(Body->getNumBlockIDs());
Stack.push_back(&ThrowBlock);
Queued[ThrowBlock.getBlockID()] = true;
while (!Stack.empty()) {
CFGBlock &UnwindBlock = *Stack.back();
Stack.pop_back();
for (auto &Succ : UnwindBlock.succs()) {
if (!Succ.isReachable() || Queued[Succ->getBlockID()])
continue;
if (Succ->getBlockID() == Body->getExit().getBlockID())
return true;
if (auto *Catch =
dyn_cast_or_null<CXXCatchStmt>(Succ->getLabel())) {
QualType Caught = Catch->getCaughtType();
if (Caught.isNull() || // catch (...) catches everything
!E->getSubExpr() || // throw; is considered cuaght by any handler
S.handlerCanCatch(Caught, E->getSubExpr()->getType()))
// Exception doesn't escape via this path.
break;
} else {
Stack.push_back(Succ);
Queued[Succ->getBlockID()] = true;
}
}
}
return false;
}
static void visitReachableThrows(
CFG *BodyCFG,
llvm::function_ref<void(const CXXThrowExpr *, CFGBlock &)> Visit) {
llvm::BitVector Reachable(BodyCFG->getNumBlockIDs());
clang::reachable_code::ScanReachableFromBlock(&BodyCFG->getEntry(), Reachable);
for (CFGBlock *B : *BodyCFG) {
if (!Reachable[B->getBlockID()])
continue;
for (CFGElement &E : *B) {
Optional<CFGStmt> S = E.getAs<CFGStmt>();
if (!S)
continue;
if (auto *Throw = dyn_cast<CXXThrowExpr>(S->getStmt()))
Visit(Throw, *B);
}
}
}
static void EmitDiagForCXXThrowInNonThrowingFunc(Sema &S, SourceLocation OpLoc,
const FunctionDecl *FD) {
if (!S.getSourceManager().isInSystemHeader(OpLoc) &&
FD->getTypeSourceInfo()) {
S.Diag(OpLoc, diag::warn_throw_in_noexcept_func) << FD;
if (S.getLangOpts().CPlusPlus11 &&
(isa<CXXDestructorDecl>(FD) ||
FD->getDeclName().getCXXOverloadedOperator() == OO_Delete ||
FD->getDeclName().getCXXOverloadedOperator() == OO_Array_Delete)) {
if (const auto *Ty = FD->getTypeSourceInfo()->getType()->
getAs<FunctionProtoType>())
S.Diag(FD->getLocation(), diag::note_throw_in_dtor)
<< !isa<CXXDestructorDecl>(FD) << !Ty->hasExceptionSpec()
<< FD->getExceptionSpecSourceRange();
} else
S.Diag(FD->getLocation(), diag::note_throw_in_function)
<< FD->getExceptionSpecSourceRange();
}
}
static void checkThrowInNonThrowingFunc(Sema &S, const FunctionDecl *FD,
AnalysisDeclContext &AC) {
CFG *BodyCFG = AC.getCFG();
if (!BodyCFG)
return;
if (BodyCFG->getExit().pred_empty())
return;
visitReachableThrows(BodyCFG, [&](const CXXThrowExpr *Throw, CFGBlock &Block) {
if (throwEscapes(S, Throw, Block, BodyCFG))
EmitDiagForCXXThrowInNonThrowingFunc(S, Throw->getThrowLoc(), FD);
});
}
static bool isNoexcept(const FunctionDecl *FD) {
const auto *FPT = FD->getType()->castAs<FunctionProtoType>();
if (FPT->isNothrow(FD->getASTContext()) || FD->hasAttr<NoThrowAttr>())
return true;
return false;
}
//===----------------------------------------------------------------------===//
// Check for missing return value.
//===----------------------------------------------------------------------===//
enum ControlFlowKind {
UnknownFallThrough,
NeverFallThrough,
MaybeFallThrough,
AlwaysFallThrough,
NeverFallThroughOrReturn
};
/// CheckFallThrough - Check that we don't fall off the end of a
/// Statement that should return a value.
///
/// \returns AlwaysFallThrough iff we always fall off the end of the statement,
/// MaybeFallThrough iff we might or might not fall off the end,
/// NeverFallThroughOrReturn iff we never fall off the end of the statement or
/// return. We assume NeverFallThrough iff we never fall off the end of the
/// statement but we may return. We assume that functions not marked noreturn
/// will return.
static ControlFlowKind CheckFallThrough(AnalysisDeclContext &AC) {
CFG *cfg = AC.getCFG();
if (!cfg) return UnknownFallThrough;
// The CFG leaves in dead things, and we don't want the dead code paths to
// confuse us, so we mark all live things first.
llvm::BitVector live(cfg->getNumBlockIDs());
unsigned count = reachable_code::ScanReachableFromBlock(&cfg->getEntry(),
live);
bool AddEHEdges = AC.getAddEHEdges();
if (!AddEHEdges && count != cfg->getNumBlockIDs())
// When there are things remaining dead, and we didn't add EH edges
// from CallExprs to the catch clauses, we have to go back and
// mark them as live.
for (const auto *B : *cfg) {
if (!live[B->getBlockID()]) {
if (B->pred_begin() == B->pred_end()) {
if (B->getTerminator() && isa<CXXTryStmt>(B->getTerminator()))
// When not adding EH edges from calls, catch clauses
// can otherwise seem dead. Avoid noting them as dead.
count += reachable_code::ScanReachableFromBlock(B, live);
continue;
}
}
}
// Now we know what is live, we check the live precessors of the exit block
// and look for fall through paths, being careful to ignore normal returns,
// and exceptional paths.
bool HasLiveReturn = false;
bool HasFakeEdge = false;
bool HasPlainEdge = false;
bool HasAbnormalEdge = false;
// Ignore default cases that aren't likely to be reachable because all
// enums in a switch(X) have explicit case statements.
CFGBlock::FilterOptions FO;
FO.IgnoreDefaultsWithCoveredEnums = 1;
for (CFGBlock::filtered_pred_iterator
I = cfg->getExit().filtered_pred_start_end(FO); I.hasMore(); ++I) {
const CFGBlock& B = **I;
if (!live[B.getBlockID()])
continue;
// Skip blocks which contain an element marked as no-return. They don't
// represent actually viable edges into the exit block, so mark them as
// abnormal.
if (B.hasNoReturnElement()) {
HasAbnormalEdge = true;
continue;
}
// Destructors can appear after the 'return' in the CFG. This is
// normal. We need to look pass the destructors for the return
// statement (if it exists).
CFGBlock::const_reverse_iterator ri = B.rbegin(), re = B.rend();
for ( ; ri != re ; ++ri)
if (ri->getAs<CFGStmt>())
break;
// No more CFGElements in the block?
if (ri == re) {
if (B.getTerminator() && isa<CXXTryStmt>(B.getTerminator())) {
HasAbnormalEdge = true;
continue;
}
// A labeled empty statement, or the entry block...
HasPlainEdge = true;
continue;
}
CFGStmt CS = ri->castAs<CFGStmt>();
const Stmt *S = CS.getStmt();
if (isa<ReturnStmt>(S) || isa<CoreturnStmt>(S)) {
HasLiveReturn = true;
continue;
}
if (isa<ObjCAtThrowStmt>(S)) {
HasFakeEdge = true;
continue;
}
if (isa<CXXThrowExpr>(S)) {
HasFakeEdge = true;
continue;
}
if (isa<MSAsmStmt>(S)) {
// TODO: Verify this is correct.
HasFakeEdge = true;
HasLiveReturn = true;
continue;
}
if (isa<CXXTryStmt>(S)) {
HasAbnormalEdge = true;
continue;
}
if (std::find(B.succ_begin(), B.succ_end(), &cfg->getExit())
== B.succ_end()) {
HasAbnormalEdge = true;
continue;
}
HasPlainEdge = true;
}
if (!HasPlainEdge) {
if (HasLiveReturn)
return NeverFallThrough;
return NeverFallThroughOrReturn;
}
if (HasAbnormalEdge || HasFakeEdge || HasLiveReturn)
return MaybeFallThrough;
// This says AlwaysFallThrough for calls to functions that are not marked
// noreturn, that don't return. If people would like this warning to be more
// accurate, such functions should be marked as noreturn.
return AlwaysFallThrough;
}
namespace {
struct CheckFallThroughDiagnostics {
unsigned diag_MaybeFallThrough_HasNoReturn;
unsigned diag_MaybeFallThrough_ReturnsNonVoid;
unsigned diag_AlwaysFallThrough_HasNoReturn;
unsigned diag_AlwaysFallThrough_ReturnsNonVoid;
unsigned diag_NeverFallThroughOrReturn;
enum { Function, Block, Lambda, Coroutine } funMode;
SourceLocation FuncLoc;
static CheckFallThroughDiagnostics MakeForFunction(const Decl *Func) {
CheckFallThroughDiagnostics D;
D.FuncLoc = Func->getLocation();
D.diag_MaybeFallThrough_HasNoReturn =
diag::warn_falloff_noreturn_function;
D.diag_MaybeFallThrough_ReturnsNonVoid =
diag::warn_maybe_falloff_nonvoid_function;
D.diag_AlwaysFallThrough_HasNoReturn =
diag::warn_falloff_noreturn_function;
D.diag_AlwaysFallThrough_ReturnsNonVoid =
diag::warn_falloff_nonvoid_function;
// Don't suggest that virtual functions be marked "noreturn", since they
// might be overridden by non-noreturn functions.
bool isVirtualMethod = false;
if (const CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(Func))
isVirtualMethod = Method->isVirtual();
// Don't suggest that template instantiations be marked "noreturn"
bool isTemplateInstantiation = false;
if (const FunctionDecl *Function = dyn_cast<FunctionDecl>(Func))
isTemplateInstantiation = Function->isTemplateInstantiation();
if (!isVirtualMethod && !isTemplateInstantiation)
D.diag_NeverFallThroughOrReturn =
diag::warn_suggest_noreturn_function;
else
D.diag_NeverFallThroughOrReturn = 0;
D.funMode = Function;
return D;
}
static CheckFallThroughDiagnostics MakeForCoroutine(const Decl *Func) {
CheckFallThroughDiagnostics D;
D.FuncLoc = Func->getLocation();
D.diag_MaybeFallThrough_HasNoReturn = 0;
D.diag_MaybeFallThrough_ReturnsNonVoid =
diag::warn_maybe_falloff_nonvoid_coroutine;
D.diag_AlwaysFallThrough_HasNoReturn = 0;
D.diag_AlwaysFallThrough_ReturnsNonVoid =
diag::warn_falloff_nonvoid_coroutine;
D.funMode = Coroutine;
return D;
}
static CheckFallThroughDiagnostics MakeForBlock() {
CheckFallThroughDiagnostics D;
D.diag_MaybeFallThrough_HasNoReturn =
diag::err_noreturn_block_has_return_expr;
D.diag_MaybeFallThrough_ReturnsNonVoid =
diag::err_maybe_falloff_nonvoid_block;
D.diag_AlwaysFallThrough_HasNoReturn =
diag::err_noreturn_block_has_return_expr;
D.diag_AlwaysFallThrough_ReturnsNonVoid =
diag::err_falloff_nonvoid_block;
D.diag_NeverFallThroughOrReturn = 0;
D.funMode = Block;
return D;
}
static CheckFallThroughDiagnostics MakeForLambda() {
CheckFallThroughDiagnostics D;
D.diag_MaybeFallThrough_HasNoReturn =
diag::err_noreturn_lambda_has_return_expr;
D.diag_MaybeFallThrough_ReturnsNonVoid =
diag::warn_maybe_falloff_nonvoid_lambda;
D.diag_AlwaysFallThrough_HasNoReturn =
diag::err_noreturn_lambda_has_return_expr;
D.diag_AlwaysFallThrough_ReturnsNonVoid =
diag::warn_falloff_nonvoid_lambda;
D.diag_NeverFallThroughOrReturn = 0;
D.funMode = Lambda;
return D;
}
bool checkDiagnostics(DiagnosticsEngine &D, bool ReturnsVoid,
bool HasNoReturn) const {
if (funMode == Function) {
return (ReturnsVoid ||
D.isIgnored(diag::warn_maybe_falloff_nonvoid_function,
FuncLoc)) &&
(!HasNoReturn ||
D.isIgnored(diag::warn_noreturn_function_has_return_expr,
FuncLoc)) &&
(!ReturnsVoid ||
D.isIgnored(diag::warn_suggest_noreturn_block, FuncLoc));
}
if (funMode == Coroutine) {
return (ReturnsVoid ||
D.isIgnored(diag::warn_maybe_falloff_nonvoid_function, FuncLoc) ||
D.isIgnored(diag::warn_maybe_falloff_nonvoid_coroutine,
FuncLoc)) &&
(!HasNoReturn);
}
// For blocks / lambdas.
return ReturnsVoid && !HasNoReturn;
}
};
} // anonymous namespace
/// CheckFallThroughForBody - Check that we don't fall off the end of a
/// function that should return a value. Check that we don't fall off the end
/// of a noreturn function. We assume that functions and blocks not marked
/// noreturn will return.
static void CheckFallThroughForBody(Sema &S, const Decl *D, const Stmt *Body,
const BlockExpr *blkExpr,
const CheckFallThroughDiagnostics &CD,
AnalysisDeclContext &AC,
sema::FunctionScopeInfo *FSI) {
bool ReturnsVoid = false;
bool HasNoReturn = false;
bool IsCoroutine = FSI->isCoroutine();
if (const auto *FD = dyn_cast<FunctionDecl>(D)) {
if (const auto *CBody = dyn_cast<CoroutineBodyStmt>(Body))
ReturnsVoid = CBody->getFallthroughHandler() != nullptr;
else
ReturnsVoid = FD->getReturnType()->isVoidType();
HasNoReturn = FD->isNoReturn();
}
else if (const auto *MD = dyn_cast<ObjCMethodDecl>(D)) {
ReturnsVoid = MD->getReturnType()->isVoidType();
HasNoReturn = MD->hasAttr<NoReturnAttr>();
}
else if (isa<BlockDecl>(D)) {
QualType BlockTy = blkExpr->getType();
if (const FunctionType *FT =
BlockTy->getPointeeType()->getAs<FunctionType>()) {
if (FT->getReturnType()->isVoidType())
ReturnsVoid = true;
if (FT->getNoReturnAttr())
HasNoReturn = true;
}
}
DiagnosticsEngine &Diags = S.getDiagnostics();
// Short circuit for compilation speed.
if (CD.checkDiagnostics(Diags, ReturnsVoid, HasNoReturn))
return;
SourceLocation LBrace = Body->getLocStart(), RBrace = Body->getLocEnd();
auto EmitDiag = [&](SourceLocation Loc, unsigned DiagID) {
if (IsCoroutine)
S.Diag(Loc, DiagID) << FSI->CoroutinePromise->getType();
else
S.Diag(Loc, DiagID);
};
// Either in a function body compound statement, or a function-try-block.
switch (CheckFallThrough(AC)) {
case UnknownFallThrough:
break;
case MaybeFallThrough:
if (HasNoReturn)
EmitDiag(RBrace, CD.diag_MaybeFallThrough_HasNoReturn);
else if (!ReturnsVoid)
EmitDiag(RBrace, CD.diag_MaybeFallThrough_ReturnsNonVoid);
break;
case AlwaysFallThrough:
if (HasNoReturn)
EmitDiag(RBrace, CD.diag_AlwaysFallThrough_HasNoReturn);
else if (!ReturnsVoid)
EmitDiag(RBrace, CD.diag_AlwaysFallThrough_ReturnsNonVoid);
break;
case NeverFallThroughOrReturn:
if (ReturnsVoid && !HasNoReturn && CD.diag_NeverFallThroughOrReturn) {
if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
S.Diag(LBrace, CD.diag_NeverFallThroughOrReturn) << 0 << FD;
} else if (const ObjCMethodDecl *MD = dyn_cast<ObjCMethodDecl>(D)) {
S.Diag(LBrace, CD.diag_NeverFallThroughOrReturn) << 1 << MD;
} else {
S.Diag(LBrace, CD.diag_NeverFallThroughOrReturn);
}
}
break;
case NeverFallThrough:
break;
}
}
//===----------------------------------------------------------------------===//
// -Wuninitialized
//===----------------------------------------------------------------------===//
namespace {
/// ContainsReference - A visitor class to search for references to
/// a particular declaration (the needle) within any evaluated component of an
/// expression (recursively).
class ContainsReference : public ConstEvaluatedExprVisitor<ContainsReference> {
bool FoundReference;
const DeclRefExpr *Needle;
public:
typedef ConstEvaluatedExprVisitor<ContainsReference> Inherited;
ContainsReference(ASTContext &Context, const DeclRefExpr *Needle)
: Inherited(Context), FoundReference(false), Needle(Needle) {}
void VisitExpr(const Expr *E) {
// Stop evaluating if we already have a reference.
if (FoundReference)
return;
Inherited::VisitExpr(E);
}
void VisitDeclRefExpr(const DeclRefExpr *E) {
if (E == Needle)
FoundReference = true;
else
Inherited::VisitDeclRefExpr(E);
}
bool doesContainReference() const { return FoundReference; }
};
} // anonymous namespace
static bool SuggestInitializationFixit(Sema &S, const VarDecl *VD) {
QualType VariableTy = VD->getType().getCanonicalType();
if (VariableTy->isBlockPointerType() &&
!VD->hasAttr<BlocksAttr>()) {
S.Diag(VD->getLocation(), diag::note_block_var_fixit_add_initialization)
<< VD->getDeclName()
<< FixItHint::CreateInsertion(VD->getLocation(), "__block ");
return true;
}
// Don't issue a fixit if there is already an initializer.
if (VD->getInit())
return false;
// Don't suggest a fixit inside macros.
if (VD->getLocEnd().isMacroID())
return false;
SourceLocation Loc = S.getLocForEndOfToken(VD->getLocEnd());
// Suggest possible initialization (if any).
std::string Init = S.getFixItZeroInitializerForType(VariableTy, Loc);
if (Init.empty())
return false;
S.Diag(Loc, diag::note_var_fixit_add_initialization) << VD->getDeclName()
<< FixItHint::CreateInsertion(Loc, Init);
return true;
}
/// Create a fixit to remove an if-like statement, on the assumption that its
/// condition is CondVal.
static void CreateIfFixit(Sema &S, const Stmt *If, const Stmt *Then,
const Stmt *Else, bool CondVal,
FixItHint &Fixit1, FixItHint &Fixit2) {
if (CondVal) {
// If condition is always true, remove all but the 'then'.
Fixit1 = FixItHint::CreateRemoval(
CharSourceRange::getCharRange(If->getLocStart(),
Then->getLocStart()));
if (Else) {
SourceLocation ElseKwLoc = S.getLocForEndOfToken(Then->getLocEnd());
Fixit2 = FixItHint::CreateRemoval(
SourceRange(ElseKwLoc, Else->getLocEnd()));
}
} else {
// If condition is always false, remove all but the 'else'.
if (Else)
Fixit1 = FixItHint::CreateRemoval(
CharSourceRange::getCharRange(If->getLocStart(),
Else->getLocStart()));
else
Fixit1 = FixItHint::CreateRemoval(If->getSourceRange());
}
}
/// DiagUninitUse -- Helper function to produce a diagnostic for an
/// uninitialized use of a variable.
static void DiagUninitUse(Sema &S, const VarDecl *VD, const UninitUse &Use,
bool IsCapturedByBlock) {
bool Diagnosed = false;
switch (Use.getKind()) {
case UninitUse::Always:
S.Diag(Use.getUser()->getLocStart(), diag::warn_uninit_var)
<< VD->getDeclName() << IsCapturedByBlock
<< Use.getUser()->getSourceRange();
return;
case UninitUse::AfterDecl:
case UninitUse::AfterCall:
S.Diag(VD->getLocation(), diag::warn_sometimes_uninit_var)
<< VD->getDeclName() << IsCapturedByBlock
<< (Use.getKind() == UninitUse::AfterDecl ? 4 : 5)
<< const_cast<DeclContext*>(VD->getLexicalDeclContext())
<< VD->getSourceRange();
S.Diag(Use.getUser()->getLocStart(), diag::note_uninit_var_use)
<< IsCapturedByBlock << Use.getUser()->getSourceRange();
return;
case UninitUse::Maybe:
case UninitUse::Sometimes:
// Carry on to report sometimes-uninitialized branches, if possible,
// or a 'may be used uninitialized' diagnostic otherwise.
break;
}
// Diagnose each branch which leads to a sometimes-uninitialized use.
for (UninitUse::branch_iterator I = Use.branch_begin(), E = Use.branch_end();
I != E; ++I) {
assert(Use.getKind() == UninitUse::Sometimes);
const Expr *User = Use.getUser();
const Stmt *Term = I->Terminator;
// Information used when building the diagnostic.
unsigned DiagKind;
StringRef Str;
SourceRange Range;
// FixIts to suppress the diagnostic by removing the dead condition.
// For all binary terminators, branch 0 is taken if the condition is true,
// and branch 1 is taken if the condition is false.
int RemoveDiagKind = -1;
const char *FixitStr =
S.getLangOpts().CPlusPlus ? (I->Output ? "true" : "false")
: (I->Output ? "1" : "0");
FixItHint Fixit1, Fixit2;
switch (Term ? Term->getStmtClass() : Stmt::DeclStmtClass) {
default:
// Don't know how to report this. Just fall back to 'may be used
// uninitialized'. FIXME: Can this happen?
continue;
// "condition is true / condition is false".
case Stmt::IfStmtClass: {
const IfStmt *IS = cast<IfStmt>(Term);
DiagKind = 0;
Str = "if";
Range = IS->getCond()->getSourceRange();
RemoveDiagKind = 0;
CreateIfFixit(S, IS, IS->getThen(), IS->getElse(),
I->Output, Fixit1, Fixit2);
break;
}
case Stmt::ConditionalOperatorClass: {
const ConditionalOperator *CO = cast<ConditionalOperator>(Term);
DiagKind = 0;
Str = "?:";
Range = CO->getCond()->getSourceRange();
RemoveDiagKind = 0;
CreateIfFixit(S, CO, CO->getTrueExpr(), CO->getFalseExpr(),
I->Output, Fixit1, Fixit2);
break;
}
case Stmt::BinaryOperatorClass: {
const BinaryOperator *BO = cast<BinaryOperator>(Term);
if (!BO->isLogicalOp())
continue;
DiagKind = 0;
Str = BO->getOpcodeStr();
Range = BO->getLHS()->getSourceRange();
RemoveDiagKind = 0;
if ((BO->getOpcode() == BO_LAnd && I->Output) ||
(BO->getOpcode() == BO_LOr && !I->Output))
// true && y -> y, false || y -> y.
Fixit1 = FixItHint::CreateRemoval(SourceRange(BO->getLocStart(),
BO->getOperatorLoc()));
else
// false && y -> false, true || y -> true.
Fixit1 = FixItHint::CreateReplacement(BO->getSourceRange(), FixitStr);
break;
}
// "loop is entered / loop is exited".
case Stmt::WhileStmtClass:
DiagKind = 1;
Str = "while";
Range = cast<WhileStmt>(Term)->getCond()->getSourceRange();
RemoveDiagKind = 1;
Fixit1 = FixItHint::CreateReplacement(Range, FixitStr);
break;
case Stmt::ForStmtClass:
DiagKind = 1;
Str = "for";
Range = cast<ForStmt>(Term)->getCond()->getSourceRange();
RemoveDiagKind = 1;
if (I->Output)
Fixit1 = FixItHint::CreateRemoval(Range);
else
Fixit1 = FixItHint::CreateReplacement(Range, FixitStr);
break;
case Stmt::CXXForRangeStmtClass:
if (I->Output == 1) {
// The use occurs if a range-based for loop's body never executes.
// That may be impossible, and there's no syntactic fix for this,
// so treat it as a 'may be uninitialized' case.
continue;
}
DiagKind = 1;
Str = "for";
Range = cast<CXXForRangeStmt>(Term)->getRangeInit()->getSourceRange();
break;
// "condition is true / loop is exited".
case Stmt::DoStmtClass:
DiagKind = 2;
Str = "do";
Range = cast<DoStmt>(Term)->getCond()->getSourceRange();
RemoveDiagKind = 1;
Fixit1 = FixItHint::CreateReplacement(Range, FixitStr);
break;
// "switch case is taken".
case Stmt::CaseStmtClass:
DiagKind = 3;
Str = "case";
Range = cast<CaseStmt>(Term)->getLHS()->getSourceRange();
break;
case Stmt::DefaultStmtClass:
DiagKind = 3;
Str = "default";
Range = cast<DefaultStmt>(Term)->getDefaultLoc();
break;
}
S.Diag(Range.getBegin(), diag::warn_sometimes_uninit_var)
<< VD->getDeclName() << IsCapturedByBlock << DiagKind
<< Str << I->Output << Range;
S.Diag(User->getLocStart(), diag::note_uninit_var_use)
<< IsCapturedByBlock << User->getSourceRange();
if (RemoveDiagKind != -1)
S.Diag(Fixit1.RemoveRange.getBegin(), diag::note_uninit_fixit_remove_cond)
<< RemoveDiagKind << Str << I->Output << Fixit1 << Fixit2;
Diagnosed = true;
}
if (!Diagnosed)
S.Diag(Use.getUser()->getLocStart(), diag::warn_maybe_uninit_var)
<< VD->getDeclName() << IsCapturedByBlock
<< Use.getUser()->getSourceRange();
}
/// DiagnoseUninitializedUse -- Helper function for diagnosing uses of an
/// uninitialized variable. This manages the different forms of diagnostic
/// emitted for particular types of uses. Returns true if the use was diagnosed
/// as a warning. If a particular use is one we omit warnings for, returns
/// false.
static bool DiagnoseUninitializedUse(Sema &S, const VarDecl *VD,
const UninitUse &Use,
bool alwaysReportSelfInit = false) {
if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(Use.getUser())) {
// Inspect the initializer of the variable declaration which is
// being referenced prior to its initialization. We emit
// specialized diagnostics for self-initialization, and we
// specifically avoid warning about self references which take the
// form of:
//
// int x = x;
//
// This is used to indicate to GCC that 'x' is intentionally left
// uninitialized. Proven code paths which access 'x' in
// an uninitialized state after this will still warn.
if (const Expr *Initializer = VD->getInit()) {
if (!alwaysReportSelfInit && DRE == Initializer->IgnoreParenImpCasts())
return false;
ContainsReference CR(S.Context, DRE);
CR.Visit(Initializer);
if (CR.doesContainReference()) {
S.Diag(DRE->getLocStart(),
diag::warn_uninit_self_reference_in_init)
<< VD->getDeclName() << VD->getLocation() << DRE->getSourceRange();
return true;
}
}
DiagUninitUse(S, VD, Use, false);
} else {
const BlockExpr *BE = cast<BlockExpr>(Use.getUser());
if (VD->getType()->isBlockPointerType() && !VD->hasAttr<BlocksAttr>())
S.Diag(BE->getLocStart(),
diag::warn_uninit_byref_blockvar_captured_by_block)
<< VD->getDeclName();
else
DiagUninitUse(S, VD, Use, true);
}
// Report where the variable was declared when the use wasn't within