зеркало из https://github.com/microsoft/clang-1.git
330 строки
13 KiB
C++
330 строки
13 KiB
C++
//===--- JumpDiagnostics.cpp - Analyze Jump Targets for VLA issues --------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements the JumpScopeChecker class, which is used to diagnose
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// jumps that enter a VLA scope in an invalid way.
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//
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//===----------------------------------------------------------------------===//
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#include "Sema.h"
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#include "clang/AST/Expr.h"
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#include "clang/AST/StmtObjC.h"
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#include "clang/AST/StmtCXX.h"
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using namespace clang;
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namespace {
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/// JumpScopeChecker - This object is used by Sema to diagnose invalid jumps
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/// into VLA and other protected scopes. For example, this rejects:
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/// goto L;
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/// int a[n];
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/// L:
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///
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class JumpScopeChecker {
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Sema &S;
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/// GotoScope - This is a record that we use to keep track of all of the
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/// scopes that are introduced by VLAs and other things that scope jumps like
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/// gotos. This scope tree has nothing to do with the source scope tree,
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/// because you can have multiple VLA scopes per compound statement, and most
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/// compound statements don't introduce any scopes.
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struct GotoScope {
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/// ParentScope - The index in ScopeMap of the parent scope. This is 0 for
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/// the parent scope is the function body.
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unsigned ParentScope;
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/// Diag - The diagnostic to emit if there is a jump into this scope.
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unsigned Diag;
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/// Loc - Location to emit the diagnostic.
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SourceLocation Loc;
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GotoScope(unsigned parentScope, unsigned diag, SourceLocation L)
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: ParentScope(parentScope), Diag(diag), Loc(L) {}
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};
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llvm::SmallVector<GotoScope, 48> Scopes;
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llvm::DenseMap<Stmt*, unsigned> LabelAndGotoScopes;
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llvm::SmallVector<Stmt*, 16> Jumps;
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public:
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JumpScopeChecker(Stmt *Body, Sema &S);
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private:
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void BuildScopeInformation(Stmt *S, unsigned ParentScope);
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void VerifyJumps();
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void CheckJump(Stmt *From, Stmt *To,
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SourceLocation DiagLoc, unsigned JumpDiag);
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};
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} // end anonymous namespace
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JumpScopeChecker::JumpScopeChecker(Stmt *Body, Sema &s) : S(s) {
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// Add a scope entry for function scope.
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Scopes.push_back(GotoScope(~0U, ~0U, SourceLocation()));
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// Build information for the top level compound statement, so that we have a
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// defined scope record for every "goto" and label.
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BuildScopeInformation(Body, 0);
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// Check that all jumps we saw are kosher.
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VerifyJumps();
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}
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/// GetDiagForGotoScopeDecl - If this decl induces a new goto scope, return a
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/// diagnostic that should be emitted if control goes over it. If not, return 0.
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static unsigned GetDiagForGotoScopeDecl(const Decl *D) {
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if (const VarDecl *VD = dyn_cast<VarDecl>(D)) {
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if (VD->getType()->isVariablyModifiedType())
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return diag::note_protected_by_vla;
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if (VD->hasAttr<CleanupAttr>())
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return diag::note_protected_by_cleanup;
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if (VD->hasAttr<BlocksAttr>())
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return diag::note_protected_by___block;
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} else if (const TypedefDecl *TD = dyn_cast<TypedefDecl>(D)) {
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if (TD->getUnderlyingType()->isVariablyModifiedType())
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return diag::note_protected_by_vla_typedef;
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}
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return 0;
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}
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/// BuildScopeInformation - The statements from CI to CE are known to form a
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/// coherent VLA scope with a specified parent node. Walk through the
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/// statements, adding any labels or gotos to LabelAndGotoScopes and recursively
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/// walking the AST as needed.
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void JumpScopeChecker::BuildScopeInformation(Stmt *S, unsigned ParentScope) {
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// If we found a label, remember that it is in ParentScope scope.
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if (isa<LabelStmt>(S) || isa<DefaultStmt>(S) || isa<CaseStmt>(S)) {
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LabelAndGotoScopes[S] = ParentScope;
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} else if (isa<GotoStmt>(S) || isa<SwitchStmt>(S) ||
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isa<IndirectGotoStmt>(S) || isa<AddrLabelExpr>(S)) {
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// Remember both what scope a goto is in as well as the fact that we have
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// it. This makes the second scan not have to walk the AST again.
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LabelAndGotoScopes[S] = ParentScope;
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Jumps.push_back(S);
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}
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for (Stmt::child_iterator CI = S->child_begin(), E = S->child_end(); CI != E;
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++CI) {
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Stmt *SubStmt = *CI;
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if (SubStmt == 0) continue;
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// FIXME: diagnose jumps past initialization: required in C++, warning in C.
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// goto L; int X = 4; L: ;
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// If this is a declstmt with a VLA definition, it defines a scope from here
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// to the end of the containing context.
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if (DeclStmt *DS = dyn_cast<DeclStmt>(SubStmt)) {
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// The decl statement creates a scope if any of the decls in it are VLAs or
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// have the cleanup attribute.
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for (DeclStmt::decl_iterator I = DS->decl_begin(), E = DS->decl_end();
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I != E; ++I) {
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// If this decl causes a new scope, push and switch to it.
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if (unsigned Diag = GetDiagForGotoScopeDecl(*I)) {
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Scopes.push_back(GotoScope(ParentScope, Diag, (*I)->getLocation()));
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ParentScope = Scopes.size()-1;
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}
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// If the decl has an initializer, walk it with the potentially new
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// scope we just installed.
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if (VarDecl *VD = dyn_cast<VarDecl>(*I))
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if (Expr *Init = VD->getInit())
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BuildScopeInformation(Init, ParentScope);
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}
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continue;
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}
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// Disallow jumps into any part of an @try statement by pushing a scope and
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// walking all sub-stmts in that scope.
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if (ObjCAtTryStmt *AT = dyn_cast<ObjCAtTryStmt>(SubStmt)) {
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// Recursively walk the AST for the @try part.
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Scopes.push_back(GotoScope(ParentScope,diag::note_protected_by_objc_try,
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AT->getAtTryLoc()));
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if (Stmt *TryPart = AT->getTryBody())
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BuildScopeInformation(TryPart, Scopes.size()-1);
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// Jump from the catch to the finally or try is not valid.
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for (ObjCAtCatchStmt *AC = AT->getCatchStmts(); AC;
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AC = AC->getNextCatchStmt()) {
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Scopes.push_back(GotoScope(ParentScope,
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diag::note_protected_by_objc_catch,
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AC->getAtCatchLoc()));
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// @catches are nested and it isn't
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BuildScopeInformation(AC->getCatchBody(), Scopes.size()-1);
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}
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// Jump from the finally to the try or catch is not valid.
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if (ObjCAtFinallyStmt *AF = AT->getFinallyStmt()) {
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Scopes.push_back(GotoScope(ParentScope,
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diag::note_protected_by_objc_finally,
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AF->getAtFinallyLoc()));
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BuildScopeInformation(AF, Scopes.size()-1);
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}
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continue;
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}
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// Disallow jumps into the protected statement of an @synchronized, but
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// allow jumps into the object expression it protects.
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if (ObjCAtSynchronizedStmt *AS = dyn_cast<ObjCAtSynchronizedStmt>(SubStmt)){
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// Recursively walk the AST for the @synchronized object expr, it is
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// evaluated in the normal scope.
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BuildScopeInformation(AS->getSynchExpr(), ParentScope);
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// Recursively walk the AST for the @synchronized part, protected by a new
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// scope.
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Scopes.push_back(GotoScope(ParentScope,
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diag::note_protected_by_objc_synchronized,
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AS->getAtSynchronizedLoc()));
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BuildScopeInformation(AS->getSynchBody(), Scopes.size()-1);
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continue;
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}
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// Disallow jumps into any part of a C++ try statement. This is pretty
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// much the same as for Obj-C.
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if (CXXTryStmt *TS = dyn_cast<CXXTryStmt>(SubStmt)) {
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Scopes.push_back(GotoScope(ParentScope, diag::note_protected_by_cxx_try,
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TS->getSourceRange().getBegin()));
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if (Stmt *TryBlock = TS->getTryBlock())
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BuildScopeInformation(TryBlock, Scopes.size()-1);
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// Jump from the catch into the try is not allowed either.
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for (unsigned I = 0, E = TS->getNumHandlers(); I != E; ++I) {
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CXXCatchStmt *CS = TS->getHandler(I);
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Scopes.push_back(GotoScope(ParentScope,
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diag::note_protected_by_cxx_catch,
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CS->getSourceRange().getBegin()));
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BuildScopeInformation(CS->getHandlerBlock(), Scopes.size()-1);
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}
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continue;
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}
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// Recursively walk the AST.
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BuildScopeInformation(SubStmt, ParentScope);
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}
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}
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/// VerifyJumps - Verify each element of the Jumps array to see if they are
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/// valid, emitting diagnostics if not.
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void JumpScopeChecker::VerifyJumps() {
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while (!Jumps.empty()) {
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Stmt *Jump = Jumps.pop_back_val();
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// With a goto,
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if (GotoStmt *GS = dyn_cast<GotoStmt>(Jump)) {
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CheckJump(GS, GS->getLabel(), GS->getGotoLoc(),
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diag::err_goto_into_protected_scope);
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continue;
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}
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if (SwitchStmt *SS = dyn_cast<SwitchStmt>(Jump)) {
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for (SwitchCase *SC = SS->getSwitchCaseList(); SC;
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SC = SC->getNextSwitchCase()) {
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assert(LabelAndGotoScopes.count(SC) && "Case not visited?");
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CheckJump(SS, SC, SC->getLocStart(),
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diag::err_switch_into_protected_scope);
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}
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continue;
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}
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unsigned DiagnosticScope;
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// We don't know where an indirect goto goes, require that it be at the
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// top level of scoping.
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if (IndirectGotoStmt *IG = dyn_cast<IndirectGotoStmt>(Jump)) {
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assert(LabelAndGotoScopes.count(Jump) &&
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"Jump didn't get added to scopes?");
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unsigned GotoScope = LabelAndGotoScopes[IG];
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if (GotoScope == 0) continue; // indirect jump is ok.
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S.Diag(IG->getGotoLoc(), diag::err_indirect_goto_in_protected_scope);
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DiagnosticScope = GotoScope;
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} else {
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// We model &&Label as a jump for purposes of scope tracking. We actually
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// don't care *where* the address of label is, but we require the *label
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// itself* to be in scope 0. If it is nested inside of a VLA scope, then
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// it is possible for an indirect goto to illegally enter the VLA scope by
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// indirectly jumping to the label.
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assert(isa<AddrLabelExpr>(Jump) && "Unknown jump type");
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LabelStmt *TheLabel = cast<AddrLabelExpr>(Jump)->getLabel();
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assert(LabelAndGotoScopes.count(TheLabel) &&
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"Referenced label didn't get added to scopes?");
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unsigned LabelScope = LabelAndGotoScopes[TheLabel];
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if (LabelScope == 0) continue; // Addr of label is ok.
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S.Diag(Jump->getLocStart(), diag::err_addr_of_label_in_protected_scope);
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DiagnosticScope = LabelScope;
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}
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// Report all the things that would be skipped over by this &&label or
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// indirect goto.
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while (DiagnosticScope != 0) {
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S.Diag(Scopes[DiagnosticScope].Loc, Scopes[DiagnosticScope].Diag);
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DiagnosticScope = Scopes[DiagnosticScope].ParentScope;
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}
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}
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}
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/// CheckJump - Validate that the specified jump statement is valid: that it is
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/// jumping within or out of its current scope, not into a deeper one.
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void JumpScopeChecker::CheckJump(Stmt *From, Stmt *To,
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SourceLocation DiagLoc, unsigned JumpDiag) {
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assert(LabelAndGotoScopes.count(From) && "Jump didn't get added to scopes?");
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unsigned FromScope = LabelAndGotoScopes[From];
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assert(LabelAndGotoScopes.count(To) && "Jump didn't get added to scopes?");
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unsigned ToScope = LabelAndGotoScopes[To];
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// Common case: exactly the same scope, which is fine.
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if (FromScope == ToScope) return;
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// The only valid mismatch jump case happens when the jump is more deeply
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// nested inside the jump target. Do a quick scan to see if the jump is valid
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// because valid code is more common than invalid code.
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unsigned TestScope = Scopes[FromScope].ParentScope;
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while (TestScope != ~0U) {
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// If we found the jump target, then we're jumping out of our current scope,
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// which is perfectly fine.
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if (TestScope == ToScope) return;
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// Otherwise, scan up the hierarchy.
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TestScope = Scopes[TestScope].ParentScope;
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}
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// If we get here, then we know we have invalid code. Diagnose the bad jump,
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// and then emit a note at each VLA being jumped out of.
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S.Diag(DiagLoc, JumpDiag);
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// Eliminate the common prefix of the jump and the target. Start by
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// linearizing both scopes, reversing them as we go.
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std::vector<unsigned> FromScopes, ToScopes;
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for (TestScope = FromScope; TestScope != ~0U;
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TestScope = Scopes[TestScope].ParentScope)
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FromScopes.push_back(TestScope);
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for (TestScope = ToScope; TestScope != ~0U;
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TestScope = Scopes[TestScope].ParentScope)
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ToScopes.push_back(TestScope);
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// Remove any common entries (such as the top-level function scope).
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while (!FromScopes.empty() && FromScopes.back() == ToScopes.back()) {
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FromScopes.pop_back();
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ToScopes.pop_back();
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}
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// Emit diagnostics for whatever is left in ToScopes.
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for (unsigned i = 0, e = ToScopes.size(); i != e; ++i)
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S.Diag(Scopes[ToScopes[i]].Loc, Scopes[ToScopes[i]].Diag);
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}
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void Sema::DiagnoseInvalidJumps(Stmt *Body) {
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JumpScopeChecker(Body, *this);
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}
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