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Chris Lattner5af280c2009-04-19 04:46:21 +00001//===--- JumpDiagnostics.cpp - Analyze Jump Targets for VLA issues --------===//
2//
3// The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file implements the JumpScopeChecker class, which is used to diagnose
11// jumps that enter a VLA scope in an invalid way.
12//
13//===----------------------------------------------------------------------===//
14
15#include "Sema.h"
16#include "clang/AST/Expr.h"
Chris Lattner16f00492009-04-26 01:32:48 +000017#include "clang/AST/StmtObjC.h"
Sebastian Redl972041f2009-04-27 20:27:31 +000018#include "clang/AST/StmtCXX.h"
Chris Lattner5af280c2009-04-19 04:46:21 +000019using namespace clang;
20
21namespace {
22
23/// JumpScopeChecker - This object is used by Sema to diagnose invalid jumps
24/// into VLA and other protected scopes. For example, this rejects:
25/// goto L;
26/// int a[n];
27/// L:
28///
29class JumpScopeChecker {
30 Sema &S;
Mike Stump1eb44332009-09-09 15:08:12 +000031
Chris Lattner5af280c2009-04-19 04:46:21 +000032 /// GotoScope - This is a record that we use to keep track of all of the
33 /// scopes that are introduced by VLAs and other things that scope jumps like
34 /// gotos. This scope tree has nothing to do with the source scope tree,
35 /// because you can have multiple VLA scopes per compound statement, and most
36 /// compound statements don't introduce any scopes.
37 struct GotoScope {
38 /// ParentScope - The index in ScopeMap of the parent scope. This is 0 for
39 /// the parent scope is the function body.
40 unsigned ParentScope;
Mike Stump1eb44332009-09-09 15:08:12 +000041
Chris Lattner5af280c2009-04-19 04:46:21 +000042 /// Diag - The diagnostic to emit if there is a jump into this scope.
43 unsigned Diag;
Mike Stump1eb44332009-09-09 15:08:12 +000044
Chris Lattner5af280c2009-04-19 04:46:21 +000045 /// Loc - Location to emit the diagnostic.
46 SourceLocation Loc;
Mike Stump1eb44332009-09-09 15:08:12 +000047
Chris Lattner5af280c2009-04-19 04:46:21 +000048 GotoScope(unsigned parentScope, unsigned diag, SourceLocation L)
49 : ParentScope(parentScope), Diag(diag), Loc(L) {}
50 };
Mike Stump1eb44332009-09-09 15:08:12 +000051
Chris Lattner5af280c2009-04-19 04:46:21 +000052 llvm::SmallVector<GotoScope, 48> Scopes;
53 llvm::DenseMap<Stmt*, unsigned> LabelAndGotoScopes;
54 llvm::SmallVector<Stmt*, 16> Jumps;
55public:
56 JumpScopeChecker(Stmt *Body, Sema &S);
57private:
58 void BuildScopeInformation(Stmt *S, unsigned ParentScope);
59 void VerifyJumps();
60 void CheckJump(Stmt *From, Stmt *To,
61 SourceLocation DiagLoc, unsigned JumpDiag);
62};
63} // end anonymous namespace
64
65
66JumpScopeChecker::JumpScopeChecker(Stmt *Body, Sema &s) : S(s) {
67 // Add a scope entry for function scope.
68 Scopes.push_back(GotoScope(~0U, ~0U, SourceLocation()));
Mike Stump1eb44332009-09-09 15:08:12 +000069
Chris Lattner5af280c2009-04-19 04:46:21 +000070 // Build information for the top level compound statement, so that we have a
71 // defined scope record for every "goto" and label.
72 BuildScopeInformation(Body, 0);
Mike Stump1eb44332009-09-09 15:08:12 +000073
Chris Lattner5af280c2009-04-19 04:46:21 +000074 // Check that all jumps we saw are kosher.
75 VerifyJumps();
76}
Mike Stump1eb44332009-09-09 15:08:12 +000077
Chris Lattner5af280c2009-04-19 04:46:21 +000078/// GetDiagForGotoScopeDecl - If this decl induces a new goto scope, return a
79/// diagnostic that should be emitted if control goes over it. If not, return 0.
Chris Lattner6d97e5e2010-03-01 20:59:53 +000080static unsigned GetDiagForGotoScopeDecl(const Decl *D, bool isCPlusPlus) {
Chris Lattner5af280c2009-04-19 04:46:21 +000081 if (const VarDecl *VD = dyn_cast<VarDecl>(D)) {
82 if (VD->getType()->isVariablyModifiedType())
83 return diag::note_protected_by_vla;
Argyrios Kyrtzidis40b598e2009-06-30 02:34:44 +000084 if (VD->hasAttr<CleanupAttr>())
Chris Lattner5af280c2009-04-19 04:46:21 +000085 return diag::note_protected_by_cleanup;
Chris Lattnerbe6d2592009-07-19 20:17:11 +000086 if (VD->hasAttr<BlocksAttr>())
87 return diag::note_protected_by___block;
Chris Lattner6d97e5e2010-03-01 20:59:53 +000088 if (isCPlusPlus && VD->hasLocalStorage() && VD->hasInit())
89 return diag::note_protected_by_variable_init;
90
Chris Lattner5af280c2009-04-19 04:46:21 +000091 } else if (const TypedefDecl *TD = dyn_cast<TypedefDecl>(D)) {
92 if (TD->getUnderlyingType()->isVariablyModifiedType())
93 return diag::note_protected_by_vla_typedef;
94 }
Mike Stump1eb44332009-09-09 15:08:12 +000095
Chris Lattner5af280c2009-04-19 04:46:21 +000096 return 0;
97}
98
99
100/// BuildScopeInformation - The statements from CI to CE are known to form a
101/// coherent VLA scope with a specified parent node. Walk through the
102/// statements, adding any labels or gotos to LabelAndGotoScopes and recursively
103/// walking the AST as needed.
104void JumpScopeChecker::BuildScopeInformation(Stmt *S, unsigned ParentScope) {
Mike Stump1eb44332009-09-09 15:08:12 +0000105
Chris Lattner5af280c2009-04-19 04:46:21 +0000106 // If we found a label, remember that it is in ParentScope scope.
107 if (isa<LabelStmt>(S) || isa<DefaultStmt>(S) || isa<CaseStmt>(S)) {
108 LabelAndGotoScopes[S] = ParentScope;
109 } else if (isa<GotoStmt>(S) || isa<SwitchStmt>(S) ||
110 isa<IndirectGotoStmt>(S) || isa<AddrLabelExpr>(S)) {
111 // Remember both what scope a goto is in as well as the fact that we have
112 // it. This makes the second scan not have to walk the AST again.
113 LabelAndGotoScopes[S] = ParentScope;
114 Jumps.push_back(S);
115 }
Mike Stump1eb44332009-09-09 15:08:12 +0000116
Chris Lattner5af280c2009-04-19 04:46:21 +0000117 for (Stmt::child_iterator CI = S->child_begin(), E = S->child_end(); CI != E;
118 ++CI) {
119 Stmt *SubStmt = *CI;
120 if (SubStmt == 0) continue;
Mike Stump1eb44332009-09-09 15:08:12 +0000121
Chris Lattner6d97e5e2010-03-01 20:59:53 +0000122 bool isCPlusPlus = this->S.getLangOptions().CPlusPlus;
Chris Lattner5af280c2009-04-19 04:46:21 +0000123
124 // If this is a declstmt with a VLA definition, it defines a scope from here
125 // to the end of the containing context.
126 if (DeclStmt *DS = dyn_cast<DeclStmt>(SubStmt)) {
Chris Lattner6d97e5e2010-03-01 20:59:53 +0000127 // The decl statement creates a scope if any of the decls in it are VLAs
128 // or have the cleanup attribute.
Chris Lattner5af280c2009-04-19 04:46:21 +0000129 for (DeclStmt::decl_iterator I = DS->decl_begin(), E = DS->decl_end();
130 I != E; ++I) {
131 // If this decl causes a new scope, push and switch to it.
Chris Lattner6d97e5e2010-03-01 20:59:53 +0000132 if (unsigned Diag = GetDiagForGotoScopeDecl(*I, isCPlusPlus)) {
Chris Lattner5af280c2009-04-19 04:46:21 +0000133 Scopes.push_back(GotoScope(ParentScope, Diag, (*I)->getLocation()));
134 ParentScope = Scopes.size()-1;
135 }
Mike Stump1eb44332009-09-09 15:08:12 +0000136
Chris Lattner5af280c2009-04-19 04:46:21 +0000137 // If the decl has an initializer, walk it with the potentially new
138 // scope we just installed.
139 if (VarDecl *VD = dyn_cast<VarDecl>(*I))
140 if (Expr *Init = VD->getInit())
141 BuildScopeInformation(Init, ParentScope);
142 }
143 continue;
144 }
145
146 // Disallow jumps into any part of an @try statement by pushing a scope and
147 // walking all sub-stmts in that scope.
148 if (ObjCAtTryStmt *AT = dyn_cast<ObjCAtTryStmt>(SubStmt)) {
149 // Recursively walk the AST for the @try part.
150 Scopes.push_back(GotoScope(ParentScope,diag::note_protected_by_objc_try,
151 AT->getAtTryLoc()));
152 if (Stmt *TryPart = AT->getTryBody())
153 BuildScopeInformation(TryPart, Scopes.size()-1);
154
155 // Jump from the catch to the finally or try is not valid.
156 for (ObjCAtCatchStmt *AC = AT->getCatchStmts(); AC;
157 AC = AC->getNextCatchStmt()) {
158 Scopes.push_back(GotoScope(ParentScope,
159 diag::note_protected_by_objc_catch,
160 AC->getAtCatchLoc()));
Mike Stump1eb44332009-09-09 15:08:12 +0000161 // @catches are nested and it isn't
Chris Lattner5af280c2009-04-19 04:46:21 +0000162 BuildScopeInformation(AC->getCatchBody(), Scopes.size()-1);
163 }
Mike Stump1eb44332009-09-09 15:08:12 +0000164
Chris Lattner5af280c2009-04-19 04:46:21 +0000165 // Jump from the finally to the try or catch is not valid.
166 if (ObjCAtFinallyStmt *AF = AT->getFinallyStmt()) {
167 Scopes.push_back(GotoScope(ParentScope,
168 diag::note_protected_by_objc_finally,
169 AF->getAtFinallyLoc()));
170 BuildScopeInformation(AF, Scopes.size()-1);
171 }
Mike Stump1eb44332009-09-09 15:08:12 +0000172
Chris Lattner5af280c2009-04-19 04:46:21 +0000173 continue;
174 }
Mike Stump1eb44332009-09-09 15:08:12 +0000175
Chris Lattner46c3c4b2009-04-21 06:01:00 +0000176 // Disallow jumps into the protected statement of an @synchronized, but
177 // allow jumps into the object expression it protects.
178 if (ObjCAtSynchronizedStmt *AS = dyn_cast<ObjCAtSynchronizedStmt>(SubStmt)){
179 // Recursively walk the AST for the @synchronized object expr, it is
180 // evaluated in the normal scope.
181 BuildScopeInformation(AS->getSynchExpr(), ParentScope);
Mike Stump1eb44332009-09-09 15:08:12 +0000182
Chris Lattner46c3c4b2009-04-21 06:01:00 +0000183 // Recursively walk the AST for the @synchronized part, protected by a new
184 // scope.
185 Scopes.push_back(GotoScope(ParentScope,
186 diag::note_protected_by_objc_synchronized,
187 AS->getAtSynchronizedLoc()));
188 BuildScopeInformation(AS->getSynchBody(), Scopes.size()-1);
189 continue;
190 }
Sebastian Redl972041f2009-04-27 20:27:31 +0000191
192 // Disallow jumps into any part of a C++ try statement. This is pretty
193 // much the same as for Obj-C.
194 if (CXXTryStmt *TS = dyn_cast<CXXTryStmt>(SubStmt)) {
195 Scopes.push_back(GotoScope(ParentScope, diag::note_protected_by_cxx_try,
196 TS->getSourceRange().getBegin()));
197 if (Stmt *TryBlock = TS->getTryBlock())
198 BuildScopeInformation(TryBlock, Scopes.size()-1);
199
200 // Jump from the catch into the try is not allowed either.
Mike Stump1eb44332009-09-09 15:08:12 +0000201 for (unsigned I = 0, E = TS->getNumHandlers(); I != E; ++I) {
Sebastian Redl972041f2009-04-27 20:27:31 +0000202 CXXCatchStmt *CS = TS->getHandler(I);
203 Scopes.push_back(GotoScope(ParentScope,
204 diag::note_protected_by_cxx_catch,
205 CS->getSourceRange().getBegin()));
206 BuildScopeInformation(CS->getHandlerBlock(), Scopes.size()-1);
207 }
208
209 continue;
210 }
211
Chris Lattner5af280c2009-04-19 04:46:21 +0000212 // Recursively walk the AST.
213 BuildScopeInformation(SubStmt, ParentScope);
214 }
215}
216
217/// VerifyJumps - Verify each element of the Jumps array to see if they are
218/// valid, emitting diagnostics if not.
219void JumpScopeChecker::VerifyJumps() {
220 while (!Jumps.empty()) {
221 Stmt *Jump = Jumps.pop_back_val();
Mike Stump1eb44332009-09-09 15:08:12 +0000222
223 // With a goto,
Chris Lattner5af280c2009-04-19 04:46:21 +0000224 if (GotoStmt *GS = dyn_cast<GotoStmt>(Jump)) {
225 CheckJump(GS, GS->getLabel(), GS->getGotoLoc(),
226 diag::err_goto_into_protected_scope);
227 continue;
228 }
Mike Stump1eb44332009-09-09 15:08:12 +0000229
Chris Lattner5af280c2009-04-19 04:46:21 +0000230 if (SwitchStmt *SS = dyn_cast<SwitchStmt>(Jump)) {
231 for (SwitchCase *SC = SS->getSwitchCaseList(); SC;
232 SC = SC->getNextSwitchCase()) {
233 assert(LabelAndGotoScopes.count(SC) && "Case not visited?");
234 CheckJump(SS, SC, SC->getLocStart(),
235 diag::err_switch_into_protected_scope);
236 }
237 continue;
238 }
239
240 unsigned DiagnosticScope;
Mike Stump1eb44332009-09-09 15:08:12 +0000241
Chris Lattner5af280c2009-04-19 04:46:21 +0000242 // We don't know where an indirect goto goes, require that it be at the
243 // top level of scoping.
244 if (IndirectGotoStmt *IG = dyn_cast<IndirectGotoStmt>(Jump)) {
245 assert(LabelAndGotoScopes.count(Jump) &&
246 "Jump didn't get added to scopes?");
247 unsigned GotoScope = LabelAndGotoScopes[IG];
248 if (GotoScope == 0) continue; // indirect jump is ok.
249 S.Diag(IG->getGotoLoc(), diag::err_indirect_goto_in_protected_scope);
250 DiagnosticScope = GotoScope;
251 } else {
252 // We model &&Label as a jump for purposes of scope tracking. We actually
253 // don't care *where* the address of label is, but we require the *label
254 // itself* to be in scope 0. If it is nested inside of a VLA scope, then
255 // it is possible for an indirect goto to illegally enter the VLA scope by
256 // indirectly jumping to the label.
257 assert(isa<AddrLabelExpr>(Jump) && "Unknown jump type");
258 LabelStmt *TheLabel = cast<AddrLabelExpr>(Jump)->getLabel();
Mike Stump1eb44332009-09-09 15:08:12 +0000259
Chris Lattner5af280c2009-04-19 04:46:21 +0000260 assert(LabelAndGotoScopes.count(TheLabel) &&
261 "Referenced label didn't get added to scopes?");
262 unsigned LabelScope = LabelAndGotoScopes[TheLabel];
263 if (LabelScope == 0) continue; // Addr of label is ok.
Mike Stump1eb44332009-09-09 15:08:12 +0000264
Chris Lattner5af280c2009-04-19 04:46:21 +0000265 S.Diag(Jump->getLocStart(), diag::err_addr_of_label_in_protected_scope);
266 DiagnosticScope = LabelScope;
267 }
268
269 // Report all the things that would be skipped over by this &&label or
270 // indirect goto.
271 while (DiagnosticScope != 0) {
272 S.Diag(Scopes[DiagnosticScope].Loc, Scopes[DiagnosticScope].Diag);
273 DiagnosticScope = Scopes[DiagnosticScope].ParentScope;
274 }
275 }
276}
277
278/// CheckJump - Validate that the specified jump statement is valid: that it is
279/// jumping within or out of its current scope, not into a deeper one.
280void JumpScopeChecker::CheckJump(Stmt *From, Stmt *To,
281 SourceLocation DiagLoc, unsigned JumpDiag) {
282 assert(LabelAndGotoScopes.count(From) && "Jump didn't get added to scopes?");
283 unsigned FromScope = LabelAndGotoScopes[From];
284
285 assert(LabelAndGotoScopes.count(To) && "Jump didn't get added to scopes?");
286 unsigned ToScope = LabelAndGotoScopes[To];
Mike Stump1eb44332009-09-09 15:08:12 +0000287
Chris Lattner5af280c2009-04-19 04:46:21 +0000288 // Common case: exactly the same scope, which is fine.
289 if (FromScope == ToScope) return;
Mike Stump1eb44332009-09-09 15:08:12 +0000290
Chris Lattner5af280c2009-04-19 04:46:21 +0000291 // The only valid mismatch jump case happens when the jump is more deeply
292 // nested inside the jump target. Do a quick scan to see if the jump is valid
293 // because valid code is more common than invalid code.
294 unsigned TestScope = Scopes[FromScope].ParentScope;
295 while (TestScope != ~0U) {
296 // If we found the jump target, then we're jumping out of our current scope,
297 // which is perfectly fine.
298 if (TestScope == ToScope) return;
Mike Stump1eb44332009-09-09 15:08:12 +0000299
Chris Lattner5af280c2009-04-19 04:46:21 +0000300 // Otherwise, scan up the hierarchy.
301 TestScope = Scopes[TestScope].ParentScope;
302 }
Mike Stump1eb44332009-09-09 15:08:12 +0000303
Chris Lattner5af280c2009-04-19 04:46:21 +0000304 // If we get here, then we know we have invalid code. Diagnose the bad jump,
305 // and then emit a note at each VLA being jumped out of.
306 S.Diag(DiagLoc, JumpDiag);
307
308 // Eliminate the common prefix of the jump and the target. Start by
309 // linearizing both scopes, reversing them as we go.
310 std::vector<unsigned> FromScopes, ToScopes;
311 for (TestScope = FromScope; TestScope != ~0U;
312 TestScope = Scopes[TestScope].ParentScope)
313 FromScopes.push_back(TestScope);
314 for (TestScope = ToScope; TestScope != ~0U;
315 TestScope = Scopes[TestScope].ParentScope)
316 ToScopes.push_back(TestScope);
317
318 // Remove any common entries (such as the top-level function scope).
319 while (!FromScopes.empty() && FromScopes.back() == ToScopes.back()) {
320 FromScopes.pop_back();
321 ToScopes.pop_back();
322 }
Mike Stump1eb44332009-09-09 15:08:12 +0000323
Chris Lattner5af280c2009-04-19 04:46:21 +0000324 // Emit diagnostics for whatever is left in ToScopes.
325 for (unsigned i = 0, e = ToScopes.size(); i != e; ++i)
326 S.Diag(Scopes[ToScopes[i]].Loc, Scopes[ToScopes[i]].Diag);
327}
328
329void Sema::DiagnoseInvalidJumps(Stmt *Body) {
Douglas Gregor6490ae52009-11-17 06:14:37 +0000330 (void)JumpScopeChecker(Body, *this);
Chris Lattner5af280c2009-04-19 04:46:21 +0000331}