Chris Lattner | 5af280c | 2009-04-19 04:46:21 +0000 | [diff] [blame] | 1 | //===--- 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 Lattner | 16f0049 | 2009-04-26 01:32:48 +0000 | [diff] [blame] | 17 | #include "clang/AST/StmtObjC.h" |
Sebastian Redl | 972041f | 2009-04-27 20:27:31 +0000 | [diff] [blame] | 18 | #include "clang/AST/StmtCXX.h" |
Chris Lattner | 5af280c | 2009-04-19 04:46:21 +0000 | [diff] [blame] | 19 | using namespace clang; |
| 20 | |
| 21 | namespace { |
| 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 | /// |
| 29 | class JumpScopeChecker { |
| 30 | Sema &S; |
| 31 | |
| 32 | /// 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; |
| 41 | |
| 42 | /// Diag - The diagnostic to emit if there is a jump into this scope. |
| 43 | unsigned Diag; |
| 44 | |
| 45 | /// Loc - Location to emit the diagnostic. |
| 46 | SourceLocation Loc; |
| 47 | |
| 48 | GotoScope(unsigned parentScope, unsigned diag, SourceLocation L) |
| 49 | : ParentScope(parentScope), Diag(diag), Loc(L) {} |
| 50 | }; |
| 51 | |
| 52 | llvm::SmallVector<GotoScope, 48> Scopes; |
| 53 | llvm::DenseMap<Stmt*, unsigned> LabelAndGotoScopes; |
| 54 | llvm::SmallVector<Stmt*, 16> Jumps; |
| 55 | public: |
| 56 | JumpScopeChecker(Stmt *Body, Sema &S); |
| 57 | private: |
| 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 | |
| 66 | JumpScopeChecker::JumpScopeChecker(Stmt *Body, Sema &s) : S(s) { |
| 67 | // Add a scope entry for function scope. |
| 68 | Scopes.push_back(GotoScope(~0U, ~0U, SourceLocation())); |
| 69 | |
| 70 | // 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); |
| 73 | |
| 74 | // Check that all jumps we saw are kosher. |
| 75 | VerifyJumps(); |
| 76 | } |
| 77 | |
| 78 | /// 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. |
Argyrios Kyrtzidis | 40b598e | 2009-06-30 02:34:44 +0000 | [diff] [blame] | 80 | static unsigned GetDiagForGotoScopeDecl(const Decl *D) { |
Chris Lattner | 5af280c | 2009-04-19 04:46:21 +0000 | [diff] [blame] | 81 | if (const VarDecl *VD = dyn_cast<VarDecl>(D)) { |
| 82 | if (VD->getType()->isVariablyModifiedType()) |
| 83 | return diag::note_protected_by_vla; |
Argyrios Kyrtzidis | 40b598e | 2009-06-30 02:34:44 +0000 | [diff] [blame] | 84 | if (VD->hasAttr<CleanupAttr>()) |
Chris Lattner | 5af280c | 2009-04-19 04:46:21 +0000 | [diff] [blame] | 85 | return diag::note_protected_by_cleanup; |
| 86 | } else if (const TypedefDecl *TD = dyn_cast<TypedefDecl>(D)) { |
| 87 | if (TD->getUnderlyingType()->isVariablyModifiedType()) |
| 88 | return diag::note_protected_by_vla_typedef; |
| 89 | } |
| 90 | |
| 91 | return 0; |
| 92 | } |
| 93 | |
| 94 | |
| 95 | /// BuildScopeInformation - The statements from CI to CE are known to form a |
| 96 | /// coherent VLA scope with a specified parent node. Walk through the |
| 97 | /// statements, adding any labels or gotos to LabelAndGotoScopes and recursively |
| 98 | /// walking the AST as needed. |
| 99 | void JumpScopeChecker::BuildScopeInformation(Stmt *S, unsigned ParentScope) { |
| 100 | |
| 101 | // If we found a label, remember that it is in ParentScope scope. |
| 102 | if (isa<LabelStmt>(S) || isa<DefaultStmt>(S) || isa<CaseStmt>(S)) { |
| 103 | LabelAndGotoScopes[S] = ParentScope; |
| 104 | } else if (isa<GotoStmt>(S) || isa<SwitchStmt>(S) || |
| 105 | isa<IndirectGotoStmt>(S) || isa<AddrLabelExpr>(S)) { |
| 106 | // Remember both what scope a goto is in as well as the fact that we have |
| 107 | // it. This makes the second scan not have to walk the AST again. |
| 108 | LabelAndGotoScopes[S] = ParentScope; |
| 109 | Jumps.push_back(S); |
| 110 | } |
| 111 | |
| 112 | for (Stmt::child_iterator CI = S->child_begin(), E = S->child_end(); CI != E; |
| 113 | ++CI) { |
| 114 | Stmt *SubStmt = *CI; |
| 115 | if (SubStmt == 0) continue; |
| 116 | |
| 117 | // FIXME: diagnose jumps past initialization: required in C++, warning in C. |
| 118 | // goto L; int X = 4; L: ; |
Chris Lattner | 5af280c | 2009-04-19 04:46:21 +0000 | [diff] [blame] | 119 | |
| 120 | // If this is a declstmt with a VLA definition, it defines a scope from here |
| 121 | // to the end of the containing context. |
| 122 | if (DeclStmt *DS = dyn_cast<DeclStmt>(SubStmt)) { |
| 123 | // The decl statement creates a scope if any of the decls in it are VLAs or |
| 124 | // have the cleanup attribute. |
| 125 | for (DeclStmt::decl_iterator I = DS->decl_begin(), E = DS->decl_end(); |
| 126 | I != E; ++I) { |
| 127 | // If this decl causes a new scope, push and switch to it. |
Argyrios Kyrtzidis | 40b598e | 2009-06-30 02:34:44 +0000 | [diff] [blame] | 128 | if (unsigned Diag = GetDiagForGotoScopeDecl(*I)) { |
Chris Lattner | 5af280c | 2009-04-19 04:46:21 +0000 | [diff] [blame] | 129 | Scopes.push_back(GotoScope(ParentScope, Diag, (*I)->getLocation())); |
| 130 | ParentScope = Scopes.size()-1; |
| 131 | } |
| 132 | |
| 133 | // If the decl has an initializer, walk it with the potentially new |
| 134 | // scope we just installed. |
| 135 | if (VarDecl *VD = dyn_cast<VarDecl>(*I)) |
| 136 | if (Expr *Init = VD->getInit()) |
| 137 | BuildScopeInformation(Init, ParentScope); |
| 138 | } |
| 139 | continue; |
| 140 | } |
| 141 | |
| 142 | // Disallow jumps into any part of an @try statement by pushing a scope and |
| 143 | // walking all sub-stmts in that scope. |
| 144 | if (ObjCAtTryStmt *AT = dyn_cast<ObjCAtTryStmt>(SubStmt)) { |
| 145 | // Recursively walk the AST for the @try part. |
| 146 | Scopes.push_back(GotoScope(ParentScope,diag::note_protected_by_objc_try, |
| 147 | AT->getAtTryLoc())); |
| 148 | if (Stmt *TryPart = AT->getTryBody()) |
| 149 | BuildScopeInformation(TryPart, Scopes.size()-1); |
| 150 | |
| 151 | // Jump from the catch to the finally or try is not valid. |
| 152 | for (ObjCAtCatchStmt *AC = AT->getCatchStmts(); AC; |
| 153 | AC = AC->getNextCatchStmt()) { |
| 154 | Scopes.push_back(GotoScope(ParentScope, |
| 155 | diag::note_protected_by_objc_catch, |
| 156 | AC->getAtCatchLoc())); |
| 157 | // @catches are nested and it isn't |
| 158 | BuildScopeInformation(AC->getCatchBody(), Scopes.size()-1); |
| 159 | } |
| 160 | |
| 161 | // Jump from the finally to the try or catch is not valid. |
| 162 | if (ObjCAtFinallyStmt *AF = AT->getFinallyStmt()) { |
| 163 | Scopes.push_back(GotoScope(ParentScope, |
| 164 | diag::note_protected_by_objc_finally, |
| 165 | AF->getAtFinallyLoc())); |
| 166 | BuildScopeInformation(AF, Scopes.size()-1); |
| 167 | } |
| 168 | |
| 169 | continue; |
| 170 | } |
| 171 | |
Chris Lattner | 46c3c4b | 2009-04-21 06:01:00 +0000 | [diff] [blame] | 172 | // Disallow jumps into the protected statement of an @synchronized, but |
| 173 | // allow jumps into the object expression it protects. |
| 174 | if (ObjCAtSynchronizedStmt *AS = dyn_cast<ObjCAtSynchronizedStmt>(SubStmt)){ |
| 175 | // Recursively walk the AST for the @synchronized object expr, it is |
| 176 | // evaluated in the normal scope. |
| 177 | BuildScopeInformation(AS->getSynchExpr(), ParentScope); |
| 178 | |
| 179 | // Recursively walk the AST for the @synchronized part, protected by a new |
| 180 | // scope. |
| 181 | Scopes.push_back(GotoScope(ParentScope, |
| 182 | diag::note_protected_by_objc_synchronized, |
| 183 | AS->getAtSynchronizedLoc())); |
| 184 | BuildScopeInformation(AS->getSynchBody(), Scopes.size()-1); |
| 185 | continue; |
| 186 | } |
Sebastian Redl | 972041f | 2009-04-27 20:27:31 +0000 | [diff] [blame] | 187 | |
| 188 | // Disallow jumps into any part of a C++ try statement. This is pretty |
| 189 | // much the same as for Obj-C. |
| 190 | if (CXXTryStmt *TS = dyn_cast<CXXTryStmt>(SubStmt)) { |
| 191 | Scopes.push_back(GotoScope(ParentScope, diag::note_protected_by_cxx_try, |
| 192 | TS->getSourceRange().getBegin())); |
| 193 | if (Stmt *TryBlock = TS->getTryBlock()) |
| 194 | BuildScopeInformation(TryBlock, Scopes.size()-1); |
| 195 | |
| 196 | // Jump from the catch into the try is not allowed either. |
| 197 | for(unsigned I = 0, E = TS->getNumHandlers(); I != E; ++I) { |
| 198 | CXXCatchStmt *CS = TS->getHandler(I); |
| 199 | Scopes.push_back(GotoScope(ParentScope, |
| 200 | diag::note_protected_by_cxx_catch, |
| 201 | CS->getSourceRange().getBegin())); |
| 202 | BuildScopeInformation(CS->getHandlerBlock(), Scopes.size()-1); |
| 203 | } |
| 204 | |
| 205 | continue; |
| 206 | } |
| 207 | |
Chris Lattner | 5af280c | 2009-04-19 04:46:21 +0000 | [diff] [blame] | 208 | // Recursively walk the AST. |
| 209 | BuildScopeInformation(SubStmt, ParentScope); |
| 210 | } |
| 211 | } |
| 212 | |
| 213 | /// VerifyJumps - Verify each element of the Jumps array to see if they are |
| 214 | /// valid, emitting diagnostics if not. |
| 215 | void JumpScopeChecker::VerifyJumps() { |
| 216 | while (!Jumps.empty()) { |
| 217 | Stmt *Jump = Jumps.pop_back_val(); |
| 218 | |
| 219 | // With a goto, |
| 220 | if (GotoStmt *GS = dyn_cast<GotoStmt>(Jump)) { |
| 221 | CheckJump(GS, GS->getLabel(), GS->getGotoLoc(), |
| 222 | diag::err_goto_into_protected_scope); |
| 223 | continue; |
| 224 | } |
| 225 | |
| 226 | if (SwitchStmt *SS = dyn_cast<SwitchStmt>(Jump)) { |
| 227 | for (SwitchCase *SC = SS->getSwitchCaseList(); SC; |
| 228 | SC = SC->getNextSwitchCase()) { |
| 229 | assert(LabelAndGotoScopes.count(SC) && "Case not visited?"); |
| 230 | CheckJump(SS, SC, SC->getLocStart(), |
| 231 | diag::err_switch_into_protected_scope); |
| 232 | } |
| 233 | continue; |
| 234 | } |
| 235 | |
| 236 | unsigned DiagnosticScope; |
| 237 | |
| 238 | // We don't know where an indirect goto goes, require that it be at the |
| 239 | // top level of scoping. |
| 240 | if (IndirectGotoStmt *IG = dyn_cast<IndirectGotoStmt>(Jump)) { |
| 241 | assert(LabelAndGotoScopes.count(Jump) && |
| 242 | "Jump didn't get added to scopes?"); |
| 243 | unsigned GotoScope = LabelAndGotoScopes[IG]; |
| 244 | if (GotoScope == 0) continue; // indirect jump is ok. |
| 245 | S.Diag(IG->getGotoLoc(), diag::err_indirect_goto_in_protected_scope); |
| 246 | DiagnosticScope = GotoScope; |
| 247 | } else { |
| 248 | // We model &&Label as a jump for purposes of scope tracking. We actually |
| 249 | // don't care *where* the address of label is, but we require the *label |
| 250 | // itself* to be in scope 0. If it is nested inside of a VLA scope, then |
| 251 | // it is possible for an indirect goto to illegally enter the VLA scope by |
| 252 | // indirectly jumping to the label. |
| 253 | assert(isa<AddrLabelExpr>(Jump) && "Unknown jump type"); |
| 254 | LabelStmt *TheLabel = cast<AddrLabelExpr>(Jump)->getLabel(); |
| 255 | |
| 256 | assert(LabelAndGotoScopes.count(TheLabel) && |
| 257 | "Referenced label didn't get added to scopes?"); |
| 258 | unsigned LabelScope = LabelAndGotoScopes[TheLabel]; |
| 259 | if (LabelScope == 0) continue; // Addr of label is ok. |
| 260 | |
| 261 | S.Diag(Jump->getLocStart(), diag::err_addr_of_label_in_protected_scope); |
| 262 | DiagnosticScope = LabelScope; |
| 263 | } |
| 264 | |
| 265 | // Report all the things that would be skipped over by this &&label or |
| 266 | // indirect goto. |
| 267 | while (DiagnosticScope != 0) { |
| 268 | S.Diag(Scopes[DiagnosticScope].Loc, Scopes[DiagnosticScope].Diag); |
| 269 | DiagnosticScope = Scopes[DiagnosticScope].ParentScope; |
| 270 | } |
| 271 | } |
| 272 | } |
| 273 | |
| 274 | /// CheckJump - Validate that the specified jump statement is valid: that it is |
| 275 | /// jumping within or out of its current scope, not into a deeper one. |
| 276 | void JumpScopeChecker::CheckJump(Stmt *From, Stmt *To, |
| 277 | SourceLocation DiagLoc, unsigned JumpDiag) { |
| 278 | assert(LabelAndGotoScopes.count(From) && "Jump didn't get added to scopes?"); |
| 279 | unsigned FromScope = LabelAndGotoScopes[From]; |
| 280 | |
| 281 | assert(LabelAndGotoScopes.count(To) && "Jump didn't get added to scopes?"); |
| 282 | unsigned ToScope = LabelAndGotoScopes[To]; |
| 283 | |
| 284 | // Common case: exactly the same scope, which is fine. |
| 285 | if (FromScope == ToScope) return; |
| 286 | |
| 287 | // The only valid mismatch jump case happens when the jump is more deeply |
| 288 | // nested inside the jump target. Do a quick scan to see if the jump is valid |
| 289 | // because valid code is more common than invalid code. |
| 290 | unsigned TestScope = Scopes[FromScope].ParentScope; |
| 291 | while (TestScope != ~0U) { |
| 292 | // If we found the jump target, then we're jumping out of our current scope, |
| 293 | // which is perfectly fine. |
| 294 | if (TestScope == ToScope) return; |
| 295 | |
| 296 | // Otherwise, scan up the hierarchy. |
| 297 | TestScope = Scopes[TestScope].ParentScope; |
| 298 | } |
| 299 | |
| 300 | // If we get here, then we know we have invalid code. Diagnose the bad jump, |
| 301 | // and then emit a note at each VLA being jumped out of. |
| 302 | S.Diag(DiagLoc, JumpDiag); |
| 303 | |
| 304 | // Eliminate the common prefix of the jump and the target. Start by |
| 305 | // linearizing both scopes, reversing them as we go. |
| 306 | std::vector<unsigned> FromScopes, ToScopes; |
| 307 | for (TestScope = FromScope; TestScope != ~0U; |
| 308 | TestScope = Scopes[TestScope].ParentScope) |
| 309 | FromScopes.push_back(TestScope); |
| 310 | for (TestScope = ToScope; TestScope != ~0U; |
| 311 | TestScope = Scopes[TestScope].ParentScope) |
| 312 | ToScopes.push_back(TestScope); |
| 313 | |
| 314 | // Remove any common entries (such as the top-level function scope). |
| 315 | while (!FromScopes.empty() && FromScopes.back() == ToScopes.back()) { |
| 316 | FromScopes.pop_back(); |
| 317 | ToScopes.pop_back(); |
| 318 | } |
| 319 | |
| 320 | // Emit diagnostics for whatever is left in ToScopes. |
| 321 | for (unsigned i = 0, e = ToScopes.size(); i != e; ++i) |
| 322 | S.Diag(Scopes[ToScopes[i]].Loc, Scopes[ToScopes[i]].Diag); |
| 323 | } |
| 324 | |
| 325 | void Sema::DiagnoseInvalidJumps(Stmt *Body) { |
| 326 | JumpScopeChecker(Body, *this); |
| 327 | } |