1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
|
//=- ReachableCodePathInsensitive.cpp ---------------------------*- C++ --*-==//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements a flow-sensitive, path-insensitive analysis of
// determining reachable blocks within a CFG.
//
//===----------------------------------------------------------------------===//
#include "llvm/ADT/BitVector.h"
#include "llvm/ADT/SmallVector.h"
#include "clang/AST/Expr.h"
#include "clang/AST/ExprCXX.h"
#include "clang/AST/StmtCXX.h"
#include "clang/Analysis/Analyses/ReachableCode.h"
#include "clang/Analysis/CFG.h"
#include "clang/Analysis/AnalysisContext.h"
#include "clang/Basic/SourceManager.h"
using namespace clang;
static SourceLocation GetUnreachableLoc(const CFGBlock &b, SourceRange &R1,
SourceRange &R2) {
const Stmt *S = 0;
unsigned sn = 0;
R1 = R2 = SourceRange();
top:
if (sn < b.size())
S = b[sn].getStmt();
else if (b.getTerminator())
S = b.getTerminator();
else
return SourceLocation();
switch (S->getStmtClass()) {
case Expr::BinaryOperatorClass: {
const BinaryOperator *BO = cast<BinaryOperator>(S);
if (BO->getOpcode() == BinaryOperator::Comma) {
if (sn+1 < b.size())
return b[sn+1].getStmt()->getLocStart();
const CFGBlock *n = &b;
while (1) {
if (n->getTerminator())
return n->getTerminator()->getLocStart();
if (n->succ_size() != 1)
return SourceLocation();
n = n[0].succ_begin()[0];
if (n->pred_size() != 1)
return SourceLocation();
if (!n->empty())
return n[0][0].getStmt()->getLocStart();
}
}
R1 = BO->getLHS()->getSourceRange();
R2 = BO->getRHS()->getSourceRange();
return BO->getOperatorLoc();
}
case Expr::UnaryOperatorClass: {
const UnaryOperator *UO = cast<UnaryOperator>(S);
R1 = UO->getSubExpr()->getSourceRange();
return UO->getOperatorLoc();
}
case Expr::CompoundAssignOperatorClass: {
const CompoundAssignOperator *CAO = cast<CompoundAssignOperator>(S);
R1 = CAO->getLHS()->getSourceRange();
R2 = CAO->getRHS()->getSourceRange();
return CAO->getOperatorLoc();
}
case Expr::ConditionalOperatorClass: {
const ConditionalOperator *CO = cast<ConditionalOperator>(S);
return CO->getQuestionLoc();
}
case Expr::MemberExprClass: {
const MemberExpr *ME = cast<MemberExpr>(S);
R1 = ME->getSourceRange();
return ME->getMemberLoc();
}
case Expr::ArraySubscriptExprClass: {
const ArraySubscriptExpr *ASE = cast<ArraySubscriptExpr>(S);
R1 = ASE->getLHS()->getSourceRange();
R2 = ASE->getRHS()->getSourceRange();
return ASE->getRBracketLoc();
}
case Expr::CStyleCastExprClass: {
const CStyleCastExpr *CSC = cast<CStyleCastExpr>(S);
R1 = CSC->getSubExpr()->getSourceRange();
return CSC->getLParenLoc();
}
case Expr::CXXFunctionalCastExprClass: {
const CXXFunctionalCastExpr *CE = cast <CXXFunctionalCastExpr>(S);
R1 = CE->getSubExpr()->getSourceRange();
return CE->getTypeBeginLoc();
}
case Expr::ImplicitCastExprClass:
++sn;
goto top;
case Stmt::CXXTryStmtClass: {
return cast<CXXTryStmt>(S)->getHandler(0)->getCatchLoc();
}
default: ;
}
R1 = S->getSourceRange();
return S->getLocStart();
}
static SourceLocation MarkLiveTop(const CFGBlock *Start,
llvm::BitVector &reachable,
SourceManager &SM) {
// Prep work worklist.
llvm::SmallVector<const CFGBlock*, 32> WL;
WL.push_back(Start);
SourceRange R1, R2;
SourceLocation top = GetUnreachableLoc(*Start, R1, R2);
bool FromMainFile = false;
bool FromSystemHeader = false;
bool TopValid = false;
if (top.isValid()) {
FromMainFile = SM.isFromMainFile(top);
FromSystemHeader = SM.isInSystemHeader(top);
TopValid = true;
}
// Solve
while (!WL.empty()) {
const CFGBlock *item = WL.back();
WL.pop_back();
SourceLocation c = GetUnreachableLoc(*item, R1, R2);
if (c.isValid()
&& (!TopValid
|| (SM.isFromMainFile(c) && !FromMainFile)
|| (FromSystemHeader && !SM.isInSystemHeader(c))
|| SM.isBeforeInTranslationUnit(c, top))) {
top = c;
FromMainFile = SM.isFromMainFile(top);
FromSystemHeader = SM.isInSystemHeader(top);
}
reachable.set(item->getBlockID());
for (CFGBlock::const_succ_iterator I=item->succ_begin(), E=item->succ_end();
I != E; ++I)
if (const CFGBlock *B = *I) {
unsigned blockID = B->getBlockID();
if (!reachable[blockID]) {
reachable.set(blockID);
WL.push_back(B);
}
}
}
return top;
}
static int LineCmp(const void *p1, const void *p2) {
SourceLocation *Line1 = (SourceLocation *)p1;
SourceLocation *Line2 = (SourceLocation *)p2;
return !(*Line1 < *Line2);
}
namespace {
struct ErrLoc {
SourceLocation Loc;
SourceRange R1;
SourceRange R2;
ErrLoc(SourceLocation l, SourceRange r1, SourceRange r2)
: Loc(l), R1(r1), R2(r2) { }
};
}
namespace clang { namespace reachable_code {
/// ScanReachableFromBlock - Mark all blocks reachable from Start.
/// Returns the total number of blocks that were marked reachable.
unsigned ScanReachableFromBlock(const CFGBlock &Start,
llvm::BitVector &Reachable) {
unsigned count = 0;
llvm::SmallVector<const CFGBlock*, 32> WL;
// Prep work queue
Reachable.set(Start.getBlockID());
++count;
WL.push_back(&Start);
// Find the reachable blocks from 'Start'.
while (!WL.empty()) {
const CFGBlock *item = WL.back();
WL.pop_back();
// Look at the successors and mark then reachable.
for (CFGBlock::const_succ_iterator I=item->succ_begin(), E=item->succ_end();
I != E; ++I)
if (const CFGBlock *B = *I) {
unsigned blockID = B->getBlockID();
if (!Reachable[blockID]) {
Reachable.set(blockID);
++count;
WL.push_back(B);
}
}
}
return count;
}
void FindUnreachableCode(AnalysisContext &AC, Callback &CB) {
CFG *cfg = AC.getCFG();
if (!cfg)
return;
// Scan for reachable blocks.
llvm::BitVector reachable(cfg->getNumBlockIDs());
unsigned numReachable = ScanReachableFromBlock(cfg->getEntry(), reachable);
// If there are no unreachable blocks, we're done.
if (numReachable == cfg->getNumBlockIDs())
return;
SourceRange R1, R2;
llvm::SmallVector<ErrLoc, 24> lines;
bool AddEHEdges = AC.getAddEHEdges();
// First, give warnings for blocks with no predecessors, as they
// can't be part of a loop.
for (CFG::iterator I = cfg->begin(), E = cfg->end(); I != E; ++I) {
CFGBlock &b = **I;
if (!reachable[b.getBlockID()]) {
if (b.pred_empty()) {
if (!AddEHEdges && dyn_cast_or_null<CXXTryStmt>(b.getTerminator())) {
// When not adding EH edges from calls, catch clauses
// can otherwise seem dead. Avoid noting them as dead.
numReachable += ScanReachableFromBlock(b, reachable);
continue;
}
SourceLocation c = GetUnreachableLoc(b, R1, R2);
if (!c.isValid()) {
// Blocks without a location can't produce a warning, so don't mark
// reachable blocks from here as live.
reachable.set(b.getBlockID());
++numReachable;
continue;
}
lines.push_back(ErrLoc(c, R1, R2));
// Avoid excessive errors by marking everything reachable from here
numReachable += ScanReachableFromBlock(b, reachable);
}
}
}
if (numReachable < cfg->getNumBlockIDs()) {
// And then give warnings for the tops of loops.
for (CFG::iterator I = cfg->begin(), E = cfg->end(); I != E; ++I) {
CFGBlock &b = **I;
if (!reachable[b.getBlockID()])
// Avoid excessive errors by marking everything reachable from here
lines.push_back(ErrLoc(MarkLiveTop(&b, reachable,
AC.getASTContext().getSourceManager()),
SourceRange(), SourceRange()));
}
}
llvm::array_pod_sort(lines.begin(), lines.end(), LineCmp);
for (llvm::SmallVectorImpl<ErrLoc>::iterator I=lines.begin(), E=lines.end();
I != E; ++I)
if (I->Loc.isValid())
CB.HandleUnreachable(I->Loc, I->R1, I->R2);
}
}} // end namespace clang::reachable_code
|