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
|
/*
This file is part of solidity.
solidity is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
solidity is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with solidity. If not, see <http://www.gnu.org/licenses/>.
*/
#include <libsolidity/analysis/ControlFlowAnalyzer.h>
#include <liblangutil/SourceLocation.h>
#include <libdevcore/Algorithms.h>
#include <boost/range/algorithm/sort.hpp>
using namespace std;
using namespace langutil;
using namespace dev::solidity;
bool ControlFlowAnalyzer::analyze(ASTNode const& _astRoot)
{
_astRoot.accept(*this);
return Error::containsOnlyWarnings(m_errorReporter.errors());
}
bool ControlFlowAnalyzer::visit(FunctionDefinition const& _function)
{
if (_function.isImplemented())
{
auto const& functionFlow = m_cfg.functionFlow(_function);
checkUninitializedAccess(functionFlow.entry, functionFlow.exit);
checkUnreachable(functionFlow.entry, functionFlow.exit, functionFlow.revert);
}
return false;
}
void ControlFlowAnalyzer::checkUninitializedAccess(CFGNode const* _entry, CFGNode const* _exit) const
{
struct NodeInfo
{
set<VariableDeclaration const*> unassignedVariablesAtEntry;
set<VariableDeclaration const*> unassignedVariablesAtExit;
set<VariableOccurrence const*> uninitializedVariableAccesses;
/// Propagate the information from another node to this node.
/// To be used to propagate information from a node to its exit nodes.
/// Returns true, if new variables were added and thus the current node has
/// to be traversed again.
bool propagateFrom(NodeInfo const& _entryNode)
{
size_t previousUnassignedVariablesAtEntry = unassignedVariablesAtEntry.size();
size_t previousUninitializedVariableAccessess = uninitializedVariableAccesses.size();
unassignedVariablesAtEntry += _entryNode.unassignedVariablesAtExit;
uninitializedVariableAccesses += _entryNode.uninitializedVariableAccesses;
return
unassignedVariablesAtEntry.size() > previousUnassignedVariablesAtEntry ||
uninitializedVariableAccesses.size() > previousUninitializedVariableAccessess
;
}
};
map<CFGNode const*, NodeInfo> nodeInfos;
set<CFGNode const*> nodesToTraverse;
nodesToTraverse.insert(_entry);
// Walk all paths starting from the nodes in ``nodesToTraverse`` until ``NodeInfo::propagateFrom``
// returns false for all exits, i.e. until all paths have been walked with maximal sets of unassigned
// variables and accesses.
while (!nodesToTraverse.empty())
{
CFGNode const* currentNode = *nodesToTraverse.begin();
nodesToTraverse.erase(nodesToTraverse.begin());
auto& nodeInfo = nodeInfos[currentNode];
auto unassignedVariables = nodeInfo.unassignedVariablesAtEntry;
for (auto const& variableOccurrence: currentNode->variableOccurrences)
{
switch (variableOccurrence.kind())
{
case VariableOccurrence::Kind::Assignment:
unassignedVariables.erase(&variableOccurrence.declaration());
break;
case VariableOccurrence::Kind::InlineAssembly:
// We consider all variables referenced in inline assembly as accessed.
// So far any reference is enough, but we might want to actually analyze
// the control flow in the assembly at some point.
case VariableOccurrence::Kind::Access:
case VariableOccurrence::Kind::Return:
if (unassignedVariables.count(&variableOccurrence.declaration()))
{
if (variableOccurrence.declaration().type()->dataStoredIn(DataLocation::Storage))
// Merely store the unassigned access. We do not generate an error right away, since this
// path might still always revert. It is only an error if this is propagated to the exit
// node of the function (i.e. there is a path with an uninitialized access).
nodeInfo.uninitializedVariableAccesses.insert(&variableOccurrence);
}
break;
case VariableOccurrence::Kind::Declaration:
unassignedVariables.insert(&variableOccurrence.declaration());
break;
}
}
nodeInfo.unassignedVariablesAtExit = std::move(unassignedVariables);
// Propagate changes to all exits and queue them for traversal, if needed.
for (auto const& exit: currentNode->exits)
if (nodeInfos[exit].propagateFrom(nodeInfo))
nodesToTraverse.insert(exit);
}
auto const& exitInfo = nodeInfos[_exit];
if (!exitInfo.uninitializedVariableAccesses.empty())
{
vector<VariableOccurrence const*> uninitializedAccessesOrdered(
exitInfo.uninitializedVariableAccesses.begin(),
exitInfo.uninitializedVariableAccesses.end()
);
boost::range::sort(
uninitializedAccessesOrdered,
[](VariableOccurrence const* lhs, VariableOccurrence const* rhs) -> bool
{
return *lhs < *rhs;
}
);
for (auto const* variableOccurrence: uninitializedAccessesOrdered)
{
SecondarySourceLocation ssl;
if (variableOccurrence->occurrence())
ssl.append("The variable was declared here.", variableOccurrence->declaration().location());
m_errorReporter.typeError(
variableOccurrence->occurrence() ?
variableOccurrence->occurrence()->location() :
variableOccurrence->declaration().location(),
ssl,
string("This variable is of storage pointer type and can be ") +
(variableOccurrence->kind() == VariableOccurrence::Kind::Return ? "returned" : "accessed") +
" without prior assignment."
);
}
}
}
void ControlFlowAnalyzer::checkUnreachable(CFGNode const* _entry, CFGNode const* _exit, CFGNode const* _revert) const
{
// collect all nodes reachable from the entry point
std::set<CFGNode const*> reachable = BreadthFirstSearch<CFGNode>{{_entry}}.run(
[](CFGNode const& _node, auto&& _addChild) {
for (CFGNode const* exit: _node.exits)
_addChild(*exit);
}
).visited;
// traverse all paths backwards from exit and revert
// and extract (valid) source locations of unreachable nodes into sorted set
std::set<SourceLocation> unreachable;
BreadthFirstSearch<CFGNode>{{_exit, _revert}}.run(
[&](CFGNode const& _node, auto&& _addChild) {
if (!reachable.count(&_node) && !_node.location.isEmpty())
unreachable.insert(_node.location);
for (CFGNode const* entry: _node.entries)
_addChild(*entry);
}
);
for (auto it = unreachable.begin(); it != unreachable.end();)
{
SourceLocation location = *it++;
// Extend the location, as long as the next location overlaps (unreachable is sorted).
for (; it != unreachable.end() && it->start <= location.end; ++it)
location.end = std::max(location.end, it->end);
m_errorReporter.warning(location, "Unreachable code.");
}
}
|
