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Fixed #4369 (false positive: Variable 'i' is assigned a value that is never used)

This commit is contained in:
Frank Zingsheim 2012-12-04 21:39:51 +01:00
parent 590704afb4
commit aebdb3769f
3 changed files with 179 additions and 37 deletions
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134
lib/checkunusedvar.cpp
View File

@ -35,6 +35,9 @@ class Variables {
public:
enum VariableType { standard, array, pointer, reference, pointerArray, referenceArray, pointerPointer, none };
typedef std::set<unsigned int> VariableSet;
typedef std::list<VariableSet> VariableListOfSets;
/** Store information about variable usage */
class VariableUsage {
public:
@ -54,7 +57,8 @@ public:
}
/** variable is used.. set both read+write */
void use() {
void use(VariableListOfSets & varReadInScope) {
varReadInScope.back().insert(_var->varId());
_read = true;
_write = true;
}
@ -78,6 +82,27 @@ public:
typedef std::map<unsigned int, VariableUsage> VariableMap;
class ScopeGuard
{
public:
ScopeGuard(Variables & guarded,
bool insideLoop)
:_guarded(guarded),
_insideLoop(insideLoop)
{
_guarded.enterScope();
}
~ScopeGuard()
{
_guarded.leaveScope(_insideLoop);
}
private:
Variables & _guarded;
bool _insideLoop;
};
void clear() {
_varUsage.clear();
}
@ -103,8 +128,17 @@ public:
void eraseAll(unsigned int varid);
void clearAliases(unsigned int varid);
ScopeGuard newScope(bool insideLoop) {
return ScopeGuard(*this, insideLoop);
}
private:
void enterScope();
void leaveScope(bool insideLoop);
VariableMap _varUsage;
VariableListOfSets _varAddedInScope;
VariableListOfSets _varReadInScope;
};
@ -123,7 +157,7 @@ void Variables::alias(unsigned int varid1, unsigned int varid2, bool replace)
// alias to self
if (varid1 == varid2) {
if (var1)
var1->use();
var1->use(_varReadInScope);
return;
}
@ -150,9 +184,11 @@ void Variables::alias(unsigned int varid1, unsigned int varid2, bool replace)
var2->_aliases.insert(varid1);
var1->_aliases.insert(varid2);
if (var2->_type == Variables::pointer)
if (var2->_type == Variables::pointer) {
_varReadInScope.back().insert(varid2);
var2->_read = true;
}
}
void Variables::clearAliases(unsigned int varid)
{
@ -196,9 +232,11 @@ void Variables::addVar(const Variable *var,
VariableType type,
bool write_)
{
if (var->varId() > 0)
if (var->varId() > 0) {
_varAddedInScope.back().insert(var->varId());
_varUsage.insert(std::make_pair(var->varId(), VariableUsage(var, type, false, write_, false)));
}
}
void Variables::allocateMemory(unsigned int varid, const Token* tok)
{
@ -215,7 +253,9 @@ void Variables::read(unsigned int varid, const Token* tok)
VariableUsage *usage = find(varid);
if (usage) {
_varReadInScope.back().insert(varid);
usage->_read = true;
if (tok)
usage->_lastAccess = tok;
}
}
@ -231,6 +271,7 @@ void Variables::readAliases(unsigned int varid, const Token* tok)
VariableUsage *aliased = find(*aliases);
if (aliased) {
_varReadInScope.back().insert(*aliases);
aliased->_read = true;
aliased->_lastAccess = tok;
}
@ -285,7 +326,7 @@ void Variables::use(unsigned int varid, const Token* tok)
VariableUsage *usage = find(varid);
if (usage) {
usage->use();
usage->use(_varReadInScope);
usage->_lastAccess = tok;
std::set<unsigned int>::iterator aliases;
@ -294,7 +335,7 @@ void Variables::use(unsigned int varid, const Token* tok)
VariableUsage *aliased = find(*aliases);
if (aliased) {
aliased->use();
aliased->use(_varReadInScope);
aliased->_lastAccess = tok;
}
}
@ -332,6 +373,47 @@ Variables::VariableUsage *Variables::find(unsigned int varid)
return 0;
}
void Variables::enterScope()
{
_varAddedInScope.push_back(VariableSet());
_varReadInScope.push_back(VariableSet());
}
void Variables::leaveScope(bool insideLoop)
{
if (insideLoop) {
// read variables are read again in subsequent run through loop
VariableSet const & currentVarReadInScope = _varReadInScope.back();
for (VariableSet::const_iterator readIter = currentVarReadInScope.begin();
readIter != currentVarReadInScope.end();
++readIter)
{
read(*readIter, NULL);
}
}
VariableListOfSets::reverse_iterator reverseReadIter = _varReadInScope.rbegin();
++reverseReadIter;
if (reverseReadIter != _varReadInScope.rend())
{
// Transfer read variables into previous scope
VariableSet const & currentVarAddedInScope = _varAddedInScope.back();
VariableSet & currentVarReadInScope = _varReadInScope.back();
for (VariableSet::const_iterator addedIter = currentVarAddedInScope.begin();
addedIter != currentVarAddedInScope.end();
++addedIter)
{
currentVarReadInScope.erase(*addedIter);
}
VariableSet & previousVarReadInScope = *reverseReadIter;
previousVarReadInScope.insert(currentVarReadInScope.begin(),
currentVarReadInScope.end());
}
_varReadInScope.pop_back();
_varAddedInScope.pop_back();
}
static const Token* doAssignment(Variables &variables, const Token *tok, bool dereference, const Scope *scope)
{
// a = a + b;
@ -589,8 +671,10 @@ static const Token * skipBracketsAndMembers(const Token *tok)
//---------------------------------------------------------------------------
// Usage of function variables
//---------------------------------------------------------------------------
void CheckUnusedVar::checkFunctionVariableUsage_iterateScopes(const Scope* const scope, Variables& variables, bool insideLoop, std::vector<unsigned int> &usedVariables)
void CheckUnusedVar::checkFunctionVariableUsage_iterateScopes(const Scope* const scope, Variables& variables, bool insideLoop)
{
Variables::ScopeGuard scopeGuard=variables.newScope(insideLoop);
// Find declarations if the scope is executable..
if (scope->isExecutable()) {
// Find declarations
@ -648,12 +732,7 @@ void CheckUnusedVar::checkFunctionVariableUsage_iterateScopes(const Scope* const
if (tok->str() == "for" || tok->str() == "while" || tok->str() == "do") {
for (std::list<Scope*>::const_iterator i = scope->nestedList.begin(); i != scope->nestedList.end(); ++i) {
if ((*i)->classDef == tok) { // Find associated scope
checkFunctionVariableUsage_iterateScopes(*i, variables, true, usedVariables); // Scan child scope
insideLoop = false;
std::vector<unsigned int>::iterator it;
for (it = usedVariables.begin(); it != usedVariables.end(); ++it) {
variables.read((*it), tok);
}
checkFunctionVariableUsage_iterateScopes(*i, variables, true); // Scan child scope
tok = (*i)->classStart->link();
break;
}
@ -664,7 +743,7 @@ void CheckUnusedVar::checkFunctionVariableUsage_iterateScopes(const Scope* const
if (tok->str() == "{") {
for (std::list<Scope*>::const_iterator i = scope->nestedList.begin(); i != scope->nestedList.end(); ++i) {
if ((*i)->classStart == tok) { // Find associated scope
checkFunctionVariableUsage_iterateScopes(*i, variables, insideLoop, usedVariables); // Scan child scope
checkFunctionVariableUsage_iterateScopes(*i, variables, false); // Scan child scope
tok = tok->link();
break;
}
@ -827,10 +906,12 @@ void CheckUnusedVar::checkFunctionVariableUsage_iterateScopes(const Scope* const
// checked for chained assignments
if (tok != start && equal && equal->str() == "=") {
Variables::VariableUsage *var = variables.find(tok->varId());
unsigned int varId = tok->varId();
Variables::VariableUsage *var = variables.find(varId);
if (var && var->_type != Variables::reference)
var->_read = true;
if (var && var->_type != Variables::reference) {
variables.read(varId,tok);
}
tok = tok->previous();
}
@ -868,62 +949,49 @@ void CheckUnusedVar::checkFunctionVariableUsage_iterateScopes(const Scope* const
variables.read(tok->next()->varId(), tok);
} else // addressof
variables.use(tok->next()->varId(), tok); // use = read + write
usedVariables.push_back(tok->next()->varId());
} else if (Token::Match(tok, ">> %var%")) {
variables.use(tok->next()->varId(), tok); // use = read + write
usedVariables.push_back(tok->next()->varId());
} else if (Token::Match(tok, "%var% >>|&") && Token::Match(tok->previous(), "[{};:]")) {
variables.read(tok->varId(), tok);
usedVariables.push_back(tok->next()->varId());
}
// function parameter
else if (Token::Match(tok, "[(,] %var% [")) {
variables.use(tok->next()->varId(), tok); // use = read + write
usedVariables.push_back(tok->next()->varId());
} else if (Token::Match(tok, "[(,] %var% [,)]") && tok->previous()->str() != "*") {
variables.use(tok->next()->varId(), tok); // use = read + write
usedVariables.push_back(tok->next()->varId());
} else if (Token::Match(tok, "[(,] (") &&
Token::Match(tok->next()->link(), ") %var% [,)]")) {
variables.use(tok->next()->link()->next()->varId(), tok); // use = read + write
usedVariables.push_back(tok->next()->link()->next()->varId());
}
// function
else if (Token::Match(tok, "%var% (")) {
variables.read(tok->varId(), tok);
usedVariables.push_back(tok->varId());
if (Token::Match(tok->tokAt(2), "%var% =")) {
variables.read(tok->tokAt(2)->varId(), tok);
usedVariables.push_back(tok->tokAt(2)->varId());
}
}
else if (Token::Match(tok, "[{,] %var% [,}]")) {
variables.read(tok->next()->varId(), tok);
usedVariables.push_back(tok->next()->varId());
}
else if (Token::Match(tok, "%var% .")) {
variables.use(tok->varId(), tok); // use = read + write
usedVariables.push_back(tok->varId());
}
else if (tok->isExtendedOp() &&
Token::Match(tok->next(), "%var%") && !Token::Match(tok->next(), "true|false|new") && tok->strAt(2) != "=") {
variables.readAll(tok->next()->varId(), tok);
usedVariables.push_back(tok->next()->varId());
}
else if (Token::Match(tok, "%var%") && tok->next() && (tok->next()->str() == ")" || tok->next()->isExtendedOp())) {
variables.readAll(tok->varId(), tok);
usedVariables.push_back(tok->varId());
}
else if (Token::Match(tok, "%var% ;") && Token::Match(tok->previous(), "[;{}:]")) {
variables.readAll(tok->varId(), tok);
usedVariables.push_back(tok->varId());
}
else if (Token::Match(tok, "++|-- %var%")) {
@ -931,7 +999,6 @@ void CheckUnusedVar::checkFunctionVariableUsage_iterateScopes(const Scope* const
variables.use(tok->next()->varId(), tok);
else
variables.modified(tok->next()->varId(), tok);
usedVariables.push_back(tok->next()->varId());
}
else if (Token::Match(tok, "%var% ++|--")) {
@ -939,7 +1006,6 @@ void CheckUnusedVar::checkFunctionVariableUsage_iterateScopes(const Scope* const
variables.use(tok->varId(), tok);
else
variables.modified(tok->varId(), tok);
usedVariables.push_back(tok->varId());
}
else if (tok->isAssignmentOp()) {
@ -949,7 +1015,6 @@ void CheckUnusedVar::checkFunctionVariableUsage_iterateScopes(const Scope* const
variables.write(tok2->varId(), tok);
else
variables.read(tok2->varId(), tok);
usedVariables.push_back(tok2->varId());
}
}
}
@ -972,8 +1037,7 @@ void CheckUnusedVar::checkFunctionVariableUsage()
// varId, usage {read, write, modified}
Variables variables;
std::vector<unsigned int> usedVariables;
checkFunctionVariableUsage_iterateScopes(&*scope, variables, false, usedVariables);
checkFunctionVariableUsage_iterateScopes(&*scope, variables, false);
// Check usage of all variables in the current scope..

2
lib/checkunusedvar.h
View File

@ -64,7 +64,7 @@ public:
}
/** @brief %Check for unused function variables */
void checkFunctionVariableUsage_iterateScopes(const Scope* const scope, Variables& variables, bool insideLoop, std::vector<unsigned int> &usedVariables);
void checkFunctionVariableUsage_iterateScopes(const Scope* const scope, Variables& variables, bool insideLoop);
void checkVariableUsage(const Scope* const scope, const Token* start, Variables& variables);
void checkFunctionVariableUsage();

78
test/testunusedvar.cpp
View File

@ -637,6 +637,32 @@ private:
"}\n");
ASSERT_EQUALS("", errout.str());
functionVariableUsage("void foo()\n"
"{\n"
" int i = 0,code=10,d=10;\n"
" for(i = 0; i < 10; i++) {\n"
" std::cout<<code<<std::endl;\n"
" code += 2;\n"
" if (i == 3) {\n"
" return d;\n"
" }\n"
" d = code;\n"
" }\n"
"}\n");
ASSERT_EQUALS("", errout.str());
functionVariableUsage("void foo()\n"
"{\n"
" int i = 0,a=10,b=20;\n"
" for(i = 0; i < 10; i++) {\n"
" std::cout<<a<<std::endl;\n"
" int tmp=a;\n"
" a=b;\n"
" b=tmp;\n"
" }\n"
"}\n");
ASSERT_EQUALS("", errout.str());
functionVariableUsage("void foo()\n"
"{\n"
" int code=10;\n"
@ -670,6 +696,32 @@ private:
"}\n");
ASSERT_EQUALS("", errout.str());
functionVariableUsage("void foo()\n"
"{\n"
" int code=10,d=10;\n"
" while(code < 20) {\n"
" std::cout<<code<<std::endl;\n"
" code += 2;\n"
" if (i == 3) {\n"
" return d;\n"
" }\n"
" d += code;\n"
" }\n"
"}\n");
ASSERT_EQUALS("", errout.str());
functionVariableUsage("void foo()\n"
"{\n"
" int a=10,b=20;\n"
" while(a != 30) {\n"
" std::cout<<a<<std::endl;\n"
" int tmp=a;\n"
" a=b;\n"
" b=tmp;\n"
" }\n"
"}\n");
ASSERT_EQUALS("", errout.str());
functionVariableUsage("void foo()\n"
"{\n"
" int code=10;\n"
@ -703,6 +755,32 @@ private:
"}\n");
ASSERT_EQUALS("", errout.str());
functionVariableUsage("void foo()\n"
"{\n"
" int code=10,d=10;\n"
" do {\n"
" std::cout<<code<<std::endl;\n"
" code += 2;\n"
" if (i == 3) {\n"
" return d;\n"
" }\n"
" d += code;\n"
" } while(code < 20);\n"
"}\n");
ASSERT_EQUALS("", errout.str());
functionVariableUsage("void foo()\n"
"{\n"
" int a=10,b=20;\n"
" do {\n"
" std::cout<<a<<std::endl;\n"
" int tmp=a;\n"
" a=b;\n"
" b=tmp;\n"
" } while( a!=30 );\n"
"}\n");
ASSERT_EQUALS("", errout.str());
functionVariableUsage("void foo()\n"
"{\n"
" int code=10;\n"