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ValueFlow: Assume constant is nonzero when its negated (#4041) 

* ValueFlow: Assume constant is nonzero when its negated

* Format

* Format
This commit is contained in:
Paul Fultz II 2022-04-22 23:19:07 -05:00 committed by GitHub
parent 4eed29502c
commit 5d5562266d
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GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 98 additions and 71 deletions
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158
lib/valueflow.cpp
View File

@ -275,6 +275,77 @@ const Token *parseCompareInt(const Token *tok, ValueFlow::Value &true_value, Val
});
}
static bool isInConstructorList(const Token* tok)
{
if (!tok)
return false;
if (!astIsRHS(tok))
return false;
const Token* parent = tok->astParent();
if (!Token::Match(parent, "{|("))
return false;
if (!Token::Match(parent->previous(), "%var% {|("))
return false;
if (!parent->astOperand1() || !parent->astOperand2())
return false;
do {
parent = parent->astParent();
} while (Token::simpleMatch(parent, ","));
return Token::simpleMatch(parent, ":") && !Token::simpleMatch(parent->astParent(), "?");
}
static std::vector<ValueType> getParentValueTypes(const Token* tok,
const Settings* settings = nullptr,
const Token** parent = nullptr)
{
if (!tok)
return {};
if (!tok->astParent())
return {};
if (isInConstructorList(tok)) {
if (parent)
*parent = tok->astParent()->astOperand1();
if (tok->astParent()->astOperand1()->valueType())
return {*tok->astParent()->astOperand1()->valueType()};
return {};
} else if (Token::Match(tok->astParent(), "(|{|,")) {
int argn = -1;
const Token* ftok = getTokenArgumentFunction(tok, argn);
if (ftok && ftok->function()) {
std::vector<ValueType> result;
std::vector<const Variable*> argsVars = getArgumentVars(ftok, argn);
const Token* nameTok = nullptr;
for (const Variable* var : getArgumentVars(ftok, argn)) {
if (!var)
continue;
if (!var->valueType())
continue;
nameTok = var->nameToken();
result.push_back(*var->valueType());
}
if (result.size() == 1 && nameTok && parent) {
*parent = nameTok;
}
return result;
}
}
if (settings && Token::Match(tok->astParent()->tokAt(-2), ". push_back|push_front|insert|push (") &&
astIsContainer(tok->astParent()->tokAt(-2)->astOperand1())) {
const Token* contTok = tok->astParent()->tokAt(-2)->astOperand1();
const ValueType* vtCont = contTok->valueType();
if (!vtCont->containerTypeToken)
return {};
ValueType vtParent = ValueType::parseDecl(vtCont->containerTypeToken, settings);
return {std::move(vtParent)};
}
if (Token::Match(tok->astParent(), "return|(|{|%assign%") && parent) {
*parent = tok->astParent();
}
if (tok->astParent()->valueType())
return {*tok->astParent()->valueType()};
return {};
}
static bool isEscapeScope(const Token* tok, TokenList * tokenlist, bool unknown = false)
{
if (!Token::simpleMatch(tok, "{"))
@ -1547,6 +1618,17 @@ static std::vector<MathLib::bigint> minUnsignedValue(const Token* tok, int depth
return result;
}
static bool isConvertedToIntegral(const Token* tok, const Settings* settings)
{
if (!tok)
return false;
std::vector<ValueType> parentTypes = getParentValueTypes(tok, settings);
if (parentTypes.empty())
return false;
const ValueType& vt = parentTypes.front();
return vt.type != ValueType::UNKNOWN_INT && vt.isIntegral();
}
static void valueFlowImpossibleValues(TokenList* tokenList, const Settings* settings)
{
for (Token* tok = tokenList->front(); tok; tok = tok->next()) {
@ -1602,6 +1684,11 @@ static void valueFlowImpossibleValues(TokenList* tokenList, const Settings* sett
ValueFlow::Value value{0};
value.setImpossible();
setTokenValue(tok, value, settings);
} else if (tok->isIncompleteVar() && tok->astParent() && tok->astParent()->isUnaryOp("-") &&
isConvertedToIntegral(tok->astParent(), settings)) {
ValueFlow::Value value{0};
value.setImpossible();
setTokenValue(tok, value, settings);
}
}
}
@ -3359,77 +3446,6 @@ static bool isDifferentType(const Token* src, const Token* dst)
return false;
}
static bool isInConstructorList(const Token* tok)
{
if (!tok)
return false;
if (!astIsRHS(tok))
return false;
const Token* parent = tok->astParent();
if (!Token::Match(parent, "{|("))
return false;
if (!Token::Match(parent->previous(), "%var% {|("))
return false;
if (!parent->astOperand1() || !parent->astOperand2())
return false;
do {
parent = parent->astParent();
} while (Token::simpleMatch(parent, ","));
return Token::simpleMatch(parent, ":") && !Token::simpleMatch(parent->astParent(), "?");
}
static std::vector<ValueType> getParentValueTypes(const Token* tok,
const Settings* settings = nullptr,
const Token** parent = nullptr)
{
if (!tok)
return {};
if (!tok->astParent())
return {};
if (isInConstructorList(tok)) {
if (parent)
*parent = tok->astParent()->astOperand1();
if (tok->astParent()->astOperand1()->valueType())
return {*tok->astParent()->astOperand1()->valueType()};
return {};
} else if (Token::Match(tok->astParent(), "(|{|,")) {
int argn = -1;
const Token* ftok = getTokenArgumentFunction(tok, argn);
if (ftok && ftok->function()) {
std::vector<ValueType> result;
std::vector<const Variable*> argsVars = getArgumentVars(ftok, argn);
const Token* nameTok = nullptr;
for (const Variable* var : getArgumentVars(ftok, argn)) {
if (!var)
continue;
if (!var->valueType())
continue;
nameTok = var->nameToken();
result.push_back(*var->valueType());
}
if (result.size() == 1 && nameTok && parent) {
*parent = nameTok;
}
return result;
}
}
if (settings && Token::Match(tok->astParent()->tokAt(-2), ". push_back|push_front|insert|push (") &&
astIsContainer(tok->astParent()->tokAt(-2)->astOperand1())) {
const Token* contTok = tok->astParent()->tokAt(-2)->astOperand1();
const ValueType* vtCont = contTok->valueType();
if (!vtCont->containerTypeToken)
return {};
ValueType vtParent = ValueType::parseDecl(vtCont->containerTypeToken, settings);
return {std::move(vtParent)};
}
if (Token::Match(tok->astParent(), "return|(|{|%assign%") && parent) {
*parent = tok->astParent();
}
if (tok->astParent()->valueType())
return {*tok->astParent()->valueType()};
return {};
}
bool isLifetimeBorrowed(const Token *tok, const Settings *settings)
{
if (!tok)

11
test/testvalueflow.cpp
View File

@ -5065,6 +5065,17 @@ private:
"}\n";
values = tokenValues(code, "x ; }", ValueFlow::Value::ValueType::UNINIT);
ASSERT_EQUALS(0, values.size());
code = "void f() {\n"
" int i;\n"
" if (x) {\n"
" int y = -ENOMEM;\n" // assume constant ENOMEM is nonzero since it's negated
" if (y != 0) return;\n"
" i++;\n"
" }\n"
"}\n";
values = tokenValues(code, "i ++", ValueFlow::Value::ValueType::UNINIT);
ASSERT_EQUALS(0, values.size());
}
void valueFlowConditionExpressions() {