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Fix 11194: FN: knownConditionTrueFalse #4452

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merged 2 commits into from
Sep 8, 2022
Merged

Fix 11194: FN: knownConditionTrueFalse #4452

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56f4845
Fix 11194: FN: knownConditionTrueFalse
pfultz2 Sep 7, 2022
e7d261d
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pfultz2 Sep 7, 2022
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174 changes: 110 additions & 64 deletions lib/valueflow.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -5084,80 +5084,127 @@ static void valueFlowSymbolic(TokenList* tokenlist, SymbolDatabase* symboldataba
}
}

static void valueFlowSymbolicIdentity(TokenList* tokenlist)
static const Token* isStrlenOf(const Token* tok, const Token* expr, int depth = 10)
{
for (Token* tok = tokenlist->front(); tok; tok = tok->next()) {
if (tok->hasKnownIntValue())
continue;
if (!Token::Match(tok, "*|/|<<|>>|^|+|-|%or%"))
continue;
if (!tok->astOperand1())
continue;
if (!tok->astOperand2())
continue;
if (!astIsIntegral(tok->astOperand1(), false) && !astIsIntegral(tok->astOperand2(), false))
continue;
const ValueFlow::Value* constant = nullptr;
const Token* vartok = nullptr;
if (tok->astOperand1()->hasKnownIntValue()) {
constant = &tok->astOperand1()->values().front();
vartok = tok->astOperand2();
}
if (tok->astOperand2()->hasKnownIntValue()) {
constant = &tok->astOperand2()->values().front();
vartok = tok->astOperand1();
}
if (!constant)
continue;
if (!vartok)
continue;
if (vartok->exprId() == 0)
continue;
if (Token::Match(tok, "<<|>>|/") && !astIsLHS(vartok))
continue;
if (Token::Match(tok, "<<|>>|^|+|-|%or%") && constant->intvalue != 0)
continue;
if (Token::Match(tok, "*|/") && constant->intvalue != 1)
continue;
std::vector<ValueFlow::Value> values = {makeSymbolic(vartok)};
std::unordered_set<nonneg int> ids = {vartok->exprId()};
std::copy_if(
vartok->values().begin(), vartok->values().end(), std::back_inserter(values), [&](const ValueFlow::Value& v) {
if (depth < 0)
return nullptr;
if (!tok)
return nullptr;
if (!expr)
return nullptr;
if (expr->exprId() == 0)
return nullptr;
if (Token::simpleMatch(tok->previous(), "strlen (")) {
if (tok->astOperand2()->exprId() == expr->exprId())
return tok;
} else {
for (const ValueFlow::Value& v : tok->values()) {
if (!v.isSymbolicValue())
return false;
if (!v.tokvalue)
return false;
return ids.insert(v.tokvalue->exprId()).second;
});
for (const ValueFlow::Value& v : values)
setTokenValue(tok, v, tokenlist->getSettings());
continue;
if (!v.isKnown())
continue;
if (v.intvalue != 0)
continue;
if (const Token* next = isStrlenOf(v.tokvalue, expr, depth - 1))
return next;
}
}
return nullptr;
}

static void valueFlowSymbolicAbs(TokenList* tokenlist, SymbolDatabase* symboldatabase)
static void valueFlowSymbolicOperators(TokenList* tokenlist, SymbolDatabase* symboldatabase)
{
for (const Scope* scope : symboldatabase->functionScopes) {
for (Token* tok = const_cast<Token*>(scope->bodyStart); tok != scope->bodyEnd; tok = tok->next()) {
if (!Token::Match(tok, "abs|labs|llabs|fabs|fabsf|fabsl ("))
continue;
if (tok->hasKnownIntValue())
continue;

const Token* arg = tok->next()->astOperand2();
if (!arg)
continue;
ValueFlow::Value c = inferCondition(">=", arg, 0);
if (!c.isKnown())
continue;
if (Token::Match(tok, "abs|labs|llabs|fabs|fabsf|fabsl (")) {
const Token* arg = tok->next()->astOperand2();
if (!arg)
continue;
ValueFlow::Value c = inferCondition(">=", arg, 0);
if (!c.isKnown())
continue;

ValueFlow::Value v = makeSymbolic(arg);
v.errorPath = c.errorPath;
v.errorPath.emplace_back(tok, "Passed to " + tok->str());
if (c.intvalue == 0)
v.setImpossible();
else
v.setKnown();
setTokenValue(tok->next(), v, tokenlist->getSettings());
ValueFlow::Value v = makeSymbolic(arg);
v.errorPath = c.errorPath;
v.errorPath.emplace_back(tok, "Passed to " + tok->str());
if (c.intvalue == 0)
v.setImpossible();
else
v.setKnown();
setTokenValue(tok->next(), v, tokenlist->getSettings());
} else if (Token::Match(tok, "*|/|<<|>>|^|+|-|%or%")) {
if (!tok->astOperand1())
continue;
if (!tok->astOperand2())
continue;
if (!astIsIntegral(tok->astOperand1(), false) && !astIsIntegral(tok->astOperand2(), false))
continue;
const ValueFlow::Value* constant = nullptr;
const Token* vartok = nullptr;
if (tok->astOperand1()->hasKnownIntValue()) {
constant = &tok->astOperand1()->values().front();
vartok = tok->astOperand2();
}
if (tok->astOperand2()->hasKnownIntValue()) {
constant = &tok->astOperand2()->values().front();
vartok = tok->astOperand1();
}
if (!constant)
continue;
if (!vartok)
continue;
if (vartok->exprId() == 0)
continue;
if (Token::Match(tok, "<<|>>|/") && !astIsLHS(vartok))
continue;
if (Token::Match(tok, "<<|>>|^|+|-|%or%") && constant->intvalue != 0)
continue;
if (Token::Match(tok, "*|/") && constant->intvalue != 1)
continue;
std::vector<ValueFlow::Value> values = {makeSymbolic(vartok)};
std::unordered_set<nonneg int> ids = {vartok->exprId()};
std::copy_if(vartok->values().begin(),
vartok->values().end(),
std::back_inserter(values),
[&](const ValueFlow::Value& v) {
if (!v.isSymbolicValue())
return false;
if (!v.tokvalue)
return false;
return ids.insert(v.tokvalue->exprId()).second;
});
for (const ValueFlow::Value& v : values)
setTokenValue(tok, v, tokenlist->getSettings());
} else if (Token::simpleMatch(tok, "[")) {
const Token* arrayTok = tok->astOperand1();
const Token* indexTok = tok->astOperand2();
if (!arrayTok)
continue;
if (!indexTok)
continue;
for (const ValueFlow::Value& value : indexTok->values()) {
if (!value.isSymbolicValue())
continue;
if (value.intvalue != 0)
continue;
if (value.bound == ValueFlow::Value::Bound::Upper)
continue;
if (value.isImpossible() && value.bound != ValueFlow::Value::Bound::Lower)
continue;
if (value.isKnown() && value.bound != ValueFlow::Value::Bound::Point)
continue;
const Token* strlenTok = isStrlenOf(value.tokvalue, arrayTok);
if (!strlenTok)
continue;
ValueFlow::Value v = value;
v.valueType = ValueFlow::Value::ValueType::INT;
v.errorPath.emplace_back(strlenTok, "Return index of string to the first element that is 0");
setTokenValue(tok, v, tokenlist->getSettings());
}
}
}
}
}
Expand Down Expand Up @@ -8760,8 +8807,7 @@ void ValueFlow::setValues(TokenList *tokenlist, SymbolDatabase* symboldatabase,
while (n > 0 && values < getTotalValues(tokenlist)) {
values = getTotalValues(tokenlist);
valueFlowImpossibleValues(tokenlist, settings);
valueFlowSymbolicIdentity(tokenlist);
valueFlowSymbolicAbs(tokenlist, symboldatabase);
valueFlowSymbolicOperators(tokenlist, symboldatabase);
valueFlowCondition(SymbolicConditionHandler{}, tokenlist, symboldatabase, errorLogger, settings);
valueFlowSymbolicInfer(tokenlist, symboldatabase);
valueFlowArrayBool(tokenlist);
Expand Down
22 changes: 22 additions & 0 deletions test/testvalueflow.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -158,6 +158,7 @@ class TestValueFlow : public TestFixture {
TEST_CASE(valueFlowNotNull);
TEST_CASE(valueFlowSymbolic);
TEST_CASE(valueFlowSymbolicIdentity);
TEST_CASE(valueFlowSymbolicStrlen);
TEST_CASE(valueFlowSmartPointer);
}

Expand Down Expand Up @@ -7502,6 +7503,27 @@ class TestValueFlow : public TestFixture {
ASSERT_EQUALS(false, testValueOfXKnown(code, 3U, "a", 0));
}

void valueFlowSymbolicStrlen()
{
const char* code;

code = "int f(char *s) {\n"
" size_t len = strlen(s);\n"
" int x = s[len];\n"
" return x;\n"
"}\n";
ASSERT_EQUALS(true, testValueOfXKnown(code, 4U, 0));

code = "int f(char *s, size_t i) {\n"
" if (i < strlen(s)) {\n"
" int x = s[i];\n"
" return x;\n"
" }\n"
" return 0;\n"
"}\n";
ASSERT_EQUALS(true, testValueOfXImpossible(code, 4U, 0));
}

void valueFlowSmartPointer()
{
const char* code;
Expand Down