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Fix 10851: False positive: known variable value below for loop (#3891) 

* Fix 10851: False positive: known variable value below for loop

* Format

* Add test for 10863

* Format
This commit is contained in:
Paul Fultz II 2022-03-11 23:15:35 -06:00 committed by GitHub
parent 705931266c
commit ff902369e0
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GPG Key ID: 4AEE18F83AFDEB23
5 changed files with 68 additions and 23 deletions
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10
lib/programmemory.cpp
View File

@ -241,11 +241,12 @@ void programMemoryParseCondition(ProgramMemory& pm, const Token* tok, const Toke
return;
if (endTok && isExpressionChanged(vartok, tok->next(), endTok, settings, true))
return;
bool impossible = (tok->str() == "==" && !then) || (tok->str() == "!=" && then);
pm.setIntValue(vartok, then ? truevalue.intvalue : falsevalue.intvalue, impossible);
const bool impossible = (tok->str() == "==" && !then) || (tok->str() == "!=" && then);
const ValueFlow::Value& v = then ? truevalue : falsevalue;
pm.setValue(vartok, impossible ? asImpossible(v) : v);
const Token* containerTok = settings->library.getContainerFromYield(vartok, Library::Container::Yield::SIZE);
if (containerTok)
pm.setContainerSizeValue(containerTok, then ? truevalue.intvalue : falsevalue.intvalue, !impossible);
pm.setContainerSizeValue(containerTok, v.intvalue, !impossible);
} else if (Token::simpleMatch(tok, "!")) {
programMemoryParseCondition(pm, tok->astOperand1(), endTok, settings, !then);
} else if (then && Token::simpleMatch(tok, "&&")) {
@ -760,6 +761,9 @@ static ValueFlow::Value execute(const Token* expr, ProgramMemory& pm, const Sett
for (const ValueFlow::Value& value : expr->values()) {
if (!value.isSymbolicValue())
continue;
// TODO: Handle possible symbolic values
if (!value.isKnown())
continue;
if (!pm.hasValue(value.tokvalue->exprId()))
continue;
ValueFlow::Value v2 = pm.at(value.tokvalue->exprId());

22
lib/valueflow.cpp
View File

@ -2111,7 +2111,10 @@ struct ValueFlowAnalyzer : Analyzer {
// Check if its assigned to the same value
if (value && !value->isImpossible() && Token::simpleMatch(tok->astParent(), "=") && astIsLHS(tok) &&
astIsIntegral(tok->astParent()->astOperand2(), false)) {
std::vector<MathLib::bigint> result = evaluate(Evaluate::Integral, tok->astParent()->astOperand2());
std::vector<MathLib::bigint> result =
evaluateInt(tok->astParent()->astOperand2(), [&] {
return ProgramMemory{getProgramState()};
});
if (!result.empty() && value->equalTo(result.front()))
return Action::Idempotent;
}
@ -2396,13 +2399,13 @@ struct ValueFlowAnalyzer : Analyzer {
return Action::None;
}
virtual std::vector<MathLib::bigint> evaluate(Evaluate e, const Token* tok, const Token* ctx = nullptr) const override
template<class F>
std::vector<MathLib::bigint> evaluateInt(const Token* tok, F getProgramMemory) const
{
if (e == Evaluate::Integral) {
if (tok->hasKnownIntValue())
return {static_cast<int>(tok->values().front().intvalue)};
std::vector<MathLib::bigint> result;
ProgramMemory pm = pms.get(tok, ctx, getProgramState());
ProgramMemory pm = getProgramMemory();
if (Token::Match(tok, "&&|%oror%")) {
if (conditionIsTrue(tok, pm, getSettings()))
result.push_back(1);
@ -2415,8 +2418,15 @@ struct ValueFlowAnalyzer : Analyzer {
if (!error)
result.push_back(out);
}
return result;
}
virtual std::vector<MathLib::bigint> evaluate(Evaluate e, const Token* tok, const Token* ctx = nullptr) const override
{
if (e == Evaluate::Integral) {
return evaluateInt(tok, [&] {
return pms.get(tok, ctx, getProgramState());
});
} else if (e == Evaluate::ContainerEmpty) {
const ValueFlow::Value* value = ValueFlow::findValue(tok->values(), nullptr, [](const ValueFlow::Value& v) {
return v.isKnown() && v.isContainerSizeValue();
@ -5387,7 +5397,7 @@ static bool isBreakScope(const Token* const endToken)
return Token::findmatch(endToken->link(), "break|goto", endToken);
}
static ValueFlow::Value asImpossible(ValueFlow::Value v)
ValueFlow::Value asImpossible(ValueFlow::Value v)
{
v.invertRange();
v.setImpossible();

2
lib/valueflow.h
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@ -458,6 +458,8 @@ namespace ValueFlow {
std::vector<ValueFlow::Value> isOutOfBounds(const Value& size, const Token* indexTok, bool possible = true);
}
ValueFlow::Value asImpossible(ValueFlow::Value v);
bool isContainerSizeChanged(const Token* tok, const Settings* settings = nullptr, int depth = 20);
struct LifetimeToken {

16
test/testcondition.cpp
View File

@ -4433,6 +4433,22 @@ private:
" if (pool) {}\n"
"}\n");
ASSERT_EQUALS("", errout.str());
// #10863
check("void f(const int A[], int Len) {\n"
" if (Len <= 0)\n"
" return;\n"
" int I = 0;\n"
" while (I < Len) {\n"
" int K = I + 1;\n"
" for (; K < Len; K++) {\n"
" if (A[I] != A[K])\n"
" break;\n"
" } \n"
" I = K; \n"
" }\n"
"}\n");
ASSERT_EQUALS("", errout.str());
}
void alwaysTrueTryCatch()

13
test/testvalueflow.cpp
View File

@ -6739,6 +6739,19 @@ private:
" bool result = x;\n"
"}\n";
ASSERT_EQUALS(false, testValueOfXKnown(code, 5U, 0));
code = "void foo() {\n"
" int x = 0;\n"
" for (int i = 0; i < 5; i++) {\n"
" int y = 0;\n"
" for (int j = 0; j < 10; j++)\n"
" y++;\n"
" if (y >= x)\n"
" x = y;\n"
" }\n"
" return x;\n"
"}\n";
ASSERT_EQUALS(false, testValueOfXKnown(code, 10U, 0));
}
void valueFlowUnsigned() {