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Fix false positives in knownConditionTrueFalse when using expressions with const variables #2469

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Merged
danmar merged 1 commit into from
Jan 3, 2020
Merged

Fix false positives in knownConditionTrueFalse when using expressions with const variables #2469

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20 changes: 12 additions & 8 deletions lib/astutils.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1411,27 +1411,31 @@ bool isCPPCast(const Token* tok)
return tok && Token::simpleMatch(tok->previous(), "> (") && tok->astOperand2() && tok->astOperand1() && tok->astOperand1()->str().find("_cast") != std::string::npos;
}

bool isConstVarExpression(const Token *tok)
bool isConstVarExpression(const Token *tok, const char* skipMatch)
{
if (!tok)
return false;
if (skipMatch && Token::Match(tok, skipMatch))
return false;
if (Token::simpleMatch(tok->previous(), "sizeof ("))
return true;
if (Token::Match(tok->previous(), "%name% (")) {
if (Token::simpleMatch(tok->astOperand1(), ".") && !isConstVarExpression(tok->astOperand1(), skipMatch))
return false;
std::vector<const Token *> args = getArguments(tok);
return std::all_of(args.begin(), args.end(), &isConstVarExpression);
return std::all_of(args.begin(), args.end(), [&](const Token* t) { return isConstVarExpression(t, skipMatch); });
}
if (isCPPCast(tok)) {
return isConstVarExpression(tok->astOperand2());
return isConstVarExpression(tok->astOperand2(), skipMatch);
}
if (Token::Match(tok, "( %type%"))
return isConstVarExpression(tok->astOperand1());
return isConstVarExpression(tok->astOperand1(), skipMatch);
if (tok->str() == "::" && tok->hasKnownValue())
return isConstVarExpression(tok->astOperand2());
return isConstVarExpression(tok->astOperand2(), skipMatch);
if (Token::Match(tok, "%cop%|[|.")) {
if (tok->astOperand1() && !isConstVarExpression(tok->astOperand1()))
if (tok->astOperand1() && !isConstVarExpression(tok->astOperand1(), skipMatch))
return false;
if (tok->astOperand2() && !isConstVarExpression(tok->astOperand2()))
if (tok->astOperand2() && !isConstVarExpression(tok->astOperand2(), skipMatch))
return false;
return true;
}
Expand All @@ -1440,7 +1444,7 @@ bool isConstVarExpression(const Token *tok)
if (tok->isEnumerator())
return true;
if (tok->variable())
return tok->variable()->isConst();
return tok->variable()->isConst() && tok->variable()->nameToken() && tok->variable()->nameToken()->hasKnownValue();
return false;
}

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2 changes: 1 addition & 1 deletion lib/astutils.h
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Expand Up @@ -205,7 +205,7 @@ bool isLikelyStreamRead(bool cpp, const Token *op);

bool isCPPCast(const Token* tok);

bool isConstVarExpression(const Token *tok);
bool isConstVarExpression(const Token *tok, const char * skipMatch = nullptr);

const Variable *getLHSVariable(const Token *tok);

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2 changes: 2 additions & 0 deletions lib/checkcondition.cpp
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Expand Up @@ -1378,6 +1378,8 @@ void CheckCondition::alwaysTrueFalse()
continue;
if (Token::Match(tok, "%comp%") && isSameExpression(mTokenizer->isCPP(), true, tok->astOperand1(), tok->astOperand2(), mSettings->library, true, true))
continue;
if (isConstVarExpression(tok, "[|(|&|+|-|*|/|%|^|>>|<<"))
continue;

const bool constIfWhileExpression =
tok->astParent() && Token::Match(tok->astTop()->astOperand1(), "if|while") && !tok->astTop()->astOperand1()->isConstexpr() &&
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3 changes: 3 additions & 0 deletions lib/checkother.cpp
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Expand Up @@ -3000,6 +3000,9 @@ static bool isVariableExpression(const Token* tok)
if (Token::simpleMatch(tok, "."))
return isVariableExpression(tok->astOperand1()) &&
isVariableExpression(tok->astOperand2());
if (Token::simpleMatch(tok, "["))
return isVariableExpression(tok->astOperand1()) &&
tok->astOperand2() && tok->astOperand2()->hasKnownIntValue();
return false;
}

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18 changes: 18 additions & 0 deletions test/testcondition.cpp
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Expand Up @@ -3329,6 +3329,24 @@ class TestCondition : public TestFixture {
" return;\n"
"}\n");
ASSERT_EQUALS("", errout.str());

check("int f(int a, int b) {\n"
" static const int x = 10;\n"
" return x == 1 ? a : b;\n"
"}\n");
ASSERT_EQUALS("", errout.str());

check("const bool x = false;\n"
"void f() {\n"
" if (x) {}\n"
"}\n");
ASSERT_EQUALS("", errout.str());

check("const bool x = false;\n"
"void f() {\n"
" if (!x) {}\n"
"}\n");
ASSERT_EQUALS("", errout.str());
}

void alwaysTrueInfer() {
Expand Down