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Fix issue 9721: ValueFlow: Comparison is always false, but ValueFlow says it is always true (#2658)

This commit is contained in:
Paul Fultz II 2020-05-23 00:15:13 -05:00 committed by GitHub
parent 4270819728
commit 0832830a95
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GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 27 additions and 8 deletions
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26
lib/valueflow.cpp
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@ -4321,9 +4321,19 @@ static void valueFlowInferCondition(TokenList* tokenlist,
} else if (tok->isComparisonOp()) { } else if (tok->isComparisonOp()) {
MathLib::bigint val = 0; MathLib::bigint val = 0;
const Token* varTok = nullptr; const Token* varTok = nullptr;
std::string op = tok->str();
if (tok->astOperand1()->hasKnownIntValue()) { if (tok->astOperand1()->hasKnownIntValue()) {
val = tok->astOperand1()->values().front().intvalue; val = tok->astOperand1()->values().front().intvalue;
varTok = tok->astOperand2(); varTok = tok->astOperand2();
// Flip the operator
if (op == ">")
op = "<";
else if (op == "<")
op = ">";
else if (op == ">=")
op = "<=";
else if (op == "<=")
op = ">=";
} else if (tok->astOperand2()->hasKnownIntValue()) { } else if (tok->astOperand2()->hasKnownIntValue()) {
val = tok->astOperand2()->values().front().intvalue; val = tok->astOperand2()->values().front().intvalue;
varTok = tok->astOperand1(); varTok = tok->astOperand1();
@ -4336,22 +4346,22 @@ static void valueFlowInferCondition(TokenList* tokenlist,
continue; continue;
const ValueFlow::Value* result = nullptr; const ValueFlow::Value* result = nullptr;
bool known = false; bool known = false;
if (Token::Match(tok, "==|!=")) { if (op == "==" || op == "!=") {
result = proveNotEqual(varTok->values(), val); result = proveNotEqual(varTok->values(), val);
known = tok->str() == "!="; known = op == "!=";
} else if (Token::Match(tok, "<|>=")) { } else if (op == "<" || op == ">=") {
result = proveLessThan(varTok->values(), val); result = proveLessThan(varTok->values(), val);
known = tok->str() == "<"; known = op == "<";
if (!result && !isSaturated(val)) { if (!result && !isSaturated(val)) {
result = proveGreaterThan(varTok->values(), val - 1); result = proveGreaterThan(varTok->values(), val - 1);
known = tok->str() == ">="; known = op == ">=";
} }
} else if (Token::Match(tok, ">|<=")) { } else if (op == ">" || op == "<=") {
result = proveGreaterThan(varTok->values(), val); result = proveGreaterThan(varTok->values(), val);
known = tok->str() == ">"; known = op == ">";
if (!result && !isSaturated(val)) { if (!result && !isSaturated(val)) {
result = proveLessThan(varTok->values(), val + 1); result = proveLessThan(varTok->values(), val + 1);
known = tok->str() == "<="; known = op == "<=";
} }
} }
if (!result) if (!result)

9
test/testcondition.cpp
View File

@ -3507,6 +3507,15 @@ private:
" return pos;\n" " return pos;\n"
"}\n"); "}\n");
ASSERT_EQUALS("[test.cpp:2] -> [test.cpp:5]: (style) Condition 'pos>0' is always true\n", errout.str()); ASSERT_EQUALS("[test.cpp:2] -> [test.cpp:5]: (style) Condition 'pos>0' is always true\n", errout.str());
// #9721
check("void f(int x) {\n"
" if (x > 127) {\n"
" if ( (x>255) || (-128>x) )\n"
" return;\n"
" }\n"
"}\n");
ASSERT_EQUALS("[test.cpp:2] -> [test.cpp:3]: (style) Condition '-128>x' is always false\n", errout.str());
} }
void alwaysTrueContainer() { void alwaysTrueContainer() {