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Fix issue 470: Condition is always true or false on logical operators (#1294) 

* Fix issue 470: Condition is always true or false on logical operators

* Dont warn on literals

* Compute logical operators using valueflow

* Fix FP when using literals

* Always warn on subconditions that are always true

* Use percent matches first

* Add test for logical operators

* Check if parent is null
This commit is contained in:
Paul Fultz II 2018-07-23 01:51:59 -05:00 committed by Daniel Marjamäki
parent 373039f034
commit 9895ea5ff2
4 changed files with 95 additions and 4 deletions
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6
lib/checkcondition.cpp
View File

@ -885,7 +885,6 @@ void CheckCondition::checkIncorrectLogicOperator()
continue;
}
// 'A && (!A || B)' is equivalent to 'A && B'
// 'A || (!A && B)' is equivalent to 'A || B'
if (printStyle &&
@ -1192,9 +1191,8 @@ void CheckCondition::alwaysTrueFalse()
continue;
const bool constIfWhileExpression =
tok->astParent()
&& Token::Match(tok->astParent()->astOperand1(), "if|while")
&& !tok->isBoolean();
tok->astParent() && Token::Match(tok->astTop()->astOperand1(), "if|while") &&
(Token::Match(tok->astParent(), "%oror%|&&") || Token::Match(tok->astParent()->astOperand1(), "if|while"));
const bool constValExpr = tok->isNumber() && Token::Match(tok->astParent(),"%oror%|&&|?"); // just one number in boolean expression
const bool compExpr = Token::Match(tok, "%comp%|!"); // a compare expression

12
lib/valueflow.cpp
View File

@ -444,6 +444,18 @@ static void setTokenValue(Token* tok, const ValueFlow::Value &value, const Setti
return;
}
// known result when a operand is true.
if (Token::simpleMatch(parent, "&&") && value.isKnown() && value.isIntValue() && value.intvalue==0) {
setTokenValue(parent, value, settings);
return;
}
// known result when a operand is false.
if (Token::simpleMatch(parent, "||") && value.isKnown() && value.isIntValue() && value.intvalue!=0) {
setTokenValue(parent, value, settings);
return;
}
for (const ValueFlow::Value &value1 : parent->astOperand1()->values()) {
if (!value1.isIntValue() && !value1.isFloatValue() && !value1.isTokValue())
continue;

31
test/testcondition.cpp
View File

@ -105,6 +105,7 @@ private:
TEST_CASE(checkInvalidTestForOverflow);
TEST_CASE(checkConditionIsAlwaysTrueOrFalseInsideIfWhile);
TEST_CASE(alwaysTrueFalseInLogicalOperators);
TEST_CASE(pointerAdditionResultNotNull);
}
@ -2507,6 +2508,36 @@ private:
ASSERT_EQUALS("[test.cpp:2]: (style) Condition 'a+1' is always true\n", errout.str());
}
void alwaysTrueFalseInLogicalOperators() {
check("bool f();\n"
"void foo() { bool x = true; if(x||f()) {}}\n");
ASSERT_EQUALS("[test.cpp:2]: (style) Condition 'x' is always true\n", errout.str());
check("void foo(bool b) { bool x = true; if(x||b) {}}\n");
ASSERT_EQUALS("[test.cpp:1]: (style) Condition 'x' is always true\n", errout.str());
check("void foo(bool b) { if(true||b) {}}\n");
ASSERT_EQUALS("", errout.str());
check("bool f();\n"
"void foo() { bool x = false; if(x||f()) {}}\n");
ASSERT_EQUALS("[test.cpp:2]: (style) Condition 'x' is always false\n", errout.str());
check("bool f();\n"
"void foo() { bool x = false; if(x&&f()) {}}\n");
ASSERT_EQUALS("[test.cpp:2]: (style) Condition 'x' is always false\n", errout.str());
check("void foo(bool b) { bool x = false; if(x&&b) {}}\n");
ASSERT_EQUALS("[test.cpp:1]: (style) Condition 'x' is always false\n", errout.str());
check("void foo(bool b) { if(false&&b) {}}\n");
ASSERT_EQUALS("", errout.str());
check("bool f();\n"
"void foo() { bool x = true; if(x&&f()) {}}\n");
ASSERT_EQUALS("[test.cpp:2]: (style) Condition 'x' is always true\n", errout.str());
}
void pointerAdditionResultNotNull() {
check("void f(char *ptr) {\n"
" if (ptr + 1 != 0);\n"

50
test/testvalueflow.cpp
View File

@ -559,6 +559,56 @@ private:
ASSERT_EQUALS(1U, values.size());
ASSERT_EQUALS(-10, values.back().intvalue);
// Logical and
code = "void f(bool b) {\n"
" bool x = false && b;\n"
" bool a = x;\n"
"}";
ASSERT_EQUALS(true, testValueOfX(code, 3U, 0));
code = "void f(bool b) {\n"
" bool x = b && false;\n"
" bool a = x;\n"
"}";
ASSERT_EQUALS(true, testValueOfX(code, 3U, 0));
code = "void f(bool b) {\n"
" bool x = true && b;\n"
" bool a = x;\n"
"}";
ASSERT_EQUALS(false, testValueOfX(code, 3U, 1));
code = "void f(bool b) {\n"
" bool x = b && true;\n"
" bool a = x;\n"
"}";
ASSERT_EQUALS(false, testValueOfX(code, 3U, 1));
// Logical or
code = "void f(bool b) {\n"
" bool x = true || b;\n"
" bool a = x;\n"
"}";
ASSERT_EQUALS(true, testValueOfX(code, 3U, 1));
code = "void f(bool b) {\n"
" bool x = b || true;\n"
" bool a = x;\n"
"}";
ASSERT_EQUALS(true, testValueOfX(code, 3U, 1));
code = "void f(bool b) {\n"
" bool x = false || b;\n"
" bool a = x;\n"
"}";
ASSERT_EQUALS(false, testValueOfX(code, 3U, 0));
code = "void f(bool b) {\n"
" bool x = b || false;\n"
" bool a = x;\n"
"}";
ASSERT_EQUALS(false, testValueOfX(code, 3U, 0));
// function call => calculation
code = "void f(int x) {\n"
" a = x + 8;\n"