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New check: Comparision of modulo results that are always true/false.

This commit is contained in:
PKEuS 2012-04-26 15:23:47 +02:00
parent 2a2d76749e
commit 5ac7552e4e
3 changed files with 61 additions and 0 deletions
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18
lib/checkother.cpp
View File

@ -3151,6 +3151,24 @@ void CheckOther::alwaysTrueStringVariableCompareError(const Token *tok, const st
"This could be a logic bug.");
}
//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------
void CheckOther::checkModuloAlwaysTrueFalse()
{
for (const Token* tok = _tokenizer->tokens(); tok; tok = tok->next()) {
if (Token::Match(tok, "% %num% ==|!=|<=|<|>|>= %num%") && (!tok->tokAt(4) || !tok->tokAt(4)->isArithmeticalOp())) {
if (MathLib::isLessEqual(tok->strAt(1), tok->strAt(3)))
moduloAlwaysTrueFalseError(tok, tok->strAt(1));
}
}
}
void CheckOther::moduloAlwaysTrueFalseError(const Token* tok, const std::string& maxVal)
{
reportError(tok, Severity::warning, "moduloAlwaysTrueFalse",
"Comparision of modulo result is predetermined, because it is always less than " + maxVal + ".");
}
//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------
void CheckOther::sizeofsizeof()

7
lib/checkother.h
View File

@ -100,6 +100,7 @@ public:
checkOther.checkComparisonOfBoolWithInt();
checkOther.checkSwitchCaseFallThrough();
checkOther.checkAlwaysTrueOrFalseStringCompare();
checkOther.checkModuloAlwaysTrueFalse();
checkOther.checkAssignBoolToPointer();
checkOther.checkBitwiseOnBoolean();
@ -225,6 +226,9 @@ public:
/** @brief %Check for suspicious code that compares string literals for equality */
void checkAlwaysTrueOrFalseStringCompare();
/** @brief %Check for suspicious usage of modulo (e.g. "if(var % 4 == 4)") */
void checkModuloAlwaysTrueFalse();
/** @brief %Check for code that gets never executed, such as duplicate break statements */
void checkUnreachableCode();
@ -310,6 +314,7 @@ private:
void SuspiciousSemicolonError(const Token *tok);
void doubleFreeError(const Token *tok, const std::string &varname);
void doubleCloseDirError(const Token *tok, const std::string &varname);
void moduloAlwaysTrueFalseError(const Token* tok, const std::string& maxVal);
void getErrorMessages(ErrorLogger *errorLogger, const Settings *settings) const {
CheckOther c(0, settings, errorLogger);
@ -374,6 +379,7 @@ private:
c.invalidPrintfArgTypeError_int(0, 1, 'u');
c.invalidPrintfArgTypeError_float(0, 1, 'f');
c.cctypefunctionCallError(0, "funname", "value");
c.moduloAlwaysTrueFalseError(0, "1");
}
std::string myName() const {
@ -431,6 +437,7 @@ private:
"* using bool in bitwise expression\n"
"* Suspicious use of ; at the end of 'if/for/while' statement.\n"
"* incorrect usage of functions from ctype library.\n"
"* Comparisions of modulo results that are always true/false.\n"
// optimisations
"* optimisation: detect post increment/decrement\n";

36
test/testother.cpp
View File

@ -112,6 +112,8 @@ private:
TEST_CASE(assignmentInAssert);
TEST_CASE(modulo);
TEST_CASE(incorrectLogicOperator1);
TEST_CASE(incorrectLogicOperator2);
TEST_CASE(incorrectLogicOperator3);
@ -2649,6 +2651,40 @@ private:
ASSERT_EQUALS("[test.cpp:3]: (warning) Assert statement modifies 'a'.\n", errout.str());
}
void modulo() {
check("bool f(bool& b1, bool& b2, bool& b3) {\n"
" b1 = a % 5 == 4;\n"
" b2 = a % c == 100000;\n"
" b3 = a % 5 == c;\n"
" return a % 5 == 5-p;\n"
"}");
ASSERT_EQUALS("", errout.str());
check("bool f(bool& b1, bool& b2, bool& b3, bool& b4, bool& b5) {\n"
" b1 = a % 5 < 5;\n"
" b2 = a % 5 <= 5;\n"
" b3 = a % 5 == 5;\n"
" b4 = a % 5 != 5;\n"
" b5 = a % 5 >= 5;\n"
" return a % 5 > 5;\n"
"}");
ASSERT_EQUALS("[test.cpp:2]: (warning) Comparision of modulo result is predetermined, because it is always less than 5.\n"
"[test.cpp:3]: (warning) Comparision of modulo result is predetermined, because it is always less than 5.\n"
"[test.cpp:4]: (warning) Comparision of modulo result is predetermined, because it is always less than 5.\n"
"[test.cpp:5]: (warning) Comparision of modulo result is predetermined, because it is always less than 5.\n"
"[test.cpp:6]: (warning) Comparision of modulo result is predetermined, because it is always less than 5.\n"
"[test.cpp:7]: (warning) Comparision of modulo result is predetermined, because it is always less than 5.\n", errout.str());
check("void f(bool& b1, bool& b2) {\n"
" b1 = bar() % 5 < 889;\n"
" if(x[593] % 5 <= 5)\n"
" b2 = x.a % 5 == 5;\n"
"}");
ASSERT_EQUALS("[test.cpp:2]: (warning) Comparision of modulo result is predetermined, because it is always less than 5.\n"
"[test.cpp:3]: (warning) Comparision of modulo result is predetermined, because it is always less than 5.\n"
"[test.cpp:4]: (warning) Comparision of modulo result is predetermined, because it is always less than 5.\n", errout.str());
}
void incorrectLogicOperator1() {
check("void f(int x) {\n"
" if ((x != 1) || (x != 3))\n"