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Add new "style" check to catch redundant pointer operations 

Doing "&*some_ptr_var" is redundant and might be the remainder
of a refactoring. Warnings for expanded macros are excluded though:
They are often used with and without pointers and
do something like this: "func(&(*macroarg))".

The new check is fully AST based and was given
strong false positive testing on a large code base.
This commit is contained in:
Thomas Jarosch 2015-01-17 14:33:14 +01:00
parent 2bcd675653
commit 58cb6cc116
3 changed files with 112 additions and 2 deletions
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37
lib/checkother.cpp
View File

@ -2853,3 +2853,40 @@ void CheckOther::ignoredReturnValueError(const Token* tok, const std::string& fu
reportError(tok, Severity::warning, "ignoredReturnValue",
"Return value of function " + function + "() is not used.", false);
}
void CheckOther::checkRedundantPointerOp()
{
if (!_settings->isEnabled("style"))
return;
const SymbolDatabase *symbolDatabase = _tokenizer->getSymbolDatabase();
for (const Token *tok = _tokenizer->tokens(); tok; tok = tok->next()) {
if (tok->str() == "&") {
// bail out for logical AND operator
if (tok->astOperand2())
continue;
// pointer dereference
const Token *astTok = tok->astOperand1();
if (!astTok || astTok->str() != "*")
continue;
// variable
const Token *varTok = astTok->astOperand1();
if (!varTok || varTok->isExpandedMacro() || varTok->varId() == 0)
continue;
const Variable *var = symbolDatabase->getVariableFromVarId(varTok->varId());
if (!var || !var->isPointer())
continue;
redundantPointerOpError(tok, var->name(), false);
}
}
}
void CheckOther::redundantPointerOpError(const Token* tok, const std::string &varname, bool inconclusive)
{
reportError(tok, Severity::style, "redundantPointerOp",
"Redundant pointer operation on " + varname + " - it's already a pointer.", inconclusive);
}

9
lib/checkother.h
View File

@ -74,6 +74,7 @@ public:
checkOther.checkNanInArithmeticExpression();
checkOther.checkCommaSeparatedReturn();
checkOther.checkIgnoredReturnValue();
checkOther.checkRedundantPointerOp();
}
/** @brief Run checks against the simplified token list */
@ -233,6 +234,9 @@ public:
/** @brief %Check for ignored return values. */
void checkIgnoredReturnValue();
/** @brief %Check for redundant pointer operations */
void checkRedundantPointerOp();
private:
// Error messages..
void checkComparisonFunctionIsAlwaysTrueOrFalseError(const Token* tok, const std::string &strFunctionName, const std::string &varName, const bool result);
@ -288,6 +292,7 @@ private:
void varFuncNullUBError(const Token *tok);
void commaSeparatedReturnError(const Token *tok);
void ignoredReturnValueError(const Token* tok, const std::string& function);
void redundantPointerOpError(const Token* tok, const std::string& varname, bool inconclusive);
void getErrorMessages(ErrorLogger *errorLogger, const Settings *settings) const {
CheckOther c(0, settings, errorLogger);
@ -345,6 +350,7 @@ private:
c.nanInArithmeticExpressionError(0);
c.commaSeparatedReturnError(0);
c.ignoredReturnValueError(0, "malloc");
c.redundantPointerOpError(0, "varname", false);
}
static std::string myName() {
@ -402,7 +408,8 @@ private:
"- NaN (not a number) value used in arithmetic expression.\n"
"- comma in return statement (the comma can easily be misread as a semicolon).\n"
"- prefer erfc, expm1 or log1p to avoid loss of precision.\n"
"- identical code in both branches of if/else or ternary operator.\n";
"- identical code in both branches of if/else or ternary operator.\n"
"- redundant pointer operation on pointer like &*some_ptr.\n";
}
};
/// @}

68
test/testother.cpp
View File

@ -176,9 +176,11 @@ private:
TEST_CASE(testReturnIgnoredReturnValue);
TEST_CASE(testReturnIgnoredReturnValuePosix);
TEST_CASE(redundantPointerOp);
}
void check(const char code[], const char *filename = nullptr, bool experimental = false, bool inconclusive = true, bool posix = false, bool runSimpleChecks=true, Settings* settings = 0) {
void check(const char raw_code[], const char *filename = nullptr, bool experimental = false, bool inconclusive = true, bool posix = false, bool runSimpleChecks=true, Settings* settings = 0) {
// Clear the error buffer..
errout.str("");
@ -197,6 +199,14 @@ private:
settings->experimental = experimental;
settings->standards.posix = posix;
// Preprocess file..
Preprocessor preprocessor(settings);
std::list<std::string> configurations;
std::string filedata = "";
std::istringstream fin(raw_code);
preprocessor.preprocess(fin, filedata, configurations, "", settings->_includePaths);
const std::string code = preprocessor.getcode(filedata, "", "");
// Tokenize..
Tokenizer tokenizer(settings, this);
std::istringstream istr(code);
@ -6455,6 +6465,62 @@ private:
);
ASSERT_EQUALS("[test.cpp:3]: (warning) Return value of function mmap() is not used.\n", errout.str());
}
void redundantPointerOp() {
check("int *f(int *x) {\n"
" return &*x;\n"
"}\n", nullptr, false, true);
ASSERT_EQUALS("[test.cpp:2]: (style) Redundant pointer operation on x - it's already a pointer.\n", errout.str());
check("int *f(int *y) {\n"
" return &(*y);\n"
"}\n", nullptr, false, true);
ASSERT_EQUALS("[test.cpp:2]: (style) Redundant pointer operation on y - it's already a pointer.\n", errout.str());
// no warning for bitwise AND
check("void f(int *b) {\n"
" int x = 0x20 & *b;\n"
"}\n", nullptr, false, true);
ASSERT_EQUALS("", errout.str());
// No message for double pointers to structs
check("void f(struct foo **my_struct) {\n"
" char **pass_to_func = &(*my_struct)->buf;\n"
"}\n", nullptr, false, true);
ASSERT_EQUALS("", errout.str());
// another double pointer to struct - with an array
check("void f(struct foo **my_struct) {\n"
" char **pass_to_func = &(*my_struct)->buf[10];\n"
"}\n", nullptr, false, true);
ASSERT_EQUALS("", errout.str());
// double pointer to array
check("void f(char **ptr) {\n"
" int *x = &(*ptr)[10];\n"
"}\n", nullptr, false, true);
ASSERT_EQUALS("", errout.str());
// function calls
check("void f(Mutex *mut) {\n"
" pthread_mutex_lock(&*mut);\n"
"}\n", nullptr, false, false);
ASSERT_EQUALS("[test.cpp:2]: (style) Redundant pointer operation on mut - it's already a pointer.\n", errout.str());
// make sure we got the AST match for "(" right
check("void f(char *ptr) {\n"
" if (&*ptr == NULL)\n"
" return;\n"
"}\n", nullptr, false, true);
ASSERT_EQUALS("[test.cpp:2]: (style) Redundant pointer operation on ptr - it's already a pointer.\n", errout.str());
// no warning for macros
check("#define MUTEX_LOCK(m) pthread_mutex_lock(&(m))\n"
"void f(struct mutex *mut) {\n"
" MUTEX_LOCK(*mut);\n"
"}\n", nullptr, false, true);
ASSERT_EQUALS("", errout.str());
}
};
REGISTER_TEST(TestOther)