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feat(unused_var): analyze global variables inside function body (#2944)

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miltolstoy 2020-12-19 09:55:19 +02:00 committed by GitHub
parent 626dcd0eba
commit 6366a577f9
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GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 146 additions and 8 deletions
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24
lib/checkunusedvar.cpp
View File

@ -1609,17 +1609,33 @@ bool CheckUnusedVar::isFunctionWithoutSideEffects(const Function& func, const To
}
bool sideEffectReturnFound = false;
std::set<const Variable*> pointersToGlobals;
for (Token* bodyToken = func.functionScope->bodyStart->next(); bodyToken != func.functionScope->bodyEnd;
bodyToken = bodyToken->next()) {
bodyToken = bodyToken->next())
{
// check variable inside function body
const Variable* bodyVariable = bodyToken->variable();
if (bodyVariable) {
// check variable for side-effects
if (!isVariableWithoutSideEffects(*bodyVariable)) {
return false;
}
// check if global variable is changed
if (bodyVariable->isGlobal()) {
return false; // TODO: analyze global variable usage
if (bodyVariable->isGlobal() || (pointersToGlobals.find(bodyVariable) != pointersToGlobals.end()) ) {
if (bodyVariable->isPointer() || bodyVariable->isArray()) {
return false; // TODO: Update astutils.cpp:1544 isVariableChanged() and remove this. Unhandled case: `*(global_arr + 1) = new_val`
}
const int depth = 20;
if (isVariableChanged(bodyToken, depth, mSettings, mTokenizer->isCPP())) {
return false;
}
// check if pointer to global variable assigned to another variable (another_var = &global_var)
if (Token::simpleMatch(bodyToken->tokAt(-1), "&") && Token::simpleMatch(bodyToken->tokAt(-2), "=")) {
const Token* assigned_var_token = bodyToken->tokAt(-3);
if (assigned_var_token && assigned_var_token->variable())
{
pointersToGlobals.insert(assigned_var_token->variable());
}
}
}
}

128
test/testunusedvar.cpp
View File

@ -615,7 +615,7 @@ private:
"void f() {\n"
" C c;\n"
"}");
TODO_ASSERT_EQUALS("[test.cpp:11]: (style) Unused variable: c\n", "", errout.str());
ASSERT_EQUALS("[test.cpp:11]: (style) Unused variable: c\n", errout.str());
// changing global variable in return
functionVariableUsage(
@ -698,6 +698,23 @@ private:
"}");
ASSERT_EQUALS("", errout.str());
// global variable use in function body without change
functionVariableUsage(
"int global = 1;\n"
"int func() {\n"
" int x = global + 1;\n"
" return x;\n"
"}\n"
"class C {\n"
"public:\n"
" C() : x(func()) {}\n"
" int x;\n"
"};\n"
"void f() {\n"
" C c;\n"
"}");
ASSERT_EQUALS("[test.cpp:12]: (style) Unused variable: c\n", errout.str());
// changing global array variable in function body
functionVariableUsage(
"int x[] = {0, 1, 3};\n"
@ -715,6 +732,38 @@ private:
"}");
ASSERT_EQUALS("", errout.str());
functionVariableUsage(
"int x[] = {0, 1, 3};\n"
"int func() {\n"
" *x = 2;\n"
" return 1;\n"
"}\n"
"class C {\n"
"public:\n"
" C() : x(func()) {}\n"
" int x;\n"
"};\n"
"void f() {\n"
" C c;\n"
"}");
ASSERT_EQUALS("", errout.str());
functionVariableUsage(
"int x[] = {0, 1, 3};\n"
"int func() {\n"
" *(x + 1) = 2;\n"
" return 1;\n"
"}\n"
"class C {\n"
"public:\n"
" C() : x(func()) {}\n"
" int x;\n"
"};\n"
"void f() {\n"
" C c;\n"
"}");
ASSERT_EQUALS("", errout.str());
// changing local variable
functionVariableUsage(
"int func() {\n"
@ -999,11 +1048,30 @@ private:
"}");
ASSERT_EQUALS("", errout.str());
// global struct variable
// global variable assigning to local pointer, but not modifying
functionVariableUsage(
"int global = 1;\n"
"int func() {\n"
" int* p = &global;\n"
" (void) p;\n"
" return 1;\n"
"}\n"
"class C {\n"
"public:\n"
" C() : x(func()) {}\n"
" int x;\n"
"};\n"
"void f() {\n"
" C c;\n"
"}");
// TODO: see TODO for global vars under CheckUnusedVar::isFunctionWithoutSideEffects()
TODO_ASSERT_EQUALS("[test.cpp:13]: (style) Unused variable: c\n", "", errout.str());
// global struct variable modification
functionVariableUsage(
"struct S { int x; } s;\n"
"int func() {\n"
" s.x = 1;;\n"
" s.x = 1;\n"
" return 1;\n"
"}\n"
"class C {\n"
@ -1015,6 +1083,60 @@ private:
" C c;\n"
"}");
ASSERT_EQUALS("", errout.str());
// global struct variable without modification
functionVariableUsage(
"struct S { int x; } s;\n"
"int func() {\n"
" int y = s.x + 1;\n"
" return y;\n"
"}\n"
"class C {\n"
"public:\n"
" C() : x(func()) {}\n"
" int x;\n"
"};\n"
"void f() {\n"
" C c;\n"
"}");
ASSERT_EQUALS("[test.cpp:12]: (style) Unused variable: c\n", errout.str());
// global pointer to struct variable modification
functionVariableUsage(
"struct S { int x; };\n"
"struct S* s = new(struct S);\n"
"int func() {\n"
" s->x = 1;\n"
" return 1;\n"
"}\n"
"class C {\n"
"public:\n"
" C() : x(func()) {}\n"
" int x;\n"
"};\n"
"void f() {\n"
" C c;\n"
"}");
ASSERT_EQUALS("", errout.str());
// global pointer to struct variable without modification
functionVariableUsage(
"struct S { int x; };\n"
"struct S* s = new(struct S);\n"
"int func() {\n"
" int y = s->x + 1;\n"
" return y;\n"
"}\n"
"class C {\n"
"public:\n"
" C() : x(func()) {}\n"
" int x;\n"
"};\n"
"void f() {\n"
" C c;\n"
"}");
// TODO: see TODO for global vars under CheckUnusedVar::isFunctionWithoutSideEffects()
TODO_ASSERT_EQUALS("[test.cpp:13]: (style) Unused variable: c\n", "", errout.str());
}
// #5355 - False positive: Variable is not assigned a value.