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Fix #15023 FN redundantInitialization with braces or parentheses #8846

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Fix #15023 FN redundantInitialization with braces or parentheses #8846

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fe83217
Update checkother.cpp
chrchr-github Sep 11, 2026
2a86e5f
Update testother.cpp
chrchr-github Sep 11, 2026
8234674
Update testother.cpp [skip ci]
chrchr-github Sep 11, 2026
5030611
Update checkother.cpp
chrchr-github Sep 11, 2026
bb8d29c
Update checkother.cpp
chrchr-github Sep 11, 2026
0155858
Merge branch 'main' into chr_15023
chrchr-github Sep 30, 2026
83c0d93
Update checkother.cpp [skip ci]
chrchr-github Sep 30, 2026
74b9be3
Update testother.cpp
chrchr-github Sep 30, 2026
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209 changes: 107 additions & 102 deletions lib/checkother.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -594,6 +594,14 @@ void CheckOtherImpl::invalidPointerCastError(const Token* tok, const std::string
// Detect redundant assignments: x = 0; x = 4;
//---------------------------------------------------------------------------

static bool isAssignmentOrInit(const Token* tok) {
if (tok->astParent() || !tok->astOperand1())
return false;
if (tok->isAssignmentOp() || tok->tokType() == Token::eIncDecOp)
return true;
return Token::Match(tok, "[{(]") && tok->astOperand1()->variable() && tok->astOperand1() == tok->astOperand1()->variable()->nameToken();
}

void CheckOtherImpl::checkRedundantAssignment()
{
if (!mSettings.severity.isEnabled(Severity::style) &&
Expand All @@ -614,122 +622,119 @@ void CheckOtherImpl::checkRedundantAssignment()
if (Token::simpleMatch(tok, "try {"))
// todo: check try blocks
tok = tok->linkAt(1);
if ((tok->isAssignmentOp() || tok->tokType() == Token::eIncDecOp) && tok->astOperand1()) {
if (tok->astParent())
continue;

// Do not warn about redundant initialization when rhs is trivial
// TODO : do not simplify the variable declarations
bool isInitialization = false;
if (Token::Match(tok->tokAt(-2), "; %var% =") && tok->tokAt(-2)->isSplittedVarDeclEq()) {
isInitialization = true;
bool trivial = true;
visitAstNodes(tok->astOperand2(),
[&](const Token *rhs) {
if (Token::simpleMatch(rhs, "{ 0 }"))
return ChildrenToVisit::none;
if (Token::Match(rhs, "%num%|%name%") && !rhs->varId())
return ChildrenToVisit::none;
if (Token::Match(rhs, ":: %name%") && rhs->hasKnownIntValue())
return ChildrenToVisit::none;
if (rhs->isCast())
return rhs->astOperand2() ? ChildrenToVisit::op2 : ChildrenToVisit::op1;
trivial = false;
return ChildrenToVisit::done;
});
if (trivial)
continue;
}

const Token* rhs = tok->astOperand2();
// Do not warn about assignment with 0 / NULL
if ((rhs && MathLib::isNullValue(rhs->str())) || isNullOperand(rhs))
continue;
if (!isAssignmentOrInit(tok))
continue;

if (tok->astOperand1()->variable() && tok->astOperand1()->variable()->isReference())
// todo: check references
// Do not warn about redundant initialization when rhs is trivial
// TODO : do not simplify the variable declarations
bool isInitialization = false;
if ((Token::Match(tok->tokAt(-2), "; %var% =") && tok->tokAt(-2)->isSplittedVarDeclEq()) || Token::Match(tok, "[{(]")) {
isInitialization = true;
bool trivial = true;
visitAstNodes(tok->astOperand2(),
[&](const Token *rhs) {
if (Token::simpleMatch(rhs, "{ 0 }"))
return ChildrenToVisit::none;
if (Token::Match(rhs, "%num%|%name%") && !rhs->varId())
return ChildrenToVisit::none;
if (Token::Match(rhs, ":: %name%") && rhs->hasKnownIntValue())
return ChildrenToVisit::none;
if (rhs->isCast())
return rhs->astOperand2() ? ChildrenToVisit::op2 : ChildrenToVisit::op1;
trivial = false;
return ChildrenToVisit::done;
});
if (trivial)
continue;
}

if (tok->astOperand1()->variable() && tok->astOperand1()->variable()->isStatic())
// todo: check static variables
continue;
const Token* rhs = tok->astOperand2();
// Do not warn about assignment with 0 / NULL
if ((rhs && MathLib::isNullValue(rhs->str())) || isNullOperand(rhs))
continue;

bool inconclusive = false;
if (tok->isCpp() && tok->astOperand1()->valueType()) {
// If there is a custom assignment operator => this is inconclusive
if (tok->astOperand1()->valueType()->typeScope) {
const std::string op = "operator" + tok->str();
const std::list<Function>& fList = tok->astOperand1()->valueType()->typeScope->functionList;
inconclusive = std::any_of(fList.cbegin(), fList.cend(), [&](const Function& f) {
return f.name() == op;
});
}
// assigning a smart pointer has side effects
if (tok->astOperand1()->valueType()->type == ValueType::SMART_POINTER)
break;
}
if (inconclusive && !mSettings.certainty.isEnabled(Certainty::inconclusive))
continue;
if (tok->astOperand1()->variable() && tok->astOperand1()->variable()->isReference())
// todo: check references
continue;

FwdAnalysis fwdAnalysis(mSettings);
if (fwdAnalysis.hasOperand(tok->astOperand2(), tok->astOperand1()))
continue;
if (tok->astOperand1()->variable() && tok->astOperand1()->variable()->isStatic())
// todo: check static variables
continue;

// Is there a redundant assignment?
const Token *start;
if (tok->isAssignmentOp())
start = tok->astOperand2();
else
start = tok->findExpressionStartEndTokens().second->next();
bool inconclusive = false;
if (tok->isCpp() && tok->astOperand1()->valueType()) {
// If there is a custom assignment operator => this is inconclusive
if (tok->astOperand1()->valueType()->typeScope) {
const std::string op = "operator" + tok->str();

@danmar danmar Oct 1, 2026

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This is an AI review. Take it with a grain of salt and feel free to reject it by resolving the comment.

For the new ( / { initialization forms, tok->str() is ( or {, so this looks for operator( / operator{ and the custom-assignment-operator check never triggers. Result with this PR:

int g();
struct A { A(int); A& operator=(int); A& operator=(const A&); };
void f1() { A a(g()); a = 1; }   // redundantInitialization (conclusive)
void f2() { A a = g(); a = 1; }  // redundantInitialization (inconclusive)

I'd expect both to be inconclusive. What matters is the later a = 1, so maybe:

Suggested change
const std::string op = "operator" + tok->str();
const std::string op = isInitialization && Token::Match(tok, "[{(]") ? "operator=" : "operator" + tok->str();

With that, f1 becomes inconclusive like f2, P p{ g(), g() }; p = P{1, 2}; for a plain struct is still reported conclusively, and TestOther passes.

FYI, this PR and #8847 restructure the same block in checkRedundantAssignment(), so whichever is merged second will need a rebase.

@chrchr-github chrchr-github Oct 1, 2026

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  • "operator" + tok->str();should always be "operator="
  • the inconclusive logic is flawed already, there is a conclusive warning for S f() { S s = g(); s = 1; return s; }

const std::list<Function>& fList = tok->astOperand1()->valueType()->typeScope->functionList;
inconclusive = std::any_of(fList.cbegin(), fList.cend(), [&](const Function& f) {
return f.name() == op;
});
}
// assigning a smart pointer has side effects
if (tok->astOperand1()->valueType()->type == ValueType::SMART_POINTER)
break;
}
if (inconclusive && !mSettings.certainty.isEnabled(Certainty::inconclusive))
continue;

const Token * tokenToCheck = tok->astOperand1();
FwdAnalysis fwdAnalysis(mSettings);
if (fwdAnalysis.hasOperand(tok->astOperand2(), tok->astOperand1()))
continue;

// Check if we are working with union
for (const Token* tempToken = tokenToCheck; Token::simpleMatch(tempToken, ".");) {
tempToken = tempToken->astOperand1();
if (tempToken && tempToken->variable() && tempToken->variable()->type() && tempToken->variable()->type()->isUnionType())
tokenToCheck = tempToken;
}
// Is there a redundant assignment?
const Token *start;
if (tok->isAssignmentOp())
start = tok->astOperand2();
else
start = tok->findExpressionStartEndTokens().second->next();
const Token * tokenToCheck = tok->astOperand1();

// Check if we are working with union
for (const Token* tempToken = tokenToCheck; Token::simpleMatch(tempToken, ".");) {
tempToken = tempToken->astOperand1();
if (tempToken && tempToken->variable() && tempToken->variable()->type() && tempToken->variable()->type()->isUnionType())
tokenToCheck = tempToken;
}

if (start->hasKnownSymbolicValue(tokenToCheck) && Token::simpleMatch(start->astParent(), "=") && !diag(tok)) {
const ValueFlow::Value* val = start->getKnownValue(ValueFlow::Value::ValueType::SYMBOLIC);
if (val->intvalue == 0) // no offset
redundantAssignmentSameValueError(tokenToCheck, val, tok->astOperand1()->expressionString());
}
if (start->hasKnownSymbolicValue(tokenToCheck) && Token::simpleMatch(start->astParent(), "=") && !diag(tok)) {
const ValueFlow::Value* val = start->getKnownValue(ValueFlow::Value::ValueType::SYMBOLIC);
if (val->intvalue == 0) // no offset
redundantAssignmentSameValueError(tokenToCheck, val, tok->astOperand1()->expressionString());
}

// Get next assignment..
const Token *nextAssign = fwdAnalysis.reassign(tokenToCheck, start, scope->bodyEnd);
// extra check for union
if (nextAssign && tokenToCheck != tok->astOperand1()) {
nextAssign = fwdAnalysis.reassign(tok->astOperand1(), start, scope->bodyEnd);
// reading another member of the same union in the rhs is a use through aliasing
if (nextAssign && fwdAnalysis.hasOperand(nextAssign->astOperand2(), tokenToCheck))
nextAssign = nullptr;
}
// Get next assignment..
const Token *nextAssign = fwdAnalysis.reassign(tokenToCheck, start, scope->bodyEnd);
// extra check for union
if (nextAssign && tokenToCheck != tok->astOperand1()) {
nextAssign = fwdAnalysis.reassign(tok->astOperand1(), start, scope->bodyEnd);
// reading another member of the same union in the rhs is a use through aliasing
if (nextAssign && fwdAnalysis.hasOperand(nextAssign->astOperand2(), tokenToCheck))
nextAssign = nullptr;
}

if (!nextAssign)
continue;
if (!nextAssign)
continue;

// there is redundant assignment. Is there a case between the assignments?
bool hasCase = false;
for (const Token *tok2 = tok; tok2 != nextAssign; tok2 = tok2->next()) {
if (tok2->str() == "break" || tok2->str() == "return")
break;
if (tok2->str() == "case") {
hasCase = true;
break;
}
// there is redundant assignment. Is there a case between the assignments?
bool hasCase = false;
for (const Token *tok2 = tok; tok2 != nextAssign; tok2 = tok2->next()) {
if (tok2->str() == "break" || tok2->str() == "return")
break;
if (tok2->str() == "case") {
hasCase = true;
break;
}
}

// warn
if (hasCase)
redundantAssignmentInSwitchError(tok, nextAssign, tok->astOperand1()->expressionString());
else if (isInitialization)
redundantInitializationError(tok, nextAssign, tok->astOperand1()->expressionString(), inconclusive);
else {
diag(nextAssign);
redundantAssignmentError(tok, nextAssign, tok->astOperand1()->expressionString(), inconclusive);
}
// warn
if (hasCase)
redundantAssignmentInSwitchError(tok, nextAssign, tok->astOperand1()->expressionString());
else if (isInitialization)
redundantInitializationError(tok, nextAssign, tok->astOperand1()->expressionString(), inconclusive);
else {
diag(nextAssign);
redundantAssignmentError(tok, nextAssign, tok->astOperand1()->expressionString(), inconclusive);
}
}
}
Expand Down
24 changes: 24 additions & 0 deletions test/testother.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -11519,6 +11519,30 @@ class TestOther : public TestFixture {
"[test.cpp:8:8]: style: Redundant initialization for 'i'. The initialized value is overwritten before it is read. [redundantInitialization]\n"
"[test.cpp:7:12]: note: i is initialized\n"
"[test.cpp:8:8]: note: i is overwritten\n", errout_str());

check("int g();\n" // #15023
"int f1() {\n"
" int i{ g() };\n"
" i = 0;\n"
" return i;\n"
"}\n"
"int f2() {\n"
" int i(g());\n"
" i = 0;\n"
" return i;\n"
"}\n"
"int f3() {\n"
" int i{ 1 };\n"
" i = 0;\n"
" return i;\n"
"}\n");
ASSERT_EQUALS("[test.cpp:4:7]: style: Redundant initialization for 'i'. The initialized value is overwritten before it is read. [redundantInitialization]\n"
"[test.cpp:3:10]: note: i is initialized\n"
"[test.cpp:4:7]: note: i is overwritten\n"
"[test.cpp:9:7]: style: Redundant initialization for 'i'. The initialized value is overwritten before it is read. [redundantInitialization]\n"
"[test.cpp:8:10]: note: i is initialized\n"
"[test.cpp:9:7]: note: i is overwritten\n",
errout_str());
}

// cppcheck-suppress unusedPrivateFunction
Expand Down
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