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Fix #11168 FP returnDanglingLifetime (local iterator points at global struct) #8979

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Fix #11168 FP returnDanglingLifetime (local iterator points at global struct) #8979

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8bf5ae7
Update valueflow.cpp
chrchr-github Oct 29, 2026
cf0a3b9
Update testautovariables.cpp
chrchr-github Oct 29, 2026
b599e41
Fix
web-flow Nov 3, 2026
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16 changes: 14 additions & 2 deletions lib/valueflow.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1473,6 +1473,19 @@ ValueFlow::Value ValueFlow::getLifetimeObjValue(const Token *tok, bool inconclus
return std::move(values.front());
}

static bool checkDotLifetime(const Token* dot, const Token* tok)
{
if (Token::simpleMatch(dot->astOperand1(), "."))
return false;
if (!dot->astOperand2())
return true;
if (dot->astOperand2()->varId() && tok->isUnaryOp("*"))

@dmcppcheck dmcppcheck Nov 3, 2026

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AI review

This breaks for every non-array member with a varId under a unary *, including class-type members whose operator* returns a reference into the member itself. With struct S { std::optional<int> o; };, both int& f() { S s; return *s.o; } and int* g() { S s; return &*s.o; } lose the returnReference and returnDanglingLifetime that base reports. The same happens with a user struct W { int v; int& operator*() { return v; } }; member. Consider breaking only when the member's valueType is a real pointer (pointer > 0 and not an array) or a smart pointer or iterator, and following the lifetime otherwise.

return dot->astOperand2()->variable() && dot->astOperand2()->variable()->isArray();
if (dot->astOperand2()->valueType() && dot->astOperand2()->valueType()->reference != Reference::None)
return false;
return true;
}

template<class Predicate>
static std::vector<ValueFlow::LifetimeToken> getLifetimeTokens(const Token* tok,
bool escape,
Expand Down Expand Up @@ -1585,8 +1598,7 @@ static std::vector<ValueFlow::LifetimeToken> getLifetimeTokens(const Token* tok,
if (vartok->str() == "[" || vartok->isUnaryOp("*"))
vartok = vartok->astOperand1();
else if (vartok->str() == ".") {
if (!Token::simpleMatch(vartok->astOperand1(), ".") &&
!(vartok->astOperand2() && vartok->astOperand2()->valueType() && vartok->astOperand2()->valueType()->reference != Reference::None))
if (checkDotLifetime(vartok, tok))
vartok = vartok->astOperand1();
else
break;
Expand Down
17 changes: 17 additions & 0 deletions test/testautovariables.cpp
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Expand Up @@ -4581,6 +4581,23 @@ class TestAutoVariables : public TestFixture {
ASSERT_EQUALS("[test.cpp:5:11] -> [test.cpp:4:9] -> [test.cpp:5:6]: (error) Non-local variable 'g.a' will use pointer to local variable 'x'. [danglingLifetime]\n"
"[test.cpp:5:11] -> [test.cpp:4:9] -> [test.cpp:6:13]: (error) Returning pointer to local variable 'x' that will be invalid when returning. [returnDanglingLifetime]\n",
errout_str());

check("int* f() {\n" // #11168
" auto x = get();\n"
" return &*x.a;\n"
"}\n");
ASSERT_EQUALS("", errout_str());

check("struct S { int a[1]; };\n"
"int& f(S s) {\n"
" return *s.a;\n"
"}\n"
"int* g(S s) {\n"
" return &*s.a;\n"
"}\n");
ASSERT_EQUALS("[test.cpp:3:12]: (error) Reference to local variable returned. [returnReference]\n"
"[test.cpp:6:12] -> [test.cpp:5:10] -> [test.cpp:6:12]: (error) Returning pointer to local variable 's' that will be invalid when returning. [returnDanglingLifetime]\n",
errout_str());
}

void danglingLifetimeClassMemberFunctions()
Expand Down
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