Skip to content

Fix #15034 FN arrayIndexOutOfBounds (ternary in subfunction) #8856

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
chrchr-github wants to merge 7 commits into
base: main
Choose a base branch
from
+23 −18
Open

Fix #15034 FN arrayIndexOutOfBounds (ternary in subfunction) #8856

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
7 commits
Select commit Hold shift + click to select a range
50b9a36
Update valueflow.cpp
chrchr-github Sep 15, 2026
67eb159
Update vf_settokenvalue.cpp
chrchr-github Sep 15, 2026
86f316f
Update testvalueflow.cpp
chrchr-github Sep 15, 2026
55d8250
Update testvalueflow.cpp
chrchr-github Sep 15, 2026
1406a57
Update testsymboldatabase.cpp
chrchr-github Sep 15, 2026
bbd2441
Merge branch 'main' into chr_15034
chrchr-github Oct 1, 2026
72fa075
Merge branch 'main' into chr_15034
chrchr-github Oct 10, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
3 changes: 2 additions & 1 deletion lib/valueflow.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -5164,8 +5164,9 @@ static void valueFlowInferCondition(TokenList& tokenlist, const Settings& settin
setTokenValue(tok, std::move(value), settings);
}
}
} else if (Token::Match(tok->astParent(), "?|&&|!|%oror%") ||
} else if (Token::Match(tok->astParent(), "&&|!|%oror%") ||
Token::Match(tok->astParent()->previous(), "if|while (") ||
(astIsLHS(tok) && Token::simpleMatch(tok->astParent(), "?")) ||
((astIsPointer(tok) || tok->function()) && isUsedAsBool(tok, settings))) {
std::vector<ValueFlow::Value> result = infer(makeIntegralInferModel(), "!=", tok->values(), 0);
if (result.size() != 1)
Expand Down
16 changes: 0 additions & 16 deletions lib/vf_settokenvalue.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -428,22 +428,6 @@ namespace ValueFlow
setTokenValue(parent, std::move(value), settings);
}
} else if (!value.isImpossible()) {

@claude claude Bot Oct 10, 2026

Copy link
Copy Markdown

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Removing the "condition depends on only 1 variable / no function call" guard entirely means any possible value from either branch now goes up to ? whatever the condition is (several variables, function calls, values that carry a varId). That's a lot wider than what #15034 needs, so I'd expect new false positives (nullPointer, arrayIndexOutOfBounds, zerodiv) downstream. The selfcheck suppression added in testsymboldatabase.cpp suggests this has already happened. Could the guard be relaxed just for the case in the ticket, where the branch values come from the same variable that's in the condition, instead of being dropped? Please also add some negative tests, e.g. x ? y : 0 where y has a possible value that's unrelated to x.

// is condition only depending on 1 variable?
nonneg int varId = 0;
bool ret = false;
visitAstNodes(parent->astOperand1(),
[&](const Token *t) {
if (t->varId()) {
if (varId > 0 || value.varId != 0)
ret = true;
varId = t->varId();
} else if (t->str() == "(" && Token::Match(t->previous(), "%name%"))
ret = true; // function call
return ret ? ChildrenToVisit::done : ChildrenToVisit::op1_and_op2;
});
if (ret)
return;

value.conditional = true;
value.changeKnownToPossible();

Expand Down
2 changes: 1 addition & 1 deletion test/testsymboldatabase.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -3633,7 +3633,7 @@ class TestSymbolDatabase : public TestFixture {
ASSERT(fredScope != nullptr);

// The struct Fred has two functions, a constructor and a destructor
ASSERT_EQUALS(2U, fredScope->functionList.size());
ASSERT_EQUALS(2U, fredScope->functionList.size()); // cppcheck-suppress nullPointer // see ticket #9747

@danmar danmar Oct 1, 2026

Copy link
Copy Markdown
Collaborator

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

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

I confirmed that this suppression is needed because of the PR. With selfcheck's options (--check-level=exhaustive --library=cppcheck-lib ...), the merge base gives no warning here, while this PR gives Possible null pointer dereference: fredScope. It is a false positive, since assert_() throws when the condition fails. The cause is that the removed "condition depends on only one variable" guard in setTokenValue() used to drop the nullptr from (it == db->scopeList.end()) ? nullptr : &*it, because the condition contains a function call. So user code with the same "ternary + throwing check" pattern will now also hit #9747.

To get a feel for how often that happens, I compared warnings for the merge base and the PR on lib/, cli/, test/cfg/, samples/, testsymboldatabase.cpp and testvalueflow.cpp (normal check level, style/warning/portability/performance, inconclusive). Both gave exactly the same 2407 warnings, so it doesn't look widespread. Some correlated-ternary probes such as d = (a > b) ? 0 : a - b; if (a > b) return 0; return 10 / d; also stayed silent. Just mentioning it so the trade-off is a conscious one.

@claude claude Bot Oct 10, 2026

Copy link
Copy Markdown

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

This suppression is only needed because of the valueflow change, so selfcheck now reports a new nullPointer false positive (after ASSERT(fredScope != nullptr)). I'd fix the regression rather than suppress it here. Users will hit the same pattern.


// Get linenumbers where the bodies for the constructor and destructor are..
unsigned int constructor = 0;
Expand Down
20 changes: 20 additions & 0 deletions test/testvalueflow.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -4325,6 +4325,26 @@ class TestValueFlow : public TestFixture {
"}\n";
auto values = tokenValues(code, "s :", ValueFlow::Value::ValueType::FLOAT);
ASSERT_EQUALS(0, values.size());

code = "int a[5];\n" // 15034
"int g(int i) {\n"
" return a[i < 0 ? -i : i];\n"
"}\n"
"int f() {\n"
" return g(-5);\n"
"}\n";
values = tokenValues(code, "?");
ASSERT_EQUALS(2, values.size());
auto it = values.begin();
ASSERT_EQUALS_ENUM(ValueFlow::Value::ValueType::INT, it->valueType);
ASSERT_EQUALS(0, it->intvalue);
ASSERT_EQUALS_ENUM(ValueFlow::Value::Bound::Lower, it->bound);
ASSERT_EQUALS_ENUM(ValueFlow::Value::ValueKind::Possible, it->valueKind);
++it;
ASSERT_EQUALS_ENUM(ValueFlow::Value::ValueType::INT, it->valueType);
ASSERT_EQUALS(5, it->intvalue);
ASSERT_EQUALS_ENUM(ValueFlow::Value::Bound::Point, it->bound);
ASSERT_EQUALS_ENUM(ValueFlow::Value::ValueKind::Possible, it->valueKind);

@claude claude Bot Oct 10, 2026

Copy link
Copy Markdown

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

The ticket is about an arrayIndexOutOfBounds false negative, but there's no checker-level test for it. Please add the ticket example to testbufferoverrun.cpp, together with a negative case such as a[i < 0 ? 0 : i] called with g(-5), which must not warn.

}

void valueFlowForwardLambda() {
Expand Down
Loading