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Fix #11125 FP unreadVariable with loop over array #8357

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Fix #11125 FP unreadVariable with loop over array #8357

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ad068da
Update testunusedvar.cpp
chrchr-github Mar 20, 2026
e6476f2
Update fwdanalysis.cpp
chrchr-github Mar 20, 2026
c62e7d6
Update fwdanalysis.cpp
chrchr-github Mar 20, 2026
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12 changes: 11 additions & 1 deletion lib/fwdanalysis.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -410,6 +410,16 @@ FwdAnalysis::Result FwdAnalysis::checkRecursive(const Token *expr, const Token *
return Result(Result::Type::NONE);
}

static bool isSimpleIndexExpression(const Token* tok)
{
const Token* idx = tok->astOperand2();
if (!idx)
return false;
if (idx->isIncDecOp())
idx = idx->astOperand1();
return idx->variable() && idx->variable()->scope() == tok->scope();
}

std::set<nonneg int> FwdAnalysis::getExprVarIds(const Token* expr, bool* localOut, bool* unknownVarIdOut) const
{
// all variable ids in expr.
Expand All @@ -418,7 +428,7 @@ std::set<nonneg int> FwdAnalysis::getExprVarIds(const Token* expr, bool* localOu
bool unknownVarId = false;
visitAstNodes(expr,
[&](const Token *tok) {
if (tok->str() == "[" && mWhat == What::UnusedValue)
if (tok->str() == "[" && mWhat == What::UnusedValue && isSimpleIndexExpression(tok))
return ChildrenToVisit::op1;
if (tok->varId() == 0 && tok->isName() && tok->strAt(-1) != ".") {
// unknown variable
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16 changes: 16 additions & 0 deletions test/testunusedvar.cpp
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Expand Up @@ -5813,6 +5813,22 @@ class TestUnusedVar : public TestFixture {
" {}\n"
"}");
ASSERT_EQUALS("", errout_str());

functionVariableUsage("void f(const int* b, int x) {\n" // #11125
" int a[6];\n"
" int i = 0;\n"
" for (int j = 0; j < 6; ++j) {\n"
" if (b[j] != 0) {\n"
" a[i] = j;\n"
" ++i;\n"
" }\n"
" }\n"
" if (i > 1) {\n"
" a[i] = a[0];\n"
" (void)a[x];\n"
" }\n"
"}\n");
ASSERT_EQUALS("", errout_str());
}

void localvarForEach() { // #4155 - foreach
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