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Fix #15116 FP stlFindInsert (modifying existing element) #8968

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Fix #15116 FP stlFindInsert (modifying existing element) #8968

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2a0a90c
Update checkstl.cpp
chrchr-github Oct 27, 2026
07dd101
Update teststl.cpp
chrchr-github Oct 27, 2026
758d6dc
Update checkstl.cpp
chrchr-github Oct 27, 2026
6d288e6
Update checkstl.cpp
chrchr-github Oct 27, 2026
99b5261
Update checkstl.cpp
chrchr-github Oct 27, 2026
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4 changes: 4 additions & 0 deletions lib/checkstl.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1636,6 +1636,10 @@ static std::pair<const Token *, const Token *> isMapFind(const Token *tok)
return {};
if (!tok->astOperand2())
return {};
if (!Token::simpleMatch(tok->astParent(), "=="))

@dmcppcheck dmcppcheck Oct 28, 2026

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AI review

Requiring == is too narrow for count(), because the operator alone does not say whether the condition means "key absent". if (s.count(x) != 1) s.insert(x); on a std::set, and if (m.count(x) < 1) m[x] = 1;, both mean "absent". Base reported stlFindInsert for both, and with this PR neither warns: lost true positives.

The fix should check the meaning of the comparison: absent means == 0, != 1 (for a set), < 1 or <= 0. It should not filter on == only. A test for one of these cases would help too.

return {};
if (tok->astOperand1()->strAt(1) == "count" && (!tok->astParent()->astOperand2()->hasKnownIntValue() || tok->astParent()->astOperand2()->getKnownIntValue() != 0))
return {};
return {contTok, tok->astOperand2()};
}

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11 changes: 11 additions & 0 deletions test/teststl.cpp
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Expand Up @@ -7424,6 +7424,17 @@ class TestStl : public TestFixture {
dinit(CheckOptions, $.inconclusive = true));
ASSERT_EQUALS("", errout_str());

check("void f(std::map<int, bool>& m) {\n" // #15116
" if (m.count(1) != 0)\n"
" m[1] = true;\n"
"}\n"
"void g(std::map<int, bool>& m) {\n"
" if (m.count(1) == 1)\n"
" m[1] = true;\n"
"}\n",
dinit(CheckOptions, $.inconclusive = true));
ASSERT_EQUALS("", errout_str()); // TODO: warn about duplicate search

@pfultz2 pfultz2 Oct 28, 2026

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Why are we removing the warning here? We should just update the warning message.

@chrchr-github chrchr-github Oct 28, 2026

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Feel free to add the logic necessary to generate a fitting error message in this case. The condition handling also needs tweaking, see https://trac.cppcheck.net/ticket/15146

@pfultz2 pfultz2 Oct 28, 2026

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I update the logic for the error message in #8975.


// #9218 - not small type => do not warn if cpp standard is < c++17
{
Settings s = settings;
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