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Partial fix for #14911 FN knownConditionTrueFalse for number literals (regression) #8737

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Partial fix for #14911 FN knownConditionTrueFalse for number literals (regression) #8737

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0a03eb2
Partial fix for #14911
web-flow Jul 15, 2026
4b6396f
Merge branch 'main' into chr_14911
chrchr-github Jul 15, 2026
33988e1
Format
web-flow Jul 15, 2026
c0c6402
Update checkcondition.cpp [skip ci]
chrchr-github Jul 16, 2026
0736e65
Update testcondition.cpp
chrchr-github Jul 16, 2026
50cff42
Merge branch 'cppcheck-opensource:main' into chr_14911
chrchr-github Jul 17, 2026
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19 changes: 14 additions & 5 deletions lib/checkcondition.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1575,10 +1575,19 @@ void CheckConditionImpl::alwaysTrueFalse()
continue;
if (Token::simpleMatch(tok->astParent(), "return") && Token::Match(tok, ".|%var%"))
continue;
if (Token::Match(tok, "%num%|%bool%|%char%"))
continue;
if (Token::Match(tok, "! %num%|%bool%|%char%"))
continue;
bool warnForNumber = false;
if (Token::Match(tok, "%num%|%bool%|%char%")) {
const bool isZeroOrOne = (tok->getKnownIntValue() >> 1) == 0;
warnForNumber = !isZeroOrOne && tok->tokType() == Token::eNumber && tok->astParent() == condition->astParent();
if (!warnForNumber)
continue;
}
if (Token::Match(tok, "! %num%|%bool%|%char%")) {
const bool isZeroOrOne = tok->next()->hasKnownIntValue() && (tok->next()->getKnownIntValue() >> 1) == 0;
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chrchr-github marked this conversation as resolved.
warnForNumber = !isZeroOrOne && tok->next()->tokType() == Token::eNumber && tok->astParent() == condition->astParent();
if (!warnForNumber)
continue;
}
if (Token::Match(tok, "%oror%|&&")) {
bool bail = false;
for (const Token* op : { tok->astOperand1(), tok->astOperand2() }) {
Expand All @@ -1603,7 +1612,7 @@ void CheckConditionImpl::alwaysTrueFalse()
true))
continue;

if (!pedantic && isConstVarExpression(tok, [](const Token* tok) {
if (!pedantic && !warnForNumber && isConstVarExpression(tok, [](const Token* tok) {
return Token::Match(tok, "[|(|&|+|-|*|/|%|^|>>|<<") && !Token::simpleMatch(tok, "( )");
}))
continue;
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22 changes: 22 additions & 0 deletions test/testcondition.cpp
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Expand Up @@ -4949,6 +4949,28 @@ class TestCondition : public TestFixture {
" return x ? false : true;\n"
"}\n");
ASSERT_EQUALS("", errout_str());

check("void f() {\n"
" if (42) {}\n"
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" if (42U) {}\n"
" if (42L) {}\n"

@danmar danmar Jul 26, 2026

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Hard to say.. I wonder if there is some intentional code that might trigger false positives. I.e. when macros are used maybe.
Do test-my-pr.py indicate that the new warnings are unintentional mistakes / true positives?

@chrchr-github chrchr-github Jul 27, 2026

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We bail out for any macros:

cppcheck/lib/checkcondition.cpp

Line 1621 in 422e90c

// Don't warn when there are expanded macros..

I ran test-my-pr for 256 packages, no differences with main.

" if (42UL) {}\n"
" if (42LL) {}\n"
" if (042) {}\n"
" if (0x42) {}\n"
" if (0b101010) {}\n"
" if (!42) {}\n"
"}\n");
ASSERT_EQUALS("[test.cpp:2:9]: (style) Condition '42' is always true [knownConditionTrueFalse]\n"
"[test.cpp:3:9]: (style) Condition '42U' is always true [knownConditionTrueFalse]\n"
"[test.cpp:4:9]: (style) Condition '42L' is always true [knownConditionTrueFalse]\n"
"[test.cpp:5:9]: (style) Condition '42UL' is always true [knownConditionTrueFalse]\n"
"[test.cpp:6:9]: (style) Condition '42LL' is always true [knownConditionTrueFalse]\n"
"[test.cpp:7:9]: (style) Condition '042' is always true [knownConditionTrueFalse]\n"
"[test.cpp:8:9]: (style) Condition '0x42' is always true [knownConditionTrueFalse]\n"
"[test.cpp:9:9]: (style) Condition '0b101010' is always true [knownConditionTrueFalse]\n"
"[test.cpp:10:9]: (style) Condition '!42' is always false [knownConditionTrueFalse]\n",
errout_str());
}

void alwaysTrueSymbolic()
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