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Fix #8192: FN condition always false in for loop condition #8446

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Fix #8192: FN condition always false in for loop condition #8446

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60 changes: 42 additions & 18 deletions lib/valueflow.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -5180,8 +5180,21 @@ static bool valueFlowForLoop2(const Token *tok,
if (error)
return false;
execute(secondExpression, programMemory, &result, &error, settings);
if (result == 0) // 2nd expression is false => no looping
if (result == 0) {
if (!error) { // 2nd expression is definitely false => no looping
ProgramMemory startMemory(programMemory);
ProgramMemory endMemory(programMemory);

if (memory1)
memory1->swap(startMemory);
if (memory2)
memory2->swap(endMemory);
if (memoryAfter)
memoryAfter->swap(programMemory);
return true;
}
return false;
}
if (error) {
// If a variable is reassigned in second expression, return false
bool reassign = false;
Expand Down Expand Up @@ -5390,23 +5403,34 @@ static void valueFlowForLoop(const TokenList &tokenlist, const SymbolDatabase& s
} else {
ProgramMemory mem1, mem2, memAfter;
if (valueFlowForLoop2(tok, &mem1, &mem2, &memAfter, settings)) {
for (const auto& p : mem1) {
if (!p.second.isIntValue())
continue;
if (p.second.isImpossible())
continue;
if (p.first.tok->varId() == 0)
continue;
valueFlowForLoopSimplify(bodyStart, p.first.tok, false, p.second.intvalue, tokenlist, errorLogger, settings);
}
for (const auto& p : mem2) {
if (!p.second.isIntValue())
continue;
if (p.second.isImpossible())
continue;
if (p.first.tok->varId() == 0)
continue;
valueFlowForLoopSimplify(bodyStart, p.first.tok, false, p.second.intvalue, tokenlist, errorLogger, settings);
if (mem1 == memAfter) { // #8192 check if loop never runs
Token* condTok = getCondTok(tok);
if (condTok && !condTok->hasKnownIntValue()) {
ValueFlow::Value v(0);
v.setKnown();
ValueFlow::setTokenValue(condTok, std::move(v), settings);
}
} else {
for (const auto& p : mem1) {
if (!p.second.isIntValue())
continue;
if (p.second.isImpossible())
continue;
if (p.first.tok->varId() == 0)
continue;

valueFlowForLoopSimplify(bodyStart, p.first.tok, false, p.second.intvalue, tokenlist, errorLogger, settings);
}
for (const auto& p : mem2) {
if (!p.second.isIntValue())
continue;
if (p.second.isImpossible())
continue;
if (p.first.tok->varId() == 0)
continue;

valueFlowForLoopSimplify(bodyStart, p.first.tok, false, p.second.intvalue, tokenlist, errorLogger, settings);
}
}
for (const auto& p : memAfter) {
if (!p.second.isIntValue())
Expand Down
2 changes: 1 addition & 1 deletion test/testcondition.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -5581,7 +5581,7 @@ class TestCondition : public TestFixture {
check("void f() {\n" // #8192
" for (int i = 0; i > 10; ++i) {}\n"
"}\n");
TODO_ASSERT_EQUALS("[test.cpp:2]: (style) Condition 'i>10' is always false\n", "", errout_str());
ASSERT_EQUALS("[test.cpp:2:23]: (style) Condition 'i>10' is always false [knownConditionTrueFalse]\n", errout_str());

check("void f() {\n"
" for (int i = 1000; i < 20; ++i) {}\n"
Expand Down
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