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Fix #13522 FP knownConditionTrueFalse after unsigned-to-signed conversion #7179

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Fix #13522 FP knownConditionTrueFalse after unsigned-to-signed conversion #7179

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2 changes: 2 additions & 0 deletions lib/vf_analyzers.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -527,6 +527,8 @@ struct ValueFlowAnalyzer : Analyzer {
continue;
if (exact && v.intvalue != 0 && !isPoint)
continue;
if (astIsUnsigned(tok) != astIsUnsigned(v.tokvalue))
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This is fine, it is a little too restrictive which could lead to FNs, but it will fix FPs. To fix FNs, we would need to check if the value is within the range of an unsigned value. I am not sure how to write a test case to demonstrate it though as most known values will be passed through with the afterAssign passes anyways. Need to think about it some more.

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@chrchr-github chrchr-github Jan 7, 2025 •
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👍 We could also wait until after the next release, so we can see the effects in daca.

continue;
std::vector<MathLib::bigint> r;
ValueFlow::Value::Bound bound = currValue->bound;
if (match(v.tokvalue)) {
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7 changes: 7 additions & 0 deletions test/testcondition.cpp
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Expand Up @@ -4947,6 +4947,13 @@ class TestCondition : public TestFixture {
" }\n"
"}\n");
ASSERT_EQUALS("", errout_str());

check("void f(unsigned x) {\n" // #13522
" unsigned u = x;\n"
" int i = u - 0;\n"
" if (i < 0) {}\n"
"}\n");
ASSERT_EQUALS("", errout_str());
}

void alwaysTrueInfer() {
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