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C++: Cleanup ScanfChecks.qll #20400

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Merged
MathiasVP merged 2 commits into from
Sep 10, 2025
Merged

C++: Cleanup ScanfChecks.qll #20400

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d097946
C++: No need for this additional case.
MathiasVP Sep 10, 2025
72d7223
C++: Small drive by cleanup. Delete unnecessary nested 'exists'.
MathiasVP Sep 10, 2025
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10 changes: 3 additions & 7 deletions cpp/ql/src/Critical/ScanfChecks.qll
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Original file line number Diff line number Diff line change
Expand Up @@ -4,13 +4,9 @@ private import semmle.code.cpp.controlflow.IRGuards
private import semmle.code.cpp.ir.ValueNumbering

private predicate exprInBooleanContext(Expr e) {
exists(IRGuardCondition gc |
exists(Instruction i |
i.getUnconvertedResultExpression() = e and
gc.comparesEq(valueNumber(i).getAUse(), 0, _, _)
)
or
gc.getUnconvertedResultExpression() = e
Comment on lines -12 to -13
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@jketema jketema Sep 10, 2025

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Why can this be removed?

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@MathiasVP MathiasVP Sep 10, 2025

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Oh, yes. Sorry I should have made that clear.

This is a left-over from back when we didn't have guard conditions for unary conditions. When we only had the binary guard conditions we did not have a guard condition logic for stuff like if(x) { } and if(!x) { }. So the workaround was to check whether the guard condition was equal to the expression.

I switched the ScanfChecks library to use the unary guard condition predicate in decede5, but I forgot to delete this disjunct.

exists(IRGuardCondition gc, Instruction i |
i.getUnconvertedResultExpression() = e and
gc.comparesEq(valueNumber(i).getAUse(), 0, _, _)
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)
}

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