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Cpp: new experimental query cpp/guarded-free #16331

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Merged
MathiasVP merged 4 commits into from
May 1, 2024
+55 −0
Merged

Cpp: new experimental query cpp/guarded-free #16331

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d7c784e
Initial commit of experimental query cpp/guarded-free.
mario-campos Apr 25, 2024
3195f0c
Use more specific `hasGlobalName()` for stdlib function free(3)
mario-campos Apr 26, 2024
c480431
C++: simplify cpp/guarded-free
mario-campos May 1, 2024
5a7a1dc
C++: forgot to import semmle.code.cpp.controlflow.Guards
mario-campos May 1, 2024
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C++: simplify cpp/guarded-free 
This new form is more declarative by use of the `GuardCondition`. Thanks to the tireless effort of @MathiasVP!
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@mario-campos
mario-campos committed May 1, 2024
commit c480431ec0aa5f67fcb472b8a58430f012090795
33 changes: 5 additions & 28 deletions cpp/ql/src/experimental/Best Practices/GuardedFree.ql
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Original file line number Diff line number Diff line change
Expand Up @@ -17,32 +17,9 @@ class FreeCall extends FunctionCall {
FreeCall() { this.getTarget().hasGlobalName("free") }
}

from IfStmt stmt, FreeCall fc, Variable v
from GuardCondition gc, FreeCall fc, Variable v, BasicBlock bb
where
stmt.getThen() = fc.getEnclosingStmt() and
(
stmt.getCondition() = v.getAnAccess() and
fc.getArgument(0) = v.getAnAccess()
or
exists(PointerDereferenceExpr cond, PointerDereferenceExpr arg |
fc.getArgument(0) = arg and
stmt.getCondition() = cond and
cond.getOperand+() = v.getAnAccess() and
arg.getOperand+() = v.getAnAccess()
)
or
exists(ArrayExpr cond, ArrayExpr arg |
fc.getArgument(0) = arg and
stmt.getCondition() = cond and
cond.getArrayBase+() = v.getAnAccess() and
arg.getArrayBase+() = v.getAnAccess()
)
or
exists(NEExpr eq |
fc.getArgument(0) = v.getAnAccess() and
stmt.getCondition() = eq and
eq.getAnOperand() = v.getAnAccess() and
eq.getAnOperand().getValue() = "0"
)
)
select stmt, "unnecessary NULL check before call to $@", fc, "free"
gc.ensuresEq(v.getAnAccess(), 0, bb, false) and
fc.getArgument(0) = v.getAnAccess() and
bb = fc.getEnclosingStmt()
select gc, "unnecessary NULL check before call to $@", fc, "free"