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C++: Fix false positive in PointlessComparison #1236

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Merged
jbj merged 1 commit into from
Apr 11, 2019
Merged

C++: Fix false positive in PointlessComparison #1236

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4 changes: 4 additions & 0 deletions cpp/ql/src/semmle/code/cpp/dataflow/EscapesTree.qll
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Original file line number Diff line number Diff line change
Expand Up @@ -198,6 +198,10 @@ private predicate valueMayEscapeMutablyAt(Expr e) {
or
t instanceof ReferenceType and
not t.(ReferenceType).getBaseType().isConst()
or
// If the address has been cast to an integral type, conservatively assume that it may eventually be cast back to a
// pointer to non-const type.
t instanceof IntegralType
)
}

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22 changes: 22 additions & 0 deletions cpp/ql/test/query-tests/Likely Bugs/Arithmetic/PointlessComparison/PointlessComparison.c
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Original file line number Diff line number Diff line change
Expand Up @@ -342,3 +342,25 @@ int nan2(double x) {
}
}
}

struct info_t {
int id;
unsigned long long value;
};

int command(void* p, unsigned int s);

int callCommand(void)
{
struct info_t info;
unsigned int tmp = 0;

info.id = 1;
info.value = (unsigned long long)& tmp;
if (command(&info, sizeof(info))) {
return 0;
}
if (tmp == 1) // tmp could have been modified by the call.
return 1;
return 0;
}