fix the condition of SVFIR::isValidPointer

[sinotca529]

Fix the issue #1002

[yuleisui]

It looks this will affect quite a few other cases. Would be good to dig it a bit or make it just for DDA.

[sinotca529]

Observation of errors in the regression test and testing with a hand-made code revealed that errors occur when passing string literals to puts/printf.

This is the hand-made code that causes an error:

#include <stdio.h>
int main(void) {
    puts("foo");
    return 0;
}

The error occured when SVF tries to analyze the 0th arg of puts.
Because puts is a declaration and SVFIRBuilder::handleExtCall does not make call edges from actual parameters to formal parameters, the 0th arg of puts has no incoming edges and no outcoming edges.
So, it satisfies SVFIR::isValidPointer wrongly.

To avoid this exception, I updated the condition of SVFIR::isValidPointer as:

/*
 * If this is a dummy node or node does not have incoming edges and outcoming edges we assume it is not a pointer here.
 * However, if it is a pointer and it is an argument of a function definition, we assume it is a pointer here.
 */
bool SVFIR::isValidPointer(NodeID nodeId) const
{
    SVFVar* node = pag->getGNode(nodeId);

    if (node->hasValue() && node->isPointer())
    {
        if(const SVFArgument* arg = SVFUtil::dyn_cast<SVFArgument>(node->getValue()))
        {
            if (!(arg->getParent()->isDeclaration()))
                return true;
        }
    }

    if ((node->getInEdges().empty() && node->getOutEdges().empty()))
        return false;
    return node->isPointer();
}

[codecov]

Codecov Report

Merging #1003 (1046275) into master (17193ff) will increase coverage by 0.00%.
The diff coverage is 100.00%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1003   +/-   ##
=======================================
  Coverage   63.71%   63.71%           
=======================================
  Files         219      219           
  Lines       22020    22023    +3     
=======================================
+ Hits        14030    14033    +3     
  Misses       7990     7990           

Impacted Files	Coverage Δ
svf/lib/SVFIR/SVFIR.cpp	79.56% <100.00%> (+0.22%)	⬆️