[LLVMbugs] [Bug 13323] New: False positive: "Assigned value is garbage or undefined"

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=13323

             Bug #: 13323
           Summary: False positive: "Assigned value is garbage or
                    undefined"
           Product: clang
           Version: 3.0
          Platform: Macintosh
        OS/Version: MacOS X
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: -New Bugs
        AssignedTo: unassignedclangbugs at nondot.org
        ReportedBy: adarpodracir at gmail.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified


Created attachment 8872
  --> http://llvm.org/bugs/attachment.cgi?id=8872
A picture showing false positive

Hi there,

The bug I am reporting here has to do with Clang logic error: "Assigned value
is
garbage or undefined". This bug can be reproduced by analyzing the following C
code and using Xcode 4 (more precisely 4.3.3). A picture showing its complains
is also given at this link:

http://i50.tinypic.com/1pxlcj.png

Alternatively, this picture can be found attached.


---------------------------------------------------------------------
#include <stdio.h>
#include <stdlib.h>
#include <math.h>

typedef struct XYPoint_type {
    double x;
    double y;
} XYPoint_t;

XYPoint_t getXYRotPoint(XYPoint_t xyPoint, double theta);
void slicePolygon(XYPoint_t * xyVertex, int numEdges, double a0, double a1);


XYPoint_t getXYRotPoint(XYPoint_t xyPoint, double theta)
{
    XYPoint_t xyRotPoint;

    xyRotPoint.x=xyPoint.x*cos(theta)+xyPoint.y*sin(theta);
    xyRotPoint.y=xyPoint.y*cos(theta)-xyPoint.x*sin(theta);

    return xyRotPoint;
}


void slicePolygon(XYPoint_t * xyVertex, const int numEdges, double a0, double
a1)
{
    int i=0;

    if (xyVertex[0].x!=xyVertex[numEdges].x ||
xyVertex[0].y!=xyVertex[numEdges].y)
    {
        fprintf(stderr, "Miscellaneous.c::slicePolygon::Error: Polygon is not
closed.");
        exit(EXIT_FAILURE);
    }

    const int numVertices=numEdges+1;
    double theta=atan(a1);
    //double a=a0*cos(theta);
    double array[numEdges];

    XYPoint_t xyRotVertex[numVertices];

    if (theta==0)
        for (i=0; i<numVertices; i++)
            xyRotVertex[i]=xyVertex[i];
    else
        for (i=0; i<numVertices; i++)
            xyRotVertex[i]=getXYRotPoint(xyVertex[i], theta);

    // Printing xyRotVertex[%i]:
    for (i=0; i<numVertices; i++)
        printf("xyRotVertex[%i]: (%.5f, %.5f)\n", i, xyRotVertex[i].x,
xyRotVertex[i].y);

    for (i=0; i<numEdges; i++)
        array[i]=xyRotVertex[i].x;

    // Printing array[%i]:
    for (i=0; i<numEdges; i++)
        printf("array[%i]: %.5f\n", i, array[i]);

    // ....
}


int main(void)
{
    int numEdges=5;
    int numVertices=numEdges+1;

    XYPoint_t xyVertex[numVertices];

    xyVertex[0].x=0;
    xyVertex[0].y=0;

    xyVertex[1].x=8.228994;
    xyVertex[1].y=0;

    xyVertex[2].x=10.771892;
    xyVertex[2].y=7.826238;

    xyVertex[3].x=4.114497;
    xyVertex[3].y=12.663119;

    xyVertex[4].x=-2.542899;
    xyVertex[4].y=7.826238;

    xyVertex[5].x=xyVertex[0].x;
    xyVertex[5].y=xyVertex[0].y;

    slicePolygon(xyVertex, numEdges, 3.913119, 0);
}

---------------------------------------------------------------------


Thank you very much.

Ricardo.

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