| Can anyone shed any light on why this code doesn't run as expected?
struct vector3D { double x, y, z;
vector3D() { } vector3D(double inX, double inY, double inZ) { x = inX; y = inY; z=inZ; } vector3D& operator += (const vector3D &n) { x += n.x; y += n.y; z += n.z; return *this; } vector3D& operator + (const vector3D &n) const { return vector3D(*this) += n; } vector3D& operator *= (double n) { x *= n; y *= n; z *= n; return *this; } vector3D& operator * (double n) const { return vector3D(*this) *= n; } vector3D operator = (const vector3D &n) { x = n.x; y = n.y; z = n.z; return *this; } void Print(void) const { printf("(%lg, %lg, %lg)", x, y, z); } };
void do_test(void) { vector3D rayPos(0, 1, 1), rayDir(1, 0, 0); double propagationDistance = 10.5; vector3D newRayPos;
newRayPos = rayPos + rayDir * propagationDistance; newRayPos.Print(); vector3D temp = rayDir * propagationDistance; newRayPos = rayPos + temp; newRayPos.Print(); }
When I run it (with all optimizations off) I see the following output:
(0, 2, 2) (10.5, 1, 1)
I would expect both lines to be identical.
The problem seems to be connected to the use of the "vector3D&" return type for the various operators. If I remove the "&" the program works as expected. Note that if I add an "&" to the return type for "operator=" then neither line of output contains the correct result.
Am I doing something illegal here or is the compiler generating bad code? I'd like to be able to understand this because the code runs much slower if I pass vector3D structures around on the stack...
Thanks Jonny |