Possible bug in dmd for Windows converting known numbers into -nan

[davidomarf]

This problems was spotted first when running dub run after pulling 36e4700.

First, source/app.d calls heightmapPerspectiveTest() defined at source/tests/heightmap-perspective.d

heightmapPerspectiveTest(), at line 68, calls fillByHeightFunction(), defined as

viare/source/heightmap/heightmap.d

Lines 40 to 45 in 36e4700

	void fillByHeightFunction(HeightFunction heightFunction)
	{
	for (uint i; i < m_xlength; i++)
	for (uint j; j < m_ylength; j++)
	this[i, j] = heightFunction(cast(float) i / m_xlength, cast(float) j / m_ylength);
	}

using QuevHeightFunction() as argument for heightFunction, defined in source/heightmap/quev.d.

QuevHeightFunction() is specified to receive (double x, double y) as arguments.

viare/source/heightmap/quev.d

Line 102 in 36e4700

double opCall(double x, double y)

And fillByHeightFunction was sending them.

viare/source/heightmap/heightmap.d

Line 44 in 36e4700

this[i, j] = heightFunction(cast(float) i / m_xlength, cast(float) j / m_ylength);

At least theoretically.

---

At the first iteration, QuevHeightFunction() should be receiving 0, 0, but it was receiving -nan, 0.

My conclusion was that error must have been coming from fillByHeightFunction().

Before calling heightFunction(cast(double) i / m_xlength, cast(double) j / m_ylength);, all i, m_xlength, j, m_ylength were numbers.

And so were the operations i / m_xlength and j / m_ylength.

And so were the casts cast(double) i / m_xlength and cast(double) j / m_ylength).

---

tl;dr

QuevHeightFunction() is called with two floats (x, y). But it receives (-nan, y).

This suggests that something happens at the moment of the function call.

Possible Solution

The only solution that I've found so far was writing the value of cast(double) i / m_xlength to console before sending it to QuevHeightFunction().

Yes. Only that. Printing.

Steps to Reproduce

(Assuming you've already cloned the repository)

1. git pull origin master
2. git checkout heightmap-perspective-test
3. git checkout 36e47004629bbe8900da9570c0271c5a18badc57
4. dub run

Environment

• DMD: v2.081.1
• DUB: 1.10.0
• OS: Windows 10 1803

[davidomarf]

Implied in the title, but need to remark:

Apparently, this only happens on Windows. Same commit in Linux runs ok.

[davidomarf]

I will close the issue now, as it appears to be solved ussing a dirty fix — b1ad7d2 —.

Keep in mind this is not optimal solution, and it must be addressed later.