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FIX: matrix3 identity and zero static #3

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FIX: matrix3 identity and zero static #3

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36 changes: 19 additions & 17 deletions G3Dcpp/Matrix4.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -17,23 +17,25 @@

namespace G3D {

const Matrix4& Matrix4::identity() {
static Matrix4 m(
1, 0, 0, 0,
0, 1, 0, 0,
0, 0, 1, 0,
0, 0, 0, 1);
return m;
}

const Matrix4& Matrix4::zero() {
static Matrix4 m(
0, 0, 0, 0,
0, 0, 0, 0,
0, 0, 0, 0,
0, 0, 0, 0);
return m;
}
// *** Read Matrix.h comment regarding identity and zero ***

// const Matrix4& Matrix4::identity() {
// static Matrix4 m(
// 1, 0, 0, 0,
// 0, 1, 0, 0,
// 0, 0, 1, 0,
// 0, 0, 0, 1);
// return m;
// }

// const Matrix4& Matrix4::zero() {
// static Matrix4 m(
// 0, 0, 0, 0,
// 0, 0, 0, 0,
// 0, 0, 0, 0,
// 0, 0, 0, 0);
// return m;
// }

// Deprecated.
const Matrix4 Matrix4::IDENTITY
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23 changes: 20 additions & 3 deletions include/G3D/Matrix3.h
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Expand Up @@ -246,6 +246,11 @@ class Matrix3 {

static const float EPSILON;

// The following comment is wrong. Modern linkers are smart enough to deduplicate
// multiple static objects into a single memory address, as long as any function with
// a static local variable is marked inline.

// *** Original G3D comment ***
// Special values.
// The unguaranteed order of initialization of static variables across
// translation units can be a source of annoying bugs, so now the static
Expand All @@ -255,7 +260,7 @@ class Matrix3 {
// "You might be tempted to write [...] them as inline functions
// inside their respective header files, but this is something you
// must definitely not do. An inline function can be duplicated
// in every file in which it appears � and this duplication
// in every file in which it appears � and this duplication
// includes the static object definition. Because inline functions
// automatically default to internal linkage, this would result in
// having multiple static objects across the various translation
Expand All @@ -264,8 +269,20 @@ class Matrix3 {
// function, and this means not making the wrapping functions inline",
// according to Chapter 10 of "Thinking in C++, 2nd ed. Volume 1" by Bruce Eckel,
// http://www.mindview.net/
static const Matrix3& zero();
static const Matrix3& identity();
// *** End of G3D comment ***

static const Matrix3& zero() {
static Matrix3 m(0, 0, 0, 0, 0, 0, 0, 0, 0);
return m;
}

static const Matrix3& identity() {
static Matrix3 m(1, 0, 0, 0, 1, 0, 0, 0, 1);
return m;
}

// static const Matrix3& zero();
// static const Matrix3& identity();

// Deprecated.
/** @deprecated Use Matrix3::zero() */
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