The Quaternion library function cogl_quaternion_init_from_array is passing a pointer to the wrong structure member to memcpy.

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diff --git a/cogl/cogl-quaternion.c b/cogl/cogl-quaternion.c
index ff59720..d7592a2 100644
--- a/cogl/cogl-quaternion.c
+++ b/cogl/cogl-quaternion.c
@@ -122,5 +122,5 @@ cogl_quaternion_init_from_array (CoglQuaternion *quaternion,
                                  const float *array)
 {
-  memcpy (&quaternion->x, array, sizeof (float) * 4);
+  memcpy (&quaternion->w, array, sizeof (float) * 4);
 }

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/* Reproducing cogl_quaternion_init_from_array bug */
#include <stdlib.h>
#include <assert.h>
#include <math.h>
#include <cogl/cogl.h>

#define FEQUALS(x,y) (fabs((x)-(y))<0.001f)

int main (int argc, char **argv)
{
  CoglQuaternion quat;
  float vals[4] =
    {
      1.0f, 2.0f,
      3.0f, 4.0f
    };
  
  cogl_quaternion_init_from_array (&quat, vals);  
  assert (FEQUALS (quat.w, 1.0f));

  return EXIT_SUCCESS;
}

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Additionally this paragraph of the C99 standard:
 6.7.2.1:13 ".. There may be unnamed padding within a structure object, .."
Would suggest that the method of memcpy-ing the array of floats into the structure produces non-portable behavior.
Initializing each of the members separately as the alternative solution:

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diff --git a/cogl/cogl-quaternion.c b/cogl/cogl-quaternion.c
index ff59720..9403fc7 100644
--- a/cogl/cogl-quaternion.c
+++ b/cogl/cogl-quaternion.c
@@ -122,5 +122,8 @@ cogl_quaternion_init_from_array (CoglQuaternion *quaternion,
                                  const float *array)
 {
-  memcpy (&quaternion->x, array, sizeof (float) * 4);
+  quaternion->w = array[0];
+  quaternion->x = array[1];
+  quaternion->y = array[2];
+  quaternion->z = array[3];
 }

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The Quaternion library function cogl_quaternion_get_rotation_axis might be broken.
Seems the intent is use of equation equivalent to
 http://www.j3d.org/matrix_faq/matrfaq_latest.html#Q57
However, only the 'x' component is set.

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diff --git a/cogl/cogl-quaternion.c b/cogl/cogl-quaternion.c
index ff59720..7ec4d4e 100644
--- a/cogl/cogl-quaternion.c
+++ b/cogl/cogl-quaternion.c
@@ -390,6 +390,6 @@ cogl_quaternion_get_rotation_axis (const CoglQuaternion *quaternion,
 
   vector->x = quaternion->x * one_over_sin_angle_over_2;
-  vector->x = quaternion->x * one_over_sin_angle_over_2;
-  vector->x = quaternion->x * one_over_sin_angle_over_2;
+  vector->y = quaternion->y * one_over_sin_angle_over_2;
+  vector->z = quaternion->z * one_over_sin_angle_over_2;
 }