[cogl] Add compile time checks for size of public structs

[Robert Bragg <rbragg src gnome org>]

commit 2da24ab86301ff75670beb4150b56d9339e590d1
Author: Robert Bragg <robert linux intel com>
Date:   Fri May 13 17:30:08 2011 +0100

    Add compile time checks for size of public structs
    
    To help catch accidental changes to the size of public structs that can
    be allocated on the stack this patch adds compile time checks that our
    struct sizes haven't changed.

 cogl/cogl-euler.h      |    1 +
 cogl/cogl-matrix.h     |    1 +
 cogl/cogl-quaternion.h |    1 +
 cogl/cogl-types.h      |   12 ++++++++++++
 4 files changed, 15 insertions(+), 0 deletions(-)
---
diff --git a/cogl/cogl-euler.h b/cogl/cogl-euler.h
index ca623e8..e82eab1 100644
--- a/cogl/cogl-euler.h
+++ b/cogl/cogl-euler.h
@@ -157,6 +157,7 @@ struct _CoglEuler
   float padding3;
   float padding4;
 };
+COGL_STRUCT_SIZE_ASSERT (CoglEuler, 32);
 
 /**
  * cogl_euler_init:
diff --git a/cogl/cogl-matrix.h b/cogl/cogl-matrix.h
index f94a644..36f21ba 100644
--- a/cogl/cogl-matrix.h
+++ b/cogl/cogl-matrix.h
@@ -108,6 +108,7 @@ struct _CoglMatrix
   unsigned long  COGL_PRIVATE (flags);
   unsigned long  COGL_PRIVATE (_padding3);
 };
+COGL_STRUCT_SIZE_ASSERT (CoglMatrix, 128 + sizeof (unsigned long) * 3);
 
 /**
  * cogl_matrix_init_identity:
diff --git a/cogl/cogl-quaternion.h b/cogl/cogl-quaternion.h
index 1b83bac..33ca984 100644
--- a/cogl/cogl-quaternion.h
+++ b/cogl/cogl-quaternion.h
@@ -132,6 +132,7 @@ struct _CoglQuaternion
   float padding2;
   float padding3;
 };
+COGL_STRUCT_SIZE_ASSERT (CoglQuaternion, 32);
 
 /**
  * cogl_quaternion_init:
diff --git a/cogl/cogl-types.h b/cogl/cogl-types.h
index 36f5269..ab610c1 100644
--- a/cogl/cogl-types.h
+++ b/cogl/cogl-types.h
@@ -47,6 +47,16 @@ G_BEGIN_DECLS
 #define COGL_PRIVATE(x) private_member_ ## x
 #endif
 
+/* To help catch accidental changes to public structs that should
+ * be stack allocated we use this macro to compile time assert that
+ * a struct size is as expected.
+ */
+#define COGL_STRUCT_SIZE_ASSERT(TYPE, SIZE) \
+typedef struct { \
+          char compile_time_assert_ ## TYPE ## _size[ \
+              (sizeof (TYPE) == (SIZE)) ? 1 : -1]; \
+        } _ ## TYPE ## SizeCheck
+
 /**
  * CoglHandle:
  *
@@ -344,6 +354,7 @@ struct _CoglColor
   guint32 COGL_PRIVATE (padding1);
   guint32 COGL_PRIVATE (padding2);
 };
+COGL_STRUCT_SIZE_ASSERT (CoglColor, 16);
 
 /**
  * CoglTextureVertex:
@@ -364,6 +375,7 @@ struct _CoglTextureVertex
 
   CoglColor color;
 };
+COGL_STRUCT_SIZE_ASSERT (CoglTextureVertex, 36);
 
 /**
  * CoglTextureFlags: