Fix (unreported) Crash: broken RNA accessors to tesselated MCol data.

Regression from rB823bcf1689a3 (VPaint 2017 GSoC, this is not in 2.79 release).

Also cleanup, using fake-array-ification to access struct members is
generally not a great idea, but when we already have a totally confusing
broken struct layout, this is pure evil, as demonstrated here!

Found while investigating T53341.

2 files changed, 42 insertions, 41 deletions

diff --git a/source/blender/makesrna/intern/rna_mesh.c b/source/blender/makesrna/intern/rna_mesh.c
index 41758758178..18fd4c64242 100644
--- a/source/blender/makesrna/intern/rna_mesh.c
+++ b/source/blender/makesrna/intern/rna_mesh.c
@@ -577,99 +577,100 @@ static void rna_MeshColor_color1_get(PointerRNA *ptr, float *values)
 {
 	MCol *mcol = (MCol *)ptr->data;
 
-	values[2] = (&mcol[0].r)[0] / 255.0f;
-	values[1] = (&mcol[0].r)[1] / 255.0f;
-	values[0] = (&mcol[0].r)[2] / 255.0f;
+	values[3] = mcol[0].a / 255.0f;
+	values[2] = mcol[0].r / 255.0f;
+	values[1] = mcol[0].g / 255.0f;
+	values[0] = mcol[0].b / 255.0f;
 }
 
 static void rna_MeshColor_color1_set(PointerRNA *ptr, const float *values)
 {
 	MCol *mcol = (MCol *)ptr->data;
 
-	(&mcol[0].r)[2] = round_fl_to_uchar_clamp(values[0] * 255.0f);
-	(&mcol[0].r)[1] = round_fl_to_uchar_clamp(values[1] * 255.0f);
-	(&mcol[0].r)[0] = round_fl_to_uchar_clamp(values[2] * 255.0f);
-	(&mcol[0].r)[3] = round_fl_to_uchar_clamp(values[3] * 255.0f);
+	mcol[0].a = round_fl_to_uchar_clamp(values[3] * 255.0f);
+	mcol[0].r = round_fl_to_uchar_clamp(values[2] * 255.0f);
+	mcol[0].g = round_fl_to_uchar_clamp(values[1] * 255.0f);
+	mcol[0].b = round_fl_to_uchar_clamp(values[0] * 255.0f);
 }
 
 static void rna_MeshColor_color2_get(PointerRNA *ptr, float *values)
 {
 	MCol *mcol = (MCol *)ptr->data;
 
-	values[3] = (&mcol[1].r)[3] / 255.0f;
-	values[2] = (&mcol[1].r)[0] / 255.0f;
-	values[1] = (&mcol[1].r)[1] / 255.0f;
-	values[0] = (&mcol[1].r)[2] / 255.0f;
+	values[3] = mcol[1].a / 255.0f;
+	values[2] = mcol[1].r / 255.0f;
+	values[1] = mcol[1].g / 255.0f;
+	values[0] = mcol[1].b / 255.0f;
 }
 
 static void rna_MeshColor_color2_set(PointerRNA *ptr, const float *values)
 {
 	MCol *mcol = (MCol *)ptr->data;
 
-	(&mcol[1].r)[2] = round_fl_to_uchar_clamp(values[0] * 255.0f);
-	(&mcol[1].r)[1] = round_fl_to_uchar_clamp(values[1] * 255.0f);
-	(&mcol[1].r)[0] = round_fl_to_uchar_clamp(values[2] * 255.0f);
-	(&mcol[1].r)[3] = round_fl_to_uchar_clamp(values[3] * 255.0f);
+	mcol[1].a = round_fl_to_uchar_clamp(values[3] * 255.0f);
+	mcol[1].r = round_fl_to_uchar_clamp(values[2] * 255.0f);
+	mcol[1].g = round_fl_to_uchar_clamp(values[1] * 255.0f);
+	mcol[1].b = round_fl_to_uchar_clamp(values[0] * 255.0f);
 }
 
 static void rna_MeshColor_color3_get(PointerRNA *ptr, float *values)
 {
 	MCol *mcol = (MCol *)ptr->data;
 
-	values[3] = (&mcol[2].r)[3] / 255.0f;
-	values[2] = (&mcol[2].r)[0] / 255.0f;
-	values[1] = (&mcol[2].r)[1] / 255.0f;
-	values[0] = (&mcol[2].r)[2] / 255.0f;
+	values[3] = mcol[2].a / 255.0f;
+	values[2] = mcol[2].r / 255.0f;
+	values[1] = mcol[2].g / 255.0f;
+	values[0] = mcol[2].b / 255.0f;
 }
 
 static void rna_MeshColor_color3_set(PointerRNA *ptr, const float *values)
 {
 	MCol *mcol = (MCol *)ptr->data;
 
-	(&mcol[2].r)[2] = round_fl_to_uchar_clamp(values[0] * 255.0f);
-	(&mcol[2].r)[1] = round_fl_to_uchar_clamp(values[1] * 255.0f);
-	(&mcol[2].r)[0] = round_fl_to_uchar_clamp(values[2] * 255.0f);
-	(&mcol[2].r)[3] = round_fl_to_uchar_clamp(values[3] * 255.0f);
+	mcol[2].a = round_fl_to_uchar_clamp(values[3] * 255.0f);
+	mcol[2].r = round_fl_to_uchar_clamp(values[2] * 255.0f);
+	mcol[2].g = round_fl_to_uchar_clamp(values[1] * 255.0f);
+	mcol[2].b = round_fl_to_uchar_clamp(values[0] * 255.0f);
 }
 
 static void rna_MeshColor_color4_get(PointerRNA *ptr, float *values)
 {
 	MCol *mcol = (MCol *)ptr->data;
 
-	values[2] = (&mcol[3].r)[0] / 255.0f;
-	values[1] = (&mcol[3].r)[1] / 255.0f;
-	values[0] = (&mcol[3].r)[2] / 255.0f;
-	values[3] = (&mcol[3].r)[3] / 255.0f;
+	values[3] = mcol[3].a / 255.0f;
+	values[2] = mcol[3].r / 255.0f;
+	values[1] = mcol[3].g / 255.0f;
+	values[0] = mcol[3].b / 255.0f;
 }
 
 static void rna_MeshColor_color4_set(PointerRNA *ptr, const float *values)
 {
 	MCol *mcol = (MCol *)ptr->data;
 
-	(&mcol[3].r)[2] = round_fl_to_uchar_clamp(values[0] * 255.0f);
-	(&mcol[3].r)[1] = round_fl_to_uchar_clamp(values[1] * 255.0f);
-	(&mcol[3].r)[0] = round_fl_to_uchar_clamp(values[2] * 255.0f);
-	(&mcol[3].r)[3] = round_fl_to_uchar_clamp(values[3] * 255.0f);
+	mcol[3].a = round_fl_to_uchar_clamp(values[3] * 255.0f);
+	mcol[3].r = round_fl_to_uchar_clamp(values[2] * 255.0f);
+	mcol[3].g = round_fl_to_uchar_clamp(values[1] * 255.0f);
+	mcol[3].b = round_fl_to_uchar_clamp(values[0] * 255.0f);
 }
 
 static void rna_MeshLoopColor_color_get(PointerRNA *ptr, float *values)
 {
-	MLoopCol *mcol = (MLoopCol *)ptr->data;
+	MLoopCol *mlcol = (MLoopCol *)ptr->data;
 
-	values[0] = (&mcol->r)[0] / 255.0f;
-	values[1] = (&mcol->r)[1] / 255.0f;
-	values[2] = (&mcol->r)[2] / 255.0f;
-	values[3] = (&mcol->r)[3] / 255.0f;
+	values[0] = mlcol->r / 255.0f;
+	values[1] = mlcol->g / 255.0f;
+	values[2] = mlcol->b / 255.0f;
+	values[3] = mlcol->a / 255.0f;
 }
 
 static void rna_MeshLoopColor_color_set(PointerRNA *ptr, const float *values)
 {
-	MLoopCol *mcol = (MLoopCol *)ptr->data;
+	MLoopCol *mlcol = (MLoopCol *)ptr->data;
 
-	(&mcol->r)[0] = round_fl_to_uchar_clamp(values[0] * 255.0f);
-	(&mcol->r)[1] = round_fl_to_uchar_clamp(values[1] * 255.0f);
-	(&mcol->r)[2] = round_fl_to_uchar_clamp(values[2] * 255.0f);
-	(&mcol->r)[3] = round_fl_to_uchar_clamp(values[3] * 255.0f);
+	mlcol->r = round_fl_to_uchar_clamp(values[0] * 255.0f);
+	mlcol->g = round_fl_to_uchar_clamp(values[1] * 255.0f);
+	mlcol->b = round_fl_to_uchar_clamp(values[2] * 255.0f);
+	mlcol->a = round_fl_to_uchar_clamp(values[3] * 255.0f);
 }
 
 static int rna_Mesh_texspace_editable(PointerRNA *ptr, const char **UNUSED(r_info))
diff --git a/source/tools b/source/tools
-Subproject 9ea62ef860cde8eb313b74cd1b23ca5a0734eef
+Subproject e10a1b031b243482371c0673ee17aa3c0f53637