Fix T61353: Crash converting a curve to a mesh

This was caused by curves pointing to each other
creating a cyclic dependency.

While the dependency graph detects this, generating a mesh for render
recursively generates data which cashes in this case.

Add in a check to detect cyclic links.

Note, this bug exists in 2.7x too - but only crashes on render
since 2.7x didn't use 'for_render' when converting data.

1 files changed, 26 insertions, 10 deletions

diff --git a/source/blender/blenkernel/intern/displist.c b/source/blender/blenkernel/intern/displist.c
index 869d5e6f362..0f3a3192d75 100644
--- a/source/blender/blenkernel/intern/displist.c
+++ b/source/blender/blenkernel/intern/displist.c
@@ -38,6 +38,7 @@
 #include "BLI_math.h"
 #include "BLI_scanfill.h"
 #include "BLI_utildefines.h"
+#include "BLI_linklist.h"
 
 #include "BKE_displist.h"
 #include "BKE_cdderivedmesh.h"
@@ -683,7 +684,7 @@ static float displist_calc_taper(Depsgraph *depsgraph, Scene *scene, Object *tap
 
 	dl = taperobj->runtime.curve_cache ? taperobj->runtime.curve_cache->disp.first : NULL;
 	if (dl == NULL) {
-		BKE_displist_make_curveTypes(depsgraph, scene, taperobj, false, false);
+		BKE_displist_make_curveTypes(depsgraph, scene, taperobj, false, false, NULL);
 		dl = taperobj->runtime.curve_cache->disp.first;
 	}
 	if (dl) {
@@ -1554,8 +1555,9 @@ static void calc_bevfac_mapping(Curve *cu, BevList *bl, Nurb *nu,
 
 static void do_makeDispListCurveTypes(
         Depsgraph *depsgraph, Scene *scene, Object *ob, ListBase *dispbase,
-        Mesh **r_final,
-        const bool for_render, const bool for_orco, const bool use_render_resolution)
+        const bool for_render, const bool for_orco, const bool use_render_resolution,
+        LinkNode *ob_cyclic_list,
+        Mesh **r_final)
 {
 	Curve *cu = ob->data;
 
@@ -1593,7 +1595,9 @@ static void do_makeDispListCurveTypes(
 		BKE_curve_bevelList_make(ob, &nubase, use_render_resolution);
 
 		/* If curve has no bevel will return nothing */
-		BKE_curve_bevel_make(depsgraph, scene, ob, &dlbev, for_render, use_render_resolution);
+		BKE_curve_bevel_make(
+		        depsgraph, scene, ob, &dlbev, for_render, use_render_resolution,
+		        ob_cyclic_list);
 
 		/* no bevel or extrude, and no width correction? */
 		if (!dlbev.first && cu->width == 1.0f) {
@@ -1801,7 +1805,8 @@ static void do_makeDispListCurveTypes(
 }
 
 void BKE_displist_make_curveTypes(
-        Depsgraph *depsgraph, Scene *scene, Object *ob, const bool for_render, const bool for_orco)
+        Depsgraph *depsgraph, Scene *scene, Object *ob, const bool for_render, const bool for_orco,
+        LinkNode *ob_cyclic_list)
 {
 	ListBase *dispbase;
 
@@ -1819,7 +1824,10 @@ void BKE_displist_make_curveTypes(
 
 	dispbase = &(ob->runtime.curve_cache->disp);
 
-	do_makeDispListCurveTypes(depsgraph, scene, ob, dispbase, &ob->runtime.mesh_eval, for_render, for_orco, false);
+	do_makeDispListCurveTypes(
+	        depsgraph, scene, ob, dispbase, for_render, for_orco, false,
+	        ob_cyclic_list,
+	        &ob->runtime.mesh_eval);
 
 	boundbox_displist_object(ob);
 }
@@ -1827,23 +1835,31 @@ void BKE_displist_make_curveTypes(
 void BKE_displist_make_curveTypes_forRender(
         Depsgraph *depsgraph, Scene *scene, Object *ob, ListBase *dispbase,
         Mesh **r_final, const bool for_orco,
-        const bool use_render_resolution)
+        const bool use_render_resolution,
+        LinkNode *ob_cyclic_list)
 {
 	if (ob->runtime.curve_cache == NULL) {
 		ob->runtime.curve_cache = MEM_callocN(sizeof(CurveCache), "CurveCache for Curve");
 	}
 
-	do_makeDispListCurveTypes(depsgraph, scene, ob, dispbase, r_final, true, for_orco, use_render_resolution);
+	do_makeDispListCurveTypes(
+	        depsgraph, scene, ob, dispbase, true, for_orco, use_render_resolution,
+	        ob_cyclic_list,
+	        r_final);
 }
 
 void BKE_displist_make_curveTypes_forOrco(
-        Depsgraph *depsgraph, Scene *scene, Object *ob, ListBase *dispbase)
+        Depsgraph *depsgraph, Scene *scene, Object *ob, ListBase *dispbase,
+        LinkNode *ob_cyclic_list)
 {
 	if (ob->runtime.curve_cache == NULL) {
 		ob->runtime.curve_cache = MEM_callocN(sizeof(CurveCache), "CurveCache for Curve");
 	}
 
-	do_makeDispListCurveTypes(depsgraph, scene, ob, dispbase, NULL, 1, 1, 1);
+	do_makeDispListCurveTypes(
+	        depsgraph, scene, ob, dispbase, 1, 1, 1,
+	        ob_cyclic_list,
+	        NULL);
 }
 
 void BKE_displist_minmax(ListBase *dispbase, float min[3], float max[3])