calling bpy.ops.wm.open_mainfile from class which is invoked from pop-up button results in crash. #49828

New Issue

Mark aka Dark · 2016-10-24T16:44:09+02:00

Mark aka Dark commented

2016-10-24 16:44:09 +02:00

Notice
I'm not sure if this is a bug. But it looks like it, because before Blender 2.78 this crash didn't occure.

System Information
OS's: Arch linux, windows 10
GPU's: nvidia gtx950m and several others.

Blender Version
Broken: 2.78 4bb1e22
Worked: 2.77a abf6f08 (is from arch linux repo i think)
The code is part of the blenchmark add-on. Several users reported that it is not working since Blender version 2.78

Short description of error
calling bpy.ops.wm.open_mainfile from class which is invoked from pop-up button results in crash.

Exact steps for others to reproduce the error

install and enable attached addon (samplescriptje)
click Render > sample
click ok in popup
crash

attachment
samplescriptje.zip

**Notice** I'm not sure if this is a bug. But it looks like it, because before Blender 2.78 this crash didn't occure. **System Information** OS's: Arch linux, windows 10 GPU's: nvidia gtx950m and several others. **Blender Version** Broken: 2.78 4bb1e22 Worked: 2.77a abf6f08 (is from arch linux repo i think) The code is part of the blenchmark add-on. Several users reported that it is not working since Blender version 2.78 **Short description of error** calling bpy.ops.wm.open_mainfile from class which is invoked from pop-up button results in crash. **Exact steps for others to reproduce the error** 1. install and enable attached addon (samplescriptje) 2. click Render > sample 3. click ok in popup 4. crash **attachment** [samplescriptje.zip](https://archive.blender.org/developer/F385809/samplescriptje.zip)

Mark aka Dark commented

2016-10-24 16:44:09 +02:00

Changed status to: 'Open'

Mark aka Dark commented

2016-10-24 16:44:09 +02:00

Added subscriber: @mark_aka_dark

Sergey Sharybin commented

2016-10-25 10:58:37 +02:00

Added subscribers: @JulianEisel, @Sergey

Julian Eisel was assigned by Sergey Sharybin

2016-10-25 10:58:37 +02:00

Sergey Sharybin commented

2016-10-25 10:58:37 +02:00

@JulianEisel, another one caused by 4559229.

@JulianEisel, another one caused by 4559229.

Julian Eisel commented

2016-10-26 00:12:41 +02:00

Changed status from 'Open' to: 'Archived'

Julian Eisel closed this issue

2016-10-26 00:12:41 +02:00

Julian Eisel commented

2016-10-26 00:12:41 +02:00

Hmmm, after quite some investigation I conclude this is wrong usage of our popup code. It's a similar issue as #49199, but much trickier.

When closing Blender or loading a new file, all open popups are closed and since 4559229163, all data of these popups is freed then to fix memory leaks. Note that your script had these memory leaks too (open a Blender version that doesn't have 4559229163 applied from a terminal, run your script and close Blender - it should print memory-leak errors). These memory leaks are fixed now, however, combined with wm.open_mainfile it causes use-after-free errors in delayed function execution... an old & ugly hack of our interface interaction code.

For #49199, it was possible to create an exception to handle data freeing properly. The difference to this case is that the confirmation button is created from .py, from which we can't register a button execution callback that sets the exception and closes the popup properly.
We could add some way to mark a button as popup confirmation button, but this would be really ugly (e.g. we had to add a is_popup_confirm boolean to uiLayout.operator).
Another (ugly) way to fix this crash would be this:
P421: (An Untitled Masterwork)

diff --git a/source/blender/makesrna/intern/rna_wm_api.c b/source/blender/makesrna/intern/rna_wm_api.c
index 8d0b704..b47eeff 100644
--- a/source/blender/makesrna/intern/rna_wm_api.c
+++ b/source/blender/makesrna/intern/rna_wm_api.c
@@ -164,6 +164,15 @@ static int rna_Operator_props_popup(bContext *C, wmOperator *op, wmEvent *event)
        return WM_operator_props_popup(C, op, event);
 }
 
+static void rna_Operator_popup_confirm(bContext *C)
+{
+       ARegion *menu = CTX_wm_menu(C);
+
+       if (menu) {
+               UI_popup_menu_retval_set(menu->uiblocks.first, UI_RETURN_OK, true);
+       }
+}
+
 static wmKeyMapItem *rna_KeyMap_item_new(wmKeyMap *km, ReportList *reports, const char *idname, int type, int value,
                                          int any, int shift, int ctrl, int alt, int oskey, int keymodifier, int head)
 {
@@ -469,6 +478,8 @@ void RNA_api_wm(StructRNA *srna)
                                        "(only to let user confirm the execution, no operator properties shown)");
        rna_generic_op_invoke(func, WM_GEN_INVOKE_EVENT | WM_GEN_INVOKE_RETURN);
 
+       func = RNA_def_function(srna, "popup_return_ok", "rna_Operator_popup_confirm");
+       RNA_def_function_flag(func, FUNC_NO_SELF | FUNC_USE_CONTEXT);
 
        /* wrap UI_popup_menu_begin */
        func = RNA_def_function(srna, "pupmenu_begin__internal", "rna_PupMenuBegin");

You simply had to call wm.popup_return_ok()before object.benchmark_operator() in the script. It would bring back the memory leak though...

After all I'd say it's luck that your script worked fine previously (except of memory leaks). You create a popup that isn't closed correctly prior to calling wm.open_mainfile and I can't see a proper way to allow doing this. There are ways to create confirmation-popups from .py that work fine even when calling wm.open_mainfile, I strongly suggest to use them instead (e.g. check wm.invoke_props_dialog). I did some modifications to your init.py file show you how that would work: init.py. Downside is that there's no "Cancel" button and that you can't edit the button text though.

I'll consider this a limitation or hard-to-fix-corner-case for now. IMHO it's a bad idea to do biggish or ugly changes to interface and BPY to get this corner-case to work while there are pre-made confirmation popups available that behave properly even in this corner-case.
Closing the report, thanks for reporting though.

Hmmm, after quite some investigation I conclude this is wrong usage of our popup code. It's a similar issue as #49199, but much trickier. When closing Blender or loading a new file, all open popups are closed and since 4559229163, all data of these popups is freed then to fix memory leaks. Note that your script had these memory leaks too (open a Blender version that doesn't have 4559229163 applied from a terminal, run your script and close Blender - it should print memory-leak errors). These memory leaks are fixed now, however, combined with `wm.open_mainfile` it causes use-after-free errors in delayed function execution... an old & ugly hack of our interface interaction code. For #49199, it was possible to create an exception to handle data freeing properly. The difference to this case is that the confirmation button is created from .py, from which we can't register a button execution callback that sets the exception and closes the popup properly. We could add some way to mark a button as popup confirmation button, but this would be really ugly (e.g. we had to add a `is_popup_confirm` boolean to `uiLayout.operator`). Another (ugly) way to fix this crash would be this: [P421: (An Untitled Masterwork)](https://archive.blender.org/developer/P421.txt) ``` diff --git a/source/blender/makesrna/intern/rna_wm_api.c b/source/blender/makesrna/intern/rna_wm_api.c index 8d0b704..b47eeff 100644 --- a/source/blender/makesrna/intern/rna_wm_api.c +++ b/source/blender/makesrna/intern/rna_wm_api.c @@ -164,6 +164,15 @@ static int rna_Operator_props_popup(bContext *C, wmOperator *op, wmEvent *event) return WM_operator_props_popup(C, op, event); } +static void rna_Operator_popup_confirm(bContext *C) +{ + ARegion *menu = CTX_wm_menu(C); + + if (menu) { + UI_popup_menu_retval_set(menu->uiblocks.first, UI_RETURN_OK, true); + } +} + static wmKeyMapItem *rna_KeyMap_item_new(wmKeyMap *km, ReportList *reports, const char *idname, int type, int value, int any, int shift, int ctrl, int alt, int oskey, int keymodifier, int head) { @@ -469,6 +478,8 @@ void RNA_api_wm(StructRNA *srna) "(only to let user confirm the execution, no operator properties shown)"); rna_generic_op_invoke(func, WM_GEN_INVOKE_EVENT | WM_GEN_INVOKE_RETURN); + func = RNA_def_function(srna, "popup_return_ok", "rna_Operator_popup_confirm"); + RNA_def_function_flag(func, FUNC_NO_SELF | FUNC_USE_CONTEXT); /* wrap UI_popup_menu_begin */ func = RNA_def_function(srna, "pupmenu_begin__internal", "rna_PupMenuBegin"); ``` You simply had to call `wm.popup_return_ok()`before `object.benchmark_operator()` in the script. It would bring back the memory leak though... ---- After all I'd say it's luck that your script worked fine previously (except of memory leaks). You create a popup that isn't closed correctly prior to calling `wm.open_mainfile` and I can't see a proper way to allow doing this. There are ways to create confirmation-popups from .py that work fine even when calling `wm.open_mainfile`, I strongly suggest to use them instead (e.g. check `wm.invoke_props_dialog`). I did some modifications to your __init__.py file show you how that would work: [__init__.py](https://archive.blender.org/developer/F386373/__init__.py). Downside is that there's no "Cancel" button and that you can't edit the button text though. I'll consider this a limitation or hard-to-fix-corner-case for now. IMHO it's a bad idea to do biggish or ugly changes to interface and BPY to get this corner-case to work while there are pre-made confirmation popups available that behave properly even in this corner-case. Closing the report, thanks for reporting though.

Mark aka Dark commented

2016-10-26 07:18:22 +02:00

Hi Julian,

Thank you for the extended explanation for this behaviour and your effort to show me a work-around. wm.invoke_props_dialog() is working fine, the downsides of it are not important. At least not for me.

Thanks again for your effort.
Mark

Hi Julian, Thank you for the extended explanation for this behaviour and your effort to show me a work-around. wm.invoke_props_dialog() is working fine, the downsides of it are not important. At least not for me. Thanks again for your effort. Mark

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calling bpy.ops.wm.open_mainfile from class which is invoked from pop-up button results in crash. #49828