Segfault populating popup menu with specific structure, scale_x, and element count. (GPUOffScreen buffer too large?) #89782

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Will · 2021-07-11T06:29:58+02:00

Will commented

2021-07-11 06:29:58 +02:00

System Information
Operating system: Linux
Graphics card: Intel

Blender Version
Broken: 2.93.0

Short description of error

I have a very specific UI hierarchy and settings that are consistently causing segfaults for me.

I think the short draw code is the best way to explain it:

def draw(self, context):
		layout = self.layout
		row = layout.row(align=True)
		row.scale_x = 2 # Needed for crash.
		col1 = row.column(align=True)
		col2 = row.column(align=True)
		for i in range(40): # Crashes with 40 and 39, but not with 20, 50, or 100.
			col1.label(text=str("a"*20)) #Doesn't matter, I think.
			col2.label(text=str("b"*20))

bpy.context.window_manager.popup_menu(draw, title="")

.scale_x = 2 is needed for the crash. The number of items from the range() also matters, and won't crash with too few or too many. I don't think the lengths of the labels matter.

Also happens with column/row layout convoluted/zipped.
Also happens with .ui_units_x = 40 replacing .scale_x = 2 (but not with all other values of .ui_units_x).
Actually seems to happen with some number (but not all numbers) of elements for any combination of UI dimensions in .popup_menu.
Note: Even when it doesn't segfault, the popup menu will often be an obvious rendering error with lots of tearing and such.

Exact steps for others to reproduce the error

Run the script:

ScaleXCrash.blend

**System Information** Operating system: Linux Graphics card: Intel **Blender Version** Broken: 2.93.0 **Short description of error** I have a very specific UI hierarchy and settings that are consistently causing segfaults for me. I think the short draw code is the best way to explain it: ``` def draw(self, context): layout = self.layout row = layout.row(align=True) row.scale_x = 2 # Needed for crash. col1 = row.column(align=True) col2 = row.column(align=True) for i in range(40): # Crashes with 40 and 39, but not with 20, 50, or 100. col1.label(text=str("a"*20)) #Doesn't matter, I think. col2.label(text=str("b"*20)) bpy.context.window_manager.popup_menu(draw, title="") ``` `.scale_x = 2` is needed for the crash. The number of items from the `range()` also matters, and won't crash with too few or too many. I don't think the lengths of the labels matter. * Also happens with column/row layout convoluted/zipped. * Also happens with `.ui_units_x = 40` replacing `.scale_x = 2` (but not with all other values of `.ui_units_x`). * Actually seems to happen with some number (but not all numbers) of elements for any combination of UI dimensions in `.popup_menu`. * Note: Even when it doesn't segfault, the popup menu will often be an obvious rendering error with lots of tearing and such. **Exact steps for others to reproduce the error** Run the script: [ScaleXCrash.blend](https://archive.blender.org/developer/F10220173/ScaleXCrash.blend)

Will commented

2021-07-11 06:29:58 +02:00

Added subscriber: @WCN

Pratik Borhade commented

2021-07-12 15:12:08 +02:00

Added subscriber: @PratikPB2123

Philipp Oeser commented

2021-07-12 15:21:31 +02:00

Added subscriber: @lichtwerk

Philipp Oeser commented

2021-07-12 15:21:31 +02:00

Changed status from 'Needs Triage' to: 'Confirmed'

Philipp Oeser commented

2021-07-12 15:21:31 +02:00

Can confirm.

note: does not happen if scale_x stays below 1 (at least here on my end)

Read blend: /ScaleXCrash.blend
./bin/blender(BLI_system_backtrace+0x26) [0x1030274e]
./bin/blender(_BLI_assert_print_backtrace+0x16) [0x101d669e]
./bin/blender(BLI_vsnprintf+0x24) [0x102f65da]
./bin/blender(BLI_snprintf+0xaa) [0x102f688c]
./bin/blender(GPU_offscreen_create+0x10f) [0xe1e34c1]
./bin/blender() [0x3d1ec83]
./bin/blender() [0x3d1f97b]
./bin/blender() [0x3d1fe02]
./bin/blender(wm_draw_update+0xc5) [0x3d2043a]
./bin/blender(WM_main+0x48) [0x3d1ca65]
./bin/blender() [0x36c665a]
/lib64/libc.so.6(+0x2b7e0) [0x7fc3290897e0]
/lib64/libc.so.6(__libc_start_main+0x7c) [0x7fc32908988c]
./bin/blender(_start+0x25) [0x36c6035]
BLI_assert failed: source/blender/blenlib/intern/string.c:218, BLI_vsnprintf(), at 'buffer != ((void *)0)'

Can confirm. note: does not happen if `scale_x` stays below 1 (at least here on my end) ``` Read blend: /ScaleXCrash.blend ./bin/blender(BLI_system_backtrace+0x26) [0x1030274e] ./bin/blender(_BLI_assert_print_backtrace+0x16) [0x101d669e] ./bin/blender(BLI_vsnprintf+0x24) [0x102f65da] ./bin/blender(BLI_snprintf+0xaa) [0x102f688c] ./bin/blender(GPU_offscreen_create+0x10f) [0xe1e34c1] ./bin/blender() [0x3d1ec83] ./bin/blender() [0x3d1f97b] ./bin/blender() [0x3d1fe02] ./bin/blender(wm_draw_update+0xc5) [0x3d2043a] ./bin/blender(WM_main+0x48) [0x3d1ca65] ./bin/blender() [0x36c665a] /lib64/libc.so.6(+0x2b7e0) [0x7fc3290897e0] /lib64/libc.so.6(__libc_start_main+0x7c) [0x7fc32908988c] ./bin/blender(_start+0x25) [0x36c6035] BLI_assert failed: source/blender/blenlib/intern/string.c:218, BLI_vsnprintf(), at 'buffer != ((void *)0)' ```

Philipp Oeser commented

2021-07-12 15:51:21 +02:00

Added subscriber: @mano-wii

Philipp Oeser commented

2021-07-12 15:51:21 +02:00

It is just that the GPUOffScreen buffer would be too large it seems and cannot be created.

The assert can be avoided by the following (but still -- this should be safeguarded against more thoroughly since this gets blender into total unstable land):
{P2246}

@mano-wii: is this something you can look into?

It is just that the `GPUOffScreen` buffer would be too large it seems and cannot be created. The assert can be avoided by the following (but still -- this should be safeguarded against more thoroughly since this gets blender into total unstable land): {P2246} @mano-wii: is this something you can look into?

Philipp Oeser changed title from ~~Segfault populating popup menu with specific structure, `scale_x`, and element count.~~ to Segfault populating popup menu with specific structure, `scale_x`, and element count. (GPUOffScreen buffer too large?)

2021-07-12 15:52:13 +02:00

Germano Cavalcante commented

2021-07-15 01:30:58 +02:00

The error is in the internals of the GPU module. Not much related to the python API
The crash happens because the offscreen texture has dimensions above the OpenGL limit, and GPU_offscreen_create requires a non-NULL err_out arg.
Checking if the err_out is NULL would do the trick too.

It can also be interesting to raise an error message in the interface.
I will propose a patch.

The error is in the internals of the GPU module. Not much related to the python API The crash happens because the offscreen texture has dimensions above the OpenGL limit, and `GPU_offscreen_create` requires a non-NULL `err_out` arg. Checking if the `err_out` is `NULL` would do the trick too. It can also be interesting to raise an error message in the interface. I will propose a patch.

blender-admin commented

2021-07-15 01:38:18 +02:00

This issue was referenced by 15cfb375a3

This issue was referenced by 15cfb375a39b9d9e35e8c83942edb8f43788427f

Will commented

2021-07-15 01:49:11 +02:00

Hm. There isn't any way to specify the popup menu size from the Python API though, AFAICT.

In fact, the example code produces a menu that's several times wider than it needs to be, with the majority of the menu being blank space.

Hm. There isn't any way to specify the popup menu size from the Python API though, AFAICT. In fact, the example code produces a menu that's several times wider than it needs to be, with the majority of the menu being blank space.

Pratik Borhade commented

2022-12-08 12:37:59 +01:00

Changed status from 'Confirmed' to: 'Resolved'

Pratik Borhade closed this issue

2022-12-08 12:37:59 +01:00

Germano Cavalcante was assigned by Pratik Borhade

2022-12-08 12:37:59 +01:00

Pratik Borhade commented

2022-12-08 12:37:59 +01:00

15cfb375a3 has fixed this, right?
I'll close this report. Please reopen it if problem persists

15cfb375a3 has fixed this, right? I'll close this report. Please reopen it if problem persists

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Segfault populating popup menu with specific structure, scale_x, and element count. (GPUOffScreen buffer too large?) #89782

Segfault populating popup menu with specific structure, `scale_x`, and element count. (GPUOffScreen buffer too large?) #89782