Occasional crashes when rescanning autoload dir on Windows

[seproDev]

I was unable to reproduce these crashes under Linux and they are not 100% consistant.

Tested on both arch1t3cht's build and this build.

Requires certain automations to be installed.
Installing l0.Nudge and rescanning the autoload dir a couple times triggers the crash. Though they can also happen on startup causing Aegisub to not even open.

I have observed different behaviors. Sometimes only a script fails to initialize with this error message:

Rarely I get this exception:

Attaching windbg I get this error on crash:

(5a0.1a88): Access violation - code c0000005 (first chance)
First chance exceptions are reported before any exception handling.
This exception may be expected and handled.
aegisub!FT_Stream_OpenLZW+0x10ac335:
00007ff7`7a59a2a5 8b4814          mov     ecx,dword ptr [rax+14h] ds:00008000`00000013=????????
0:035> g
(5a0.1a88): Access violation - code c0000005 (!!! second chance !!!)
aegisub!FT_Stream_OpenLZW+0x10ac335:
00007ff7`7a59a2a5 8b4814          mov     ecx,dword ptr [rax+14h] ds:00008000`00000013=????????

[petzku]

Are you able to trace which commit introduces this?

[seproDev]

I did a bunch more testing and it seems to only happen when local config files are being used, as was the case with the two portable CI builds I tried initally.

Using the CI builds with a config file from the appdata folder the crashes no longer happen.

I tested build 8962 from here and that version is also affected.
Just using aegisub after setup the crashes don't appear, but switching over to a local config file 8962 also crashes.
AegisubDC 9215 also crashes in a simmilar way when using local config files.

So probably an issue with the local config logic used in Aegisub in general.

[seproDev]

Figured this out on the discord. For future reference here the summary.
The default autoload/include location is set like this:

Aegisub/src/libresrc/default_config.json

Lines 290 to 294 in c218db6

	"Automation" : {
	"Autoload" : "?user/automation/autoload/|?data/automation/autoload/",
	"Base" : "?data/automation/",
	"Include" : "?user/automation/include/|?data/automation/include/"
	},

When using a local config ?user gets set to the value of ?data

Aegisub/src/main.cpp

Lines 182 to 184 in c218db6

	// Local config, make ?user mean ?data so all user settings are placed in install dir
	config::path->SetToken("?user", config::path->Decode("?data"));
	config::path->SetToken("?local", config::path->Decode("?data"));

Causing the lines to effectively be ?data/automation/autoload/|?data/automation/autoload/, which means the automation folders get loaded twice.

Aegisub/src/auto4_base.cpp

Line 325 in c218db6

for (auto tok : agi::Split(path, '|')) {

I would assueme the actual crash happens because of some race condition.