Bug 20812 – _d_assocarrayliteralTX segfault assigning a shared associative array an AA literal

Manjaro/Arch x86_64, dmd 2.091.1. ldc does not seem to be affected. shared string[string] aa; void main() { aa = [ "abc" : "123" ]; } > Program received signal SIGSEGV, Segmentation fault. > 0x00007ffff7de2239 in _d_assocarrayliteralTX () from /usr/lib/libphobos2.so.0.91 https://run.dlang.io/is/D7AhPD Could not get a real backtrace into phobos as dmd built with digger crashes when compiling due to issue #18026.

Encountered this bug again today with DMD64 D Compiler v2.104.0 You can also try on the run.dlang.org link, the bug still there. Sigh, we have so many such basic bugs for more than 3 years now, with no fix. Does anyone know how to fix it? or any work-around? Thanks.

I investigate this bug and the problem is that ti.key (field of TypeInfo_AssociativeArray) is null. The sigsegv obviously occurs at this line https://github.com/dlang/dmd/blob/342a226833a0e9c7a90bbb64ae8dc35aa6d6bfdc/druntime/src/rt/aaA.d#L766 I'm trying to figure out what the reason for this would be and how to fix it.

I further diagnosed this. You don't need to declare the shared aa separately, this will do: ```d void main() { shared aa = ["abc": "123"]; } ``` If you declare `aa` as const instead, the `ti` parameter passed to `_d_assocarrayliteralTX` is a legit `TypeInfo_AssociativeArray`. However, when you use shared, the `ti` parameter is pointing to the wrapping `TypeInfo_Shared`. Note that this is a *reinterpret cast*, not a dynamic cast, and so it really thinks it's pointing at a `TypeInfo_AssociativeArray`. Therefore the `key` field doesn't actually exists, and is garbage. I'm not sure on LDC if this is a similar problem but it's possible since it's reading invalid memory it happens to work? I tend to think not. I ran on run.dlang.io for all compilers, and all segfault. So this has been happening for a while. const, immutable, and inout all do not have this problem, only shared. I also confirmed this is a problem on gdc.

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