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Dave Airlie Linux Graphics blog

Fedora 38 LLVM vs Team Fortress 2 (TF2)

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April 23, 2023

F38 just released and seeing a bunch of people complain that TF2 dies
on AMD or other platforms when lavapipe is installed. Who's at fault?
I've no real idea. How to fix it? I've no real idea.

What's happening?

AMD OpenGL drivers use LLVM as the backend compiler. Fedora 38
updated to LLVM 16. LLVM 16 is built with c++17 by default. C++17
introduces new "operator new/delete" interfaces[1].

TF2 ships with it's own libtcmalloc_minimal.so implementation,
tcmalloc expects to replace all the new/delete interfaces, but the
version in TF2 must not support or had incorrect support for the new
align interfaces.

What happens is when TF2 probes OpenGL and LLVM is loaded, when
DenseMap initializes, one "new" path fails to go into tcmalloc, but
the "delete" path does, and this causes tcmalloc to explode with

"src/tcmalloc.cc:278] Attempt to free invalid pointer"

Fixing it?

I'll talk to Valve and see if we can work out something, LLVM 16
doesn't seem to support building with C++14 anymore. I'm not sure if
static linking libstdc++ into LLVM might avoid the tcmalloc
overrides, it might not also be acceptable to the wider Fedora
community.

[1] https://www.cppstories.com/2019/08/newnew-align/

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