I am trying to build my companies compiler using –std=c++23. Unfortunately some header files in MLIR are not compatible. To be clear, I am not asking about/for any c++23 features in MLIR. Just that downstream projects that use MLIR and want to compile their codebases with c++23 can. My 2 concrete …

If it could be done in a stand-alone build bot that would be easiest. In tree probably with some cmake optional compilation & testing too (given LLVM repo is still on and required to compile with C++17 only compilers, restricted in test requiring more for all consumers). Although here, couldn’t one …

Isn’t C++17, (C++20?) a subset of C++=23 ?

Although here, couldn’t one just set the standard during cmake configuration/bazel compilation option rather than needing a new file/test? Adding a standard cmake configuration instead of adding a new test would mean that I would have to change all the source files to be compatible with C++23 com…

Mostly. But things can be deprecated. And example being std::aligned_union : https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2021/p1413r3.pdf

[image] philass: They seem to be related to AnalysisState’s full definition not being available to mlir/Analysis/DataFlowFramework.h. It is only forward declared. llvm-project/mlir/include/mlir/Analysis/DataFlowFramework.h at main · llvm/llvm-project · GitHub I’m curious why is this a C++23-o…

I believe C++ may have tightened the rules. P0722R3: Efficient sized delete for variable sized classes For what its worth, this was only an issue in clang and not gcc. I was able to get the mlir/Analysis/DataFlowFramework.h part to compile with C++23 with the following change diff --git a/mlir/in…

IMO it’s perfectly fine to land forward-compat changes for C++, but I wouldn’t want this to become a (blocking) CI check until we actually decide on making the switch to C++23 and the new minimum toolchains required. We are going to switch to C++23 eventually, but until this becomes a thing, the int…

the interested parties should cover the maintenance cost. I struggle to see what the maintenance cost is. The vast majority of all code passes with C++23 out of the box. For context to build LLVM/MLIR with C++ I had to make the following changes git diff --stat llvm/include/llvm/CodeGen/Machine…

I think it should be similar to how we approach bazel support – it lives inside the repo but contributors are not required to update the bazel build files. Many folks do it anyway because most cmake changes map 1:1 to bazel changes, but everything else that was not handled is patched by the bazel ma…

[image] kuhar: We are going to switch to C++23 eventually, but until this becomes a thing, the interested parties should cover the maintenance cost. I tend to separate the minimum C++ version (which is the default one we use) with the supported version: we supported C++17 much earlier than th…

What is the status of C++23 Support in MLIR

MLIR

mehdi_amini August 4, 2025, 8:39pm 12

Thanks! Let’s just add the missing include though. I wasn’t pushing back on this, that was a curiosity.

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RFC: Raise the minimum compiler requirements to move toward C++20 LLVM Project	26	1909	February 26, 2026
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[RFC] Upgrading LLVM's minimum required CMake version LLVM Project	23	3712	January 12, 2024

What is the status of C++23 Support in MLIR

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