CMake Error at /usr/local/share/cmake-3.18/Modules/FindPython/Support.cmake:615 (if):

[xkszltl]

🐛 Bug

This is a recent issue.

CMake Error at /usr/local/share/cmake-3.18/Modules/FindPython/Support.cmake:615 (if):
  Syntax error in cmake code at

    /usr/local/share/cmake-3.18/Modules/FindPython/Support.cmake:615 

  when parsing string

    python${version_major}\.${version_minor}+([dmu]*)

  Invalid escape sequence \.
Call Stack (most recent call first):
  /usr/local/share/cmake-3.18/Modules/FindPython/Support.cmake:2756 (_python_get_version)
  /usr/local/share/cmake-3.18/Modules/FindPython3.cmake:389 (include)
  CMakeLists.txt:14 (find_package)


-- Configuring incomplete, errors occurred!

Given 3.18.3 is recently released (we use latest, was 3.18.2), we're not sure whether it's from torchvision or cmake.

Environment

• PyTorch / torchvision Version (e.g., 1.0 / 0.4.0): master/master
• OS (e.g., Linux): CentOS 7 / Ubuntu 18.04
• How you installed PyTorch / torchvision (conda, pip, source): source
• Build command you used (if compiling from source): cmake-3.18.3 + ninja + (gcc-9 from devtoolset-9/stock gcc-8)
• Python version: Distro stock python3.
• CUDA/cuDNN version: 11.0/8

[xkszltl]

Note pytorch was built just fine. Only torchvision has the issue.

[xkszltl]

Also filed the issue here in case it's caused by cmake bug: https://gitlab.kitware.com/cmake/cmake/-/issues/21223

[fmassa]

Could you try seeing if #2684 is the culprit, and if reverting it makes it work for you?

[xkszltl]

That's probably not the root cause.
CMake side found their regex bug in 3.18.3.

[xkszltl]

I tried their patch and works.

[xkszltl]

Meanwhile there's a hack to make it work in 3.18.3 without patching cmake.
The issue is there's \. which should be \\. instead.
Could you change this line to 3.1?

vision/CMakeLists.txt

Line 1 in 662373f

cmake_minimum_required(VERSION 3.0)

That will set CMP0053=New, which makes the \. recognizable as . (escaped .), and matches everything in regex, including a dot in version.
https://cmake.org/cmake/help/v3.18/policy/CMP0053.html

[fmassa]

@xkszltl can you send a PR with the proposed fix, linking to this issue?

[xkszltl]

Sure, I thought you guys would just put it in whatever PR that comes next.