HOMEBREW_SDKROOT not set on macOS 15.1.1

[Vdaleke]

brew doctor output

Your system is ready to brew.

Verification

• My "brew doctor output" above says Your system is ready to brew. and am still able to reproduce my issue.
• I ran brew update twice and am still able to reproduce my issue.
• This issue's title and/or description do not reference a single formula e.g. brew install wget. If they do, open an issue at https://github.com/Homebrew/homebrew-core/issues/new/choose instead.

brew config output

HOMEBREW_VERSION: 4.4.14
ORIGIN: https://github.com/Homebrew/brew
HEAD: f84082963da8af8c9ccd6dffbe932eba457e2b78
Last commit: 4 days ago
Branch: stable
Core tap JSON: 03 Jan 16:57 UTC
Core cask tap JSON: 03 Jan 16:57 UTC
HOMEBREW_PREFIX: /opt/homebrew
HOMEBREW_CASK_OPTS: []
HOMEBREW_MAKE_JOBS: 10
Homebrew Ruby: 3.3.6 => /opt/homebrew/Library/Homebrew/vendor/portable-ruby/3.3.6/bin/ruby
CPU: 10-core 64-bit arm_firestorm_icestorm
Clang: 16.0.0 build 1600
Git: 2.39.5 => /Library/Developer/CommandLineTools/usr/bin/git
Curl: 8.7.1 => /usr/bin/curl
macOS: 15.1.1-arm64
CLT: 16.2.0.0.1.1733547573
Xcode: N/A
Rosetta 2: false

What were you trying to do (and why)?

I want to set HOMEBREW_SDKROOT=/Library/Developer/CommandLineTools/SDKs/MacOSX14.sdk with HOMEBREW_CC=gcc-14 HOMEBREW_CXX=g++-14 HOMEBREW_SDKROOT=/Library/Developer/CommandLineTools/SDKs/MacOSX14.sdk brew --env

This needed for me to make 'brew install boost' with gcc-14 which is not compatible with MacOSX15.sdk (https://gist.github.com/scivision/d69faebbc56da9714798087b56de925a)

What happened (include all command output)?

HOMEBREW_CC: gcc-14
HOMEBREW_CXX: g++-14
MAKEFLAGS: -j10
CMAKE_PREFIX_PATH: /opt/homebrew
CMAKE_INCLUDE_PATH: /Library/Developer/CommandLineTools/SDKs/MacOSX15.sdk/System/Library/Frameworks/OpenGL.framework/Versions/Current/Headers
CMAKE_LIBRARY_PATH: /Library/Developer/CommandLineTools/SDKs/MacOSX15.sdk/System/Library/Frameworks/OpenGL.framework/Versions/Current/Libraries
PKG_CONFIG_LIBDIR: /usr/lib/pkgconfig:/opt/homebrew/Library/Homebrew/os/mac/pkgconfig/15
HOMEBREW_MAKE_JOBS: 10
HOMEBREW_GIT: git
HOMEBREW_SDKROOT: /Library/Developer/CommandLineTools/SDKs/MacOSX15.sdk
ACLOCAL_PATH: /opt/homebrew/share/aclocal
PATH: /opt/homebrew/Library/Homebrew/shims/mac/super:/usr/bin:/bin:/usr/sbin:/sbin:/opt/homebrew/opt/gcc/bin

What did you expect to happen?

SDKROOT is MacOSX14.sdk instead of MacOSX15.sdk

Step-by-step reproduction instructions (by running brew commands)

HOMEBREW_CC=gcc-14 HOMEBREW_CXX=g++-14 HOMEBREW_SDKROOT=/Library/Developer/CommandLineTools/SDKs/MacOSX14.sdk brew --env

[MikeMcQuaid]

HOMEBREW_SDKROOT is not a documented variable that users can set. What are you trying to do here?

[Bo98]

This needed for me to make 'brew install boost' with gcc-14 which is not compatible with MacOSX15.sdk

GCC 14 is compatible with macOS 15 SDK since October. You may need to do brew reinstall gcc if you have an older version.

GCC 13 and earlier isn't compatible yet, but that doesn't seem to be an issue here.

[Vdaleke]

HOMEBREW_SDKROOT is not a documented variable that users can set. What are you trying to do here?

Ok, I found out that I can set HOMEBREW_CC and HOMEBREW_CXX without problems and thought that was normal behaviour. As for SDKROOT I wanted to change it to 14 version for building boost.