Proposal to Update ITK's Minimum macOS Deployment Target to 10.15 (Catalina)

[thewtex]

Rationale

1. Apple’s Deprecation of Older macOS Versions

• macOS 10.15 (Catalina) loses security support on June 30, 2025, creating vulnerabilities for users on older systems¹.
• Current ITK Python builds default to macOS 10.9 (Intel), macOS 10.11 (ARM), which are no longer receiving security updates¹².

2. C++17 and SDK Compatibility

• Full C++17 support (e.g., <filesystem>, <variant>) requires macOS 10.15 or newer³⁴⁵.
• Legacy deployment targets (e.g., 10.9–10.13) force workarounds like <experimental/filesystem>, increasing maintenance complexity³⁶.
• Modern compilers (Xcode 15+) and SDKs increasingly enforce stricter compatibility checks, causing build failures on older targets⁷⁸.

3. Compiler Optimizations

• Newer macOS SDKs enable advanced optimizations (e.g., autovectorization, LTO) that are restricted on older deployment targets.

4. Maintenance Burden

• Third-party projects (e.g., PyTorch) are dropping support for macOS <10.15, creating compatibility gaps⁹⁷⁵.

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Proposed Changes

1. Update Minimum Deployment Target
   • Set MACOSX_DEPLOYMENT_TARGET to 10.15 for ITK 6.x in Python wheels.
   • Document 10.15 as the new baseline for macOS support.
2. CI/CD Pipeline Updates
   • Update macOS runners with macos-15+ runners⁹⁸ We may need self-hosted runners for Intel support (Proposal for macOS Intel Support deprecation timeline in ITK 6 (Retained in ITK 5) #5326).
3. C++17 Modernization
   • Replace deprecated headers (e.g., <experimental/filesystem>) with standard C++17 equivalents.

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Impact Mitigation

• LTS Branch: Maintain ITK 5.x with macOS 10.9 support for legacy workflows ⁹¹⁰.

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Supporting Data

Key Point	Source
macOS 10.15 security EOL: June 2025	12
C++17 <filesystem> requires 10.15	345
Xcode 15+ enforces 10.13+ targets	78

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Request for Feedback

1. Are there critical use cases requiring macOS <10.15?
2. Concerns about dependency compatibility (e.g., hardware drivers)?

Proposed timeline: Target ITK 6.0 (2025) to align with macOS 10.15’s security EOL.

CC @seanm @blowekamp @hjmjohnson @cookpa @imikejackson @SimonRit @jcfr @jamesobutler

Footnotes

1. https://access.tufts.edu/macos-1015-support-ends-june-30-2025-take-action-now ↩ ↩² ↩³

2. https://discussions.apple.com/thread/255690857 ↩ ↩²

3. https://cibuildwheel.pypa.io/en/stable/cpp_standards/ ↩ ↩² ↩³

4. https://forum.juce.com/t/c-17-minimum-deployment-target/32109 ↩ ↩²

5. https://github.com/nlohmann/json/issues/3156 ↩ ↩² ↩³

6. https://forum.juce.com/t/fix-for-using-c-11-features-with-osx-10-7-deployment-target/25247 ↩

7. https://github.com/apple/swift/issues/68163 ↩ ↩² ↩³

8. https://github.com/sparkle-project/Sparkle/issues/2186 ↩ ↩² ↩³

9. https://github.com/InsightSoftwareConsortium/ITK/issues/5326 ↩ ↩² ↩³

10. https://computercity.com/desktops/mac/how-long-will-intel-macs-be-supported ↩

[seanm]

This is ok for me. I've therefore retired the Rogue22 bot from submitting to CDash. You can unexpect it now.

[dzenanz]

You can unexpect it now

Done.