Fix: fix SIGSEGV/SIGBUS crash in macOS keyboard functions

[PekingSpades]

Description

Fix SIGSEGV/SIGBUS crashes in macOS keyboard functions.

Fixes: #690, #732, #486

Related Issues Analysis

Issue	Title	Environment	Symptom
#690	Keyboard Function Crashes on macOS	macOS 15.0, M3 (arm64), Go 1.22.4	SIGSEGV/SIGBUS in _Cfunc_keyCodeForChar() when calling KeyTap/KeyToggle/KeyUp/KeyDown
#732	robotgo.KeyTap Fails on Macos X86	macOS X86, Go 1.24.0	SIGSEGV at address 0x8 in _Cfunc_keyCodeForChar(0x76) when calling KeyTap("v","cmd")
#486	KeyTap Segmentation Violation	macOS 10.13.4 ~ 14.4+, Intel & Apple Silicon	Long-standing issue (since 2022) with 13+ reports, crash in keyCodeForChar()

Common pattern: All three issues crash at the same location (keyCodeForChar) with SIGSEGV at address 0x8, which is the signature of stack corruption from writing 8 bytes into a 2-byte variable.

Root Cause

In keyCodeForChar(), the code passes a CGKeyCode* (2 bytes) to CFDictionaryGetValueIfPresent() which expects const void** (8 bytes on 64-bit). This overwrites adjacent stack memory, causing crashes when critical data is affected.

Technical details with official documentation:

• CGKeyCode is defined as UInt16 (16-bit / 2 bytes)
• CFDictionaryGetValueIfPresent() third parameter is const void**, which writes a pointer-sized value
• On 64-bit macOS (LP64 data model), pointers are 8 bytes

When CFDictionaryGetValueIfPresent() writes 8 bytes into a 2-byte CGKeyCode variable, it corrupts 6 bytes of adjacent stack memory.

The crash manifests on different macOS configurations depending on stack layout (compiler version, optimization level, ABI). Affected reports span:

• Apple Silicon M1/M3 (Crash on KeyTap, KeyToggle, KeyUp and KeyDown. Mac m3 macOS 15 #690)
• Intel x86_64 (robotgo.KeyTap Fails on Macos X86 #732)
• Multiple macOS versions 10.13 - 15.x (KeyTap panic runtime from v1.0.0-beta4 : segmentation violation #486)

Changes

key/keycode_c.h:

1. keyCodeForChar(): Use pointer-sized variable for CFDictionaryGetValueIfPresent()
2. createStringForKey(): Add NULL check for TISCopyCurrentKeyboardLayoutInputSource() and fix memory leak when layoutData is nil
   • Note: TISGetInputSourceProperty can return NULL with certain input methods (e.g., Japanese keyboards). See Apple Developer Forums discussion.

References

• CFDictionaryGetValueIfPresent | Apple Developer Documentation
• CGKeyCode | Apple Developer Documentation
• Major 64-Bit Changes (LP64) | Apple Developer Documentation
• Making Code 64-Bit Clean | Apple Developer Documentation
• TISGetInputSourceProperty documentation | Apple Developer Forums

Testing

• Tested on macOS (Apple Silicon)
• Verified with reproduction code from Crash on KeyTap, KeyToggle, KeyUp and KeyDown. Mac m3 macOS 15 #690

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Signed-off-by: PekingSpades [email protected]

Summary by CodeRabbit

• Bug Fixes
  • Improved keyboard handling stability on macOS with enhanced pointer management
  • Fixed potential memory leak in keyboard layout data processing
  • Added safety checks to prevent crashes from null keyboard data

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[CLAassistant]

All committers have signed the CLA.

[coderabbitai]

📝 Walkthrough

Walkthrough

The fix addresses 64-bit pointer handling and memory management issues in keyboard code mapping on macOS. It improves safety in keyCodeForChar by using CFDictionaryGetValueIfPresent with a pointer-sized temporary, and adds NULL checks with proper resource cleanup in createStringForKey to prevent crashes and memory leaks.

Changes

Cohort / File(s)	Summary
Keyboard pointer handling safety key/keycode_c.h	Replaced direct pointer casting with pointer-sized temporary (codePtr) in keyCodeForChar for safer 64-bit value retrieval; added NULL checks for currentKeyboard in createStringForKey with early return; added layoutData NULL check with currentKeyboard cleanup to prevent memory leak

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Poem

🐰 Pointers behaved so very wild,
Causing crashes, unreconciled,
Now with checks both safe and sound,
Keyboard keys won't crash around!
Memory leaks now cleaned with care, 🔧✨

Pre-merge checks and finishing touches

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	You can run @coderabbitai generate docstrings to improve docstring coverage.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description check	✅ Passed	The description is comprehensive, well-structured, and provides detailed context including root cause analysis, technical details, changes made, and testing information.
Linked Issues check	✅ Passed	The PR addresses SIGSEGV/SIGBUS crashes in macOS keyboard functions by fixing pointer size mismatch in CFDictionaryGetValueIfPresent() calls and adding NULL checks for keyboard layout data, directly resolving the crashes reported in #690.
Out of Scope Changes check	✅ Passed	All changes in key/keycode_c.h are directly related to fixing the stack corruption issue and memory leak in keyboard functions, with no extraneous modifications.
Title check	✅ Passed	The title accurately describes the main change: fixing SIGSEGV/SIGBUS crashes in macOS keyboard functions, which is the primary objective of the pull request.

✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment

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