fix(mac): correct memory width mismatch in keyCodeForChar

[PekingSpades]

Summary

Fix a memory corruption bug in keyCodeForChar() function in mac/TestInput/TestInput/TestInputController.m where a 64-bit pointer-sized value was being written into a 16-bit CGKeyCode variable, causing stack corruption.

Problem

The original code had a dangerous pointer/memory width mismatch:

CGKeyCode code;  // uint16_t, 16 bits
// ...
CFDictionaryGetValueIfPresent(charToCodeDict, charStr, (const void **)&code)

CFDictionaryGetValueIfPresent writes a pointer-sized value (64 bits on modern systems) to the memory location provided. Casting &code (a pointer to a 16-bit variable) to const void ** causes the function to write 8 bytes into a 2-byte memory location, corrupting 6 bytes of adjacent stack memory.

This is undefined behavior and can lead to:

• Stack corruption
• Random crashes
• Incorrect return values

Solution

Use an intermediate pointer-sized variable to safely receive the dictionary value, then cast to CGKeyCode:

const void *value = NULL;
CGKeyCode code;
if (CFDictionaryGetValueIfPresent(charToCodeDict, charStr, &value)) {
    code = (CGKeyCode)(uintptr_t)value;
} else {
    code = UINT16_MAX;
}

References

Apple Documentation

• CFDictionaryGetValueIfPresent | Apple Developer Documentation
• Apple CF Source - CFDictionary.h - The value parameter is documented as: "A pointer to memory which should be filled with the pointer-sized value if a matching key is found."

64-bit Porting Best Practices

• 20 issues of porting C++ code to the 64-bit platform (PVS-Studio) - Documents similar pointer truncation bugs: "Both examples do not take into account that the pointer size may differ from 32-bits. They use explicit type conversion which truncates high bits in the pointer, and this is an error on the 64-bit system."

may related issues: #3084 #894 #1005 #1072 #1143 #11674 #11673 #11057

[keymanapp-test-bot]

User Test Results

Test specification and instructions

ERROR: user tests have not yet been defined

[keyman-server]

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