common: Cast via uintptr_t rather than unsigned long in UNCONST

[jrtc27]

On ILP32 and LP64 systems, unsigned long is sufficient to round-trip pointers, but on LLP64 systems it is too small, and on systems like CHERI where pointers are capabilities, it does not propagate capability metadata, and casting back to a pointer to yield a pointer that cannot be dereferenced.

Instead, cast via uintptr_t to ensure we always use an integral type that can losslessly round-trip pointers.

[coderabbitai]

Walkthrough

A single macro UNCONST(a) in src/common.h was updated to use uintptr_t instead of unsigned long for casting, improving portability and width-safety when converting const void pointers to void pointers.

Changes

Cohort / File(s)	Summary
Macro cast type update src/common.h	Updated UNCONST(a) macro cast from unsigned long to uintptr_t for width-safe pointer conversion

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~2 minutes

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately summarizes the main change: replacing unsigned long with uintptr_t in the UNCONST macro cast.
Description check	✅ Passed	The description clearly explains the rationale for the change, detailing why uintptr_t is more appropriate than unsigned long across different architectures.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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✨ Finishing touches

• 📝 Generate docstrings

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📜 Recent review details

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between cd0b269 and f5d3a4c.

📒 Files selected for processing (1)

• src/common.h

🔇 Additional comments (1)

src/common.h (1)

58-58: Excellent portability fix!

This change correctly addresses critical issues on LLP64 and CHERI systems. Using uintptr_t instead of unsigned long ensures:

• LLP64 (Windows x64): Prevents pointer truncation (where unsigned long is 32 bits but pointers are 64 bits)
• CHERI capability systems: Preserves capability metadata during the cast
• Standards compliance: uintptr_t is the C99/C11 standard type designed specifically for lossless pointer-to-integer round-trips

The required <stdint.h> header is already included (Line 35), so the change is safe to deploy immediately.

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[rsmarples]

Thanks!