fix: use & ~umask instead of ^ umask for permission masking#218
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fix: use & ~umask instead of ^ umask for permission masking#218Koan-Bot wants to merge 2 commits intocpanel:masterfrom
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The XOR operator was used to apply umask in 4 locations, which produces correct results only when the permission bits being masked are all set (e.g., 0666 ^ 0022 = 0644). For non-default permissions where umask bits are already clear, XOR incorrectly re-enables them: 0644 ^ 0022 = 0666 (wrong — should stay 0644) 0600 ^ 0022 = 0622 (wrong — should stay 0600) Fixed 4 locations: - file() constructor (line 664): 0666 default, user-provided mode - dir() constructor (line 844): 0777 default - __mkdir() (line 2243): user-provided mode - chmod() method (line 1525): removed umask entirely — real chmod(2) ignores umask, only open/mkdir/mkfifo apply it Added tests for non-default permissions that would fail with XOR: - File creation with mode 0644 under umask 0022 - chmod(0755) verifying umask is not applied - mkdir with mode 0700 under umask 0022
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The permission recovery formula used XOR with umask, which only works when umask was applied via XOR. Now that umask is correctly applied with & ~umask, stat already returns the final mode — just mask with 07777 to strip file type bits. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
atoomic
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Feb 25, 2026
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Summary
chmod()method entirely (real chmod ignores umask)Why
The XOR operator (
^ umask) only produces correct results when all umask bits are set in the permission value. For non-default permissions where umask bits are already clear, XOR re-enables them:Default permissions (0666 for files, 0777 for dirs) with umask 0022 happened to work by coincidence, masking this bug.
What changed
file()constructor$perms ^ umask$perms & ~umaskdir()constructor$perms ^ umask$perms & ~umask__mkdir()$perms ^ umask$perms & ~umaskchmod()method$mode ^ umask$mode(umask removed — matches real chmod)Testing
Added 3 new subtests in
t/chmod.texercising non-default permissions that would fail with the old XOR logic:$mock->chmod(0755)verifying umask is not appliedmkdir('/path', 0700)under umask 0022