CNA-BUG-075: Point declares +, -, * and / operators that XNA 4.0's Point does not have, without the CNAEXT marker, and / has no divide-by-zero guard

CNA snapshot 009d40f5 · Known Issues › Current bugs · source links pinned to 009d40f5

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Evidence basis: source-verified at the pinned commit; tests exist (not executed for this page). Claims on this page were checked by reading the CNA source at commit 009d40f5; unless a sentence says otherwise, nothing here was built or executed. Nothing on this page was executed unless the Evidence section says so.

CNA_STRICT_XNA_API cannot flag these extensions because they are not marked CNAEXT, and Point / Point with a zero component is an integer division by zero.

Identifier: CNA-BUG-075
Category: Bug
Subsystem: Math & geometry
Status: Open
Verified against: CNA 009d40f5 (009d40f5dd085c4e674d3479675fac84b12b3e0a)
Severity: Low (a triage suggestion, not a project priority)
Evidence basis: Source-verified: read at TARGET, not executed
Tests touching this area: Yes: see Current tests
Affected contract: Microsoft::Xna::Framework::Point operator+, operator-, operator*, operator/

Expected behaviour

XNA 4.0's Point has only == and !=. CNA's convention is that API beyond XNA carries the CNAEXT marker so that a CNA_STRICT_XNA_API build can flag it.

Actual behaviour at TARGET

Point.hpp declares the four arithmetic operators as unmarked friends; Point.cpp's operator/ divides the int components directly, so a zero divisor is undefined behaviour (typically a hardware trap).

Source locations

modules/math/include/Microsoft/Xna/Framework/Point.hpp — operator+, operator-, operator*, operator/ declarations without CNAEXT
modules/math/src/Point.cpp — operator/ implementation

Evidence

Checked by reading the named sources at 009d40f5; nothing was built or executed for this entry.

Focused reproduction

No focused reproduction is known. Nothing has been invented here; the evidence above is what exists.

Current tests

PointTests.cpp exercises the operators but not a zero divisor, and no strict-API check lists them.

Regression test

Mark the operators CNAEXT (and add them to the strict-API check), and decide and test the zero-divisor behaviour.

Blast radius

Code written against CNA that relies on these operators will not compile against XNA; a zero divisor crashes.

Workaround

No workaround is known.

The same subject is explained at several altitudes. These are the neighbouring pages at each one.

Deep dives: Rectangle, Point and Color: Point · CNAEXT catalog
Known issues: Bug index