davidbyttow / govips / 22505438302

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Add runtime.KeepAlive to prevent GC finalization during CGo calls (#494)

ImageRef methods that pass r.image to CGo functions without
referencing r afterward are vulnerable to a use-after-free: the GC
can finalize the ImageRef (via runtime.SetFinalizer) while the CGo
call is still executing on the underlying C.VipsImage pointer.

This manifests as flaky segfaults, e.g. TestImageRef_FindTrim_White
crashing with "instance of invalid non-instantiatable type" from GLib.

Fix: add defer runtime.KeepAlive(r) to all 33 vulnerable methods,
ensuring the receiver stays alive for the duration of each CGo call.
This is the standard Go idiom (used in os.File, net.Conn, etc.).

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

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2238 of 3119 relevant lines covered (71.75%)

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