[quinnj-bot]

A StackOf{T} holds a reference to each element:

• push! takes one: X509_up_ref for certificates, a copy (X509_EXTENSION_dup, X509_ATTRIBUTE_dup, BN_dup) for the rest.
• The stacks OpenSSL returns hand over their elements: req.extensions (X509_REQ_get_extensions) and the CA stack from unpack (PKCS12_parse).
• pop! already passes the stack's reference on to the wrapper it returns.

But free (also the finalizer) called only OPENSSL_sk_free, which frees the stack and none of its elements. Every element still in a stack when it went leaked: the pushed certificate (its count never reached zero), and the copied extension. Each req.extensions call leaked the request's extensions.

Fix

• free pops and frees the remaining elements before freeing the stack.
• pop! on an empty stack throws ArgumentError. Before, it wrapped the NULL that OPENSSL_sk_pop returns, and the first use of that wrapper crashed.

Verification

• New testset StackOwnsElements:

  • It counts certificate frees with an ex_data free callback (CRYPTO_get_ex_new_index on CRYPTO_EX_INDEX_X509), with GC disabled around the count.
  • It pushes three certificates and frees each wrapper, then frees the stack: three frees.
  • On main, none (4 == 7 fails), and the pop! check fails.

• Memory growth (maxrss) over N rounds, main → this branch:

  Round	N	main	this branch
  push a new certificate, free stack and wrapper	40,000	227.9 MiB	2.5 MiB
  push an extension, free both	100,000	6.6 MiB	0.7 MiB
  req.extensions (left to the finalizer)	100,000	8.1 MiB	1.2 MiB

• Full suite on Julia 1.12 -t 4: passes. The existing StackOf tests push, pop, finalize and free in every order.

Self-review

• Every StackOf the package makes owns its elements: StackOf{T}() with push!, get_extensions, and unpack (OpenSSL's documentation: the caller frees *ca with OSSL_STACK_OF_X509_free). No code in the package wraps a borrowed stack such as SSL_get_peer_cert_chain.
• A NULL stack (unpack of a PKCS#12 with no CA certificates leaves *ca NULL): OPENSSL_sk_num(NULL) is -1, so nothing is popped.
• The finalizer now allocates one wrapper per element and frees it at once. Allocation and finalizer registration are allowed in a finalizer, and nothing there waits or takes a lock.
• pop! on an empty stack used to return a wrapper around NULL; it now throws, as pop! on an empty Vector does.

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.12%. Comparing base (14a9842) to head (867771d).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #112      +/-   ##
==========================================
+ Coverage   83.07%   83.12%   +0.05%     
==========================================
  Files           2        2              
  Lines        1341     1345       +4     
==========================================
+ Hits         1114     1118       +4     
  Misses        227      227              

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