Change #276551

Comments

lib5004: fix memleak on OOM, check all slist append results (httpsig)
Detected by torture tests:
```
test 5004...[HTTP RFC 9421 B.2.6: Ed25519 POST with headers (RFC test vector)]
 105 functions found, but only fail 25 (23.81%)
** MEMORY FAILURE
Leak detected: memory still allocated: 99 bytes
At 6000022c9408, there is 36 bytes.
 allocated by /Users/runner/work/curl/curl/lib/slist.c:87
At 6000039c8e78, there is 31 bytes.
 allocated by /Users/runner/work/curl/curl/lib/slist.c:87
At 6000037dd688, there is 16 bytes.
 allocated by /Users/runner/work/curl/curl/lib/slist.c:62
At 6000037dd628, there is 16 bytes.
 allocated by /Users/runner/work/curl/curl/lib/slist.c:62
LIMIT /Users/runner/work/curl/curl/lib/slist.c:62 malloc reached memlimit
 5004: torture FAILED: function number 10 in test.
```
Ref: https://github.com/curl/curl/actions/runs/30497660391/job/90730128599?pr=22437#step:16:2331

Also:
- enable HTTPSIG in torture tests.
- NULL check all `curl_slist_append()` results.
- apply a NULL check to sibling test 5000 also.

Co-authored-by: Daniel Stenberg
Follow-up to a55731050e8c3dbea0b96205cf916443118f6acb #22386 #21239

Closes #22437

Changed files

• .github/workflows/linux.yml
• tests/libtest/lib5000.c
• tests/libtest/lib5004.c