CURLOPT_SHARE: warn about early remove

Add a warning to removing a SHARE from an EASY handle before it is
finished.

Closes #21633

diff --git a/docs/libcurl/opts/CURLOPT_SHARE.md b/docs/libcurl/opts/CURLOPT_SHARE.md
index 2c6a496593fdc9a04979a695ca129bbf37696aa2..907e4f280519ea67d6038058ecbcf88669d4c910 100644 (file)
--- a/docs/libcurl/opts/CURLOPT_SHARE.md
+++ b/docs/libcurl/opts/CURLOPT_SHARE.md
@@ -43,6 +43,9 @@ if no share was used.
 
 Set this option to NULL again to stop using that share object.
 
+Warning: adding a *share* and then setting it to NULL while the transfer
+is ongoing is discouraged and may lead to undefined behavior.
+
 # DEFAULT
 
 NULL