Don't free regex objects in exit-time finalizer calls (#57834)

Fixes #57817 on 1.11

Author: IanButterworth

base/regex.jl

@@ -39,7 +39,12 @@ mutable struct Regex <: AbstractPattern
         end
         re = compile(new(pattern, compile_options, match_options, C_NULL))
         finalizer(re) do re
-            re.regex == C_NULL || PCRE.free_re(re.regex)
+            # don't free during exit because tasks may still be running and
+            # using it. Issue #57817
+            during_exit = Base._atexit_hooks_finished
+            if re.regex != C_NULL && !during_exit
+                PCRE.free_re(re.regex)
+            end
         end
         re
     end

test/regex.jl

@@ -245,3 +245,11 @@ end
         @test match(re, "ababc").match === SubString("ababc", 3:5)
     end
 end
+
+@testset "#57817: Don't free Regex during exit finalizer calls" begin
+    # this shouldn't segfault
+    cmd = `$(Base.julia_cmd()) -t2 --startup-file=no -e 're = Regex(""); Threads.@spawn match(re, "", 1, UInt32(0))'`
+    for i in 1:10
+        @test success(pipeline(cmd, stderr=stderr))
+    end
+end