Fix for CAF retention when dynamically loading & unloading code

In a situaion where we have some statically-linked code and we want to
load and unload a series of objects, we need the CAFs in the
statically-linked code to be retained indefinitely, while the CAFs in
the dynamically-linked code should be GC'd as normal, so that we can
detect when the code is unloadable.  This was wrong before - we GC'd
CAFs in the static code, leading to a crash in the rare case where we
use a CAF, GC it, and then load a new object that uses it again.

I also did some tidy up: RtsConfig now has a field keep_cafs to
indicate whether we want CAFs to be retained in static code.

1 files changed, 5 insertions, 1 deletions

diff --git a/rts/RtsStartup.c b/rts/RtsStartup.c
index c50bb07f75..f6544b6aba 100644
--- a/rts/RtsStartup.c
+++ b/rts/RtsStartup.c
@@ -138,12 +138,16 @@ hs_init_ghc(int *argc, char **argv[], RtsConfig rts_config)
     stat_startInit();
 
     /* Set the RTS flags to default values. */
-
     initRtsFlagsDefaults();
 
     /* Call the user hook to reset defaults, if present */
     rts_config.defaultsHook();
 
+    /* Whether to GC CAFs */
+    if (rts_config.keep_cafs) {
+        setKeepCAFs();
+    }
+
     /* Parse the flags, separating the RTS flags from the programs args */
     if (argc == NULL || argv == NULL) {
         // Use a default for argc & argv if either is not supplied