feature/native-comp 566f0f1 4/5: * Improve load_comp_unit

[Andrea Corallo]

branch: feature/native-comp
commit 566f0f1b639c7cba5b7d6763fb13aa42a5cc4535
Author: AndreaCorallo <address@hidden>
Commit: Andrea Corallo <address@hidden>

    * Improve load_comp_unit
    
    Fix uninitialized ephemeral data relocation for the case when a dumped
    compilation unit is manually reloaded.
    
    Guard also data_ephemeral_vec against compiler optimizations.
---
 src/comp.c | 47 ++++++++++++++++++++++++++---------------------
 1 file changed, 26 insertions(+), 21 deletions(-)

diff --git a/src/comp.c b/src/comp.c
index 4940ae5..8176ba2 100644
--- a/src/comp.c
+++ b/src/comp.c
@@ -3388,6 +3388,8 @@ load_comp_unit (struct Lisp_Native_Comp_Unit *comp_u, 
bool loading_dump)
   if (!saved_cu)
     xsignal1 (Qnative_lisp_file_inconsistent, comp_u->file);
   bool reloading_cu = *saved_cu ? true : false;
+  Lisp_Object *data_eph_relocs =
+    dynlib_sym (handle, DATA_RELOC_EPHEMERAL_SYM);
 
   /* While resurrecting from an image dump loading more than once the
      same compilation unit does not make any sense.  */
@@ -3419,19 +3421,7 @@ load_comp_unit (struct Lisp_Native_Comp_Unit *comp_u, 
bool loading_dump)
       EMACS_INT ***pure_reloc = dynlib_sym (handle, PURE_RELOC_SYM);
       Lisp_Object *data_relocs = dynlib_sym (handle, DATA_RELOC_SYM);
       Lisp_Object *data_imp_relocs = dynlib_sym (handle, 
DATA_RELOC_IMPURE_SYM);
-      Lisp_Object *data_eph_relocs =
-       dynlib_sym (handle, DATA_RELOC_EPHEMERAL_SYM);
       void **freloc_link_table = dynlib_sym (handle, FUNC_LINK_TABLE_SYM);
-      Lisp_Object volatile data_ephemeral_vec;
-
-      /* Note: data_ephemeral_vec is not GC protected except than by
-        this function frame.  After this functions will be
-        deactivated GC will be free to collect it, but it MUST
-        survive till 'top_level_run' has finished his job.  We store
-        into the ephemeral allocation class only objects that we know
-        are necessary exclusively during the first load.  Once these
-        are collected we don't have to maintain them in the heap
-        forever.  */
 
       if (!(current_thread_reloc
            && pure_reloc
@@ -3457,12 +3447,6 @@ load_comp_unit (struct Lisp_Native_Comp_Unit *comp_u, 
bool loading_dump)
          comp_u->data_vec = load_static_obj (comp_u, TEXT_DATA_RELOC_SYM);
          comp_u->data_impure_vec =
            load_static_obj (comp_u, TEXT_DATA_RELOC_IMPURE_SYM);
-         data_ephemeral_vec =
-           load_static_obj (comp_u, TEXT_DATA_RELOC_EPHEMERAL_SYM);
-
-         EMACS_INT d_vec_len = XFIXNUM (Flength (data_ephemeral_vec));
-         for (EMACS_INT i = 0; i < d_vec_len; i++)
-           data_eph_relocs[i] = AREF (data_ephemeral_vec, i);
 
          if (!NILP (Vpurify_flag))
            /* Non impure can be copied into pure space.  */
@@ -3479,9 +3463,30 @@ load_comp_unit (struct Lisp_Native_Comp_Unit *comp_u, 
bool loading_dump)
     }
 
   if (!loading_dump)
-    /* Executing this will perform all the expected environment
-       modifications.  */
-    top_level_run (comp_u_lisp_obj);
+    {
+      /* Note: data_ephemeral_vec is not GC protected except than by
+        this function frame.  After this functions will be
+        deactivated GC will be free to collect it, but it MUST
+        survive till 'top_level_run' has finished his job.  We store
+        into the ephemeral allocation class only objects that we know
+        are necessary exclusively during the first load.  Once these
+        are collected we don't have to maintain them in the heap
+        forever.  */
+
+      Lisp_Object volatile data_ephemeral_vec  =
+       load_static_obj (comp_u, TEXT_DATA_RELOC_EPHEMERAL_SYM);
+
+      EMACS_INT d_vec_len = XFIXNUM (Flength (data_ephemeral_vec));
+      for (EMACS_INT i = 0; i < d_vec_len; i++)
+       data_eph_relocs[i] = AREF (data_ephemeral_vec, i);
+
+      /* Executing this will perform all the expected environment
+        modifications.  */
+      top_level_run (comp_u_lisp_obj);
+      /* Make sure data_ephemeral_vec still exists after top_level_run has run.
+        Guard against sibling call optimization (or any other).  */
+      data_ephemeral_vec = data_ephemeral_vec;
+    }
 
   return;
 }