Reflect the status of the naked pointer checker in the exit code (#10171

)

If the out-of-heap pointer test is tripped at any point, don't allow the
process to exit normally with code 0. If `caml_sys_exit` is ultimately
passed 0, change it to 70 (but any other non-zero code is preserved).

Changes

@@ -61,6 +61,10 @@ Working version
 - #10136: Minor clean-ups in runtime/io.c and runtime/caml/io.h
   (Xavier Leroy, review by David Allsopp and Guillaume Munch-Maccagnoni)
 
+- #10171: Tweak the naked pointers checker so that processes which trigger the
+  alarm always exit with non-zero status (i.e. exit(0) becomes exit(70)).
+  (David Allsopp, review by Xavier Leroy)
+
 - #10188, #10213: Switch the default allocation policy to best-fit and adjust
   the default overhead parameter accordingly.
   (Damien Doligez, review by Josh Berdine and Xavier Leroy)

runtime/caml/major_gc.h

@@ -98,6 +98,10 @@ void caml_set_major_window (int);
 */
 void caml_finalise_heap (void);
 
+#ifdef NAKED_POINTERS_CHECKER
+extern int caml_naked_pointers_detected;
+#endif
+
 #endif /* CAML_INTERNALiS */
 
 #endif /* CAML_MAJOR_GC_H */

runtime/major_gc.c

@@ -127,6 +127,10 @@ double caml_gc_clock = 0.0;
 static unsigned long major_gc_counter = 0;
 #endif
 
+#ifdef NAKED_POINTERS_CHECKER
+int caml_naked_pointers_detected = 0;
+#endif
+
 void (*caml_major_gc_hook)(void) = NULL;
 
 /* This function prunes the mark stack if it's about to overflow. It does so
@@ -1163,6 +1167,7 @@ static void is_naked_pointer_safe (value v, value *p)
   if (Is_black_hd(h) && Wosize_hd(h) < (INT64_LITERAL(1) << 40))
     return;
 
+  caml_naked_pointers_detected = 1;
   if (!Is_black_hd(h)) {
     fprintf (stderr, "Out-of-heap pointer at %p of value %p has "
                      "non-black head (tag=%d)\n", p, (void*)v, t);
@@ -1175,6 +1180,7 @@ static void is_naked_pointer_safe (value v, value *p)
   return;
 
  on_segfault:
+  caml_naked_pointers_detected = 1;
   fprintf (stderr, "Out-of-heap pointer at %p of value %p. "
            "Cannot read head.\n", p, (void*)v);
 }

runtime/sys.c

@@ -49,6 +49,7 @@
 #include "caml/debugger.h"
 #include "caml/fail.h"
 #include "caml/gc_ctrl.h"
+#include "caml/major_gc.h"
 #include "caml/io.h"
 #include "caml/misc.h"
 #include "caml/mlvalues.h"
@@ -159,6 +160,13 @@ CAMLprim value caml_sys_exit(value retcode_v)
     caml_shutdown();
 #ifdef _WIN32
   caml_restore_win32_terminal();
+#endif
+#ifdef NAKED_POINTERS_CHECKER
+  if (retcode == 0 && caml_naked_pointers_detected) {
+    fprintf (stderr, "\nOut-of-heap pointers were detected by the runtime.\n"
+                     "The process would otherwise have terminated normally.\n");
+    retcode = 70; /* EX_SOFTWARE; see sysexits.h */
+  }
 #endif
   exit(retcode);
 }