[ruby-core:79349] [Ruby trunk Bug#4630][Closed] PROCDEBUG to non-zero values causes segmentation faults in check_env in trunk

Issue #4630 has been updated by Koichi Sasada.

Description updated
Status changed from Assigned to Closed

Now, we don't see this issue.

----------------------------------------
Bug #4630: PROCDEBUG to non-zero values causes segmentation faults in check_env in trunk
https://bugs.ruby-lang.org/issues/4630#change-62772

* Author: Elise Huard
* Status: Closed
* Priority: Normal
* Assignee: Koichi Sasada
* Target version: next minor
* ruby -v: -
* Backport: 2.2: UNKNOWN, 2.3: UNKNOWN, 2.4: UNKNOWN
----------------------------------------

PROCDEBUG is meant to show debugging output from the vm.
However, when it's activated in vm.c
#define PROCDEBUG 1
The make process fails in segmentation faults.

I've narrowed it down to the following variables displayed in check_env: env->block.dfp[3] and env->block.dfp[4]
Commenting them out like so makes the segfaults disappear. 

```
  static int
  check_env(rb_env_t * const env)
  {
      printf("---\n");
      printf("envptr: %p\n", (void *)&env->block.dfp[0]);
      printf("orphan: %p\n", (void *)env->block.dfp[1]);
      printf("inheap: %p\n", (void *)env->block.dfp[2]);
      /* printf("envval: %10p ", (void *)env->block.dfp[3]);
      dp(env->block.dfp[3]);
      printf("penvv : %10p ", (void *)env->block.dfp[4]);
       dp(env->block.dfp[4]); */
      printf("lfp:    %10p\n", (void *)env->block.lfp);
      printf("dfp:    %10p\n", (void *)env->block.dfp);
    /*  if (env->block.dfp[4]) {
          printf(">>\n");
          check_env_value(env->block.dfp[4]);
          printf("<<\n");
      } */
      return 1;
  }
```

However, I'm not clued up enough on the inner workings of the VM to say why or how that should be fixed intelligently.





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