From: "ko1 (Koichi Sasada)" <redmine@...>
Date: 2012-11-26T09:21:24+09:00
Subject: [ruby-core:50125] [ruby-trunk - Bug #4630] PROCDEBUG to non-zero values causes segmentation faults in check_env in trunk


Issue #4630 has been updated by ko1 (Koichi Sasada).

Target version changed from 2.0.0 to next minor


----------------------------------------
Bug #4630: PROCDEBUG to non-zero values causes segmentation faults in check_env in trunk
https://bugs.ruby-lang.org/issues/4630#change-33908

Author: ehuard (Elise Huard)
Status: Assigned
Priority: Low
Assignee: ko1 (Koichi Sasada)
Category: core
Target version: next minor
ruby -v: -


=begin
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.
=end



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