Feature #839: Add code on each line of a backtrace output to the screen

• Status: Rejected
• Assignee: matz (Yukihiro Matsumoto)
• Target version: 2.0.0

[rogerdpack (Roger Pack)]

=begin
This patch adds output to unrescued exceptions' output to the command line:

C:\dev\downloads\snap_snapshot>cat bad2.rb
def bad
raise
end
def good
bad
end
good

ruby19 bad2.rb
bad2.rb:2:in bad': unhandled exception raise from bad2.rb:5:in good'
bad
from bad2.rb:7:in `'
good

Wasn't sure if there is a better way to code this up or what not, but here it is. Similar measures could be applied to 1.8.7.
Thanks!
-=R
=end

[nobu (Nobuyoshi Nakada)]

=begin
Hi,

At Mon, 8 Dec 2008 18:23:04 +0900,
Roger Pack wrote in [ruby-core:20416]:

This patch adds output to unrescued exceptions' output to the command line:

Rereading from scripts would have problems:

• they can be removed or changed
• -e and stdin are N/A
• slow.

Instead, isn't it enough only when debugging?

$ ./ruby -rtracer -e 'def foo;raise;end' -e foo
-e:1:in foo': unhandled exception foo from -e:2:in '

Index: error.c

--- error.c (revision 20580)
+++ error.c (working copy)
@@ -510,16 +510,31 @@ rb_check_backtrace(VALUE bt)
long i;
static const char err[] = "backtrace must be Array of String";

• extern VALUE rb_cBacktrace;

  if (!NIL_P(bt)) {

• int t = TYPE(bt);
• if (t == T_STRING) return rb_ary_new3(1, bt);
• if (t != T_ARRAY) {

• if (IMMEDIATE_P(bt)) {

•  rb_raise(rb_eTypeError, err);
  

• }
• switch (BUILTIN_TYPE(bt)) {
• case T_STRING:

•  return rb_ary_new3(1, bt);
  

• case T_ARRAY:

•  break;
  

• case T_STRUCT:

•  if (CLASS_OF(bt) == rb_cBacktrace)
  

•  return rb_ary_new3(1, bt);
  

• default:
  rb_raise(rb_eTypeError, err);
  }
  for (i=0;i<RARRAY_LEN(bt);i++) {

•  if (TYPE(RARRAY_PTR(bt)[i]) != T_STRING) {
  

•  rb_raise(rb_eTypeError, err);
  

•  VALUE a = RARRAY_PTR(bt)[i];
  

•  if (!IMMEDIATE_P(a)) {
  

•  switch (BUILTIN_TYPE(a)) {
  

•    case T_STRING: continue;
  

•    case T_STRUCT:
  

•      if (CLASS_OF(a) == rb_cBacktrace) continue;
  

•  }
   }
  

•  rb_raise(rb_eTypeError, err);
  

  }
  }
  Index: eval_error.c
  ===================================================================
  --- eval_error.c (revision 20580)
  +++ eval_error.c (working copy)
  @@ -64,4 +64,25 @@ set_backtrace(VALUE info, VALUE bt)
  }

+static void
+print_debug_line(VALUE *debug_lines, VALUE at)
+{

• extern VALUE rb_cBacktrace;
• VALUE hash = *debug_lines, lines, line, *p;
• if (TYPE(at) != T_STRUCT || CLASS_OF(at) != rb_cBacktrace) return;
• if (!hash) {
• if (!rb_const_defined_at(rb_cObject, rb_intern("SCRIPT_LINES__"))) return;
• hash = rb_const_get_at(rb_cObject, rb_intern("SCRIPT_LINES__"));
• if (TYPE(hash) != T_HASH) return;
• *debug_lines = hash;
• }
• p = RSTRUCT_PTR(at);
• lines = rb_hash_lookup(hash, p[0]);
• if (NIL_P(lines)) return;
• line = rb_ary_entry(lines, NUM2INT(p[1]));
• if (NIL_P(line)) return;
• warn_printf("\t\t %s", RSTRING_PTR(line));
  +}

static void
error_print(void)
@@ -72,4 +93,5 @@ error_print(void)
const char *einfo;
long elen;

• VALUE debug_lines = 0;

  if (NIL_P(errinfo))
  @@ -99,4 +121,5 @@ error_print(void)
  VALUE mesg = RARRAY_PTR(errat)[0];

• mesg = rb_check_string_type(mesg);
  if (NIL_P(mesg))
  error_pos();
  @@ -121,4 +144,7 @@ error_print(void)
  if (eclass == rb_eRuntimeError && elen == 0) {
  warn_print(": unhandled exception\n");

•    if (!NIL_P(errat)) {
  

•  print_debug_line(&debug_lines, RARRAY_PTR(errat)[0]);
  

• }
  }
  else {
  @@ -166,6 +192,9 @@ error_print(void)

  for (i = 1; i < len; i++) {

•  if (TYPE(ptr[i]) == T_STRING) {
  

•  warn_printf("\tfrom %s\n", RSTRING_PTR(ptr[i]));
  

•  VALUE a = ptr[i], s;
  

•  s = rb_check_string_type(a);
  

•  if (!NIL_P(s)) {
  

•  warn_printf("\tfrom %s\n", RSTRING_PTR(s));
  

•  print_debug_line(&debug_lines, a);
   }
   if (skip && i == TRACE_HEAD && len > TRACE_MAX) {
  

Index: vm.c

--- vm.c (revision 20580)
+++ vm.c (working copy)
@@ -33,4 +33,5 @@ VALUE rb_cThread;
VALUE rb_cEnv;
VALUE rb_mRubyVMFrozenCore;
+VALUE rb_cBacktrace;

VALUE ruby_vm_global_state_version = 1;
@@ -629,4 +630,22 @@ rb_lastline_set(VALUE val)
/* backtrace */

+static VALUE
+backtrace_to_str(VALUE self)
+{

• VALUE *p = RSTRUCT_PTR(self);
• VALUE file = p[0], line = p[1], name = p[2];
• VALUE str = p[3];
• if (NIL_P(str)) {
• str = rb_sprintf("%s:%d:in `%s'",

•  	 NIL_P(file) ? "" : StringValueCStr(file),
  

•  	 NUM2INT(line), StringValueCStr(name));
  

• if (!OBJ_FROZEN(self) &&

•  (OBJ_UNTRUSTED(self) || rb_safe_level() < 4)) {
  

•  p[3] = str;
  

• }
• }
• return str;
  +}

int
vm_get_sourceline(const rb_control_frame_t *cfp)
@@ -654,10 +673,10 @@ static VALUE
vm_backtrace_each(rb_thread_t *th,
const rb_control_frame_t *limit_cfp, const rb_control_frame_t *cfp,

•    const char * file, int line_no, VALUE ary)
  

•    VALUE ary)
  

{

• VALUE str;

• VALUE bt, b[3];

• int line_no;

  while (cfp > limit_cfp) {

• str = 0;
  if (cfp->iseq != 0) {
  if (cfp->pc != 0) {
  @@ -665,15 +684,17 @@ vm_backtrace_each(rb_thread_t *th,

  line_no = vm_get_sourceline(cfp);
  

•  file = RSTRING_PTR(iseq->filename);
  

•  str = rb_sprintf("%s:%d:in `%s'",
  

•  		 file, line_no, RSTRING_PTR(iseq->name));
  

•  rb_ary_push(ary, str);
  

•  b[0] = iseq->filename;
  

•  b[1] = INT2NUM(line_no);
  

•  b[2] = iseq->name;
  

•  bt = rb_class_new_instance(sizeof(b) / sizeof(*b), b, rb_cBacktrace);
  

•  rb_ary_push(ary, bt);
   }
  

  }
  else if (RUBYVM_CFUNC_FRAME_P(cfp)) {

•  str = rb_sprintf("%s:%d:in `%s'",
  

•  	     file, line_no,
  

•  	     rb_id2name(cfp->method_id));
  

•  rb_ary_push(ary, str);
  

•  b[0] = Qnil;
  

•  b[1] = INT2FIX(0);
  

•  b[2] = rb_id2str(cfp->method_id);
  

•  bt = rb_class_new_instance(sizeof(b) / sizeof(*b), b, rb_cBacktrace);
  

•  rb_ary_push(ary, bt);
  

  }
  cfp = RUBY_VM_NEXT_CONTROL_FRAME(cfp);
  @@ -704,6 +725,5 @@ vm_backtrace(rb_thread_t *th, int lev)
  }

• ary = vm_backtrace_each(th, RUBY_VM_NEXT_CONTROL_FRAME(cfp),

•  	    top_of_cfp, "", 0, ary);
  

• ary = vm_backtrace_each(th, RUBY_VM_NEXT_CONTROL_FRAME(cfp), top_of_cfp, ary);
  return ary;
  }
  @@ -1847,4 +1867,9 @@ Init_VM(void)
  rb_define_const(rb_cRubyVM, "INSTRUCTION_NAMES", ruby_insns_name_array());

• rb_cBacktrace = rb_struct_define((char*)0, "file", "line", "name", "str", (char*)0);

• rb_define_const(rb_cRubyVM, "Backtrace", rb_cBacktrace);

• rb_define_method(rb_cBacktrace, "to_str", backtrace_to_str, 0);

• rb_define_method(rb_cBacktrace, "inspect", backtrace_to_str, 0);

• /* debug functions ::VM::SDR(), ::VM::NSDR() */
  #if VMDEBUG
  

--
Nobu Nakada

=end

[rogerdpack (Roger Pack)]

=begin
I'd love to try it out, but am having trouble patching TRUNK with it. Could you give me a hint as to which revision it is a patch from? Is it from trunk?
Thanks!
-=R
=end

[rogerdpack (Roger Pack)]

=begin
heh--I see it--revision 20850, from the diff. That one works for applying it.

You're right--something that didn't require reading files would be nice.
I suppose the only drawback would be...shouldn't tracer output

enter x
<< leave x

and if so, wouldn't requiring users to include tracer possibly cause too much console output to be worth the added verbose output?

Here's an interesting related request:

I also wonder if someday something like this would be possible [1]
NoMethodError: undefined method `capitalize' for nil:NilClass
from /home/pwilliams/projects/tmp/test.rb:18:in main.greet_user(nil, "williams")
from /home/pwilliams/projects/tmp/test.rb:14:in main.third(nil, "williams")
from /home/pwilliams/projects/tmp/test.rb:10:in main.second("williams, peter")
from /home/pwilliams/projects/tmp/test.rb:4:in main.first("Peter Williams")
from (irb):41
from :0

I can think of a way to do this using set_trace_func style stuff to track parameters but that's about it...

I'll look at it more sometime.

Thoughts?
-=R

[1] http://barelyenough.org/blog/2005/04/ruby-backtraces/

=end

[rogerdpack (Roger Pack)]

=begin
How about a compromise to propagate SCRIPT_LINES__ after the fact with the appropriate files if they're not in it yet? I'd be happy to do it, and it thus wouldn't result in a large slowdown [and if files have changed recently, the user will probably be quite aware of that fact].
Or maybe running it -r"something" would be sufficient.

Thoughts?
-=R
=end

[rogerdpack (Roger Pack)]

=begin
I suppose another option would be to only retrieve the line for the topmost line of the backtrace. Thoughts?
=end

[shyouhei (Shyouhei Urabe)]

• Assignee set to matz (Yukihiro Matsumoto)
• Target version set to 1.9.2

=begin

=end

[rogerdpack (Roger Pack)]

=begin
I like this patch (nobu's). Would it be possible to get it applied?
-r
=end

[rogerdpack (Roger Pack)]

=begin
I still like this patch (applied to caller and/or Exception#backtrace).

Who needs to approve it...?

Thanks.
-r

Related previous requests:

http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-core/4822
http://barelyenough.org/blog/2005/04/ruby-backtraces
http://www.ruby-forum.com/topic/198847
http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-core/4822
=end

[mame (Yusuke Endoh)]

=begin
Hi,

Matz, what do you think about this ticket and #1906?

There is a patch nobu has written (though I have not tested):
http://redmine.ruby-lang.org/issues/show/839#note-1

But it might take some time to make stable the feature, so please
let us know your opinion or decision as soon as possible.

--
Yusuke Endoh [e-mail]
=end

[znz (Kazuhiro NISHIYAMA)]

• Category set to core
• Target version changed from 1.9.2 to 2.0.0

=begin

=end

[rogerdpack (Roger Pack)]

=begin
Matz if you get a chance to look at this patch, it "objectify's" Exception#backtrace which might be nice.
Thank you.
-roger
=end

[rogerdpack (Roger Pack)]

=begin
Any feedback on this? (objectify Exception#backtrace et al)
Thanks.
=end

[shyouhei (Shyouhei Urabe)]

• Status changed from Open to Assigned

=begin

=end

[kosaki (Motohiro KOSAKI)]

Matz if you get a chance to look at this patch, it "objectify's" Exception#backtrace which might be nice.
Thank you.
-roger

Can anyone take a feedback? If nothing, I have to close this ticket sadly.

[trans (Thomas Sawyer)]

If all it is, is to add source code line to backtrace then I don think that's enough.

I think the feature people would like to see in this area is an objectified backtrace, e.g.

error.objectified_backtrace.each do |b|
  b.file    #=> '/home/pwilliams/projects/tmp/test.rb'
  b.line    #=> 18
  b.in      #=> "<main>"
  b.source  #=> "greet_user(nil, \"williams\")"
  b.to_s    #=> "from /home/pwilliams/projects/tmp/test.rb:18:in `<main>'"

I believe there is a gem called 'callsite' which does something like this. Maybe others too.

[kosaki (Motohiro KOSAKI)]

• Status changed from Assigned to Rejected

I believe there is a gem called 'callsite' which does something like this. Maybe others too.

OK, thank you for giving very useful comment. now I can close this one safely.