Skip to content

Latest commit

 

History

History
400 lines (381 loc) · 10.3 KB

DEVELOPMENT_NOTES.adoc

File metadata and controls

400 lines (381 loc) · 10.3 KB
Raw

Development Notes

Ideas to explore

Understand why rb_profile_frames does not return the correct iseq for a block.

Given

def run
  puts "Backtracie: " + Backtracie.caller_locations.first.label
  puts "Ruby:       " + caller_locations.first.label
end

def run2
  1.times do
    run
  end
end

the output is

Backtracie: run2
Ruby:       block in run2

this is because inside rb_profile_frames the code goes

/* record frame info */
cme = rb_vm_frame_method_entry(cfp);
if (cme && cme->def->type == VM_METHOD_TYPE_ISEQ) {
  buff[i] = (VALUE)cme;
}
else {
  buff[i] = (VALUE)cfp->iseq;
}

and in this case the first branch is taken (we get the cme, not the cfp→iseq). I have no idea why.

Update:

When using the cfp→iseq instead of the cme, in many cases, the full_label, classpath, qualified_method_name, singleton_method_p and first_lineno become less accurate.

Why "less accurate"? Consider the following slightly compacted diff taken with backtracie and either cme or cfp→iseq usage, using the interesting_backtrace_helper.rb, looking at the output in the debug fields for the Backtracie::Location instances:

--- cfp->iseq
+++ cme
@@ -6,16 +6,16 @@
     "/ruby/backtracie/spec/unit/interesting_backtrace_helper.rb",
     "hello",
     "hello",
-    "ClassA#hello",
+    "hello",
     18,
-    "ClassA",
+    nil,
     false,
     "hello",
-    "ClassA#hello"],
+    "hello"],
@@ -23,16 +23,16 @@
     "/ruby/backtracie/spec/unit/interesting_backtrace_helper.rb",
     "hello",
     "hello",
-    "ModuleB::ClassB#hello",
+    "hello",
     27,
-    "ModuleB::ClassB",
+    nil,
     false,
     "hello",
-    "ModuleB::ClassB#hello"],
+    "hello"],
@@ -40,16 +40,16 @@
     "/ruby/backtracie/spec/unit/interesting_backtrace_helper.rb",
     "hello",
     "hello",
-    "ModuleC.hello",
+    "hello",
     34,
-    "ModuleC",
-    true,
+    nil,
+    false,
     "hello",
-    "ModuleC.hello"],
+    "hello"],
@@ -57,16 +57,16 @@
     "/ruby/backtracie/spec/unit/interesting_backtrace_helper.rb",
     "hello",
     "hello",
-    "ClassWithStaticMethod.hello",
+    "hello",
     40,
-    "ClassWithStaticMethod",
-    true,
+    nil,
+    false,
     "hello",
-    "ClassWithStaticMethod.hello"],
+    "hello"],
@@ -74,16 +74,16 @@
     "/ruby/backtracie/spec/unit/interesting_backtrace_helper.rb",
     "hello",
     "hello",
-    "ModuleD#hello",
+    "hello",
     46,
-    "ModuleD",
+    nil,
     false,
     "hello",
-    "ModuleD#hello"],
+    "hello"],
@@ -125,16 +125,16 @@
     "/ruby/backtracie/spec/unit/interesting_backtrace_helper.rb",
     "hello",
     "hello",
-    "#<ClassD:0x0000556485af28e8>.hello",
+    "hello",
     63,
-    "#<ClassD:0x0000556485af28e8>",
-    true,
+    nil,
+    false,
     "hello",
-    "#<ClassD:0x0000556485af28e8>.hello"],
+    "hello"],
@@ -142,16 +142,16 @@
     "/ruby/backtracie/spec/unit/interesting_backtrace_helper.rb",
     "hello",
     "hello",
-    "ClassE#hello",
+    "hello",
     68,
-    "ClassE",
+    nil,
     false,
     "hello",
-    "ClassE#hello"],
+    "hello"],
@@ -176,16 +176,16 @@
     "/ruby/backtracie/spec/unit/interesting_backtrace_helper.rb",
     "hello",
     "hello",
-    "#<Module:0x0000556485af2140>#hello",
+    "hello",
     82,
-    "#<Module:0x0000556485af2140>",
+    nil,
     false,
     "hello",
-    "#<Module:0x0000556485af2140>#hello"],
+    "hello"],
@@ -193,16 +193,16 @@
     "/ruby/backtracie/spec/unit/interesting_backtrace_helper.rb",
     "hello",
     "hello",
-    "ModuleE.hello",
+    "hello",
     92,
-    "ModuleE",
-    true,
+    nil,
+    false,
     "hello",
-    "ModuleE.hello"],
+    "hello"],
@@ -210,33 +210,33 @@
     "/ruby/backtracie/spec/unit/interesting_backtrace_helper.rb",
     "method_missing",
     "method_missing",
-    "ClassH#method_missing",
+    "method_missing",
     98,
-    "ClassH",
+    nil,
     false,
     "method_missing",
-    "ClassH#method_missing"],
+    "method_missing"],
   @label="method_missing",
   @lineno=101,
   @path="/ruby/backtracie/spec/unit/interesting_backtrace_helper.rb">,
- #<Backtracie::Location:0x0000556486191a00
+ #<Backtracie::Location:0x0000563ca3800df0
   @absolute_path="/ruby/backtracie/spec/unit/interesting_backtrace_helper.rb",
   @base_label="hello",
   @debug=
    ["/ruby/backtracie/spec/unit/interesting_backtrace_helper.rb",
     "/ruby/backtracie/spec/unit/interesting_backtrace_helper.rb",
+    "block in hello",
     "hello",
-    "hello",
-    "ClassF#hello",
-    106,
-    "ClassF",
+    "block in hello",
+    107,
+    nil,
     false,
     "hello",
-    "ClassF#hello"],
-  @label="hello",
+    "hello"],
+  @label="block in hello",
@@ -252,16 +252,16 @@
     "/ruby/backtracie/spec/unit/interesting_backtrace_helper.rb",
     "hello",
     "hello",
-    "ClassF#hello",
+    "hello",
     106,
-    "ClassF",
+    nil,
     false,
     "hello",
-    "ClassF#hello"],
+    "hello"],
@@ -286,16 +286,16 @@
     "/ruby/backtracie/spec/unit/interesting_backtrace_helper.rb",
     "hello",
     "hello",
-    "#<Class:0x0000556485af0a70>.hello",
+    "hello",
     121,
-    "#<Class:0x0000556485af0a70>",
-    true,
+    nil,
+    false,
     "hello",
-    "#<Class:0x0000556485af0a70>.hello"],
+    "hello"],
@@ -303,16 +303,16 @@
     "/ruby/backtracie/spec/unit/interesting_backtrace_helper.rb",
     "hello",
     "hello",
-    "#<Class:0x0000556485af07a0>#hello",
+    "hello",
     126,
-    "#<Class:0x0000556485af07a0>",
+    nil,
     false,
     "hello",
-    "#<Class:0x0000556485af07a0>#hello"],
+    "hello"],
@@ -320,16 +320,16 @@
     "/ruby/backtracie/spec/unit/interesting_backtrace_helper.rb",
     "hello",
     "hello",
-    "#<Module:0x0000556485af0430>.hello",
+    "hello",
     132,
-    "#<Module:0x0000556485af0430>",
-    true,
+    nil,
+    false,
     "hello",
-    "#<Module:0x0000556485af0430>.hello"],
+    "hello"],
@@ -337,33 +337,33 @@
     "/ruby/backtracie/spec/unit/interesting_backtrace_helper.rb",
     "method_with_complex_parameters",
     "method_with_complex_parameters",
-    "Object#method_with_complex_parameters",
+    "method_with_complex_parameters",
     137,
-    "Object",
+    nil,
     false,
     "method_with_complex_parameters",
-    "Object#method_with_complex_parameters"],
+    "method_with_complex_parameters"],
   @label="method_with_complex_parameters",
   @lineno=138,
   @path="/ruby/backtracie/spec/unit/interesting_backtrace_helper.rb">,
- #<Backtracie::Location:0x00005564861925e0
+ #<Backtracie::Location:0x0000563ca3801d90
   @absolute_path="/ruby/backtracie/spec/unit/interesting_backtrace_helper.rb",
   @base_label="hello",
   @debug=
    ["/ruby/backtracie/spec/unit/interesting_backtrace_helper.rb",
     "/ruby/backtracie/spec/unit/interesting_backtrace_helper.rb",
+    "block (2 levels) in hello",
     "hello",
-    "hello",
-    "ClassJ#hello",
-    146,
-    "ClassJ",
+    "block (2 levels) in hello",
+    148,
+    nil,
     false,
     "hello",
-    "ClassJ#hello"],
-  @label="hello",
+    "hello"],
@@ -371,33 +371,33 @@
     "/ruby/backtracie/spec/unit/interesting_backtrace_helper.rb",
     "hello_helper",
     "hello_helper",
-    "ClassJ#hello_helper",
+    "hello_helper",
     142,
-    "ClassJ",
+    nil,
     false,
     "hello_helper",
-    "ClassJ#hello_helper"],
+    "hello_helper"],
   @label="hello_helper",
   @lineno=143,
   @path="/ruby/backtracie/spec/unit/interesting_backtrace_helper.rb">,
- #<Backtracie::Location:0x0000556486192928
+ #<Backtracie::Location:0x0000563ca3801f70
   @absolute_path="/ruby/backtracie/spec/unit/interesting_backtrace_helper.rb",
   @base_label="hello",
   @debug=
    ["/ruby/backtracie/spec/unit/interesting_backtrace_helper.rb",
     "/ruby/backtracie/spec/unit/interesting_backtrace_helper.rb",
+    "block in hello",
     "hello",
-    "hello",
-    "ClassJ#hello",
-    146,
-    "ClassJ",
+    "block in hello",
+    147,
+    nil,
     false,
     "hello",
-    "ClassJ#hello"],
-  @label="hello",
+    "hello"],
@@ -405,16 +405,16 @@
     "/ruby/backtracie/spec/unit/interesting_backtrace_helper.rb",
     "hello_helper",
     "hello_helper",
-    "ClassJ#hello_helper",
+    "hello_helper",
     142,
-    "ClassJ",
+    nil,
     false,
     "hello_helper",
-    "ClassJ#hello_helper"],
+    "hello_helper"],
@@ -422,16 +422,16 @@
     "/ruby/backtracie/spec/unit/interesting_backtrace_helper.rb",
     "hello",
     "hello",
-    "ClassJ#hello",
+    "hello",
     146,
-    "ClassJ",
+    nil,
     false,
     "hello",
-    "ClassJ#hello"],
+    "hello"],
@@ -439,16 +439,16 @@
     "/ruby/backtracie/spec/unit/interesting_backtrace_helper.rb",
     "top_level_hello",
     "top_level_hello",
-    "Object#top_level_hello",
+    "top_level_hello",
     155,
-    "Object",
+    nil,
     false,
     "top_level_hello",
-    "Object#top_level_hello"],
+    "top_level_hello"],

We can see that we miss the information about module/class names (we only get methods), we lose the singleton info, etc. The first_lineno numbers that move (which is not very important since we get the exact line via a different method). The only thing that is correct in the cfp→iseq version is getting "block in method" in the few places where we were missing it.

So clearly the cme version in upstream Ruby is correct almost all of the time, except for the label missing the "block in method" in a few cases.

This seems to point to the "block in method" issue either being an implementation bug (I still don’t quite understand what the two different objects being used here represent) OR more of a "limitation" — perhaps it’s awkward to provide the correct label on the objects that miss it, and since the current MRI object returns one VALUE per stack frame, not two, the slight issue is just ignored.

TODO