Re: [PATCH 1/2] Improve readability of represent helper function.

[Giuliano Procida <gprocida@google.com>]

Hi.

On Wed, 8 Apr 2020 at 13:47, Matthias Maennich <maennich@google.com> wrote:
>
> On Wed, Apr 08, 2020 at 01:20:43PM +0100, Giuliano Procida wrote:
> >This change:
> >
> >    - makes local variables const where possible
> >    - gives local variables more descriptive names
> >    - factors out some more expressions as local variables
> >    - simplifies the logic around anonymous data members
> >
> >There are no behavioural changes.
> >
> >       * src/abg-reporter-priv.cc (represent): In the var_diff_sptr
> >       overload, rename pretty_representation to
> >       o_pretty_representation, introduce n_pretty_representation
> >       where needed and replace the duplicate tr1 and tr2 with these;
> >       rename all other variables foo1 and foo2 to o_foo and n_foo
> >       respectively, using _type instead of _t; introduce o_anon and
> >       n_anon and use them to make the local variable
> >       is_strict_anonymous_data_member_change const, make ABG_ASSERT
> >       in anonymous data member handling more obvious in the case
> >       where anonymity has changed and allow simplification of
> >       formatting in this case; move declarations of const local
> >       variables above those of the non-const, state-tracking,
> >       variables.
> >
> >Signed-off-by: Giuliano Procida <gprocida@google.com>
> >---
> > src/abg-reporter-priv.cc | 117 +++++++++++++++++----------------------
> > 1 file changed, 50 insertions(+), 67 deletions(-)
> >
> >diff --git a/src/abg-reporter-priv.cc b/src/abg-reporter-priv.cc
> >index 5fb5fbc5..a46c0e9d 100644
> >--- a/src/abg-reporter-priv.cc
> >+++ b/src/abg-reporter-priv.cc
> >@@ -409,14 +409,21 @@ represent(const var_diff_sptr    &diff,
> >   if (!ctxt->get_reporter()->diff_to_be_reported(diff.get()))
> >     return;
> >
> >-  var_decl_sptr o = diff->first_var();
> >-  var_decl_sptr n = diff->second_var();
> >-  string name1 = o->get_qualified_name();
> >-  string name2 = n->get_qualified_name();
> >-  uint64_t size1 = get_var_size_in_bits(o);
> >-  uint64_t size2 = get_var_size_in_bits(n);
> >-  uint64_t offset1 = get_data_member_offset(o);
> >-  uint64_t offset2 = get_data_member_offset(n);
> >+  const var_decl_sptr o = diff->first_var();
> >+  const var_decl_sptr n = diff->second_var();
> >+  const bool o_anon = !!is_anonymous_data_member(o);
> >+  const bool n_anon = !!is_anonymous_data_member(n);
> >+  const bool is_strict_anonymous_data_member_change = o_anon && n_anon;
> >+  const string o_name = o->get_qualified_name();
> >+  const string n_name = n->get_qualified_name();
> >+  const uint64_t o_size = get_var_size_in_bits(o);
> >+  const uint64_t n_size = get_var_size_in_bits(n);
> >+  const uint64_t o_offset = get_data_member_offset(o);
> >+  const uint64_t n_offset = get_data_member_offset(n);
> >+  const string o_pretty_representation = o->get_pretty_representation();
>
> Any reason to not have n_pretty_representation also already defined
> here?

That's what I had originally. However, it may be a fairly expensive
operation and it's only needed in relatively rare cases.

Regards,
Giuliano.

> Otherwise nice cleanup!
>
> Reviewed-by: Matthias Maennich <maennich@google.com>
>
> Cheers,
> Matthias
>
> >+
> >+  const bool show_size_offset_changes = ctxt->get_allowed_category()
> >+                                      & SIZE_OR_OFFSET_CHANGE_CATEGORY;
> >
> >   // Has the main diff text been output?
> >   bool emitted = false;
> >@@ -424,39 +431,31 @@ represent(const var_diff_sptr    &diff,
> >   bool begin_with_and = false;
> >   // Have we reported a size change already?
> >   bool size_reported = false;
> >-  // Are we reporting a change to an anonymous member?
> >-  bool is_strict_anonymous_data_member_change = false;
> >
> >-  string pretty_representation = o->get_pretty_representation();
> >-  bool show_size_offset_changes = ctxt->get_allowed_category()
> >-                                & SIZE_OR_OFFSET_CHANGE_CATEGORY;
> >-
> >-  if (is_anonymous_data_member(o) && is_anonymous_data_member(n))
> >+  if (is_strict_anonymous_data_member_change)
> >     {
> >-      is_strict_anonymous_data_member_change = true;
> >-      string tr1 = o->get_pretty_representation();
> >-      string tr2 = n->get_pretty_representation();
> >-      type_base_sptr t1 = o->get_type(), t2 = n->get_type();
> >-      if (tr1 != tr2)
> >+      const string n_pretty_representation = n->get_pretty_representation();
> >+      const type_base_sptr o_type = o->get_type(), n_type = n->get_type();
> >+      if (o_pretty_representation != n_pretty_representation)
> >       {
> >         show_offset_or_size(indent + "anonymous data member at offset",
> >-                            offset1, *ctxt, out);
> >+                            o_offset, *ctxt, out);
> >
> >         out << " changed from:\n"
> >-            << indent << "  " << tr1 << "\n"
> >+            << indent << "  " << o_pretty_representation << "\n"
> >             << indent << "to:\n"
> >-            << indent << "  " << tr2 << "\n";
> >+            << indent << "  " << n_pretty_representation << "\n";
> >
> >         begin_with_and = true;
> >         emitted = true;
> >       }
> >-      else if (get_type_name(t1) != get_type_name(t2)
> >-             && is_decl(t1) && is_decl(t2)
> >-             && is_decl(t1)->get_is_anonymous()
> >-             && is_decl(t2)->get_is_anonymous())
> >+      else if (get_type_name(o_type) != get_type_name(n_type)
> >+             && is_decl(o_type) && is_decl(n_type)
> >+             && is_decl(o_type)->get_is_anonymous()
> >+             && is_decl(n_type)->get_is_anonymous())
> >       {
> >         out << indent << "while looking at anonymous data member '"
> >-            << tr1 << "':\n"
> >+            << o_pretty_representation << "':\n"
> >             << indent << "the internal name of that anonymous data member"
> >                          "changed from:\n"
> >             << indent << " " << get_type_name(o->get_type()) << "\n"
> >@@ -472,36 +471,20 @@ represent(const var_diff_sptr    &diff,
> >     }
> >   else if (filtering::has_anonymous_data_member_change(diff))
> >     {
> >+      ABG_ASSERT(o_anon != n_anon);
> >       // So we are looking at a non-anonymous data member change from
> >       // or to anonymous data member.
> >-      if (is_anonymous_data_member(o))
> >-      {
> >-        string repr = "anonymous data member "
> >-          + o->get_pretty_representation()
> >-          + " at offset";
> >-
> >-        show_offset_or_size(indent + repr, offset1, *ctxt, out);
> >-        out << " became data member '"
> >-            << n->get_pretty_representation()
> >-            << "'\n";
> >-      }
> >-      else
> >-      {
> >-        ABG_ASSERT(is_anonymous_data_member(n));
> >-        string repr = "data member "
> >-          + o->get_pretty_representation()
> >-          + " at offset";
> >-
> >-        show_offset_or_size(indent + repr, offset1, *ctxt, out);
> >-        out << " became anonymous data member '"
> >-            << n->get_pretty_representation()
> >-            << "'\n";
> >-      }
> >+      const string n_pretty_representation = n->get_pretty_representation();
> >+      out << indent << (o_anon ? "anonymous " : "")
> >+        << "data member " << o_pretty_representation;
> >+      show_offset_or_size(" at offset", o_offset, *ctxt, out);
> >+      out << " became " << (n_anon ? "anonymous " : "")
> >+        << "data member '" << n_pretty_representation << "'\n";
> >
> >       begin_with_and = true;
> >       emitted = true;
> >     }
> >-  else if (diff_sptr d = diff->type_diff())
> >+  else if (const diff_sptr d = diff->type_diff())
> >     {
> >       if (ctxt->get_reporter()->diff_to_be_reported(d.get()))
> >       {
> >@@ -511,7 +494,7 @@ represent(const var_diff_sptr      &diff,
> >               << "' changed";
> >         else
> >           out << indent
> >-              << "type of '" << pretty_representation << "' changed";
> >+              << "type of '" << o_pretty_representation << "' changed";
> >
> >         if (d->currently_reporting())
> >           out << ", as being reported\n";
> >@@ -529,7 +512,7 @@ represent(const var_diff_sptr      &diff,
> >       }
> >     }
> >
> >-  if (!filtering::has_anonymous_data_member_change(diff) && name1 != name2)
> >+  if (!filtering::has_anonymous_data_member_change(diff) && o_name != n_name)
> >     {
> >       if (filtering::has_harmless_name_change(o, n)
> >         && !(ctxt->get_allowed_category()
> >@@ -546,7 +529,7 @@ represent(const var_diff_sptr      &diff,
> >           out << indent;
> >         else
> >           out << ", ";
> >-        out << "name of '" << name1 << "' changed to '" << name2 << "'";
> >+        out << "name of '" << o_name << "' changed to '" << n_name << "'";
> >         report_loc_info(n, *ctxt, out);
> >         emitted = true;
> >       }
> >@@ -561,7 +544,7 @@ represent(const var_diff_sptr      &diff,
> >         begin_with_and = false;
> >       }
> >       else if (!emitted)
> >-      out << indent << "'" << pretty_representation << "' ";
> >+      out << indent << "'" << o_pretty_representation << "' ";
> >       else
> >       out << ", ";
> >       if (get_data_member_is_laid_out(o))
> >@@ -572,7 +555,7 @@ represent(const var_diff_sptr      &diff,
> >     }
> >   if (show_size_offset_changes)
> >     {
> >-      if (offset1 != offset2)
> >+      if (o_offset != n_offset)
> >       {
> >         if (begin_with_and)
> >           {
> >@@ -584,17 +567,17 @@ represent(const var_diff_sptr    &diff,
> >             out << indent;
> >             if (is_strict_anonymous_data_member_change)
> >               out << "anonymous data member ";
> >-            out << "'" << pretty_representation << "' ";
> >+            out << "'" << o_pretty_representation << "' ";
> >           }
> >         else
> >           out << ", ";
> >
> >-        show_numerical_change("offset", offset1, offset2, *ctxt, out);
> >+        show_numerical_change("offset", o_offset, n_offset, *ctxt, out);
> >         maybe_show_relative_offset_change(diff, *ctxt, out);
> >         emitted = true;
> >       }
> >
> >-      if (!size_reported && size1 != size2)
> >+      if (!size_reported && o_size != n_size)
> >       {
> >         if (begin_with_and)
> >           {
> >@@ -606,12 +589,12 @@ represent(const var_diff_sptr    &diff,
> >             out << indent;
> >             if (is_strict_anonymous_data_member_change)
> >               out << "anonymous data member ";
> >-            out << "'" << pretty_representation << "' ";
> >+            out << "'" << o_pretty_representation << "' ";
> >           }
> >         else
> >           out << ", ";
> >
> >-        show_numerical_change("size", size1, size2, *ctxt, out);
> >+        show_numerical_change("size", o_size, n_size, *ctxt, out);
> >         maybe_show_relative_size_change(diff, *ctxt, out);
> >         emitted = true;
> >       }
> >@@ -624,7 +607,7 @@ represent(const var_diff_sptr      &diff,
> >         begin_with_and = false;
> >       }
> >       else if (!emitted)
> >-      out << indent << "'" << pretty_representation << "' ";
> >+      out << indent << "'" << o_pretty_representation << "' ";
> >       else
> >       out << ", ";
> >       out << "elf binding changed from " << o->get_binding()
> >@@ -639,7 +622,7 @@ represent(const var_diff_sptr      &diff,
> >         begin_with_and = false;
> >       }
> >       else if (!emitted)
> >-      out << indent << "'" << pretty_representation << "' ";
> >+      out << indent << "'" << o_pretty_representation << "' ";
> >       else
> >       out << ", ";
> >       out << "visibility changed from " << o->get_visibility()
> >@@ -656,7 +639,7 @@ represent(const var_diff_sptr      &diff,
> >         begin_with_and = false;
> >       }
> >       else if (!emitted)
> >-      out << indent << "'" << pretty_representation << "' ";
> >+      out << indent << "'" << o_pretty_representation << "' ";
> >       else
> >       out << ", ";
> >
> >@@ -675,7 +658,7 @@ represent(const var_diff_sptr      &diff,
> >         begin_with_and = false;
> >       }
> >       else if (!emitted)
> >-      out << indent << "'" << pretty_representation << "' ";
> >+      out << indent << "'" << o_pretty_representation << "' ";
> >       else
> >       out << ", ";
> >
> >@@ -691,7 +674,7 @@ represent(const var_diff_sptr      &diff,
> >     ;
> >   else if (!emitted)
> >     // We appear to have fallen off the edge of the map.
> >-    out << indent << "'" << pretty_representation
> >+    out << indent << "'" << o_pretty_representation
> >       << "' has *some* difference - please report as a bug";
> >   else
> >     // do nothing
> >--
> >2.26.0.110.g2183baf09c-goog
> >