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

[Matthias Maennich <maennich@google.com>]

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?

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
>