[PATCH] Make decl_names_equal more accurate

[Giuliano Procida]

This utility function compares qualified names component-wise with
special handling of components that are anonymous names.

The code is incorrect for some cases when there are different numbers
of components on each side. Also, the control flow in the loop body is
more complex than it needs to be.

This commit simplifies the control flow, fixes the comparison bugs and
adds some extra tests to cover these cases.

	* src/abg-tools-utils.cc (decl_names_equal): Move {l,r}_pos2
	declarations into the loop and make {l,r}_length const. Avoid
	chance of arithmetic on string::npos values. Rework
	logic so there is a single test for "names compare equal" and
	a single test for different numbers of name components.
	* tests/test-tools-utils.cc (main): Add nine more tests.

Signed-off-by: Giuliano Procida <gprocida@google.com>
---
 src/abg-tools-utils.cc    | 72 +++++++++++++++------------------------
 tests/test-tools-utils.cc | 10 ++++++
 2 files changed, 38 insertions(+), 44 deletions(-)

diff --git a/src/abg-tools-utils.cc b/src/abg-tools-utils.cc
index dfbec879..38e2f175 100644
--- a/src/abg-tools-utils.cc
+++ b/src/abg-tools-utils.cc
@@ -510,61 +510,45 @@ get_anonymous_enum_internal_name_prefix()
 bool
 decl_names_equal(const string& l, const string& r)
 {
-  string::size_type l_pos1 = 0, l_pos2 = 0, r_pos1 = 0, r_pos2 = 0;
-  string::size_type l_length = l.length(), r_length = r.length();
+  string::size_type l_pos1 = 0, r_pos1 = 0;
+  const string::size_type l_length = l.length(), r_length = r.length();
 
   while (l_pos1 < l_length && r_pos1 < r_length)
     {
-      l_pos2 = l.find("::", l_pos1);
-      r_pos2 = r.find("::", r_pos1);
+      string::size_type l_pos2 = l.find("::", l_pos1);
+      string::size_type r_pos2 = r.find("::", r_pos1);
+      if (l_pos2 == string::npos)
+	l_pos2 = l_length;
+      if (r_pos2 == string::npos)
+	r_pos2 = r_length;
 
-      if ((l.compare(l_pos1,
-		     ANONYMOUS_STRUCT_INTERNAL_NAME_LEN,
-		     ANONYMOUS_STRUCT_INTERNAL_NAME) == 0
-	   && r.compare(r_pos1,
+      if (l.compare(l_pos1, l_pos2 - l_pos1, r,
+		    r_pos1, r_pos2 - r_pos1)
+	  && (l.compare(l_pos1,
 			ANONYMOUS_STRUCT_INTERNAL_NAME_LEN,
-			ANONYMOUS_STRUCT_INTERNAL_NAME) == 0)
-	  ||
-	  (l.compare(l_pos1,
-		     ANONYMOUS_UNION_INTERNAL_NAME_LEN,
-		     ANONYMOUS_UNION_INTERNAL_NAME) == 0
-	   && r.compare(r_pos1,
+			ANONYMOUS_STRUCT_INTERNAL_NAME)
+	      || r.compare(r_pos1,
+			   ANONYMOUS_STRUCT_INTERNAL_NAME_LEN,
+			   ANONYMOUS_STRUCT_INTERNAL_NAME))
+	  && (l.compare(l_pos1,
 			ANONYMOUS_UNION_INTERNAL_NAME_LEN,
-			ANONYMOUS_UNION_INTERNAL_NAME) == 0)
-	  ||
-	  (l.compare(l_pos1,
-		     ANONYMOUS_ENUM_INTERNAL_NAME_LEN,
-		     ANONYMOUS_ENUM_INTERNAL_NAME) == 0
-	   && r.compare(r_pos1,
+			ANONYMOUS_UNION_INTERNAL_NAME)
+	      || r.compare(r_pos1,
+			   ANONYMOUS_UNION_INTERNAL_NAME_LEN,
+			   ANONYMOUS_UNION_INTERNAL_NAME))
+	  && (l.compare(l_pos1,
 			ANONYMOUS_ENUM_INTERNAL_NAME_LEN,
-			ANONYMOUS_ENUM_INTERNAL_NAME) == 0))
-	{
-	  if (l_pos2 == l.npos || r_pos2 == r.npos)
-	    return true;
-
-	  l_pos1 = l_pos2 + 2;
-	  r_pos1 = r_pos2 + 2;
-	  continue;
-	}
-
-      if (l_pos2 == l.npos || r_pos2 == r.npos)
-	{
-	  if (l_pos2 != r_pos2)
-	    return false;
-
-	  return !l.compare(l_pos1, l_pos2, r,
-			    r_pos1, r_pos2);
-	}
-
-      if (l.compare(l_pos1, l_pos2 - l_pos1, r,
-		    r_pos1, r_pos2 - r_pos1))
+			ANONYMOUS_ENUM_INTERNAL_NAME)
+	      || r.compare(r_pos1,
+			   ANONYMOUS_ENUM_INTERNAL_NAME_LEN,
+			   ANONYMOUS_ENUM_INTERNAL_NAME)))
 	return false;
 
-      l_pos1 = l_pos2 + 2;
-      r_pos1 = r_pos2 + 2;
+      l_pos1 = l_pos2 == l_length ? l_pos2 : l_pos2 + 2;
+      r_pos1 = r_pos2 == r_length ? r_pos2 : r_pos2 + 2;
     }
 
-  return true;
+  return (l_pos1 == l_length) == (r_pos1 == r_length);
 }
 
 /// If a given file is a symbolic link, get the canonicalized absolute
diff --git a/tests/test-tools-utils.cc b/tests/test-tools-utils.cc
index d29bb8c9..5597873f 100644
--- a/tests/test-tools-utils.cc
+++ b/tests/test-tools-utils.cc
@@ -86,5 +86,15 @@ main(int, char**)
 
   ABG_ASSERT(decl_names_equal("S0::m2", "S0::m12") == false);
 
+  ABG_ASSERT(!decl_names_equal("S0::S1", "S0"));
+  ABG_ASSERT(!decl_names_equal("S0", "S0::S1"));
+  ABG_ASSERT(!decl_names_equal("S1::S0", "S0::S1"));
+  ABG_ASSERT(!decl_names_equal("__anonymous_struct__::S0", "__anonymous_struct__"));
+  ABG_ASSERT(!decl_names_equal("__anonymous_struct__", "__anonymous_struct__::S1"));
+  ABG_ASSERT(!decl_names_equal("__anonymous_struct__::S0", "__anonymous_struct__::S1"));
+  ABG_ASSERT(!decl_names_equal("S0::__anonymous_struct__", "__anonymous_struct__"));
+  ABG_ASSERT(!decl_names_equal("__anonymous_struct__", "S1::__anonymous_struct__"));
+  ABG_ASSERT(!decl_names_equal("S0::__anonymous_struct__", "S1::__anonymous_struct__"));
+
   return 0;
 }
-- 
2.28.0.rc0.105.gf9edc3c819-goog