[C++] PR 44783

Index: doc/invoke.texi
===================================================================
--- doc/invoke.texi	(revision 185392)
+++ doc/invoke.texi	(working copy)
@@ -192,7 +192,8 @@  in the following sections.
 -fno-nonansi-builtins  -fnothrow-opt  -fno-operator-names @gol
 -fno-optional-diags  -fpermissive @gol
 -fno-pretty-templates @gol
--frepo  -fno-rtti  -fstats  -ftemplate-depth=@var{n} @gol
+-frepo  -fno-rtti  -fstats  -ftemplate-backtrace-limit=@var{n} @gol
+-ftemplate-depth=@var{n} @gol
 -fno-threadsafe-statics -fuse-cxa-atexit  -fno-weak  -nostdinc++ @gol
 -fno-default-inline  -fvisibility-inlines-hidden @gol
 -fvisibility-ms-compat @gol
@@ -2124,6 +2125,11 @@  represented in the minimum number of bits needed t
 enumerators).  This assumption may not be valid if the program uses a
 cast to convert an arbitrary integer value to the enumerated type.
 
+@item -ftemplate-backtrace-limit=@var{n}
+@opindex ftemplate-backtrace-limit
+Set the maximum number of template instantiation notes for a single
+warning or error to @var{n}.  The default value is 10.
+
 @item -ftemplate-depth=@var{n}
 @opindex ftemplate-depth
 Set the maximum instantiation depth for template classes to @var{n}.
Index: c-family/c.opt
===================================================================
--- c-family/c.opt	(revision 185392)
+++ c-family/c.opt	(working copy)
@@ -1035,6 +1035,10 @@  ftabstop=
 C ObjC C++ ObjC++ Joined RejectNegative UInteger
 -ftabstop=<number>	Distance between tab stops for column reporting
 
+ftemplate-backtrace-limit=
+C++ ObjC++ Joined RejectNegative UInteger Var(template_backtrace_limit) Init(10)
+Set the maximum number of template instantiation notes for a single warning or error
+
 ftemplate-depth-
 C++ ObjC++ Joined RejectNegative Undocumented Alias(ftemplate-depth=)
 
Index: cp/error.c
===================================================================
--- cp/error.c	(revision 185392)
+++ cp/error.c	(working copy)
@@ -3076,10 +3076,20 @@  print_instantiation_partial_context (diagnostic_co
 
   t = t0;
 
-  if (n_total >= 12) 
+  if (template_backtrace_limit
+      && n_total > template_backtrace_limit) 
     {
-      int skip = n_total - 10;
-      for (n = 0; n < 5; n++)
+      int skip = n_total - template_backtrace_limit;
+      int head = template_backtrace_limit / 2;
+
+      /* Avoid skipping just 1.  If so, skip 2.  */
+      if (skip == 1)
+       {
+         skip = 2;
+         head = (template_backtrace_limit - 1) / 2;
+       }
+     
+      for (n = 0; n < head; n++)
 	{
 	  gcc_assert (t != NULL);
 	  if (loc != t->locus)
@@ -3088,17 +3098,19 @@  print_instantiation_partial_context (diagnostic_co
 	  loc = t->locus;
 	  t = t->next;
 	}
-      if (t != NULL && skip > 1)
+      if (t != NULL && skip > 0)
 	{
 	  expanded_location xloc;
 	  xloc = expand_location (loc);
 	  if (context->show_column)
 	    pp_verbatim (context->printer,
-			 _("%s:%d:%d:   [ skipping %d instantiation contexts ]\n"),
+			 _("%s:%d:%d:   [ skipping %d instantiation contexts, "
+			   "use -ftemplate-backtrace-limit=0 to disable ]\n"),
 			 xloc.file, xloc.line, xloc.column, skip);
 	  else
 	    pp_verbatim (context->printer,
-			 _("%s:%d:   [ skipping %d instantiation contexts ]\n"),
+			 _("%s:%d:   [ skipping %d instantiation contexts, "
+			   "use -ftemplate-backtrace-limit=0 to disable ]\n"),
 			 xloc.file, xloc.line, skip);
 	  
 	  do {