PR9167 Derived class static member CRTP infinite recursion on print

[Chris Moller <cmoller@redhat.com>]

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Attached is a patch for this.

The problem was that, at some point in history, pushes and pops to a 
stack implemented in an obstack were done with a sequence that looked like

    base_ptr = obstack_base(...)
    obstack_grow(...)
    obstack_grow(...)
        .
        .
        .
    obstack_free(..., base_ptr)

You can't do that.  obstack_base() returns a pointer to the current 
allocation, which may change depending on what's stuffed into the 
obstack--by the time the obstack_free is hit, the base may have changed.

This patch fixes this.  Unfortunately, there are at least two other 
identical abuses of obstacks in cp-valprint.c alone, one of which I 
introduced myself in the patch to PR9067 (the down-side of 
cut'n'paste...).  I'll fix that in a separate patch.  Also 
unfortunately, this current patch conflicts with the patch I sent out a 
day or two ago for PR10687--I'll reconcile that before committing anything.



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Index: cp-valprint.c
===================================================================
RCS file: /cvs/src/src/gdb/cp-valprint.c,v
retrieving revision 1.64
diff -u -r1.64 cp-valprint.c
--- cp-valprint.c	8 Feb 2010 18:04:16 -0000	1.64
+++ cp-valprint.c	16 Apr 2010 03:24:22 -0000
@@ -157,7 +157,7 @@
   int fields_seen = 0;
 
   CHECK_TYPEDEF (type);
-  
+
   if (recurse == 0
       && obstack_object_size (&dont_print_statmem_obstack) > 0)
     obstack_free (&dont_print_statmem_obstack, NULL);
@@ -180,14 +180,10 @@
     fprintf_filtered (stream, "<No data fields>");
   else
     {
-      void *statmem_obstack_top = NULL;
+      int obstack_initial_size = 0;
       
       if (dont_print_statmem == 0)
-	{
-	  /* Set the current printed-statics stack top.  */
-	  statmem_obstack_top
-	    = obstack_next_free (&dont_print_statmem_obstack);
-	}
+	  obstack_initial_size = obstack_object_size (&dont_print_statmem_obstack);
 
       for (i = n_baseclasses; i < len; i++)
 	{
@@ -307,9 +303,19 @@
 
       if (dont_print_statmem == 0)
 	{
-	  /* In effect, a pop of the printed-statics stack.  */
-	  if (obstack_object_size (&dont_print_statmem_obstack) > 0) 
-	    obstack_free (&dont_print_statmem_obstack, statmem_obstack_top);
+	  int obstack_final_size =
+	    obstack_object_size (&dont_print_statmem_obstack);
+
+	  if (obstack_final_size > obstack_initial_size) {
+	    /* In effect, a pop of the printed-statics stack.  */
+
+	    void * free_to_ptr =
+	      obstack_next_free (&dont_print_statmem_obstack) -
+	      (obstack_final_size - obstack_initial_size);
+
+	    obstack_free (&dont_print_statmem_obstack,
+			  free_to_ptr);
+	  }
 	}
 
       if (options->pretty)
@@ -508,6 +514,7 @@
 		       const struct value_print_options *options)
 {
   struct value_print_options opts;
+
   if (TYPE_CODE (type) == TYPE_CODE_STRUCT)
     {
       CORE_ADDR *first_dont_print;
@@ -533,7 +540,6 @@
       addr = value_address (val);
       obstack_grow (&dont_print_statmem_obstack, (char *) &addr,
 		    sizeof (CORE_ADDR));
-
       CHECK_TYPEDEF (type);
       cp_print_value_fields (type, value_enclosing_type (val),
 			     value_contents_all (val),
Index: testsuite/gdb.cp/Makefile.in
===================================================================
RCS file: /cvs/src/src/gdb/testsuite/gdb.cp/Makefile.in,v
retrieving revision 1.9
diff -u -r1.9 Makefile.in
--- testsuite/gdb.cp/Makefile.in	8 Feb 2010 18:27:53 -0000	1.9
+++ testsuite/gdb.cp/Makefile.in	16 Apr 2010 03:24:24 -0000
@@ -5,7 +5,7 @@
 	derivation inherit local member-ptr method misc \
         overload ovldbreak ref-typ ref-typ2 templates userdef virtfunc namespace \
 	ref-types ref-params method2 pr9594 gdb2495 virtfunc2 pr9067 \
-	pr1072
+	pr1072 pr9167
 
 all info install-info dvi install uninstall installcheck check:
 	@echo "Nothing to be done for $@..."
Index: testsuite/gdb.cp/pr9167.cc
===================================================================
RCS file: testsuite/gdb.cp/pr9167.cc
diff -N testsuite/gdb.cp/pr9167.cc
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ testsuite/gdb.cp/pr9167.cc	16 Apr 2010 03:24:25 -0000
@@ -0,0 +1,36 @@
+#include <iostream>
+
+template<typename DATA>
+struct ATB
+{
+    int data;
+    ATB() : data(0) {}
+};
+
+
+template<typename DATA,
+	 typename DerivedType >
+class A : public ATB<DATA>
+{
+public:
+    static DerivedType const DEFAULT_INSTANCE;
+};
+
+template<typename DATA, typename DerivedType>
+const DerivedType A<DATA, DerivedType>::DEFAULT_INSTANCE;
+
+class B : public A<int, B>
+{
+    
+};
+
+int main()
+{
+    B b;
+    // If this if-block is removed then GDB shall
+    // not infinitely recurse when trying to print b.
+
+    return 0;		// marker
+}
+
+
Index: testsuite/gdb.cp/pr9167.exp
===================================================================
RCS file: testsuite/gdb.cp/pr9167.exp
diff -N testsuite/gdb.cp/pr9167.exp
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ testsuite/gdb.cp/pr9167.exp	16 Apr 2010 03:24:25 -0000
@@ -0,0 +1,31 @@
+#Copyright 2010 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+set testfile pr9167
+set srcfile ${testfile}.cc
+if [prepare_for_testing $testfile.exp $testfile $srcfile {debug c++}] {
+    return -1
+}
+
+if ![runto_main] then {
+    fail "Can't run to main"
+    return
+}
+
+gdb_breakpoint [gdb_get_line_number "marker"]
+gdb_continue_to_breakpoint "marker"
+
+gdb_test "p b" "{<A<int, B>> = {<ATB<int>> = {data = 0}, static DEFAULT_INSTANCE = <optimized out>}, <No data fields>}"
+

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1c1
< Test Run By moller on Wed Apr 14 10:53:26 2010
---
> Test Run By moller on Thu Apr 15 23:21:07 2010
12271a12272,12274
> Running ../../../src/gdb/testsuite/gdb.cp/pr9167.exp ...
> PASS: gdb.cp/pr9167.exp: continue to breakpoint: marker
> PASS: gdb.cp/pr9167.exp: p b
16431c16434
< PASS: gdb.threads/watchthreads.exp: disable 3
---
> PASS: gdb.threads/watchthreads.exp: disable 2
16444c16447
< PASS: gdb.threads/watchthreads2.exp: all threads incremented x
---
> KFAIL: gdb.threads/watchthreads2.exp: gdb can drop watchpoints in multithreaded app (PRMS: gdb/10116)
16712c16715
< # of expected passes		15889
---
> # of expected passes		15890