gdb/testuite/

* gdb.trace/unavailable.cc (a, b, c): New globals.
	(main): Set and clear them.
	* gdb.trace/unavailable.exp (gdb_collect_globals_test): Collect
	`a' and `c', and check that `b' isn't collected, although `a' and
	`c' are.

	gdb/
	* tracepoint.c (memrange_sortmerge): Don't merge ranges that are
	almost but not quite adjacent.

gdb/ChangeLog

@@ -1,3 +1,8 @@
+2011-02-14  Pedro Alves  <pedro@codesourcery.com>
+
+	* tracepoint.c (memrange_sortmerge): Don't merge ranges that are
+	almost but not quite adjacent.
+
 2011-02-14  Pedro Alves  <pedro@codesourcery.com>
 
 	* value.h (value_entirely_available): Declare.

gdb/testsuite/ChangeLog

@@ -1,3 +1,11 @@
+2011-02-14  Pedro Alves  <pedro@codesourcery.com>
+
+	* gdb.trace/unavailable.cc (a, b, c): New globals.
+	(main): Set and clear them.
+	* gdb.trace/unavailable.exp (gdb_collect_globals_test): Collect
+	`a' and `c', and check that `b' isn't collected, although `a' and
+	`c' are.
+
 2011-02-14  Pedro Alves  <pedro@codesourcery.com>
 
 	* gdb.trace/unavailable.cc (struct Virtual): New.

gdb/testsuite/gdb.trace/unavailable.cc

@@ -71,6 +71,25 @@ struct tuple
 
 struct tuple tarray[8];
 
+/* Test for overcollection.  GDB used to merge memory ranges to
+   collect if they were close enough --- say, collect `a' and 'c'
+   below, and you'd get 'b' as well.  This had been presumably done to
+   cater for some target's inefficient trace buffer layout, but it is
+   really not GDB's business to assume how the target manages its
+   buffer.  If the target wants to overcollect, that's okay, since it
+   knows what is and what isn't safe to touch (think memory mapped
+   registers), and knows it's buffer layout.
+
+   The test assumes these three variables are laid out consecutively
+   in memory.  Unfortunately, we can't use an array instead, since the
+   agent expression generator does not even do constant folding,
+   meaning that anything that's more complicated than collecting a
+   global will generate an agent expression action to evaluate on the
+   target, instead of a simple "collect memory" action.  */
+int a;
+int b;
+int c;
+
 /* Random tests.  */
 
 struct StructA
@@ -185,6 +204,7 @@ main (int argc, char **argv, char **envp)
   memcpy (g_string_unavail, g_const_string, sizeof (g_const_string));
   memcpy (g_string_partial, g_const_string, sizeof (g_const_string));
   g_string_p = g_const_string;
+  a = 1; b = 2; c = 3;
 
   /* Call test functions, so they can be traced and data collected.  */
   i = 0;
@@ -212,6 +232,8 @@ main (int argc, char **argv, char **envp)
   memset (g_string_partial, 0, sizeof (g_string_partial));
   g_string_p = NULL;
 
+  a = b = c = 0;
+
   g_int = 0;
 
   g_structref.clear ();

gdb/testsuite/gdb.trace/unavailable.exp

@@ -92,6 +92,9 @@ proc gdb_collect_globals_test { } {
 	"collect struct_b.struct_a.array\[2\]" "^$" \
 	"collect struct_b.struct_a.array\[100\]" "^$" \
 	\
+	"collect a" "^$" \
+	"collect c" "^$" \
+	\
 	"collect tarray\[0\].a" "^$" \
 	"collect tarray\[1\].a" "^$" \
 	"collect tarray\[3\].a" "^$" \
@@ -145,6 +148,15 @@ proc gdb_collect_globals_test { } {
 
     gdb_test "print /x struct_b.struct_a.array\[2\]" " = 0xaaaaaaaa"
 
+    # Check the target doesn't overcollect.  GDB used to merge memory
+    # ranges to collect if they were close enough (collecting the hole
+    # as well), but does not do that anymore.  It's plausible that a
+    # target may do this on its end, but as of this writing, no known
+    # target does it.
+    gdb_test "print {a, b, c}" \
+	" = \\{1, <unavailable>, 3\\}" \
+	"No overcollect of almost but not quite adjacent memory ranges"
+
     # Check <unavailable> isn't confused with 0 in array element repetitions
 
     gdb_test_no_output "set print repeat 1"

gdb/tracepoint.c

@@ -841,13 +841,12 @@ memrange_sortmerge (struct collection_list *memranges)
     {
       for (a = 0, b = 1; b < memranges->next_memrange; b++)
 	{
-	  if (memranges->list[a].type == memranges->list[b].type &&
+	  /* If memrange b overlaps or is adjacent to memrange a,
-	      memranges->list[b].start - memranges->list[a].end <=
+	     merge them.  */
-	      MAX_REGISTER_SIZE)
+	  if (memranges->list[a].type == memranges->list[b].type
+	      && memranges->list[b].start <= memranges->list[a].end)
 	    {
-	      /* memrange b starts before memrange a ends; merge them.  */
+	      memranges->list[a].end = memranges->list[b].end;
-	      if (memranges->list[b].end > memranges->list[a].end)
-		memranges->list[a].end = memranges->list[b].end;
 	      continue;		/* next b, same a */
 	    }
 	  a++;			/* next a */