[RFA 21/42] Move the context stack to buildsym_compunit

[Tom Tromey <tom at tromey dot com>]

This moves the context stack globals to be members of
buildsym_compunit, changing the type to a std::vector in the process.

Note that the context stack works in a somewhat odd way, where callers
can pop the stack and expect the returned pointer to remain valid
until the next pop.  In the new code we handle this by having a
"popped context" object that remains valid in this way.

gdb/ChangeLog
2018-05-22  Tom Tromey  <tom@tromey.com>

	* dwarf2read.c (new_symbol): Update.
	* dbxread.c (process_one_symbol): Update.
	* buildsym.h (context_stack, context_stack_depth): Don't declare.
	(outermost_context_p): Remove macro.
	(outermost_context_p, get_current_context_stack)
	(get_context_stack_depth): Declare.
	* buildsym.c (struct buildsym_compunit) <m_context_stack,
	m_popped_context>: New members.
	(context_stack_size): Remove.
	(INITIAL_CONTEXT_STACK_SIZE): Remove.
	(prepare_for_building, end_symtab_get_static_block)
	(augment_type_symtab, push_context, pop_context): Update.
	(outermost_context_p, get_current_context_stack)
	(get_context_stack_depth): New functions.
	(buildsym_init): Update.
---
 gdb/ChangeLog    | 18 +++++++++++++
 gdb/buildsym.c   | 82 ++++++++++++++++++++++++++++++++------------------------
 gdb/buildsym.h   | 22 ++++++++-------
 gdb/dbxread.c    |  4 +--
 gdb/dwarf2read.c | 40 ++++++++++++++-------------
 5 files changed, 101 insertions(+), 65 deletions(-)

diff --git a/gdb/buildsym.c b/gdb/buildsym.c
index 4e3ca5e4b1..54592b7795 100644
--- a/gdb/buildsym.c
+++ b/gdb/buildsym.c
@@ -213,6 +213,9 @@ struct buildsym_compunit
   /* global "using" directives.  */
 
   struct using_direct *m_global_using_directives = nullptr;
+
+  std::vector<struct context_stack> m_context_stack;
+  struct context_stack m_popped_context {};
 };
 
 /* The work-in-progress of the compunit we are building.
@@ -260,10 +263,6 @@ struct pending_block
 
 static struct pending_block *pending_blocks;
 
-/* Currently allocated size of context stack.  */
-
-static int context_stack_size;
-
 static void free_buildsym_compunit (void);
 
 static int compare_line_numbers (const void *ln1p, const void *ln2p);
@@ -278,7 +277,6 @@ static void free_pending_blocks ();
    needed, and realloc'd down to the size actually used, when
    completed.  */
 
-#define	INITIAL_CONTEXT_STACK_SIZE	10
 #define	INITIAL_LINE_VECTOR_LENGTH	1000
 
 
@@ -1032,8 +1030,6 @@ prepare_for_building ()
 {
   local_symbols = NULL;
 
-  context_stack_depth = 0;
-
   /* These should have been reset either by successful completion of building
      a symtab, or by the scoped_free_pendings destructor.  */
   gdb_assert (file_symbols == NULL);
@@ -1222,7 +1218,7 @@ end_symtab_get_static_block (CORE_ADDR end_addr, int expandable, int required)
   /* Finish the lexical context of the last function in the file; pop
      the context stack.  */
 
-  if (context_stack_depth > 0)
+  if (!buildsym_compunit->m_context_stack.empty ())
     {
       struct context_stack *cstk = pop_context ();
 
@@ -1230,7 +1226,7 @@ end_symtab_get_static_block (CORE_ADDR end_addr, int expandable, int required)
       finish_block (cstk->name, &local_symbols, cstk->old_blocks, NULL,
 		    cstk->start_addr, end_addr);
 
-      if (context_stack_depth > 0)
+      if (!buildsym_compunit->m_context_stack.empty ())
 	{
 	  /* This is said to happen with SCO.  The old coffread.c
 	     code simply emptied the context stack, so we do the
@@ -1239,7 +1235,7 @@ end_symtab_get_static_block (CORE_ADDR end_addr, int expandable, int required)
 	     it used to be an abort().  */
 	  complaint (&symfile_complaints,
 	             _("Context stack not empty in end_symtab"));
-	  context_stack_depth = 0;
+	  buildsym_compunit->m_context_stack.clear ();
 	}
     }
 
@@ -1583,12 +1579,9 @@ augment_type_symtab (void)
   struct compunit_symtab *cust = buildsym_compunit->compunit_symtab;
   const struct blockvector *blockvector = COMPUNIT_BLOCKVECTOR (cust);
 
-  if (context_stack_depth > 0)
-    {
-      complaint (&symfile_complaints,
-		 _("Context stack not empty in augment_type_symtab"));
-      context_stack_depth = 0;
-    }
+  if (!buildsym_compunit->m_context_stack.empty ())
+    complaint (&symfile_complaints,
+	       _("Context stack not empty in augment_type_symtab"));
   if (pending_blocks != NULL)
     complaint (&symfile_complaints, _("Blocks in a type symtab"));
   if (buildsym_compunit->m_pending_macros != NULL)
@@ -1629,17 +1622,11 @@ augment_type_symtab (void)
 struct context_stack *
 push_context (int desc, CORE_ADDR valu)
 {
-  struct context_stack *newobj;
+  gdb_assert (buildsym_compunit != nullptr);
 
-  if (context_stack_depth == context_stack_size)
-    {
-      context_stack_size *= 2;
-      context_stack = (struct context_stack *)
-	xrealloc ((char *) context_stack,
-		  (context_stack_size * sizeof (struct context_stack)));
-    }
+  buildsym_compunit->m_context_stack.emplace_back ();
+  struct context_stack *newobj = &buildsym_compunit->m_context_stack.back ();
 
-  newobj = &context_stack[context_stack_depth++];
   newobj->depth = desc;
   newobj->locals = local_symbols;
   newobj->old_blocks = pending_blocks;
@@ -1660,8 +1647,12 @@ push_context (int desc, CORE_ADDR valu)
 struct context_stack *
 pop_context (void)
 {
-  gdb_assert (context_stack_depth > 0);
-  return (&context_stack[--context_stack_depth]);
+  gdb_assert (buildsym_compunit != nullptr);
+  gdb_assert (!buildsym_compunit->m_context_stack.empty ());
+  buildsym_compunit->m_popped_context
+    = buildsym_compunit->m_context_stack.back ();
+  buildsym_compunit->m_context_stack.pop_back ();
+  return &buildsym_compunit->m_popped_context;
 }
 
 
@@ -1745,6 +1736,35 @@ get_global_using_directives ()
   return &buildsym_compunit->m_global_using_directives;
 }
 
+/* See buildsym.h.  */
+
+bool
+outermost_context_p ()
+{
+  gdb_assert (buildsym_compunit != nullptr);
+  return buildsym_compunit->m_context_stack.empty ();
+}
+
+/* See buildsym.h.  */
+
+struct context_stack *
+get_current_context_stack ()
+{
+  gdb_assert (buildsym_compunit != nullptr);
+  if (buildsym_compunit->m_context_stack.empty ())
+    return nullptr;
+  return &buildsym_compunit->m_context_stack.back ();
+}
+
+/* See buildsym.h.  */
+
+int
+get_context_stack_depth ()
+{
+  gdb_assert (buildsym_compunit != nullptr);
+  return buildsym_compunit->m_context_stack.size ();
+}
+
 
 
 /* Initialize anything that needs initializing when starting to read a
@@ -1756,14 +1776,6 @@ buildsym_init ()
 {
   pending_addrmap_interesting = 0;
 
-  /* Context stack is initially empty.  Allocate first one with room
-     for a few levels; reuse it forever afterward.  */
-  if (context_stack == NULL)
-    {
-      context_stack_size = INITIAL_CONTEXT_STACK_SIZE;
-      context_stack = XNEWVEC (struct context_stack, context_stack_size);
-    }
-
   /* Ensure the scoped_free_pendings destructor was called after
      the last time.  */
   gdb_assert (free_pendings == NULL);
diff --git a/gdb/buildsym.h b/gdb/buildsym.h
index efb35c907b..fe158d183c 100644
--- a/gdb/buildsym.h
+++ b/gdb/buildsym.h
@@ -133,15 +133,6 @@ struct context_stack
 
   };
 
-EXTERN struct context_stack *context_stack;
-
-/* Index of first unused entry in context stack.  */
-
-EXTERN int context_stack_depth;
-
-/* Non-zero if the context stack is empty.  */
-#define outermost_context_p() (context_stack_depth == 0)
-
 /* The type of the record_line function.  */
 typedef void (record_line_ftype) (struct subfile *subfile, int line,
 				  CORE_ADDR pc);
@@ -270,6 +261,19 @@ extern void set_local_using_directives (struct using_direct *new_local);
 
 extern struct using_direct **get_global_using_directives ();
 
+/* Non-zero if the context stack is empty.  */
+
+extern bool outermost_context_p ();
+
+/* Return the top of the context stack, or nullptr if there is
+   entry.  */
+
+extern struct context_stack *get_current_context_stack ();
+
+/* Return the context stack depth.  */
+
+extern int get_context_stack_depth ();
+
 #undef EXTERN
 
 #endif /* defined (BUILDSYM_H) */
diff --git a/gdb/dbxread.c b/gdb/dbxread.c
index ed6e6be458..fe7f4a2815 100644
--- a/gdb/dbxread.c
+++ b/gdb/dbxread.c
@@ -2648,7 +2648,7 @@ process_one_symbol (int type, int desc, CORE_ADDR valu, const char *name,
 	}
       local_symbols = newobj->locals;
 
-      if (context_stack_depth > 1)
+      if (get_context_stack_depth () > 1)
 	{
 	  /* This is not the outermost LBRAC...RBRAC pair in the
 	     function, its local symbols preceded it, and are the ones
@@ -2942,7 +2942,7 @@ process_one_symbol (int type, int desc, CORE_ADDR valu, const char *name,
 
 	      within_function = 1;
 
-	      if (context_stack_depth > 1)
+	      if (get_context_stack_depth () > 1)
 		{
 		  complaint (&symfile_complaints,
 			     _("unmatched N_LBRAC before symtab pos %d"),
diff --git a/gdb/dwarf2read.c b/gdb/dwarf2read.c
index b39c14365a..354ff920e5 100644
--- a/gdb/dwarf2read.c
+++ b/gdb/dwarf2read.c
@@ -21467,26 +21467,28 @@ new_symbol (struct die_info *die, struct type *type, struct dwarf2_cu *cu,
 	    }
 	  break;
 	case DW_TAG_formal_parameter:
-	  /* If we are inside a function, mark this as an argument.  If
-	     not, we might be looking at an argument to an inlined function
-	     when we do not have enough information to show inlined frames;
-	     pretend it's a local variable in that case so that the user can
-	     still see it.  */
-	  if (!outermost_context_p ()
-	      && context_stack[context_stack_depth - 1].name != NULL)
-	    SYMBOL_IS_ARGUMENT (sym) = 1;
-	  attr = dwarf2_attr (die, DW_AT_location, cu);
-	  if (attr)
-	    {
-	      var_decode_location (attr, sym, cu);
-	    }
-	  attr = dwarf2_attr (die, DW_AT_const_value, cu);
-	  if (attr)
-	    {
-	      dwarf2_const_value (attr, sym, cu);
-	    }
+	  {
+	    /* If we are inside a function, mark this as an argument.  If
+	       not, we might be looking at an argument to an inlined function
+	       when we do not have enough information to show inlined frames;
+	       pretend it's a local variable in that case so that the user can
+	       still see it.  */
+	    struct context_stack *curr = get_current_context_stack ();
+	    if (curr != nullptr && curr->name != nullptr)
+	      SYMBOL_IS_ARGUMENT (sym) = 1;
+	    attr = dwarf2_attr (die, DW_AT_location, cu);
+	    if (attr)
+	      {
+		var_decode_location (attr, sym, cu);
+	      }
+	    attr = dwarf2_attr (die, DW_AT_const_value, cu);
+	    if (attr)
+	      {
+		dwarf2_const_value (attr, sym, cu);
+	      }
 
-	  list_to_add = cu->list_in_scope;
+	    list_to_add = cu->list_in_scope;
+	  }
 	  break;
 	case DW_TAG_unspecified_parameters:
 	  /* From varargs functions; gdb doesn't seem to have any
-- 
2.13.6