[PATCH 01/13] gdb: make demangle_parse_info own the memory its tree points into

[Simon Marchi <simon.marchi@efficios.com>]

mangled_name_to_comp returns, through output parameters, some memory
that the caller needs to hold onto while it uses the returned
demangle_component.  The `memory` parameter is used if we take the
gdb_cplus_demangle_v3_components branch, while the `demangled_p`
parameter is used if we take the fallback.

To make it easier for the callers, move these two fields inside
demangle_parse_info.  demangle_parse_info already contains other objects
whose lifetime is tied to the demangle_component.

Change-Id: Ib22c73d07706096771ba74284da19f8597497286
---
 gdb/cp-support.c | 59 ++++++++++++++++++++++--------------------------
 gdb/cp-support.h |  7 ++++++
 2 files changed, 34 insertions(+), 32 deletions(-)

diff --git a/gdb/cp-support.c b/gdb/cp-support.c
index 7a1b07a3b161..0f1ead6a4e98 100644
--- a/gdb/cp-support.c
+++ b/gdb/cp-support.c
@@ -75,9 +75,8 @@ static void
 		    canonicalization_ftype *finder,
 		    void *data);
 
-static struct demangle_component *
-  gdb_cplus_demangle_v3_components (const char *mangled,
-				    int options, void **mem);
+static demangle_parse_info_up gdb_cplus_demangle_v3_components
+  (const char *mangled, int options);
 
 /* A convenience function to copy STRING into OBSTACK, returning a pointer
    to the newly allocated string and saving the number of bytes saved in LEN.
@@ -665,32 +664,23 @@ cp_canonicalize_string (const char *string)
   return us;
 }
 
-/* Convert a mangled name to a demangle_component tree.  *MEMORY is
-   set to the block of used memory that should be freed when finished
-   with the tree.  DEMANGLED_P is set to the char * that should be
-   freed when finished with the tree, or NULL if none was needed.
-   OPTIONS will be passed to the demangler.  */
+/* Convert a mangled name to a demangle_component tree.  OPTIONS is passed to
+   the demangler.
+
+   The returned tree may point into MANGLED_NAME, so MANGLED_NAME must
+   outlive it.  */
 
 static demangle_parse_info_up
-mangled_name_to_comp (const char *mangled_name, int options,
-		      void **memory,
-		      gdb::unique_xmalloc_ptr<char> *demangled_p)
+mangled_name_to_comp (const char *mangled_name, int options)
 {
   /* If it looks like a v3 mangled name, then try to go directly
      to trees.  */
   if (mangled_name[0] == '_' && mangled_name[1] == 'Z')
     {
-      struct demangle_component *ret;
-
-      ret = gdb_cplus_demangle_v3_components (mangled_name,
-					      options, memory);
-      if (ret)
-	{
-	  auto info = std::make_unique<demangle_parse_info> ();
-	  info->tree = ret;
-	  *demangled_p = NULL;
-	  return info;
-	}
+      if (demangle_parse_info_up info
+	    = gdb_cplus_demangle_v3_components (mangled_name, options);
+	  info != nullptr)
+	return info;
     }
 
   /* If it doesn't, or if that failed, then try to demangle the
@@ -708,7 +698,7 @@ mangled_name_to_comp (const char *mangled_name, int options,
   if (info == NULL)
     return NULL;
 
-  *demangled_p = std::move (demangled_name);
+  info->demangled_name = std::move (demangled_name);
   return info;
 }
 
@@ -717,12 +707,9 @@ mangled_name_to_comp (const char *mangled_name, int options,
 gdb::unique_xmalloc_ptr<char>
 cp_class_name_from_physname (const char *physname)
 {
-  void *storage = NULL;
-  gdb::unique_xmalloc_ptr<char> demangled_name;
   gdb::unique_xmalloc_ptr<char> ret;
   struct demangle_component *ret_comp, *prev_comp, *cur_comp;
-  demangle_parse_info_up info
-    = mangled_name_to_comp (physname, DMGL_ANSI, &storage, &demangled_name);
+  demangle_parse_info_up info = mangled_name_to_comp (physname, DMGL_ANSI);
   int done;
 
   if (info == nullptr)
@@ -796,7 +783,6 @@ cp_class_name_from_physname (const char *physname)
       ret = cp_comp_to_string (ret_comp, 10);
     }
 
-  xfree (storage);
   return ret;
 }
 
@@ -1666,11 +1652,20 @@ gdb_cplus_demangle_print (int options,
 /* A wrapper for cplus_demangle_v3_components that forces
    DMGL_VERBOSE.  */
 
-static struct demangle_component *
-gdb_cplus_demangle_v3_components (const char *mangled,
-				  int options, void **mem)
+static demangle_parse_info_up
+gdb_cplus_demangle_v3_components (const char *mangled, int options)
 {
-  return cplus_demangle_v3_components (mangled, options | DMGL_VERBOSE, mem);
+  void *storage;
+  demangle_component *tree
+    = cplus_demangle_v3_components (mangled, options | DMGL_VERBOSE,
+				    &storage);
+  if (tree == nullptr)
+    return nullptr;
+
+  auto info = std::make_unique<demangle_parse_info> ();
+  info->tree = tree;
+  info->demangler_storage.reset (storage);
+  return info;
 }
 
 /* See cp-support.h.  */
diff --git a/gdb/cp-support.h b/gdb/cp-support.h
index 00703c52c880..103cbf0cd652 100644
--- a/gdb/cp-support.h
+++ b/gdb/cp-support.h
@@ -67,6 +67,13 @@ struct demangle_parse_info
   /* Any memory used during processing.  */
   auto_obstack obstack;
 
+  /* Memory allocated by cplus_demangle_v3_components that TREE points
+     into, if any.  */
+  gdb::unique_xmalloc_ptr<void> demangler_storage;
+
+  /* The demangled name TREE was parsed from and points into, if any.  */
+  gdb::unique_xmalloc_ptr<char> demangled_name;
+
   /* True if the parser had to add a dummy '()' at the end of the
      input text to make it parse.  */
   bool added_parens = false;
-- 
2.56.0