[PATCH 4/9] Remove minsym termination

[Tom Tromey <tom at tromey dot com>]

I was curious what used the terminating "null" minimal symbol; and
after looking I could not find anything.  This patch removes
terminate_minimal_symbol_table and the extra minimal symbol that is
allocated for it.

gdb/ChangeLog
2019-03-07  Tom Tromey  <tom@tromey.com>

	* symfile.c (reread_symbols): Update.
	* objfiles.c (objfile::objfile): Update.
	* minsyms.h (terminate_minimal_symbol_table): Don't declare.
	* minsyms.c (lookup_minimal_symbol_by_pc_section): Update
	comment.
	(minimal_symbol_reader::install): Update.
	(terminate_minimal_symbol_table): Remove.
	* jit.c (jit_object_close_impl): Update.
---
 gdb/ChangeLog  | 11 +++++++++++
 gdb/jit.c      |  2 --
 gdb/minsyms.c  | 40 +++-------------------------------------
 gdb/minsyms.h  |  7 -------
 gdb/objfiles.c |  2 --
 gdb/symfile.c  |  1 -
 6 files changed, 14 insertions(+), 49 deletions(-)

diff --git a/gdb/jit.c b/gdb/jit.c
index 81c4af40f92..1f87bf2538d 100644
--- a/gdb/jit.c
+++ b/gdb/jit.c
@@ -805,8 +805,6 @@ jit_object_close_impl (struct gdb_symbol_callbacks *cb,
 				OBJF_NOT_FILENAME);
   objfile->per_bfd->gdbarch = target_gdbarch ();
 
-  terminate_minimal_symbol_table (objfile);
-
   j = NULL;
   for (i = obj->symtabs; i; i = j)
     {
diff --git a/gdb/minsyms.c b/gdb/minsyms.c
index 3c91853e780..d937e5d2a99 100644
--- a/gdb/minsyms.c
+++ b/gdb/minsyms.c
@@ -728,11 +728,8 @@ lookup_minimal_symbol_by_pc_section (CORE_ADDR pc_in, struct obj_section *sectio
     {
       CORE_ADDR pc = pc_in;
 
-      /* If this objfile has a minimal symbol table, go search it using
-         a binary search.  Note that a minimal symbol table always consists
-         of at least two symbols, a "real" symbol and the terminating
-         "null symbol".  If there are no real symbols, then there is no
-         minimal symbol table at all.  */
+      /* If this objfile has a minimal symbol table, go search it
+         using a binary search.  */
 
       if (objfile->per_bfd->minimal_symbol_count > 0)
 	{
@@ -1356,7 +1353,7 @@ minimal_symbol_reader::install ()
          compact out the duplicate entries.  Once we have a final table,
          we will give back the excess space.  */
 
-      alloc_count = m_msym_count + m_objfile->per_bfd->minimal_symbol_count + 1;
+      alloc_count = m_msym_count + m_objfile->per_bfd->minimal_symbol_count;
       obstack_blank (&m_objfile->per_bfd->storage_obstack,
 		     alloc_count * sizeof (struct minimal_symbol));
       msymbols = (struct minimal_symbol *)
@@ -1399,16 +1396,6 @@ minimal_symbol_reader::install ()
       msymbols = (struct minimal_symbol *)
 	obstack_finish (&m_objfile->per_bfd->storage_obstack);
 
-      /* We also terminate the minimal symbol table with a "null symbol",
-         which is *not* included in the size of the table.  This makes it
-         easier to find the end of the table when we are handed a pointer
-         to some symbol in the middle of it.  Zero out the fields in the
-         "null symbol" allocated at the end of the array.  Note that the
-         symbol count does *not* include this null symbol, which is why it
-         is indexed by mcount and not mcount-1.  */
-
-      memset (&msymbols[mcount], 0, sizeof (struct minimal_symbol));
-
       /* Attach the minimal symbol table to the specified objfile.
          The strings themselves are also located in the storage_obstack
          of this objfile.  */
@@ -1424,27 +1411,6 @@ minimal_symbol_reader::install ()
     }
 }
 
-/* See minsyms.h.  */
-
-void
-terminate_minimal_symbol_table (struct objfile *objfile)
-{
-  if (! objfile->per_bfd->msymbols)
-    objfile->per_bfd->msymbols = XOBNEW (&objfile->per_bfd->storage_obstack,
-					 minimal_symbol);
-
-  {
-    struct minimal_symbol *m
-      = &objfile->per_bfd->msymbols[objfile->per_bfd->minimal_symbol_count];
-
-    memset (m, 0, sizeof (*m));
-    /* Don't rely on these enumeration values being 0's.  */
-    MSYMBOL_TYPE (m) = mst_unknown;
-    MSYMBOL_SET_LANGUAGE (m, language_unknown,
-			  &objfile->per_bfd->storage_obstack);
-  }
-}
-
 /* Check if PC is in a shared library trampoline code stub.
    Return minimal symbol for the trampoline entry or NULL if PC is not
    in a trampoline code stub.  */
diff --git a/gdb/minsyms.h b/gdb/minsyms.h
index 532436c16c1..3e414f6ff7b 100644
--- a/gdb/minsyms.h
+++ b/gdb/minsyms.h
@@ -148,13 +148,6 @@ class minimal_symbol_reader
   int m_msym_count;
 };
 
-/* Create the terminating entry of OBJFILE's minimal symbol table.
-   If OBJFILE->msymbols is zero, allocate a single entry from
-   OBJFILE->objfile_obstack; otherwise, just initialize
-   OBJFILE->msymbols[OBJFILE->minimal_symbol_count].  */
-
-void terminate_minimal_symbol_table (struct objfile *objfile);
-
 
 
 /* Return whether MSYMBOL is a function/method.  If FUNC_ADDRESS_P is
diff --git a/gdb/objfiles.c b/gdb/objfiles.c
index 4091b42dbf1..2468ca7a3f7 100644
--- a/gdb/objfiles.c
+++ b/gdb/objfiles.c
@@ -411,8 +411,6 @@ objfile::objfile (bfd *abfd, const char *name, objfile_flags flags_)
 
   per_bfd = get_objfile_bfd_data (this, abfd);
 
-  terminate_minimal_symbol_table (this);
-
   /* Add this file onto the tail of the linked list of other such files.  */
 
   if (object_files == NULL)
diff --git a/gdb/symfile.c b/gdb/symfile.c
index 2214f16b431..68ec491d357 100644
--- a/gdb/symfile.c
+++ b/gdb/symfile.c
@@ -2580,7 +2580,6 @@ reread_symbols (void)
 	  objfile_set_sym_fns (objfile, find_sym_fns (objfile->obfd));
 
 	  build_objfile_section_table (objfile);
-	  terminate_minimal_symbol_table (objfile);
 
 	  /* We use the same section offsets as from last time.  I'm not
 	     sure whether that is always correct for shared libraries.  */
-- 
2.17.2