[binutils-gdb] Don't derive partial_symbol from general_symbol_info

[binutils-gdb] Don't derive partial_symbol from general_symbol_info

[Tom Tromey]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=af97b4161f07a716783183f1b17fa5cac9f99a49

commit af97b4161f07a716783183f1b17fa5cac9f99a49
Author: Tom Tromey <tom@tromey.com>
Date:   Tue Apr 23 16:42:14 2019 -0600

    Don't derive partial_symbol from general_symbol_info
    
    This patch partly reverts commit 8a6d42345 ("Change representation of
    psymbol to flush out accessors"); specifically, it changes
    partial_symbol to no longer derive from general_symbol_info.
    
    The basic problem here is that the bcache compares objects bitwise,
    and this change made it less likely that the relevant fields in the
    psymbol would be fully initialized.  This could be seen by running a
    test under valgrind on the Fedora-i686 buildbot.
    
    I considered a simpler patch, namely just zeroing the psymbol's
    "value" field in add_psymbol_to_bcache.  However, it wasn't clear to
    me that this memset could not then be optimized away by the compiler.
    
    Regression tested by the buildbot.  I think this should go in 8.3 as
    well.
    
    gdb/ChangeLog
    2019-05-04  Tom Tromey  <tom@tromey.com>
    
    	* psymtab.c (psymbol_name_matches, match_partial_symbol)
    	(lookup_partial_symbol, print_partial_symbols)
    	(recursively_search_psymtabs, sort_pst_symbols, psymbol_hash)
    	(psymbol_compare): Update.
    	(add_psymbol_to_bcache): Clear the entire psymbol.
    	(maintenance_check_psymtabs): Update.
    	* psympriv.h (struct partial_symbol): Don't derive from
    	general_symbol_info.
    	<obj_section, unrelocated_address, address,
    	set_unrelocated_address>: Update.
    	<ginfo>: New member.
    	* dwarf-index-write.c (write_psymbols, debug_names::insert)
    	(debug_names::write_psymbols): Update.

Diff:
---
 gdb/ChangeLog           | 16 +++++++++++
 gdb/dwarf-index-write.c |  8 +++---
 gdb/psympriv.h          | 18 ++++++++----
 gdb/psymtab.c           | 76 ++++++++++++++++++++++++++-----------------------
 4 files changed, 72 insertions(+), 46 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 09a4a0a..383b353 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,19 @@
+2019-05-04  Tom Tromey  <tom@tromey.com>
+
+	* psymtab.c (psymbol_name_matches, match_partial_symbol)
+	(lookup_partial_symbol, print_partial_symbols)
+	(recursively_search_psymtabs, sort_pst_symbols, psymbol_hash)
+	(psymbol_compare): Update.
+	(add_psymbol_to_bcache): Clear the entire psymbol.
+	(maintenance_check_psymtabs): Update.
+	* psympriv.h (struct partial_symbol): Don't derive from
+	general_symbol_info.
+	<obj_section, unrelocated_address, address,
+	set_unrelocated_address>: Update.
+	<ginfo>: New member.
+	* dwarf-index-write.c (write_psymbols, debug_names::insert)
+	(debug_names::write_psymbols): Update.
+
 2019-05-04  Tom de Vries  <tdevries@suse.de>
 
 	* contrib/cc-with-tweaks.sh: Support -n arg.
diff --git a/gdb/dwarf-index-write.c b/gdb/dwarf-index-write.c
index 3f96ffd..8734f99 100644
--- a/gdb/dwarf-index-write.c
+++ b/gdb/dwarf-index-write.c
@@ -540,7 +540,7 @@ write_psymbols (struct mapped_symtab *symtab,
     {
       struct partial_symbol *psym = *psymp;
 
-      if (psym->language == language_ada)
+      if (psym->ginfo.language == language_ada)
 	error (_("Ada is not currently supported by the index"));
 
       /* Only add a given psymbol once.  */
@@ -548,7 +548,7 @@ write_psymbols (struct mapped_symtab *symtab,
 	{
 	  gdb_index_symbol_kind kind = symbol_kind (psym);
 
-	  add_index_entry (symtab, symbol_search_name (psym),
+	  add_index_entry (symtab, symbol_search_name (&psym->ginfo),
 			   is_static, kind, cu_index);
 	}
     }
@@ -684,7 +684,7 @@ public:
     const int dwarf_tag = psymbol_tag (psym);
     if (dwarf_tag == 0)
       return;
-    const char *const name = symbol_search_name (psym);
+    const char *const name = symbol_search_name (&psym->ginfo);
     const auto insertpair
       = m_name_to_value_set.emplace (c_str_view (name),
 				     std::set<symbol_value> ());
@@ -1181,7 +1181,7 @@ private:
       {
 	struct partial_symbol *psym = *psymp;
 
-	if (psym->language == language_ada)
+	if (psym->ginfo.language == language_ada)
 	  error (_("Ada is not currently supported by the index"));
 
 	/* Only add a given psymbol once.  */
diff --git a/gdb/psympriv.h b/gdb/psympriv.h
index 7d2ce30..61d73a3 100644
--- a/gdb/psympriv.h
+++ b/gdb/psympriv.h
@@ -33,37 +33,43 @@
 /* This structure is space critical.  See space comments at the top of
    symtab.h.  */
 
-struct partial_symbol : public general_symbol_info
+struct partial_symbol
 {
   /* Return the section for this partial symbol, or nullptr if no
      section has been set.  */
   struct obj_section *obj_section (struct objfile *objfile) const
   {
-    if (section >= 0)
-      return &objfile->sections[section];
+    if (ginfo.section >= 0)
+      return &objfile->sections[ginfo.section];
     return nullptr;
   }
 
   /* Return the unrelocated address of this partial symbol.  */
   CORE_ADDR unrelocated_address () const
   {
-    return value.address;
+    return ginfo.value.address;
   }
 
   /* Return the address of this partial symbol, relocated according to
      the offsets provided in OBJFILE.  */
   CORE_ADDR address (const struct objfile *objfile) const
   {
-    return value.address + ANOFFSET (objfile->section_offsets, section);
+    return (ginfo.value.address
+	    + ANOFFSET (objfile->section_offsets, ginfo.section));
   }
 
   /* Set the address of this partial symbol.  The address must be
      unrelocated.  */
   void set_unrelocated_address (CORE_ADDR addr)
   {
-    value.address = addr;
+    ginfo.value.address = addr;
   }
 
+  /* Note that partial_symbol does not derive from general_symbol_info
+     due to the bcache.  See add_psymbol_to_bcache.  */
+
+  struct general_symbol_info ginfo;
+
   /* Name space code.  */
 
   ENUM_BITFIELD(domain_enum_tag) domain : SYMBOL_DOMAIN_BITS;
diff --git a/gdb/psymtab.c b/gdb/psymtab.c
index 584a5e9..78a4699 100644
--- a/gdb/psymtab.c
+++ b/gdb/psymtab.c
@@ -528,10 +528,10 @@ static bool
 psymbol_name_matches (partial_symbol *psym,
 		      const lookup_name_info &lookup_name)
 {
-  const language_defn *lang = language_def (psym->language);
+  const language_defn *lang = language_def (psym->ginfo.language);
   symbol_name_matcher_ftype *name_match
     = get_symbol_name_matcher (lang, lookup_name);
-  return name_match (symbol_search_name (psym), lookup_name, NULL);
+  return name_match (symbol_search_name (&psym->ginfo), lookup_name, NULL);
 }
 
 /* Look in PST for a symbol in DOMAIN whose name matches NAME.  Search
@@ -581,11 +581,12 @@ match_partial_symbol (struct objfile *objfile,
 	  center = bottom + (top - bottom) / 2;
 	  gdb_assert (center < top);
 
-	  enum language lang = (*center)->language;
+	  enum language lang = (*center)->ginfo.language;
 	  const char *lang_ln
 	    = lookup_name.language_lookup_name (lang).c_str ();
 
-	  if (ordered_compare (symbol_search_name (*center), lang_ln) >= 0)
+	  if (ordered_compare (symbol_search_name (&(*center)->ginfo),
+			       lang_ln) >= 0)
 	    top = center;
 	  else
 	    bottom = center + 1;
@@ -595,7 +596,7 @@ match_partial_symbol (struct objfile *objfile,
       while (top <= real_top
 	     && psymbol_name_matches (*top, lookup_name))
 	{
-	  if (symbol_matches_domain ((*top)->language,
+	  if (symbol_matches_domain ((*top)->ginfo.language,
 				     (*top)->domain, domain))
 	    return *top;
 	  top++;
@@ -609,7 +610,7 @@ match_partial_symbol (struct objfile *objfile,
     {
       for (psym = start; psym < start + length; psym++)
 	{
-	  if (symbol_matches_domain ((*psym)->language,
+	  if (symbol_matches_domain ((*psym)->ginfo.language,
 				     (*psym)->domain, domain)
 	      && psymbol_name_matches (*psym, lookup_name))
 	    return *psym;
@@ -692,7 +693,7 @@ lookup_partial_symbol (struct objfile *objfile,
 	  if (!(center < top))
 	    internal_error (__FILE__, __LINE__,
 			    _("failed internal consistency check"));
-	  if (strcmp_iw_ordered (symbol_search_name (*center),
+	  if (strcmp_iw_ordered (symbol_search_name (&(*center)->ginfo),
 				 search_name.get ()) >= 0)
 	    {
 	      top = center;
@@ -708,15 +709,17 @@ lookup_partial_symbol (struct objfile *objfile,
 
       /* For `case_sensitivity == case_sensitive_off' strcmp_iw_ordered will
 	 search more exactly than what matches SYMBOL_MATCHES_SEARCH_NAME.  */
-      while (top >= start && symbol_matches_search_name (*top, lookup_name))
+      while (top >= start && symbol_matches_search_name (&(*top)->ginfo,
+							 lookup_name))
 	top--;
 
       /* Fixup to have a symbol which matches SYMBOL_MATCHES_SEARCH_NAME.  */
       top++;
 
-      while (top <= real_top && symbol_matches_search_name (*top, lookup_name))
+      while (top <= real_top && symbol_matches_search_name (&(*top)->ginfo,
+							    lookup_name))
 	{
-	  if (symbol_matches_domain ((*top)->language,
+	  if (symbol_matches_domain ((*top)->ginfo.language,
 				     (*top)->domain, domain))
 	    return *top;
 	  top++;
@@ -730,9 +733,9 @@ lookup_partial_symbol (struct objfile *objfile,
     {
       for (psym = start; psym < start + length; psym++)
 	{
-	  if (symbol_matches_domain ((*psym)->language,
+	  if (symbol_matches_domain ((*psym)->ginfo.language,
 				     (*psym)->domain, domain)
-	      && symbol_matches_search_name (*psym, lookup_name))
+	      && symbol_matches_search_name (&(*psym)->ginfo, lookup_name))
 	    return *psym;
 	}
     }
@@ -832,10 +835,11 @@ print_partial_symbols (struct gdbarch *gdbarch, struct objfile *objfile,
   while (count-- > 0)
     {
       QUIT;
-      fprintf_filtered (outfile, "    `%s'", (*p)->name);
-      if (symbol_demangled_name (*p) != NULL)
+      fprintf_filtered (outfile, "    `%s'", (*p)->ginfo.name);
+      if (symbol_demangled_name (&(*p)->ginfo) != NULL)
 	{
-	  fprintf_filtered (outfile, "  `%s'", symbol_demangled_name (*p));
+	  fprintf_filtered (outfile, "  `%s'",
+			    symbol_demangled_name (&(*p)->ginfo));
 	}
       fputs_filtered (", ", outfile);
       switch ((*p)->domain)
@@ -1305,7 +1309,8 @@ recursively_search_psymtabs
 	       || (domain == TYPES_DOMAIN
 		   && (*psym)->aclass == LOC_TYPEDEF))
 	      && psymbol_name_matches (*psym, lookup_name)
-	      && (sym_matcher == NULL || sym_matcher (symbol_search_name (*psym))))
+	      && (sym_matcher == NULL
+		  || sym_matcher (symbol_search_name (&(*psym)->ginfo))))
 	    {
 	      /* Found a match, so notify our caller.  */
 	      result = PST_SEARCHED_AND_FOUND;
@@ -1500,8 +1505,8 @@ sort_pst_symbols (struct objfile *objfile, struct partial_symtab *pst)
 
   std::sort (begin, end, [] (partial_symbol *s1, partial_symbol *s2)
     {
-      return strcmp_iw_ordered (symbol_search_name (s1),
-				symbol_search_name (s2)) < 0;
+      return strcmp_iw_ordered (symbol_search_name (&s1->ginfo),
+				symbol_search_name (&s2->ginfo)) < 0;
     });
 }
 
@@ -1548,18 +1553,18 @@ psymbol_hash (const void *addr, int length)
 {
   unsigned long h = 0;
   struct partial_symbol *psymbol = (struct partial_symbol *) addr;
-  unsigned int lang = psymbol->language;
+  unsigned int lang = psymbol->ginfo.language;
   unsigned int domain = psymbol->domain;
   unsigned int theclass = psymbol->aclass;
 
-  h = hash_continue (&psymbol->value, sizeof (psymbol->value), h);
+  h = hash_continue (&psymbol->ginfo.value, sizeof (psymbol->ginfo.value), h);
   h = hash_continue (&lang, sizeof (unsigned int), h);
   h = hash_continue (&domain, sizeof (unsigned int), h);
   h = hash_continue (&theclass, sizeof (unsigned int), h);
   /* Note that psymbol names are interned via symbol_set_names, so
      there's no need to hash the contents of the name here.  */
-  h = hash_continue (&psymbol->name,
-		     sizeof (psymbol->name), h);
+  h = hash_continue (&psymbol->ginfo.name,
+		     sizeof (psymbol->ginfo.name), h);
 
   return h;
 }
@@ -1574,15 +1579,15 @@ psymbol_compare (const void *addr1, const void *addr2, int length)
   struct partial_symbol *sym1 = (struct partial_symbol *) addr1;
   struct partial_symbol *sym2 = (struct partial_symbol *) addr2;
 
-  return (memcmp (&sym1->value, &sym2->value,
-                  sizeof (sym1->value)) == 0
-	  && sym1->language == sym2->language
+  return (memcmp (&sym1->ginfo.value, &sym2->ginfo.value,
+                  sizeof (sym1->ginfo.value)) == 0
+	  && sym1->ginfo.language == sym2->ginfo.language
           && sym1->domain == sym2->domain
           && sym1->aclass == sym2->aclass
 	  /* Note that psymbol names are interned via
 	     symbol_set_names, so there's no need to compare the
 	     contents of the name here.  */
-          && sym1->name == sym2->name);
+          && sym1->ginfo.name == sym2->ginfo.name);
 }
 
 /* Helper function, initialises partial symbol structure and stashes
@@ -1601,17 +1606,16 @@ add_psymbol_to_bcache (const char *name, int namelength, int copy_name,
 		       int *added)
 {
   struct partial_symbol psymbol;
+  memset (&psymbol, 0, sizeof (psymbol));
 
   psymbol.set_unrelocated_address (coreaddr);
-  psymbol.section = section;
+  psymbol.ginfo.section = section;
   psymbol.domain = domain;
   psymbol.aclass = theclass;
-
-  memset (&psymbol.language_specific, 0, sizeof (psymbol.language_specific));
-  psymbol.ada_mangled = 0;
-  symbol_set_language (&psymbol, language,
+  symbol_set_language (&psymbol.ginfo, language,
 		       objfile->partial_symtabs->obstack ());
-  symbol_set_names (&psymbol, name, namelength, copy_name, objfile->per_bfd);
+  symbol_set_names (&psymbol.ginfo, name, namelength, copy_name,
+		    objfile->per_bfd);
 
   /* Stash the partial symbol away in the cache.  */
   return ((struct partial_symbol *)
@@ -2133,13 +2137,13 @@ maintenance_check_psymtabs (const char *ignore, int from_tty)
 	length = ps->n_static_syms;
 	while (length--)
 	  {
-	    sym = block_lookup_symbol (b, symbol_search_name (*psym),
+	    sym = block_lookup_symbol (b, symbol_search_name (&(*psym)->ginfo),
 				       symbol_name_match_type::SEARCH_NAME,
 				       (*psym)->domain);
 	    if (!sym)
 	      {
 		printf_filtered ("Static symbol `");
-		puts_filtered ((*psym)->name);
+		puts_filtered ((*psym)->ginfo.name);
 		printf_filtered ("' only found in ");
 		puts_filtered (ps->filename);
 		printf_filtered (" psymtab\n");
@@ -2151,13 +2155,13 @@ maintenance_check_psymtabs (const char *ignore, int from_tty)
 	length = ps->n_global_syms;
 	while (length--)
 	  {
-	    sym = block_lookup_symbol (b, symbol_search_name (*psym),
+	    sym = block_lookup_symbol (b, symbol_search_name (&(*psym)->ginfo),
 				       symbol_name_match_type::SEARCH_NAME,
 				       (*psym)->domain);
 	    if (!sym)
 	      {
 		printf_filtered ("Global symbol `");
-		puts_filtered ((*psym)->name);
+		puts_filtered ((*psym)->ginfo.name);
 		printf_filtered ("' only found in ");
 		puts_filtered (ps->filename);
 		printf_filtered (" psymtab\n");