Add name canonicalization for C

PR symtab/29105 shows a number of situations where symbol lookup can
result in the expansion of too many CUs.

What happens is that lookup_signed_typename will try to look up a type
like "signed int".  In cooked_index_functions::expand_symtabs_matching,
when looping over languages, the C++ case will canonicalize this type
name to be "int" instead.  Then this method will proceed to expand
every CU that has an entry for "int" -- i.e., nearly all of them.  A
crucial component of this is that the caller, objfile::lookup_symbol,
does not do this canonicalization, so when it tries to find the symbol
for "signed int", it fails -- causing the loop to continue.

This patch fixes the problem by introducing name canonicalization for
C.  The idea here is that, by making C and C++ agree on the canonical
name when a symbol name can have multiple spellings, we avoid the bad
behavior in objfile::lookup_symbol (and any other such code -- I don't
know if there is any).

Unlike C++, C only has a few situations where canonicalization is
needed.  And, in particular, due to the lack of overloading (thus
avoiding any issues in linespec) and due to the way c-exp.y works, I
think that no canonicalization is needed during symbol lookup -- only
during symtab construction.  This explains why lookup_name_info is not
touched.

The stabs reader is modified on a "best effort" basis.

The DWARF reader needed one small tweak in dwarf2_name to avoid a
regression in dw2-unusual-field-names.exp.  I think this is adequately
explained by the comment, but basically this is a scenario that should
not occur in real code, only the gdb test suite.

lookup_signed_typename is simplified.  It used to search for two
different type names, but now gdb can search just for the canonical
form.

gdb.dwarf2/enum-type.exp needed a small tweak, because the
canonicalizer turns "unsigned integer" into "unsigned int integer".
It seems better here to use the correct C type name.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=29105
Tested-by: Simon Marchi <simark@simark.ca>
Reviewed-by: Andrew Burgess <aburgess@redhat.com>

1 files changed, 19 insertions, 11 deletions

diff --git a/gdb/stabsread.c b/gdb/stabsread.c
index 6124435..74d0885 100644
--- a/gdb/stabsread.c
+++ b/gdb/stabsread.c
@@ -736,11 +736,13 @@ define_symbol (CORE_ADDR valu, const char *string, int desc, int type,
 
       if (sym->language () == language_cplus)
 	{
-	  char *name = (char *) alloca (p - string + 1);
-
-	  memcpy (name, string, p - string);
-	  name[p - string] = '\0';
-	  new_name = cp_canonicalize_string (name);
+	  std::string name (string, p - string);
+	  new_name = cp_canonicalize_string (name.c_str ());
+	}
+      else if (sym->language () == language_c)
+	{
+	  std::string name (string, p - string);
+	  new_name = c_canonicalize_name (name.c_str ());
 	}
       if (new_name != nullptr)
 	sym->compute_and_set_names (new_name.get (), true, objfile->per_bfd);
@@ -1592,12 +1594,18 @@ again:
 	  type_name = NULL;
 	  if (get_current_subfile ()->language == language_cplus)
 	    {
-	      char *name = (char *) alloca (p - *pp + 1);
-
-	      memcpy (name, *pp, p - *pp);
-	      name[p - *pp] = '\0';
-
-	      gdb::unique_xmalloc_ptr<char> new_name = cp_canonicalize_string (name);
+	      std::string name (*pp, p - *pp);
+	      gdb::unique_xmalloc_ptr<char> new_name
+		= cp_canonicalize_string (name.c_str ());
+	      if (new_name != nullptr)
+		type_name = obstack_strdup (&objfile->objfile_obstack,
+					    new_name.get ());
+	    }
+	  else if (get_current_subfile ()->language == language_c)
+	    {
+	      std::string name (*pp, p - *pp);
+	      gdb::unique_xmalloc_ptr<char> new_name
+		= c_canonicalize_name (name.c_str ());
 	      if (new_name != nullptr)
 		type_name = obstack_strdup (&objfile->objfile_obstack,
 					    new_name.get ());