[gcc r16-2559] Prevent mixups of IDENTIFIER_TRANSPARENT_ALIAS and IDENTIFIER_INTERNAL_P better [PR120855]

[Nathaniel Shead via Gcc-cvs]

https://gcc.gnu.org/g:4a8fd4a8ee3f83c330deb0dd494b27f66a748fb5

commit r16-2559-g4a8fd4a8ee3f83c330deb0dd494b27f66a748fb5
Author: Nathaniel Shead <nathanielosh...@gmail.com>
Date:   Thu Jul 24 09:41:00 2025 +1000

    Prevent mixups of IDENTIFIER_TRANSPARENT_ALIAS and IDENTIFIER_INTERNAL_P 
better [PR120855]
    
    The assertion failure on ASM_OUTPUT_WEAKREF targets since my r16-1738
    was caused because the 'TREE_CHAIN (id)' check in assemble_name_resolve
    no longer implies that ID is a transparent alias, since internal
    identifiers can have a TREE_CHAIN as well.
    
    I still don't think it's possible for a transparent alias to be an
    internal identifier in the sense added, so this patch simply constrains
    the assertion better so that it doesn't fail spuriously.  I also added a
    couple of other assertions to help validate this assumption.
    
            PR middle-end/120855
    
    gcc/ChangeLog:
    
            * cgraphunit.cc (symbol_table::compile): Assert a transparent
            alias is not an internal identifier.
            * symtab.cc (symbol_table::change_decl_assembler_name):
            Likewise.
            * varasm.cc (assemble_name_resolve): Check for
            IDENTIFIER_TRANSPARENT_ALIAS instead of just TREE_CHAIN.
    
    Signed-off-by: Nathaniel Shead <nathanielosh...@gmail.com>
    Reviewed-by: Jason Merrill <ja...@redhat.com>

Diff:
---
 gcc/cgraphunit.cc | 7 ++++---
 gcc/symtab.cc     | 1 +
 gcc/varasm.cc     | 2 +-
 3 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/gcc/cgraphunit.cc b/gcc/cgraphunit.cc
index 8e8d85562b03..9f4af63b7dc0 100644
--- a/gcc/cgraphunit.cc
+++ b/gcc/cgraphunit.cc
@@ -2400,9 +2400,10 @@ symbol_table::compile (void)
     if (node->alias
        && lookup_attribute ("weakref", DECL_ATTRIBUTES (node->decl)))
       {
-       IDENTIFIER_TRANSPARENT_ALIAS
-          (DECL_ASSEMBLER_NAME (node->decl)) = 1;
-       TREE_CHAIN (DECL_ASSEMBLER_NAME (node->decl))
+       tree id = DECL_ASSEMBLER_NAME (node->decl);
+       gcc_assert (!IDENTIFIER_INTERNAL_P (id));
+       IDENTIFIER_TRANSPARENT_ALIAS (id) = 1;
+       TREE_CHAIN (id)
           = (node->alias_target ? node->alias_target
              : DECL_ASSEMBLER_NAME (node->get_alias_target ()->decl));
       }
diff --git a/gcc/symtab.cc b/gcc/symtab.cc
index fc1155f46964..652f66a5d2f8 100644
--- a/gcc/symtab.cc
+++ b/gcc/symtab.cc
@@ -305,6 +305,7 @@ symbol_table::change_decl_assembler_name (tree decl, tree 
name)
       SET_DECL_ASSEMBLER_NAME (decl, name);
       if (alias)
        {
+         gcc_assert (!IDENTIFIER_INTERNAL_P (name));
          IDENTIFIER_TRANSPARENT_ALIAS (name) = 1;
          TREE_CHAIN (name) = alias;
        }
diff --git a/gcc/varasm.cc b/gcc/varasm.cc
index 8384e8b635c7..82662822395a 100644
--- a/gcc/varasm.cc
+++ b/gcc/varasm.cc
@@ -2908,7 +2908,7 @@ assemble_name_resolve (const char *name)
       ultimate_transparent_alias_target (&id);
       if (id != id_orig)
        name = IDENTIFIER_POINTER (id);
-      gcc_assert (! TREE_CHAIN (id));
+      gcc_assert (!IDENTIFIER_TRANSPARENT_ALIAS (id));
     }
 
   return name;