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c++: duplicate block-scope extern [PR 97877]

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We ICED with a duplicated block-scope extern, as duplicate_decls was
dropping the decl_lang_specific of olddecl.  Simplys adding
appropriate retrofitting and copying turned out to be insufficient
because you can get a block-scope using decl also matching the extern.
The latter seems a little suspicious and I have asked CWG for advice.
While there robustified the assert about releasing olddecls'
lang-specific -- if it had one, the new decl better have one.

	PR c++/97877
	gcc/cp/
	* decl.c (duplicate_decls): Deal with duplicated DECL_LOCAL_DECL_P
	decls.  Extend decl_lang_specific checking assert.
	gcc/testsuite/
	* g++.dg/lookup/pr97877.C: New.
This commit is contained in:
Nathan Sidwell 2020-11-17 13:16:47 -08:00
parent 066c89d1e1
commit e0da4aed17
2 changed files with 25 additions and 2 deletions
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19
gcc/cp/decl.c
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@ -2452,6 +2452,20 @@ duplicate_decls (tree newdecl, tree olddecl, bool hiding, bool was_hidden)
if (! DECL_COMDAT (olddecl))
DECL_COMDAT (newdecl) = 0;
if (VAR_OR_FUNCTION_DECL_P (newdecl) && DECL_LOCAL_DECL_P (newdecl))
{
if (!DECL_LOCAL_DECL_P (olddecl))
/* This can happen if olddecl was brought in from the
enclosing namespace via a using-decl. The new decl is
then not a block-scope extern at all. */
DECL_LOCAL_DECL_P (newdecl) = false;
else
{
retrofit_lang_decl (newdecl);
DECL_LOCAL_DECL_ALIAS (newdecl) = DECL_LOCAL_DECL_ALIAS (olddecl);
}
}
new_template_info = NULL_TREE;
if (DECL_LANG_SPECIFIC (newdecl) && DECL_LANG_SPECIFIC (olddecl))
{
@ -2735,8 +2749,9 @@ duplicate_decls (tree newdecl, tree olddecl, bool hiding, bool was_hidden)
with that from NEWDECL below. */
if (DECL_LANG_SPECIFIC (olddecl))
{
gcc_assert (DECL_LANG_SPECIFIC (olddecl)
!= DECL_LANG_SPECIFIC (newdecl));
gcc_checking_assert (DECL_LANG_SPECIFIC (newdecl)
&& (DECL_LANG_SPECIFIC (olddecl)
!= DECL_LANG_SPECIFIC (newdecl)));
ggc_free (DECL_LANG_SPECIFIC (olddecl));
}

8
gcc/testsuite/g++.dg/lookup/pr97877.C Normal file
View File

@ -0,0 +1,8 @@
// PR 97877, duplicate decls smashed decl_lang_specific
void f ()
{
extern int a;
extern int a;
a = 2;
}