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GET /api/1.1/patches/2221534/?format=api
{ "id": 2221534, "url": "http://patchwork.ozlabs.org/api/1.1/patches/2221534/?format=api", "web_url": "http://patchwork.ozlabs.org/project/gcc/patch/adfVRQUvuvgBZXuF@tucnak/", "project": { "id": 17, "url": "http://patchwork.ozlabs.org/api/1.1/projects/17/?format=api", "name": "GNU Compiler Collection", "link_name": "gcc", "list_id": "gcc-patches.gcc.gnu.org", "list_email": "gcc-patches@gcc.gnu.org", "web_url": null, "scm_url": null, "webscm_url": null }, "msgid": "<adfVRQUvuvgBZXuF@tucnak>", "date": "2026-04-09T16:35:17", "name": "c++: Unshare expr in get_template_parm_object [PR124792]", "commit_ref": null, "pull_url": null, "state": "new", "archived": false, "hash": "47e53f61fb28e44e9a603685aacd907b93d4f994", "submitter": { "id": 671, "url": "http://patchwork.ozlabs.org/api/1.1/people/671/?format=api", "name": "Jakub Jelinek", "email": "jakub@redhat.com" }, "delegate": null, "mbox": "http://patchwork.ozlabs.org/project/gcc/patch/adfVRQUvuvgBZXuF@tucnak/mbox/", "series": [ { "id": 499328, "url": "http://patchwork.ozlabs.org/api/1.1/series/499328/?format=api", "web_url": "http://patchwork.ozlabs.org/project/gcc/list/?series=499328", "date": "2026-04-09T16:35:17", "name": "c++: Unshare expr in get_template_parm_object [PR124792]", "version": 1, "mbox": "http://patchwork.ozlabs.org/series/499328/mbox/" } ], "comments": "http://patchwork.ozlabs.org/api/patches/2221534/comments/", "check": "pending", "checks": "http://patchwork.ozlabs.org/api/patches/2221534/checks/", "tags": {}, "headers": { "Return-Path": "<gcc-patches-bounces~incoming=patchwork.ozlabs.org@gcc.gnu.org>", "X-Original-To": [ "incoming@patchwork.ozlabs.org", "gcc-patches@gcc.gnu.org" ], "Delivered-To": [ "patchwork-incoming@legolas.ozlabs.org", "gcc-patches@gcc.gnu.org" ], "Authentication-Results": [ "legolas.ozlabs.org;\n\tdkim=pass (1024-bit key;\n unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256\n header.s=mimecast20190719 header.b=NG9OqtPz;\n\tdkim-atps=neutral", "legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=gcc.gnu.org\n (client-ip=38.145.34.32; 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Thu, 9 Apr 2026 16:35:22 +0000 (UTC)", "from tucnak.zalov.cz (localhost [127.0.0.1])\n by tucnak.zalov.cz (8.18.1/8.18.1) with ESMTPS id 639GZJSR732337\n (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NOT);\n Thu, 9 Apr 2026 18:35:19 +0200", "(from jakub@localhost)\n by tucnak.zalov.cz (8.18.1/8.18.1/Submit) id 639GZHLG732336;\n Thu, 9 Apr 2026 18:35:17 +0200" ], "DKIM-Filter": [ "OpenDKIM Filter v2.11.0 sourceware.org B2B244BA2E35", "OpenDKIM Filter v2.11.0 sourceware.org 286A74BA5439" ], "DMARC-Filter": "OpenDMARC Filter v1.4.2 sourceware.org 286A74BA5439", "ARC-Filter": "OpenARC Filter v1.0.0 sourceware.org 286A74BA5439", "ARC-Seal": "i=1; a=rsa-sha256; d=sourceware.org; s=key; t=1775752526; cv=none;\n b=pzL13DDulvStqCDeVqMtzQ++WybGwD4rtr6G+H30kkEXO+GHPiATBW7ZhBOcJhohusO94Tg5ASiSQvsIeBj8vz7LkBAnHyNNF4ePT68ZXHUARuZW5tcqvCeB7cZ6xN2i728SeSDseOSB2zhuYvEY7ZHN2b/S9UvrscGVv6lXYSA=", "ARC-Message-Signature": "i=1; a=rsa-sha256; d=sourceware.org; s=key;\n t=1775752526; c=relaxed/simple;\n bh=KGd4BIrLOxFf/9kq95/6uLtPVi5WUEa7bjd4kGvgI5I=;\n h=DKIM-Signature:Date:From:To:Subject:Message-ID:MIME-Version;\n b=nnhWcUGRzMN+92yUHFSZwAHZrS+xYligvMKRzzfHE1VNWvYK/jeYVzIdiRWj3XOV2DCW1uVHkBpxi8szcHAkfbDNAJxrqa4xxJKjHrltQoKMVVGYvhAtjZpRrcv9F/b/tIhopypWeVuLQHsvYE3k2u9shU5JB3dDLt4JsMGtjWM=", "ARC-Authentication-Results": "i=1; server2.sourceware.org", "DKIM-Signature": "v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com;\n s=mimecast20190719; t=1775752525;\n h=from:from:reply-to:reply-to:subject:subject:date:date:\n message-id:message-id:to:to:cc:cc:mime-version:mime-version:\n content-type:content-type:in-reply-to:in-reply-to: references:references;\n bh=wSC+ipNw+TW+pxUCSIQg0kpmwEeZNcrAatWqpPFdCvA=;\n b=NG9OqtPzRp5NsAq9dCP5ks7G599Hvozo8DkgAuvskgCXbo5RzqZL/G/gje02Z2xB25GNmn\n MeOhE20ZtDBDU7YkymcLXYiGX7Ye/h5g4D3vIaHwB6wyofUQZG8Bz3WcARfZsoGOdw+vkg\n DBF5wl+0Defd0djEz1AmiAKpVyi4eKU=", "X-MC-Unique": "FLXQ5ygdOBaAADsB7Qu4fg-1", "X-Mimecast-MFC-AGG-ID": "FLXQ5ygdOBaAADsB7Qu4fg_1775752523", "Date": "Thu, 9 Apr 2026 18:35:17 +0200", "From": "Jakub Jelinek <jakub@redhat.com>", "To": "Jason Merrill <jason@redhat.com>", "Cc": "Patrick Palka <ppalka@redhat.com>, chzn@mail.ustc.edu.cn,\n gcc-patches@gcc.gnu.org", "Subject": "[PATCH] c++: Unshare expr in get_template_parm_object [PR124792]", "Message-ID": "<adfVRQUvuvgBZXuF@tucnak>", "References": "<15b4a0ee.835e2.19d6ab44456.Coremail.chzn@mail.ustc.edu.cn>\n <58536bff.85d93.19d6cecd862.Coremail.chzn@mail.ustc.edu.cn>\n <0ce6469a-6ef2-2d0a-f9e2-6c54d7caff01@idea>\n <1be00eb4-570e-41af-8349-770940eee76e@redhat.com>\n <addVcdge2uqtSg2T@tucnak>\n <a59bb4a6-0b88-40c9-b84a-2df21f214704@redhat.com>", "MIME-Version": "1.0", "In-Reply-To": "<a59bb4a6-0b88-40c9-b84a-2df21f214704@redhat.com>", "X-Scanned-By": "MIMEDefang 3.0 on 10.30.177.17", "X-Mimecast-Spam-Score": "0", "X-Mimecast-MFC-PROC-ID": "feqhGyC47eVVMEynLjEN62hxrPIb2pNj_0izvrwua8A_1775752523", "X-Mimecast-Originator": "redhat.com", "Content-Type": "text/plain; charset=us-ascii", "Content-Disposition": "inline", "X-BeenThere": "gcc-patches@gcc.gnu.org", "X-Mailman-Version": "2.1.30", "Precedence": "list", "List-Id": "Gcc-patches mailing list <gcc-patches.gcc.gnu.org>", "List-Unsubscribe": "<https://gcc.gnu.org/mailman/options/gcc-patches>,\n <mailto:gcc-patches-request@gcc.gnu.org?subject=unsubscribe>", "List-Archive": "<https://gcc.gnu.org/pipermail/gcc-patches/>", "List-Post": "<mailto:gcc-patches@gcc.gnu.org>", "List-Help": "<mailto:gcc-patches-request@gcc.gnu.org?subject=help>", "List-Subscribe": "<https://gcc.gnu.org/mailman/listinfo/gcc-patches>,\n <mailto:gcc-patches-request@gcc.gnu.org?subject=subscribe>", "Reply-To": "Jakub Jelinek <jakub@redhat.com>", "Errors-To": "gcc-patches-bounces~incoming=patchwork.ozlabs.org@gcc.gnu.org" }, "content": "On Thu, Apr 09, 2026 at 12:07:42PM -0400, Jason Merrill wrote:\n> > With reflection, we can create the NTTPOs during constant evaluation rather than\n> > after cxx_eval_outermost_constant_expr has unshared those, so later\n> > processing within the same cxx_eval_outermost_constant_expr call can modify\n> > those not unshared trees.\n> > Now, from reflect.cc get_template_parm_object is called directly from\n> > eval_reflect_constant_string (I think not a problem, the argument should be\n> > always STRING_CST in that case), eval_reflect_constant_array (also not\n> > a problem IMHO, as the outer CONSTRUCTOR is freshly created by\n> > get_range_elts and what is inside of it is unshared by\n> > if (VAR_P (expr))\n> > expr = unshare_expr (DECL_INITIAL (expr));\n> > ) and then indirectly (convert_reflect_constant_arg ->\n> > convert_nontype_argument -> create_template_parm_object) from\n> > within get_range_elts, eval_reflect_constant, eval_reflect_object,\n> > eval_reflect_function. So, if we don't do unsharing in\n> > get_template_parm_object because it is philosophically attractive but\n> > wastes compile time memory too much when things are usually unshared,\n> \n> Actually, I'm not sure it does waste too much memory; a quick check with\n> -fmem-report shows no difference in the totals on compiling stdc++.h as\n> C++26. And since we'd only unshare in the case where we're actually\n> creating a new variable, it might actually mean less unsharing in the case\n> of repetitive patterns.\n> \n> > (and yet another question is unshare_constructor vs. unshare_expr),\n> \n> Or even unshare_expr_without_location (like PR91165) if we unshare in\n> get_TPO since all occurrences of the same value get the same variable.\n> \n> It seems that many places use unshare_constructor to protect against things\n> like split_nonconstant_init or cxx_eval_store_expression but not a modifying\n> walk_tree like cp_genericize.\n\nSo, do you want something like the patch below then?\nI think in the modules.cc (aka !check_init) case the CONSTRUCTOR is already\nnot shared because it has been read from the module, but I could be wrong.\n\nAnd another question is about that\n /* If EXPR contains any PTRMEM_CST, they will get clobbered by\n lower_var_init before we're done mangling. So store the original\n value elsewhere. We only need to unshare EXPR if it's not yet\n been processed. */\n tree copy = check_init ? unshare_constructor (expr) : expr;\n hash_map_safe_put<hm_ggc> (tparm_obj_values, decl, copy);\nI guess lower_var_init is done late these days, but still, if we need\ntparm_obj_values at all, couldn't we do it solely for the cases where\nexpr contains any PTRMEM_CSTs inside of it (so search all the nested\nCONSTRUCTORs if we find PTRMEM_CSTs, similarly how cplus_expand_constant\ndoes that, just don't expand anything, just return bool that it contains\nthem and unshare/register in that case), and otherwise just use\nDECL_INITIAL?\n\n2026-04-09 Jakub Jelinek <jakub@redhat.com>\n\n\tPR c++/124792\n\t* pt.cc (get_template_parm_object): Call unshare_expr_without_location\n\ton expr if check_init.\n\n\t* g++.dg/reflect/pr124792.C: New test.\n\n\n\n\tJakub", "diff": "--- gcc/cp/pt.cc.jj\t2026-04-09 18:18:26.461536563 +0200\n+++ gcc/cp/pt.cc\t2026-04-09 18:23:33.840288646 +0200\n@@ -7551,6 +7551,8 @@ get_template_parm_object (tree expr, tre\n DECL_NAME (decl) = name;\n SET_DECL_ASSEMBLER_NAME (decl, name);\n comdat_linkage (decl);\n+ if (check_init)\n+ expr = unshare_expr_without_location (expr);\n \n if (!zero_init_p (type))\n {\n--- gcc/testsuite/g++.dg/reflect/pr124792.C.jj\t2026-04-09 18:18:08.189674154 +0200\n+++ gcc/testsuite/g++.dg/reflect/pr124792.C\t2026-04-09 18:18:08.189674154 +0200\n@@ -0,0 +1,11 @@\n+// PR c++/124792\n+// { dg-do compile { target c++26 } }\n+// { dg-additional-options \"-freflection\" }\n+\n+#include <meta>\n+\n+struct S { const char *name = nullptr; };\n+\n+constexpr auto a = std::define_static_array (std::vector { S { std::define_static_string (\"foo\") } });\n+constexpr auto b = std::define_static_array (std::vector { S { std::define_static_string (\"foo\") },\n+\t\t\t\t\t\t\t S { std::define_static_string (\"bar\") } });\n", "prefixes": [] }