{"id":2222986,"url":"http://patchwork.ozlabs.org/api/patches/2222986/?format=json","web_url":"http://patchwork.ozlabs.org/project/gcc/patch/ad3oBsKzdenydbTa@tucnak/","project":{"id":17,"url":"http://patchwork.ozlabs.org/api/projects/17/?format=json","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,"list_archive_url":"","list_archive_url_format":"","commit_url_format":""},"msgid":"","list_archive_url":null,"date":"2026-04-14T07:08:54","name":"c++: Fix up constexpr EH handling of TARGET_EXPR temporaries [PR124755]","commit_ref":null,"pull_url":null,"state":"new","archived":false,"hash":"08b59facd65a8706615f03b5f0cf12192abbf9a4","submitter":{"id":671,"url":"http://patchwork.ozlabs.org/api/people/671/?format=json","name":"Jakub Jelinek","email":"jakub@redhat.com"},"delegate":null,"mbox":"http://patchwork.ozlabs.org/project/gcc/patch/ad3oBsKzdenydbTa@tucnak/mbox/","series":[{"id":499790,"url":"http://patchwork.ozlabs.org/api/series/499790/?format=json","web_url":"http://patchwork.ozlabs.org/project/gcc/list/?series=499790","date":"2026-04-14T07:08:54","name":"c++: Fix up constexpr EH handling of TARGET_EXPR temporaries [PR124755]","version":1,"mbox":"http://patchwork.ozlabs.org/series/499790/mbox/"}],"comments":"http://patchwork.ozlabs.org/api/patches/2222986/comments/","check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/2222986/checks/","tags":{},"related":[],"headers":{"Return-Path":"","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=ciigC89W;\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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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 ","List-Unsubscribe":",\n ","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n ","Reply-To":"Jakub Jelinek ","Errors-To":"gcc-patches-bounces~incoming=patchwork.ozlabs.org@gcc.gnu.org"},"content":"Hi!\n\nThe following testcase is incorrectly rejected with spurious error about\n used outside of its lifetime.\nWe constant evaluate\n <, n + D.2693) >>>>>;\nin a loop, D.2693 is integral TARGET_EXPR_SLOT and foo throws in the second\nor later iteration. Because D.2693 is not is_complex nor has\naggregate/vector type, we don't ctx->global->put_value (slot, something)\nuntil the TARGET_EXPR_INITIAL evaluation successfully finishes, at which\npoint we ctx->save_exprs->safe_push (slot); and\nctx->global->put_value (slot, r); Because of the save_exprs push, the\nCLEANUP_POINT_EXPR handling then\n /* Forget SAVE_EXPRs and TARGET_EXPRs created by this\n full-expression. */\n for (tree save_expr : save_exprs)\n destroy_value_checked (ctx, save_expr, non_constant_p);\nand that ctx->global->put_value (slot, void_node); (i.e. marks it out of\nlifetime). In the second iteration, we again don't call put_value on the\nslot early, notice TARGET_EXPR_INITIAL evaluation throws, still\nctx->save_exprs->safe_push (slot); but then return. That means\nthe remembered value is still void_node and so destroy_value_checked\ncomplains.\n\nThe following patch fixes that by calling put_value in the case where\nwe know we haven't changed it yet (i.e. it is not is_complex and it doesn't\nhave aggregate/vector type), so that destroy_value_checked doesn't complain.\n\nBoptstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?\n\n2026-04-14 Jakub Jelinek \n\n\tPR c++/124755\n\t* constexpr.cc (cxx_eval_constant_expression): If TARGET_EXPR_INITIAL\n\tthrows and !is_complex and type is neither aggregate nor vector,\n\tcall ctx->global->put_value (slot, NULL) before returning.\n\n\t* g++.dg/cpp26/constexpr-eh19.C: New test.\n\n\n\tJakub","diff":"--- gcc/cp/constexpr.cc.jj\t2026-04-03 20:46:22.849229712 +0200\n+++ gcc/cp/constexpr.cc\t2026-04-13 16:17:30.760424372 +0200\n@@ -9504,7 +9504,16 @@ cxx_eval_constant_expression (const cons\n \tif (ctx->save_exprs)\n \t ctx->save_exprs->safe_push (slot);\n \tif (*jump_target)\n-\t return NULL_TREE;\n+\t {\n+\t if (!is_complex\n+\t\t&& !(AGGREGATE_TYPE_P (type) || VECTOR_TYPE_P (type)))\n+\t /* If TARGET_EXPR_INITIAL throws exception and slot's value\n+\t\t has not been changed yet, CLEANUP_POINT_EXPR handling\n+\t\t could see there void_node from a previous evaluation\n+\t\t and complain. */\n+\t ctx->global->put_value (slot, NULL_TREE);\n+\t return NULL_TREE;\n+\t }\n \tif (!is_complex)\n \t {\n \t r = unshare_constructor (r);\n--- gcc/testsuite/g++.dg/cpp26/constexpr-eh19.C.jj\t2026-04-13 16:22:53.086944490 +0200\n+++ gcc/testsuite/g++.dg/cpp26/constexpr-eh19.C\t2026-04-13 16:23:15.592561870 +0200\n@@ -0,0 +1,33 @@\n+// PR c++/124755\n+// { dg-do compile { target c++26 } }\n+\n+constexpr int\n+foo (int a)\n+{\n+ return a ? throw 1 : 0;\n+}\n+\n+consteval int\n+bar ()\n+{\n+ int n = 0;\n+ int a[] = { 0, 1 };\n+ for (int m : a)\n+ n += foo (m);\n+ return n;\n+}\n+\n+consteval int\n+baz ()\n+{\n+ try\n+ {\n+ return bar ();\n+ }\n+ catch (...)\n+ {\n+ return -1;\n+ }\n+}\n+\n+static_assert (baz () == -1);\n","prefixes":[]}