From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ed1-x531.google.com (mail-ed1-x531.google.com [IPv6:2a00:1450:4864:20::531]) by sourceware.org (Postfix) with ESMTPS id DE6903858D28; Mon, 18 Jul 2022 10:10:43 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org DE6903858D28 Received: by mail-ed1-x531.google.com with SMTP id w12so14518713edd.13; Mon, 18 Jul 2022 03:10:43 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:from:date:message-id:subject:to; bh=17s4qr3LJ0LkaC/mlxZSN8FYPfuUGvgIRH0RLFLXfhQ=; b=jgcfSyRwW0FyRJBzYtRPmPbCGG19fG4u3AskzULis7+7RiRT7YfZL87JslSYtzcbdY jdv/Kjh3xFYwRpDkG4+k6XVwc4ewXVBV909z/UaMg65QvVYKVtU6yPFEZrag8eTuQe+I wIRyZsD8NkVyFc42UuunAu8aKbBFl4eyyaU3wVvYY/j7cE8KuxYPqMXIpWN0uB+/V/9O /yYY7rdDIeKAHgjBZUJOEksCtUi8cuHsOg/AcC+LTYPJ8tMMq0VxB2xKn172ntC00TD0 G71fGuSzHZYgOPXzG4AK7bP87LMQoTHiPonTu0P2/74W20ITqrCvS2AqBhbDYjpeDe7N 1Isw== X-Gm-Message-State: AJIora/6sgww6+Wpiuj1D77hRTeIU0ta3lREPryQB8g491Atetmf5rRL 31LJM3u60rZJPkA9Pn0MBhxjAUtWbh3b8I3hgRc= X-Google-Smtp-Source: AGRyM1uFzsKDQRakqHk9k1nnAxXMr6VBpr9l/yWMHF++UVBw9Les8nvfmgmrUbdXdyaImAlyr/zAQDZiQWj8a/qYFfI= X-Received: by 2002:a05:6402:440c:b0:43a:1124:e56a with SMTP id y12-20020a056402440c00b0043a1124e56amr36908310eda.134.1658139042433; Mon, 18 Jul 2022 03:10:42 -0700 (PDT) MIME-Version: 1.0 From: Marco Falke Date: Mon, 18 Jul 2022 12:10:31 +0200 Message-ID: Subject: Re: Re: [PATCH] libstdc++: Make __from_chars_alnum_to_val conversion explicit To: Marco Falke , libstdc++@gcc.gnu.org, gcc-patches@gcc.gnu.org Content-Type: multipart/mixed; boundary="0000000000009d59f505e411949c" X-Spam-Status: No, score=-10.3 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, FREEMAIL_FROM, GIT_PATCH_0, KAM_SHORT, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org X-BeenThere: libstdc++@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libstdc++ mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 18 Jul 2022 10:10:45 -0000 --0000000000009d59f505e411949c Content-Type: text/plain; charset="UTF-8" (in reply to https://gcc.gnu.org/pipermail/gcc-patches/2022-July/598412.html, adding libstdc++ to CC, with the same patch attached again) To clarify, this is not a fix for a user-facing issue of gcc or a fix for UB. It is just a minor UX improvement for developers that use the clang integer sanitizer to detect implicit int conversions. To reproduce: $ cat 1.cpp #include int main() { const auto a{"-1"}; unsigned b{}; std::from_chars(a, a + 2, b); } $ clang++ -fsanitize=integer -std=c++17 1.cpp -o exe && ./exe /usr/bin/../lib64/gcc/x86_64-s use-linux/12/../../../../include/c++/12/charconv:439:9: runtime error: implicit conversion from type 'int' of value -3 (32-bit, signed) to type 'unsigned char' changed the value to 253 (8-bit, unsigned) SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior /usr/bin/../lib64/gcc/x86_64-suse-linux/12/../../../../include/c++/12/charconv:439:9 Best, Marco --0000000000009d59f505e411949c Content-Type: text/x-patch; charset="US-ASCII"; name="0001-libstdc-Make-__from_chars_alnum_to_val-conversion-ex.patch" Content-Disposition: attachment; filename="0001-libstdc-Make-__from_chars_alnum_to_val-conversion-ex.patch" Content-Transfer-Encoding: base64 Content-ID: X-Attachment-Id: f_l5ql2pqk0 RnJvbSAyZDRlN2NkMWQ0NzZhMDY1ZDgyNGUxMTA0NWM4ZGJjMDQ5ZDVmMGEwIE1vbiBTZXAgMTcg MDA6MDA6MDAgMjAwMQpGcm9tOiBNYWNyb0Zha2UgPGZhbGtlLm1hcmNvQGdtYWlsLmNvbT4KRGF0 ZTogVGh1LCAxNCBKdWwgMjAyMiAxNToyNjoxMiArMDIwMApTdWJqZWN0OiBbUEFUQ0hdIGxpYnN0 ZGMrKzogTWFrZSBfX2Zyb21fY2hhcnNfYWxudW1fdG9fdmFsIGNvbnZlcnNpb24gZXhwbGljaXQK ClRoZSBvcHRpbWl6YXRpb25zIGZyb20gY29tbWl0IGE1NDEzN2M4ODA2MWM3NDk1NzI4ZmM2Yjhk ZmQwNDc0ZTgxMmIyY2IKaW50cm9kdWNlZCBhIGNsYW5nIGludGVnZXIgc2FuaXRpemVyIGVycm9y LgoKRml4IHRoaXMgd2l0aCBhbiBleHBsaWNpdCBzdGF0aWNfY2FzdCwgc2ltaWxhciB0byB0aGUg Zml4IGluIGNvbW1pdAowNzQ0MzZjZjhjZGQyYTljZTc1Y2FkZDM2ZGViODMwMWYwMGU1NWI5LgoK bGlic3RkYysrLXYzL0NoYW5nZUxvZzoKCiAgICAgICAgKiBpbmNsdWRlL3N0ZC9jaGFyY29udiAo X19mcm9tX2NoYXJzX2FsbnVtX3RvX3ZhbCk6IFJlcGxhY2UKICAgICAgICAgIGltcGxpY2l0IGNv bnZlcnNpb25zIGZyb20gaW50IHRvIHVuc2lnbmVkIGNoYXIgd2l0aCBleHBsaWNpdAogICAgICAg ICAgY2FzdHMuCi0tLQogbGlic3RkYysrLXYzL2luY2x1ZGUvc3RkL2NoYXJjb252IHwgMiArLQog MSBmaWxlIGNoYW5nZWQsIDEgaW5zZXJ0aW9uKCspLCAxIGRlbGV0aW9uKC0pCgpkaWZmIC0tZ2l0 IGEvbGlic3RkYysrLXYzL2luY2x1ZGUvc3RkL2NoYXJjb252IGIvbGlic3RkYysrLXYzL2luY2x1 ZGUvc3RkL2NoYXJjb252CmluZGV4IDIxODgxM2U0Nzk3Li5iZGYyM2U0YTVhZCAxMDA2NDQKLS0t IGEvbGlic3RkYysrLXYzL2luY2x1ZGUvc3RkL2NoYXJjb252CisrKyBiL2xpYnN0ZGMrKy12My9p bmNsdWRlL3N0ZC9jaGFyY29udgpAQCAtNDM2LDcgKzQzNiw3IEBAIG5hbWVzcGFjZSBfX2RldGFp bAogICAgIF9fZnJvbV9jaGFyc19hbG51bV90b192YWwodW5zaWduZWQgY2hhciBfX2MpCiAgICAg ewogICAgICAgaWYgX0dMSUJDWFgxN19DT05TVEVYUFIgKF9EZWNPbmx5KQotCXJldHVybiBfX2Mg LSAnMCc7CisgICAgICAgcmV0dXJuIHN0YXRpY19jYXN0PHVuc2lnbmVkIGNoYXI+KF9fYyAtICcw Jyk7CiAgICAgICBlbHNlCiAJewogCSAgLy8gVGhpcyBpbml0aWFsaXplciBpcyBkZWxpYmVyYXRl bHkgbWFkZSBkZXBlbmRlbnQgaW4gb3JkZXIgdG8gd29yawotLSAKMi4zNS4zCgo= --0000000000009d59f505e411949c--