Newsgroups: php.internals Path: news.php.net Xref: news.php.net php.internals:104596 Return-Path: Delivered-To: mailing list internals@lists.php.net Received: (qmail 25690 invoked from network); 6 Mar 2019 11:26:19 -0000 Received: from unknown (HELO mail-pf1-f172.google.com) (209.85.210.172) by pb1.pair.com with SMTP; 6 Mar 2019 11:26:19 -0000 Received: by mail-pf1-f172.google.com with SMTP id h1so7953701pfo.7 for ; Wed, 06 Mar 2019 00:14:39 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:cc:references:from:openpgp:autocrypt:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=g4r0O3l+HqdjYqPDqckZysO7CEFLsFqV7YFLVybjkY8=; b=hCeg59mdDD3jqly53a7Dnr/L1jhXlX1ONfS49awGQ42w9JaSgAfrZYFvhEEzbXtqx7 OWUttEs9LezLU1sswH8BmstZHOJKrqZuFOux0i1JuFrqK0yywoJRgPeFB9upgJgyMRB+ XzsXLlAdxIKj7PASpRNYgivOKMDp/+JFZRlO5P1l9tHSIJv6ZpmbTUZ63YI/mQ9xwWDM 1IzrlSIL+EpL41uH9xfaduj+FIfxzRAvwyBeT6kcmGpn/5x25j6Bi/WF42Yt4+/Kf0LB K3rtVlBG6M+O/FHsqQkooXof6INn0HBem6zFbnCOZ3UxgzVqrVvsiahaTHiPb6Py4ru8 5Ddw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:openpgp:autocrypt :message-id:date:user-agent:mime-version:in-reply-to :content-language:content-transfer-encoding; bh=g4r0O3l+HqdjYqPDqckZysO7CEFLsFqV7YFLVybjkY8=; b=Pi8JG/gUtcpmL9AQ5sMbqQY31H5UPHqF8/67a8OxWArO/JCTpmQ/0OyP1T4PC7Jpku G8kDn4ym2wUFH0myesHgeszQR+AQZsxDbcU2dlRhUmsGLrQUdrFkYM7J0+PknoKfh/f+ TbYj1zGdodOP7gsA1wLCCN8MCN9rbKbiQj9KopzkuGXjQi7Sa91EEjlHNyYZC5tqY/eM CGxl9GBwyyOf0BycndRTk986yzhnHfVBEQgx9vFxkXyQewk/xzS/KfyFYR/SHVXXUXCm iGjfdkfBvCHr1BFEpL3bxua4VuOqxK5Kxz2vq/6uxM3eYg2WlRwfvkJ3hvbQqUMbiBB5 QLjg== X-Gm-Message-State: APjAAAWftMShBMEpSvLh15tITKUo5NdPeT5U8tQuOzvEwBBp2lwAgBN7 hq7wETEfMOu9/wBmhBZ9PDMRX1Q= X-Google-Smtp-Source: APXvYqxVtQ2mqHCqUHJeuBCmpUJzSLNZ8UC1rn2ecYmIyi86pd02r5YdZc8qxBsaC7Rg2IzsK21Jww== X-Received: by 2002:a17:902:8d89:: with SMTP id v9mr5796882plo.254.1551860078660; Wed, 06 Mar 2019 00:14:38 -0800 (PST) Received: from Stas-Pro-2016.local (c-24-4-176-254.hsd1.ca.comcast.net. [24.4.176.254]) by smtp.gmail.com with ESMTPSA id 23sm2374588pft.187.2019.03.06.00.14.37 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 06 Mar 2019 00:14:37 -0800 (PST) To: Nikita Popov Cc: PHP Internals , Dmitry Stogov References: Openpgp: preference=signencrypt Autocrypt: addr=smalyshev@gmail.com; prefer-encrypt=mutual; keydata= mQMuBE9mqaARCACFSqcGmNunkjQQu3X+yXnTmFeEkvM4JXZTOBdR8aEevNGmmFEfyvjaDjWi 9hcwp4E/lYtC+P7VsVjM1OSX9eq0jC/lGL0ZyRXek+mNy0n5H1NSuTpf9Y18LMqhc4G+RU+L cNiZ9K0DJuOOvNLPxW7OHZguxb3wdKPXNVa2jyRfJAKm2uaJJMT1mTmFT9a0Q8SKr+mUrrJk uG0H2o6SzrKt8Wwoint1eh67zVsJaJtQFchnEZnlawIcqP2yC4nLGR3MkubowxoEBYCZet18 aHVVRbvpG2Qtob8Lu5xrsGbmXymTkHTdpvkfcJFADa8MzOL90zOxXwbGfbIZOlh5En8jAQCX lfnx2eQL3BSW/6XANa51dbWiEp1d1BAkpGKtZvlk0Qf+M9WAi+9aXMe3xP5krxtgnRNUf2WN 6Zdy2MxL1RRJCFbytLhl0ronC49BsGYVGshdEH8xhBbiIOJKuVZ/DTl9bEm7P9c7CC7iJyVC khUAhouH6xzZQNLR+RU+QebYzXypVfl99Qk7EdMmr/WAZCHLuvanyqepC5EBsa3VnAfQemSN oBeGBKWWLiOsPjvS72+y1z4RUMAfXHn4l/sFMt8zt7/74AmJPwZquV41p4mPO12V4+xPyc6R sB84sfsk2QVivU8w8AkvGQeYjXoz7Iwao95+fWteVzZ36KRQvUckP8pGjHlDXnHxJ0HI1I/k OBZSjwRwUf0dd73y6erPhbLk+gf+NdI3H9KGJBzG5/rVyWKwUeQ9d5ud4jTJRkQGvAP5pg76 vEa9dogbpe4W5Z+0BfbiJSnQmQWSHiZddj/t33ptbup44Ck6ZTgdlmFYMLF1hR47PIZTDKER EuKYGci/vq8snZvEJP9YCw/TtiHcMdrMKcY/+Lp8lQO0GHLPB9glVhnC0db6l1Xpg1CMI8/R ozBMcij30EgATggC/y2zbiqAFoS9FN9nXPbe4phStqABEyeZ+nXudt7PUYTjVgcrqo8bHZCi sBobWC7OnKyUzxVxzUeuPkIfmZuzkLaMw2McQdvwwsNvQ0DzaLP30c1Xsm/7EIYJcOWpzlVJ 5QrdmE0/BbQyU3RhbmlzbGF2IE1hbHlzaGV2IChQSFAga2V5KSA8c21hbHlzaGV2QGdtYWls LmNvbT6IegQTEQgAIgUCT2aqtAIbAwYLCQgHAwIGFQgCCQoLBBYCAwECHgECF4AACgkQL3lW vF2gS12XMwD9HuRIolSwIK77u8EY461y2u6sbX36n5/uo/LDQuxoi3sA/0MvpnvzOhv9Iufv vsZEj3E7i3h+iD5648YMwfTFCij+uQINBE9mqaAQCADfZPMpjZkkGZj3BY/7ApoLq4mwqzbh +CpLXwNn20tFNvSXfb8RdeXvVEb7Scx+W9qYpiaun2iXJgCVH8fgpZpR856ulT1q6uCG++CX ubEvip/eJkZl93/84h04KQJwsgOrAh0Om3OePRn8Pr+++0LNS0EL8uX/YHeTOGOnnmTqYTey SBVFdov6L4mepddfjekicKQqhL7mZh/xuq29JijT0uNNX8v4vDWQDu5dlAcdd+uB3gcXMD/P ginD11zp+6wtrWCm/+yBqpvDwXQX5PGUnwvbRfl7Ay3MmwmoXiecZMg0dwTSc7e0lhB4HGRH ZdBMJB4rHUVGdzqujK/ctOvrAAMFB/0Utb76Qe6sCMlHxVAmeE/fbo7Pi05btZ/x01r67dHf aMSP0riCKJ7M0OW+jAXtu9+z/BVnYisW67WWfxl2cS5tZDgiHgJARXWUOO72+sScHP8KQmTl 1z16gyKbwY3SmyBkwcpOL35nhUWNLy93syPoY6sZUTikr2bZYukHDQ33XBPs4e6MbWKfsa9q aVmnlOF3k5UqChjutfHaEa4Q7VP4wBIpphHBi9MI16oJIzzBPbGl2uoedjwiZ6QeQZnSuOVY ZxU2d3lRA8PrtfFN1VSlpEm/VcAvtieHUYWHN0wOu+cp3Slr5XJVNjTjJhl28SlinMME54mK AGf2Ldr/dRwXiGEEGBEIAAkFAk9mqaACGwwACgkQL3lWvF2gS126EQD/VVd3FgjLKglClRQP zdfU847tqDK4zJjbmRv5vLLwoE0A+wbrQs7jVGU3NrS0AIl5vUmewpp2BKzSkepy23nWmejw Message-ID: <82bc21c8-b6a1-15d1-4248-5ee8af1f7611@gmail.com> Date: Wed, 6 Mar 2019 00:14:37 -0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.13; rv:60.0) Gecko/20100101 Thunderbird/60.5.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Subject: Re: [PHP-DEV] Weird bitset shift offset in zend_alloc From: smalyshev@gmail.com (Stanislav Malyshev) Hi! > But I'm not sure how it's supposed to work. Is it correct that on GCC > (and clang, presumably, since it defines __GNUC__) accept long bitshifts > and do the right thing with argument like 138? Is it documented > anywhere? Or is there a bug here? > > > This is a bug, yes. Oversize shifts are UB, and the only thing > preventing this from being miscompiled is the fact that the compiler > cannot figure out that the shift is oversized. > > I'm not sure why this code was introduced, as the compiler should > generally be able to eliminate this masking if it is unnecessary. See > for example these isel patterns in clang: > https://github.com/llvm-mirror/llvm/blob/46b09a3368af1be5005d31fd1d70bad08df352f9/lib/Target/X86/X86InstrCompiler.td#L1753 This was introduced by Dmitry in https://github.com/php/php-src/commit/4ad9cf460595efd1151faec0780b6ae5a4e0bc57, so I wonder how that code works in allocators... -- Stas Malyshev smalyshev@gmail.com