220 40319 <4489f889-977c-45f2-8a2f-186ee3b06bff@isocpp.org> article Path: news.gmane.org!.POSTED!not-for-mail From: Matthew Fioravante Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Runtime code generation and self modifying code Date: Thu, 4 Oct 2018 17:35:50 -0700 (PDT) Lines: 66 Approved: news@gmane.org Message-ID: <4489f889-977c-45f2-8a2f-186ee3b06bff@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_530_1020567351.1538699750987" X-Trace: blaine.gmane.org 1538699627 8165 195.159.176.226 (5 Oct 2018 00:33:47 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Fri, 5 Oct 2018 00:33:47 +0000 (UTC) To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBDELF54RTIGRB2HD3LOQKGQENRIJFEI@isocpp.org Fri Oct 05 02:33:43 2018 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-yb1-f198.google.com ([209.85.219.198]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1g8E3r-000230-7O for gclcip-std-proposals@m.gmane.org; Fri, 05 Oct 2018 02:33:43 +0200 Original-Received: by mail-yb1-f198.google.com with SMTP id o2-v6sf5937504ybq.18 for ; Thu, 04 Oct 2018 17:35:54 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=date:from:to:message-id:subject:mime-version:x-original-sender :reply-to:precedence:mailing-list:list-id:list-post:list-help :list-archive:list-subscribe:list-unsubscribe; bh=5bC+B7Xz24a8BaWf6nrcvYJnbbR3azeVkNMMCJnh9+M=; b=e4ximYX2rGLd9HcIcJrMGeSWbP/ggonwarg7Y3wIkK8hT2S/pRMyAa6qy/HRkqRyDS CO2sTJ3mfrIITfAzNPVy9wkGSDRFOi6tS7VUo3ut3K3SvE2eoosEXU29Xl86bSR4s2Lt PujRL9sxr3nlWoOlXneKd6ugjOMdfxuicV4jiBAW6wVbh2JNBlP/YiiLEUs8GBSvMo66 oEYynBxJ63DRO91wgWkbbWwfBZLLXuur4LsLGoyEgbw2UhwLGBsmCQQARBSPgOvNeAIz O2HjY2DS8uV2A5HiBc+xYr9xH0DQ0Nydclyzsr4+ltCJPY/K9sej0vAcprSvPaPYc/qz VWyg== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:message-id:subject:mime-version:x-original-sender :reply-to:precedence:mailing-list:list-id:list-post:list-help :list-archive:list-subscribe:list-unsubscribe; bh=5bC+B7Xz24a8BaWf6nrcvYJnbbR3azeVkNMMCJnh9+M=; b=nRpjvmi2rPS1qnOJXEkJ4P8+Z3nVE9vb64H55fl+w03CUEfFOtsJwYlvq+X/dCbV3u XSYSOxQ+lYl1xKv3N0blk+dF6fUbyp8sBPNARPS3DvrW0AgTjJD3ZtcG3MtyNolCC5v+ nzONAczYzpno9SujVr+dMfkFKHcHcAxcfHJdMdcgqnqAu5ZWp7HDGtCXgrJuigH9W54G f33sXrr8Vga8PX01B8nOQa3T/5J+K4CY+D8UaQWz0XioWktSSGiSsMC01PDXptISkfv0 HrzRMctyMM7gfcbYBgn0RY5MlJ4yxs/qT2KR7l1wGFH7w4a2pyRzncKsWps+oVGB2wlF 4avQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:message-id:subject:mime-version :x-original-sender:reply-to:precedence:mailing-list:list-id :x-spam-checked-in-group:list-post:list-help:list-archive :list-subscribe:list-unsubscribe; bh=5bC+B7Xz24a8BaWf6nrcvYJnbbR3azeVkNMMCJnh9+M=; b=Ooi/TuYiUmO8xpK9nlGTlNE93tUOnj4b/SnhDKhXOLfUvcN4RXGmD2VTPovs5Wwj9l J0pUMTZ0NT+kmYn3yWyWg2TjGEUqzH48LDWQIMvI5HDsPtsjKCmxMrDOUwnduPNshEPe gX9boQ8vdS5DRE0t/FPVeJzNyS7Hje6+RS9q6jQYhcGO/5tMYjK2ieBjNwfhcp+SlVbA DFUCDGGDgZhJmXlnp2oSgCHwD2Env8v74hqIGTtXEt35N8N1nXCG3/5i3gaSZyhCtazG xnpLq+OhRQZl7yLVMBvXKyk7yJWpADkPrO85/fsaQxTNIbEtX7fUdPukiBtCPDw2u0uH xGMA== X-Gm-Message-State: ABuFfojnNsN0zi+ZisV1uhfyN+ZwYefMCY7E5IZcDgaQRuJNzMwFHXnT /w73dByJlR7klFZ9gLWVo4RUvw== X-Google-Smtp-Source: ACcGV60Mnxt+M9wbLnbQEp9aan7vSjmn3c+uD5EJNXchXj8H4LUdLE3hHZPJHnSEanV56ZzPwDUpSA== X-Received: by 2002:a25:38d1:: with SMTP id f200-v6mr4461517yba.59.1538699753504; Thu, 04 Oct 2018 17:35:53 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 2002:a81:ae21:: with SMTP id m33-v6ls1042504ywh.9.gmail; Thu, 04 Oct 2018 17:35:52 -0700 (PDT) X-Received: by 2002:a81:78c6:: with SMTP id t189-v6mr95421ywc.7.1538699751765; Thu, 04 Oct 2018 17:35:51 -0700 (PDT) X-Original-Sender: fmatthew5876@gmail.com Precedence: list Mailing-list: list std-proposals@isocpp.org; contact std-proposals+owners@isocpp.org List-ID: X-Spam-Checked-In-Group: std-proposals@isocpp.org X-Google-Group-Id: 399137483710 List-Post: , List-Help: , List-Archive: List-Subscribe: , List-Unsubscribe: , Xref: news.gmane.org gmane.comp.lang.c++.isocpp.proposals:40319 Archived-At: ------=_Part_530_1020567351.1538699750987 Content-Type: multipart/alternative; boundary="----=_Part_531_1032808767.1538699750987" ------=_Part_531_1032808767.1538699750987 Content-Type: text/plain; charset="UTF-8" One big area where dynamic languages are way ahead of C++ is runtime dynamic code generation or self modifying code. One tiny example is singleton initialization. The only safe way in C++ to do non-constexpr singletons is by lazy init. The problem with lazy init is that you have to pay for a branch on every access, and that usually involves an atomic check. What if you instead you atomically overwrote the check with NOPS. Then the branch is gone and accessing the object is as efficient as if it weren't lazy. Has anyone considered writing proposals for improving runtime code gen with C++? -- You received this message because you are subscribed to the Google Groups "ISO C++ Standard - Future Proposals" group. To unsubscribe from this group and stop receiving emails from it, send an email to std-proposals+unsubscribe@isocpp.org. To post to this group, send email to std-proposals@isocpp.org. To view this discussion on the web visit https://groups.google.com/a/isocpp.org/d/msgid/std-proposals/4489f889-977c-45f2-8a2f-186ee3b06bff%40isocpp.org. ------=_Part_531_1032808767.1538699750987 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
One big area where dynamic languages are way ahead of= C++ is runtime dynamic code generation or self modifying code.


One tiny example is singleton initializati= on. The only safe way in C++ to do non-constexpr singletons is by lazy init= ..

The problem with lazy init is that you have= to pay for a branch on every access, and that usually involves an atomic c= heck.

What if you instead you atomically overwrote= the check with NOPS. Then the branch is gone and accessing the object is a= s efficient as if it weren't lazy.

Has any= one considered writing proposals for improving runtime code gen with C++?

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To unsubscribe from this group and stop receiving emails from it, send an e= mail to std-proposa= ls+unsubscribe@isocpp.org.
To post to this group, send email to std-proposals@isocpp.org.
To view this discussion on the web visit https://groups.google.= com/a/isocpp.org/d/msgid/std-proposals/4489f889-977c-45f2-8a2f-186ee3b06bff= %40isocpp.org.
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