From nobody Thu Feb 20 11:03:39 2025 X-Original-To: current@mlmmj.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id 4Yz9Nx42zSz5nk6X for ; Thu, 20 Feb 2025 11:03:45 +0000 (UTC) (envelope-from grembo@freebsd.org) Received: from smtp.freebsd.org (smtp.freebsd.org [IPv6:2610:1c1:1:606c::24b:4]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256 client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "smtp.freebsd.org", Issuer "R10" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4Yz9Nx3HNpz3w3j; Thu, 20 Feb 2025 11:03:45 +0000 (UTC) (envelope-from grembo@freebsd.org) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=freebsd.org; s=dkim; t=1740049425; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=4fxZRXCaXViuwkr/QxtVFahEx9HJy8f/+BJWUNlaHg0=; b=uba0wHBi8bOyA/AYqPJpAalqDNQRwhF13aMTWPGp9MDt5bPZwjlA2EnWTCVRGzUKJ2EXC4 diEbHVeAfjeb1nm3NGyBM+BBst6aQXhZpqcwOjE9uwtPCxhpQBaeGQeEWaeAEUuS5SoGs+ liuZ3czRBnOK4L/7FhYsmtbUsJi5lujZG3cG/NMGNr5gdjtFPc3zLbD353n0TF8YB3DRhr xTs67SDtOIhpOmO8/CvKbjXVTdKWKrtj1tHxci7Us0Vk91QERwN+m3wsazgZVxIQaLOFlF Z6/buKd7QzEsuP9IGsciBDPtbTOR00DwR6h1+7stRxu7vM+NFBh0kI8vT89LWg== ARC-Seal: i=1; s=dkim; d=freebsd.org; t=1740049425; a=rsa-sha256; cv=none; b=kJCcmQZH9D2o4m54oZxuTpdqfe/Al9otVoIcszh7Hj9oocFdPbHuhC4P26rq+pQ0d5f/aZ 5EhFD9x46/sF/p17e212VaRrJ08h5ubsx5/o5Ta4fUnv5LX6MoKE7mzkAWu+bQJvAzDW7n 5tjwYl/YCnaYTPo8+SJvykV9ZuavpCYvTdmzhDXGef2ldmVCO8CSwjpJkUT2d9+JpQPo/7 H66Ekgmiajt4/E35y7/X3TJGNwh+HrQEi6//Tzq/EYQyWZyDsOy7OMpOWUUdFG4KYnz0Jf APTezrHJ51uyNSfXyIXaj9N8cIXxTosurGZkXACQtTT5HadGN7qH7VsOwZuE+g== ARC-Authentication-Results: i=1; mx1.freebsd.org; none ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=freebsd.org; s=dkim; t=1740049425; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=4fxZRXCaXViuwkr/QxtVFahEx9HJy8f/+BJWUNlaHg0=; b=JCJVBRMMXGhBGxa3GSkA74NiU9veJ6BZPQGJn4Iuf2qA69HB8tZJ3VEsY74/jv4eA6eQ5l bxkkpCdGB7gQxzp+sXGuI0q2Xa3VsKC3xih8JU5VO5AzY7j0qKsF4sRxrik03wy3NZ5mP+ xdxek92MWz7pknF9KImw7PVnsDTWnBLKBmOZNNLRVQ12xrHqOSeyKv8tqRaIiYaVuUmxWn KKkpuNdpll/cFp/teW9xPH2w/T0u/9Zkg80DgzHKRdJYfTFX95u4MjMSjkKomVjDmlAN31 6/RX/lj6tEW+Hpl1Cl11s7UygJ9s+8GHfb78wahoq0geBnBMv9MFuiz78yaUOw== Received: from mail.evolve.de (mail.evolve.de [213.239.217.29]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA512) (Client did not present a certificate) (Authenticated sender: grembo/mail) by smtp.freebsd.org (Postfix) with ESMTPSA id 4Yz9Nx0Bhlzqdf; Thu, 20 Feb 2025 11:03:44 +0000 (UTC) (envelope-from grembo@freebsd.org) Received: by mail.evolve.de (OpenSMTPD) with ESMTPSA id cce14b8d (TLSv1.3:TLS_AES_256_GCM_SHA384:256:NO); Thu, 20 Feb 2025 11:03:42 +0000 (UTC) Date: Thu, 20 Feb 2025 12:03:39 +0100 From: Michael Gmelin To: Poul-Henning Kamp Cc: current@freebsd.org Subject: Re: Empty structures have sizeof(1) in C++ now ? Message-ID: <20250220120339.2f1af442.grembo@freebsd.org> In-Reply-To: <202502200940.51K9eswS003142@critter.freebsd.dk> References: <202502200940.51K9eswS003142@critter.freebsd.dk> X-Face: $wrgCtfdVw_H9WAY?S&9+/F"!41z'L$uo*WzT8miX?kZ~W~Lr5W7v?j0Sde\mwB&/ypo^}> +a'4xMc^^KroE~+v^&^#[B">soBo1y6(TW6#UZiC]o>C6`ej+i Face: iVBORw0KGgoAAAANSUhEUgAAADAAAAAwBAMAAAClLOS0AAAAJFBMVEWJBwe5BQDl LASZU0/LTEWEfHbyj0Txi32+sKrp1Mv944X8/fm1rS+cAAAACXBIWXMAAAsTAAAL EwEAmpwYAAAAB3RJTUUH3wESCxwC7OBhbgAAACFpVFh0Q29tbWVudAAAAAAAQ3Jl YXRlZCB3aXRoIFRoZSBHSU1QbbCXAAAAAghJREFUOMu11DFvEzEUAGCfEhBVFzuq AKkLd0O6VrIQsLXVSZXoWE5N1K3DobBBA9fQpRWc8OkWouaIjedWKiyREOKs+3PY fvalCNjgLVHeF7/3bMtBzV8C/VsQ8tecEgCcDgrzjekwKZ7TwsJZd/ywEKwwP+ZM 8P3drTsAwWn2mpWuDDuYiK1bFs6De0KUUFw0tWxm+D4AIhuuvZqtyWYeO7jQ4Aea 7jUqI+ixhQoHex4WshEvSXdood7stlv4oSuFOC4tqGcr0NjEqXgV4mMJO38nld4+ xKNxRDon7khyKVqY7YR4d+Cg0OMrkWXZOM7YDkEfKiilCn1qYv4mighZiynuHHOA Wq9QJq+BIES7lMFUtcikMnkDGHUoncA+uHgrP0ctIEqfwLHzeSo+eUA66AqzwN6n 2ZHJhw6Qh/PoyC/QENyEyC/AyNjq74Bs+3UH0xYwzDUC4B97HgLocg1QLYgDDO1v f3UX9Y307Ew4AHh67YAFFsxEpkXwpXY3eIgMhAAE3R19L919nNnuD2wlPcDE3UeT L2ytEICQib9BXgS2fU8PrD82ToYO1OEmMSnYTjSqSv9wdC0tPYC+rQRQD9ESnldF CyqfmiYW+tlALt8gH2xrMdC/youbjzPXEun+/ReXsMCDyve3dZc09fn2Oas8oXGc Jj6/fOeK5UmSMPmf/jL+GD8BEj0k/Fn6IO4AAAAASUVORK5CYII= List-Id: Discussions about the use of FreeBSD-current List-Archive: https://lists.freebsd.org/archives/freebsd-current List-Help: List-Post: List-Subscribe: List-Unsubscribe: Sender: owner-freebsd-current@FreeBSD.org MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Thu, 20 Feb 2025 09:40:54 +0000 Poul-Henning Kamp wrote: > Is this a bug ? > > > critter phk> cat /tmp/_.c > > #include > struct foo { > }; > > int > main(int argc, char **argv) > { > struct foo bar; > printf("%jd %jd\n", sizeof(struct foo), sizeof(bar)); > return (0); > } > critter phk> cc -o /tmp/a.out /tmp/_.c > critter phk> /tmp/a.out > 0 0 > critter phk> c++ -o /tmp/a.out /tmp/_.c > c++: warning: treating 'c' input as 'c++' when in C++ mode, > this behavior is deprecated [-Wdeprecated] critter phk> /tmp/a.out > 1 1 > AFAIK it has always been like that, see https://www.stroustrup.com/bs_faq2.html#sizeof-empty : To ensure that the addresses of two different objects will be different. For the same reason, "new" always returns pointers to distinct objects. -m -- Michael Gmelin