From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by sourceware.org (Postfix) with ESMTPS id 2BF083858D28 for ; Wed, 18 Jan 2023 21:49:26 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org 2BF083858D28 Authentication-Results: sourceware.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=redhat.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1674078565; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=CQAit+Nad+K+oIqwIIST/8r55dDY6qRwBaXASq2yRQ8=; b=BrW2MGN6bMyEvfkfalEEMWoZw2MXivBUpCtSBKfBAPD8vaucrTLHndqItJs/Q6UXBj3baJ BdnN37arWqCoz48rMDcWdpfs4evCT7XzxX2mpufalNP1X5EVid0FC4eXPpgyTZVll32u6O gMlKR9bFaNPsgZ2beDWzFBCOodCf5/I= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-231-lsUL64-fPjKtmPSR5L_P4w-1; Wed, 18 Jan 2023 16:49:23 -0500 X-MC-Unique: lsUL64-fPjKtmPSR5L_P4w-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 8B01B1C0513C; Wed, 18 Jan 2023 21:49:23 +0000 (UTC) Received: from localhost (unknown [10.33.36.201]) by smtp.corp.redhat.com (Postfix) with ESMTP id 53E402026D4B; Wed, 18 Jan 2023 21:49:23 +0000 (UTC) From: Jonathan Wakely To: libstdc++@gcc.gnu.org, gcc-patches@gcc.gnu.org Subject: [committed] libstdc++: Fix std::random_device::entropy() for non-posix targets Date: Wed, 18 Jan 2023 21:49:22 +0000 Message-Id: <20230118214922.440230-1-jwakely@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.4 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=-12.2 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,GIT_PATCH_0,RCVD_IN_DNSWL_NONE,RCVD_IN_MSPIKE_H2,SPF_HELO_NONE,SPF_NONE,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 List-Id: Tested x86_64-linux. Pushed to trunk. -- >8 -- Since the r12-4515-g58f339fc5eaae7 change std::random_device::entropy() returns non-zero for hardware sources such as RDRAND. However, the call to the underlying _M_getentropy function is conditionally compiled according to #if _GLIBCXX_USE_DEV_RANDOM which means it only happens for targets that support /dev/random and /dev/urandom. This means entropy() always returns zero for x86 Windows, even though the RDRAND and RDSEED sources work there. The _M_getentropy() function is always compiled into the library, it just doesn't get called for targets without /dev/random. We can change that just by removing the #if conditional. This is not an ABI change, because new code will just start calling the existing _M_getentropy function, old code that has inlined entropy() will not call it. Similarly, the std::random_device destructor doesn't call the underlying _M_fini function unless _GLIBCXX_USE_DEV_RANDOM is defined. That's less of a problem because it's still true that the only resources that need to be freed are when one of /dev/random or /dev/urandom has been opened for reading, which is only possible when _GLIBCXX_USE_DEV_RANDOM is defined. The _M_fini function does also destroy a random engine object if a std::linear_congruential_engine object is used, but that destructor is trivial and so no resources are leaked if it's not called. Remove the preprocessor condition in the destructor too, so that we always call the _M_fini function even if it doesn't have side effects. This makes the destructor non-trivial for Windows and bare metal targets, but as the class is non-copyable that shouldn't cause any ABI change in practice. libstdc++-v3/ChangeLog: * include/bits/random.h (random_device) [!_GLIBCXX_USE_DEV_RANDOM]: Always call _M_fini and _M_getentropy. --- libstdc++-v3/include/bits/random.h | 10 +--------- 1 file changed, 1 insertion(+), 9 deletions(-) diff --git a/libstdc++-v3/include/bits/random.h b/libstdc++-v3/include/bits/random.h index e2b9bdf568c..42f37c1e77e 100644 --- a/libstdc++-v3/include/bits/random.h +++ b/libstdc++-v3/include/bits/random.h @@ -1639,10 +1639,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION explicit random_device(const std::string& __token) { _M_init(__token); } -#if defined _GLIBCXX_USE_DEV_RANDOM ~random_device() { _M_fini(); } -#endif static constexpr result_type min() @@ -1654,13 +1652,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION double entropy() const noexcept - { -#ifdef _GLIBCXX_USE_DEV_RANDOM - return this->_M_getentropy(); -#else - return 0.0; -#endif - } + { return this->_M_getentropy(); } result_type operator()() -- 2.39.0