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Mon, 11 Mar 2019 06:20:27 -0700 (PDT) Subject: Re: [PATCH v2 4/4] kernel-shark: Fix a bug in KsPluginManager To: Slavomir Kaslev , Yordan Karadzhov Cc: Steven Rostedt , linux-trace-devel@vger.kernel.org References: <20190307154316.19194-1-ykaradzhov@vmware.com> <20190307154316.19194-5-ykaradzhov@vmware.com> From: "Yordan Karadzhov (VMware)" Message-ID: <351105f9-557d-5a2d-99f1-0f93db2848be@gmail.com> Date: Mon, 11 Mar 2019 15:20:25 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-trace-devel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-trace-devel@vger.kernel.org On 11.03.19 г. 14:09 ч., Slavomir Kaslev wrote: > On Thu, Mar 7, 2019 at 5:44 PM Yordan Karadzhov wrote: >> >> const char *lib = plugin.toStdString().c_str(); >> >> This line is a bad idea because the returned array may (will) be >> invalidated when the destructor of std::string is called. >> >> Signed-off-by: Yordan Karadzhov >> --- >> kernel-shark/src/KsUtils.cpp | 4 ++-- >> 1 file changed, 2 insertions(+), 2 deletions(-) >> >> diff --git a/kernel-shark/src/KsUtils.cpp b/kernel-shark/src/KsUtils.cpp >> index 34b2e2d..d7b1753 100644 >> --- a/kernel-shark/src/KsUtils.cpp >> +++ b/kernel-shark/src/KsUtils.cpp >> @@ -439,7 +439,7 @@ void KsPluginManager::registerFromList(kshark_context *kshark_ctx) >> >> auto lamRegUser = [&kshark_ctx](const QString &plugin) >> { >> - const char *lib = plugin.toStdString().c_str(); >> + const char *lib = plugin.toLocal8Bit().data(); >> kshark_register_plugin(kshark_ctx, lib); >> }; >> >> @@ -474,7 +474,7 @@ void KsPluginManager::unregisterFromList(kshark_context *kshark_ctx) >> >> auto lamUregUser = [&kshark_ctx](const QString &plugin) >> { >> - const char *lib = plugin.toStdString().c_str(); >> + const char *lib = plugin.toLocal8Bit().data(); >> kshark_unregister_plugin(kshark_ctx, lib); >> }; > > Doesn't the new version have the same problem with the temporary QByteArray? > > How about saving the data in a local std::string/QByteArray variable? > > std::string lib = plugin.toStdString(); > kshark_register_plugin(kshark_ctx, lib.c_str()); > Hi Slavi, As far I can understand toStdString() will create a fresh std::string and this string will has its own copy of the characters. However, this copy gets out-of-scope as soon as we hit the semicolon of the line. My understanding was that toLocal8Bit().data() makes no copy so the array will go out-of-scope only when the QString is destroyed. But anyway, your solution looks cleaner and safer. I will send another version of the patch. Thanks a lot! Y. > Thanks! > > > -- > Slavomir Kaslev >