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Ip=[63.35.35.123]; Helo=[64aa7808-outbound-1.mta.getcheckrecipient.com] X-MS-Exchange-CrossTenant-AuthSource: AM7EUR03FT053.eop-EUR03.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: AS4PR08MB7856 X-Spam-Status: No, score=-6.4 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, FORGED_SPF_HELO, KAM_DMARC_NONE, NICE_REPLY_A, RCVD_IN_DNSWL_NONE, RCVD_IN_MSPIKE_H2, SPF_HELO_PASS, SPF_NONE, TXREP, T_SCC_BODY_TEXT_LINE, UNPARSEABLE_RELAY autolearn=no autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org X-BeenThere: gdb@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gdb mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 16 Aug 2022 13:27:23 -0000 On 8/16/22 13:48, Andrew Dinn wrote: > On 16/08/2022 11:16, hilbert wrote: >> @Andrew Dinn >> Now I totally understand. Thank you very much for your patience. > > You are very welcome. > >> By the way, when a multithreaded program hits a breakpoint, GDB can use the command: /*thread ID */ >> /**/to switch between threads arbitrarily,  and view the memory and other information of each thread. >> This is also implemented using ptrace, right? > I would assume it relies on ptrace to stop all the threads. However, I have almost zero knowledge of how gdb actually controls the inferior process (my knowledge of gdb is exclusively on the gdb-process side of the fence). You will need to find someone else to obtain a definitive answer. Sorry, for some funny reason (mailing list software/mail server) I'm not getting hilbert's replies. But Andrew provided great answers. Reading memory is usually done through /proc//mem these days, as it is fastest. Reading registers for each thread is done by ptrace. > > regards, > > > Andrew Dinn > ----------- > Red Hat Distinguished Engineer > Red Hat UK Ltd > Registered in England and Wales under Company Registration No. 03798903 > Directors: Michael Cunningham, Michael ("Mike") O'Neill >