Compiler warnings in In constructor ‘Log_event::Log_event(...)

MySQL version / commit

26.7

Steps to reproduce

Compiling MySQL 26.7.0 produces these warnings - maybe, the compiler doesn't see the correct path, but this shouldn't happen:

In constructor ‘Log_event::Log_event(mysql::binlog::event::Log_event_header*, mysql::binlog::event::Log_event_footer*)’,
    inlined from ‘Rows_log_event::Rows_log_event(const char*, const mysql::binlog::event::Format_description_event*)’ at /builds/mysql-server-trunk-26.7.0./sql/log_event.cc:7858:25:
/builds/mysql-server-trunk-26.7.0./sql/log_event.cc:973:30: warning: ‘((mysql::binlog::event::Log_event_header*)this)[7].mysql::binlog::event::Log_event_header::unmasked_server_id’ is used uninitialized [-Wuninitialized]
  973 |   server_id = common_header->unmasked_server_id & opt_server_id_mask;
      |               ~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~
In file included from /builds/mysql-server-trunk-26.7.0./sql/log_event.h:56,
                 from /builds/mysql-server-trunk-26.7.0./sql/log_event.cc:27:
In member function ‘bool mysql::binlog::event::Log_event_header::get_is_valid()’,
    inlined from ‘bool Log_event::is_valid()’ at /builds/mysql-server-trunk-26.7.0./sql/log_event.cc:1312:65,
    inlined from ‘Rows_log_event::Rows_log_event(const char*, const mysql::binlog::event::Format_description_event*)’ at /builds/mysql-server-trunk-26.7.0./sql/log_event.cc:7870:16:
/builds/mysql-server-trunk-26.7.0./libs/mysql/binlog/event/binlog_event.h:750:32: warning: ‘((mysql::binlog::event::Log_event_header*)this)[7].mysql::binlog::event::Log_event_header::m_is_valid’ is used uninitialized [-Wuninitialized]
  750 |   bool get_is_valid() { return m_is_valid; }
      |                                ^~~~~~~~~~
/builds/mysql-server-trunk-26.7.0./sql/log_event.cc: In constructor ‘Rows_log_event::Rows_log_event(const char*, const mysql::binlog::event::Format_description_event*)’:
/builds/mysql-server-trunk-26.7.0./sql/log_event.cc:7895:27: warning: ‘((mysql::binlog::event::Rows_event*)((char*)this + 64))[1].mysql::binlog::event::Rows_event::m_width’ may be used uninitialized [-Wmaybe-uninitialized]
 7895 |                           m_width))) {
      |                           ^~~~~~~

Expected vs actual result

No warnings.

Platform / compiler

SLES 15.7, gcc 15

Start by reproducing the reported MySQL 26.7.0 build with GCC 15 on SLES 15.7, then inspect the Rows_log_event constructor in sql/log_event.cc and the related declarations in sql/log_event.h and libs/mysql/binlog/event/binlog_event.h. Trace the reported uninitialized values in Log_event_header and Rows_event; done means the build no longer emits these warnings.