[Bug 1840511] Re: Eoan FTBFS with gcc-9 and MySQL 8

[Rafael David Tinoco]

Im attaching 2 patches to the case:

- Fixing MySQL building issue (proposed upstream)
- Mitigating GCC 9 issue (reported upstream)

Package maintainer already mitigated both with different patches.

clickhouse (18.16.1+ds-4ubuntu1) eoan; urgency=medium

  * Use gcc-8 to build: see https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91500
  * Patch to make it build with mysql

 -- Gianfranco Costamagna <locutusofborg at debian.org>  Tue, 20 Aug 2019
13:39:54 +0200

Forcing GCC 8 instead and including mysql.h to a C++ header. These 2
patches could be considered now or in a near future merge, when upstream
issues are addressed.

** Also affects: clickhouse (Ubuntu Eoan)
   Importance: Medium
     Assignee: Rafael David Tinoco (rafaeldtinoco)
       Status: In Progress

** Also affects: mysql-8.0 (Ubuntu)
   Importance: Undecided
       Status: New

** Also affects: gcc-9 (Ubuntu)
   Importance: Undecided
       Status: New

** Bug watch added: GCC Bugzilla #91500
   https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91500

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https://bugs.launchpad.net/bugs/1840511

Title:
  Eoan FTBFS with gcc-9 and MySQL 8

Status in clickhouse package in Ubuntu:
  Fix Released
Status in gcc-9 package in Ubuntu:
  In Progress
Status in mysql-8.0 package in Ubuntu:
  Fix Released
Status in clickhouse source package in Eoan:
  Fix Released
Status in gcc-9 source package in Eoan:
  In Progress
Status in mysql-8.0 source package in Eoan:
  Fix Released

Bug description:
  
  C and C++ differ in the form of types being defined. While C++ structs are defined also as new types, in C you have to explicitly typedef the struct to have a new type. From clickhouse source code, we are getting:

  https://launchpadlibrarian.net/429654087/buildlog_ubuntu-eoan-
  amd64.clickhouse_18.16.1+ds-4build1_BUILDING.txt.gz

  ----

  [  6%] Building CXX object libs/libmysqlxx/CMakeFiles/mysqlxx.dir/src/Connection.cpp.o
  cd /<<BUILDDIR>>/clickhouse-18.16.1+ds/obj-x86_64-linux-gnu/libs/libmysqlxx && /usr/bin/c++   -I/<<BUILDDIR>>/clickhouse-18.16.1+ds/libs/libmysqlxx/include -I/<<BUILDDIR>>/clickhouse-18.16.1+ds/libs/libcommon/include -I/<<BUILDDIR>>/clickhouse-18.16.1+ds/obj-x86_64-linux-gnu/libs/libcommon/include -I/<<BUILDDIR>>/clickhouse-18.16.1+ds/contrib/cityhash102/include  -g -O2 -fdebug-prefix-map=/<<BUILDDIR>>/clickhouse-18.16.1+ds=. -fstack-protector-strong -Wformat -Werror=format-security -Wdate-time -D_FORTIFY_SOURCE=2  -pipe  -fno-omit-frame-pointer  -Wall  -Wnon-virtual-dtor -O2 -g -DNDEBUG -O3  -flto -fno-fat-lto-objects -fPIC   -std=c++17 -o CMakeFiles/mysqlxx.dir/src/Connection.cpp.o -c /<<BUILDDIR>>/clickhouse-18.16.1+ds/libs/libmysqlxx/src/Connection.cpp
  In file included from /<<BUILDDIR>>/clickhouse-18.16.1+ds/libs/libmysqlxx/include/mysqlxx/ResultBase.h:4,
                   from /<<BUILDDIR>>/clickhouse-18.16.1+ds/libs/libmysqlxx/include/mysqlxx/UseQueryResult.h:3,
                   from /<<BUILDDIR>>/clickhouse-18.16.1+ds/libs/libmysqlxx/include/mysqlxx/Query.h:6,
                   from /<<BUILDDIR>>/clickhouse-18.16.1+ds/libs/libmysqlxx/include/mysqlxx/Connection.h:10,
                   from /<<BUILDDIR>>/clickhouse-18.16.1+ds/libs/libmysqlxx/src/Connection.cpp:7:
  /<<BUILDDIR>>/clickhouse-18.16.1+ds/libs/libmysqlxx/include/mysqlxx/Types.h:7:23: error: conflicting declaration ‘using MYSQL = struct st_mysql’
   using MYSQL = st_mysql;
                         ^
  In file included from /<<BUILDDIR>>/clickhouse-18.16.1+ds/libs/libmysqlxx/src/Connection.cpp:4:
  /usr/include/mysql/mysql.h:335:3: note: previous declaration as ‘typedef struct MYSQL MYSQL’
   } MYSQL;

  ----

  If I edit file libs/libmysqlxx/include/mysqlxx/Types.h and comment the
  following lines:

  
  //struct st_mysql;
  //using MYSQL = st_mysql;
  //
  //struct st_mysql_res;
  //using MYSQL_RES = st_mysql_res;
  //
  //using MYSQL_ROW = char**;
  //
  //struct st_mysql_field;
  //using MYSQL_FIELD = st_mysql_field;

  and add

  #include <mysql/mysql.h>

  I solve the issue, as MYSQL, MYSQL_RES, MYSQL_ROW and MYSQL_FIELD
  types are defined by the mysql.h header file (as C++ would expect).

  ----

  Unfortunately doing that with gcc-9 was not successful not because of
  the change, per se, but gcc-9 crashed during clickhouse compilation.
  When changing gcc-9 to gcc-8 as the default compiler (Ubuntu Eoan
  userland) I was able to compile clickhouse libmysqlxx library
  successfully.

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