Having issue when installing mysql2 gem on ubuntu 24.04

[simogeo]

I'm using ruby 3.1.0p0 (2021-12-25 revision fb4df44d16) [x86_64-linux] (installed with RVM) on Ubuntu 24.04 and I get this error when trying to install mysql2 :

bundle install
Fetching gem metadata from https://rubygems.org/.........
Resolving dependencies...
Installing mysql2 0.5.6 with native extensions
Gem::Ext::BuildError: ERROR: Failed to build gem native extension.

    current directory: /home/ubuntu/.rvm/gems/ruby-3.1.0/gems/mysql2-0.5.6/ext/mysql2
/home/ubuntu/.rvm/rubies/ruby-3.1.0/bin/ruby -I /home/ubuntu/.rvm/rubies/ruby-3.1.0/lib/ruby/3.1.0 -r
./siteconf20240601-64133-pej7bb.rb extconf.rb
checking for rb_absint_size()... yes
checking for rb_absint_singlebit_p()... yes
checking for rb_gc_mark_movable()... yes
checking for rb_wait_for_single_fd()... yes
checking for rb_enc_interned_str() in ruby.h... yes
-----
Cannot find library dir(s) 
-----
*** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of necessary
libraries and/or headers.  Check the mkmf.log file for more details.  You may
need configuration options.

Provided configuration options:
	--with-opt-dir
	--without-opt-dir
	--with-opt-include
	--without-opt-include=${opt-dir}/include
	--with-opt-lib
	--without-opt-lib=${opt-dir}/lib
	--with-make-prog
	--without-make-prog
	--srcdir=.
	--curdir
	--ruby=/home/ubuntu/.rvm/rubies/ruby-3.1.0/bin/$(RUBY_BASE_NAME)
	--with-openssl-dir
	--with-openssl-dir
	--with-openssl-include
	--without-openssl-include=${openssl-dir}/include
	--with-openssl-lib
	--without-openssl-lib=${openssl-dir}/lib

To see why this extension failed to compile, please check the mkmf.log which can be found here:

  /home/ubuntu/.rvm/gems/ruby-3.1.0/extensions/x86_64-linux/3.1.0/mysql2-0.5.6/mkmf.log

extconf failed, exit code 1

Gem files will remain installed in /home/ubuntu/.rvm/gems/ruby-3.1.0/gems/mysql2-0.5.6 for inspection.
Results logged to
/home/ubuntu/.rvm/gems/ruby-3.1.0/extensions/x86_64-linux/3.1.0/mysql2-0.5.6/gem_make.out

  /home/ubuntu/.rvm/rubies/ruby-3.1.0/lib/ruby/3.1.0/rubygems/ext/builder.rb:95:in `run'
/home/ubuntu/.rvm/rubies/ruby-3.1.0/lib/ruby/3.1.0/rubygems/ext/ext_conf_builder.rb:47:in `block in
build'
  /home/ubuntu/.rvm/rubies/ruby-3.1.0/lib/ruby/3.1.0/tempfile.rb:317:in `open'
  /home/ubuntu/.rvm/rubies/ruby-3.1.0/lib/ruby/3.1.0/rubygems/ext/ext_conf_builder.rb:26:in `build'
  /home/ubuntu/.rvm/rubies/ruby-3.1.0/lib/ruby/3.1.0/rubygems/ext/builder.rb:161:in `build_extension'
/home/ubuntu/.rvm/rubies/ruby-3.1.0/lib/ruby/3.1.0/rubygems/ext/builder.rb:195:in `block in
build_extensions'
  /home/ubuntu/.rvm/rubies/ruby-3.1.0/lib/ruby/3.1.0/rubygems/ext/builder.rb:192:in `each'
  /home/ubuntu/.rvm/rubies/ruby-3.1.0/lib/ruby/3.1.0/rubygems/ext/builder.rb:192:in `build_extensions'
  /home/ubuntu/.rvm/rubies/ruby-3.1.0/lib/ruby/3.1.0/rubygems/installer.rb:847:in `build_extensions'
/home/ubuntu/.rvm/gems/ruby-3.1.0/gems/bundler-2.5.11/lib/bundler/rubygems_gem_installer.rb:76:in
`build_extensions'
/home/ubuntu/.rvm/gems/ruby-3.1.0/gems/bundler-2.5.11/lib/bundler/rubygems_gem_installer.rb:28:in
`install'
  /home/ubuntu/.rvm/gems/ruby-3.1.0/gems/bundler-2.5.11/lib/bundler/source/rubygems.rb:206:in `install'
/home/ubuntu/.rvm/gems/ruby-3.1.0/gems/bundler-2.5.11/lib/bundler/installer/gem_installer.rb:54:in
`install'
/home/ubuntu/.rvm/gems/ruby-3.1.0/gems/bundler-2.5.11/lib/bundler/installer/gem_installer.rb:16:in
`install_from_spec'
/home/ubuntu/.rvm/gems/ruby-3.1.0/gems/bundler-2.5.11/lib/bundler/installer/parallel_installer.rb:132:in
`do_install'
/home/ubuntu/.rvm/gems/ruby-3.1.0/gems/bundler-2.5.11/lib/bundler/installer/parallel_installer.rb:123:in
`block in worker_pool'
  /home/ubuntu/.rvm/gems/ruby-3.1.0/gems/bundler-2.5.11/lib/bundler/worker.rb:62:in `apply_func'
/home/ubuntu/.rvm/gems/ruby-3.1.0/gems/bundler-2.5.11/lib/bundler/worker.rb:57:in `block in
process_queue'
  /home/ubuntu/.rvm/gems/ruby-3.1.0/gems/bundler-2.5.11/lib/bundler/worker.rb:54:in `loop'
  /home/ubuntu/.rvm/gems/ruby-3.1.0/gems/bundler-2.5.11/lib/bundler/worker.rb:54:in `process_queue'
/home/ubuntu/.rvm/gems/ruby-3.1.0/gems/bundler-2.5.11/lib/bundler/worker.rb:90:in `block (2 levels) in
create_threads'

An error occurred while installing mysql2 (0.5.6), and Bundler cannot continue.

In Gemfile:
  mysql2

Mysql server is 8.0.36-2ubuntu3

I've also tried :
gem install mysql2 -v '0.5.6' -- --srcdir=/var/lib/mysql
gem install mysql2 -v '0.5.6' -- --srcdir=/lib/x86_64-linux-gnu

And :
gem install mysql2 --with-mysql-dir=/lib/x86_64-linux-gnu/ but I get this error message :

ERROR: While executing gem ... (Gem::OptionParser::InvalidOption)
invalid option: --with-mysql-dir=/lib/x86_64-linux-gnu

Thanks for your support

[simogeo]

By the way, I've seen this topic but it is related to MAC environment

[simogeo]

And from the log located in /home/ubuntu/.rvm/gems/ruby-3.1.0/extensions/x86_64-linux/3.1.0/mysql2-0.5.6/mkmf.log, I can find these information - but I'm not able to understand the problem :

have_func: checking for rb_absint_size()... -------------------- yes

LD_LIBRARY_PATH=.:/home/ubuntu/.rvm/rubies/ruby-3.1.0/lib "gcc -o conftest -I/home/ubuntu/.rvm/rubies/ruby-3.1.0/include/ruby-3.1.0/x86_64-linux -I/home/ubuntu/.rvm/rubies/ruby-3.1.0/include/ruby-3.1.0/ruby/backward -I/home/ubuntu/.rvm/rubies/ruby-3.1.0/include/ruby-3.1.0 -I.    -O3 -fno-fast-math -ggdb3 -Wall -Wextra -Wdeprecated-declarations -Wduplicated-cond -Wimplicit-function-declaration -Wimplicit-int -Wmisleading-indentation -Wpointer-arith -Wwrite-strings -Wimplicit-fallthrough=0 -Wmissing-noreturn -Wno-cast-function-type -Wno-constant-logical-operand -Wno-long-long -Wno-missing-field-initializers -Wno-overlength-strings -Wno-packed-bitfield-compat -Wno-parentheses-equality -Wno-self-assign -Wno-tautological-compare -Wno-unused-parameter -Wno-unused-value -Wsuggest-attribute=format -Wsuggest-attribute=noreturn -Wunused-variable -Wundef  -fPIC conftest.c  -L. -L/home/ubuntu/.rvm/rubies/ruby-3.1.0/lib -Wl,-rpath,/home/ubuntu/.rvm/rubies/ruby-3.1.0/lib -L. -fstack-protector-strong -rdynamic -Wl,-export-dynamic -Wl,--no-as-needed     -Wl,-rpath,/home/ubuntu/.rvm/rubies/ruby-3.1.0/lib -L/home/ubuntu/.rvm/rubies/ruby-3.1.0/lib -lruby  -lm  -lc" 
checked program was:
/* begin */
1: #include "ruby.h" 
2: 
3: int main(int argc, char **argv)
4: {
5:   return !!argv[argc];
6: }
/* end */

LD_LIBRARY_PATH=.:/home/ubuntu/.rvm/rubies/ruby-3.1.0/lib "gcc -o conftest -I/home/ubuntu/.rvm/rubies/ruby-3.1.0/include/ruby-3.1.0/x86_64-linux -I/home/ubuntu/.rvm/rubies/ruby-3.1.0/include/ruby-3.1.0/ruby/backward -I/home/ubuntu/.rvm/rubies/ruby-3.1.0/include/ruby-3.1.0 -I.    -O3 -fno-fast-math -ggdb3 -Wall -Wextra -Wdeprecated-declarations -Wduplicated-cond -Wimplicit-function-declaration -Wimplicit-int -Wmisleading-indentation -Wpointer-arith -Wwrite-strings -Wimplicit-fallthrough=0 -Wmissing-noreturn -Wno-cast-function-type -Wno-constant-logical-operand -Wno-long-long -Wno-missing-field-initializers -Wno-overlength-strings -Wno-packed-bitfield-compat -Wno-parentheses-equality -Wno-self-assign -Wno-tautological-compare -Wno-unused-parameter -Wno-unused-value -Wsuggest-attribute=format -Wsuggest-attribute=noreturn -Wunused-variable -Wundef  -fPIC conftest.c  -L. -L/home/ubuntu/.rvm/rubies/ruby-3.1.0/lib -Wl,-rpath,/home/ubuntu/.rvm/rubies/ruby-3.1.0/lib -L. -fstack-protector-strong -rdynamic -Wl,-export-dynamic -Wl,--no-as-needed     -Wl,-rpath,/home/ubuntu/.rvm/rubies/ruby-3.1.0/lib -L/home/ubuntu/.rvm/rubies/ruby-3.1.0/lib -lruby  -lm  -lc" 
checked program was:
/* begin */
 1: #include "ruby.h" 
 2: 
 3: /*top*/
 4: extern int t(void);
 5: int main(int argc, char **argv)
 6: {
 7:   if (argc > 1000000) {
 8:     int (* volatile tp)(void)=(int (*)(void))&t;
 9:     printf("%d", (*tp)());
10:   }
11: 
12:   return !!argv[argc];
13: }
14: int t(void) { void ((*volatile p)()); p = (void ((*)()))rb_absint_size; return !p; }
/* end */

--------------------

have_func: checking for rb_absint_singlebit_p()... -------------------- yes

LD_LIBRARY_PATH=.:/home/ubuntu/.rvm/rubies/ruby-3.1.0/lib "gcc -o conftest -I/home/ubuntu/.rvm/rubies/ruby-3.1.0/include/ruby-3.1.0/x86_64-linux -I/home/ubuntu/.rvm/rubies/ruby-3.1.0/include/ruby-3.1.0/ruby/backward -I/home/ubuntu/.rvm/rubies/ruby-3.1.0/include/ruby-3.1.0 -I.    -O3 -fno-fast-math -ggdb3 -Wall -Wextra -Wdeprecated-declarations -Wduplicated-cond -Wimplicit-function-declaration -Wimplicit-int -Wmisleading-indentation -Wpointer-arith -Wwrite-strings -Wimplicit-fallthrough=0 -Wmissing-noreturn -Wno-cast-function-type -Wno-constant-logical-operand -Wno-long-long -Wno-missing-field-initializers -Wno-overlength-strings -Wno-packed-bitfield-compat -Wno-parentheses-equality -Wno-self-assign -Wno-tautological-compare -Wno-unused-parameter -Wno-unused-value -Wsuggest-attribute=format -Wsuggest-attribute=noreturn -Wunused-variable -Wundef  -fPIC conftest.c  -L. -L/home/ubuntu/.rvm/rubies/ruby-3.1.0/lib -Wl,-rpath,/home/ubuntu/.rvm/rubies/ruby-3.1.0/lib -L. -fstack-protector-strong -rdynamic -Wl,-export-dynamic -Wl,--no-as-needed     -Wl,-rpath,/home/ubuntu/.rvm/rubies/ruby-3.1.0/lib -L/home/ubuntu/.rvm/rubies/ruby-3.1.0/lib -lruby  -lm  -lc" 
checked program was:
/* begin */
 1: #include "ruby.h" 
 2: 
 3: /*top*/
 4: extern int t(void);
 5: int main(int argc, char **argv)
 6: {
 7:   if (argc > 1000000) {
 8:     int (* volatile tp)(void)=(int (*)(void))&t;
 9:     printf("%d", (*tp)());
10:   }
11: 
12:   return !!argv[argc];
13: }
14: int t(void) { void ((*volatile p)()); p = (void ((*)()))rb_absint_singlebit_p; return !p; }
/* end */

--------------------

have_func: checking for rb_gc_mark_movable()... -------------------- yes

LD_LIBRARY_PATH=.:/home/ubuntu/.rvm/rubies/ruby-3.1.0/lib "gcc -o conftest -I/home/ubuntu/.rvm/rubies/ruby-3.1.0/include/ruby-3.1.0/x86_64-linux -I/home/ubuntu/.rvm/rubies/ruby-3.1.0/include/ruby-3.1.0/ruby/backward -I/home/ubuntu/.rvm/rubies/ruby-3.1.0/include/ruby-3.1.0 -I.    -O3 -fno-fast-math -ggdb3 -Wall -Wextra -Wdeprecated-declarations -Wduplicated-cond -Wimplicit-function-declaration -Wimplicit-int -Wmisleading-indentation -Wpointer-arith -Wwrite-strings -Wimplicit-fallthrough=0 -Wmissing-noreturn -Wno-cast-function-type -Wno-constant-logical-operand -Wno-long-long -Wno-missing-field-initializers -Wno-overlength-strings -Wno-packed-bitfield-compat -Wno-parentheses-equality -Wno-self-assign -Wno-tautological-compare -Wno-unused-parameter -Wno-unused-value -Wsuggest-attribute=format -Wsuggest-attribute=noreturn -Wunused-variable -Wundef  -fPIC conftest.c  -L. -L/home/ubuntu/.rvm/rubies/ruby-3.1.0/lib -Wl,-rpath,/home/ubuntu/.rvm/rubies/ruby-3.1.0/lib -L. -fstack-protector-strong -rdynamic -Wl,-export-dynamic -Wl,--no-as-needed     -Wl,-rpath,/home/ubuntu/.rvm/rubies/ruby-3.1.0/lib -L/home/ubuntu/.rvm/rubies/ruby-3.1.0/lib -lruby  -lm  -lc" 
checked program was:
/* begin */
 1: #include "ruby.h" 
 2: 
 3: /*top*/
 4: extern int t(void);
 5: int main(int argc, char **argv)
 6: {
 7:   if (argc > 1000000) {
 8:     int (* volatile tp)(void)=(int (*)(void))&t;
 9:     printf("%d", (*tp)());
10:   }
11: 
12:   return !!argv[argc];
13: }
14: int t(void) { void ((*volatile p)()); p = (void ((*)()))rb_gc_mark_movable; return !p; }
/* end */

--------------------

have_func: checking for rb_wait_for_single_fd()... -------------------- yes

LD_LIBRARY_PATH=.:/home/ubuntu/.rvm/rubies/ruby-3.1.0/lib "gcc -o conftest -I/home/ubuntu/.rvm/rubies/ruby-3.1.0/include/ruby-3.1.0/x86_64-linux -I/home/ubuntu/.rvm/rubies/ruby-3.1.0/include/ruby-3.1.0/ruby/backward -I/home/ubuntu/.rvm/rubies/ruby-3.1.0/include/ruby-3.1.0 -I.    -O3 -fno-fast-math -ggdb3 -Wall -Wextra -Wdeprecated-declarations -Wduplicated-cond -Wimplicit-function-declaration -Wimplicit-int -Wmisleading-indentation -Wpointer-arith -Wwrite-strings -Wimplicit-fallthrough=0 -Wmissing-noreturn -Wno-cast-function-type -Wno-constant-logical-operand -Wno-long-long -Wno-missing-field-initializers -Wno-overlength-strings -Wno-packed-bitfield-compat -Wno-parentheses-equality -Wno-self-assign -Wno-tautological-compare -Wno-unused-parameter -Wno-unused-value -Wsuggest-attribute=format -Wsuggest-attribute=noreturn -Wunused-variable -Wundef  -fPIC conftest.c  -L. -L/home/ubuntu/.rvm/rubies/ruby-3.1.0/lib -Wl,-rpath,/home/ubuntu/.rvm/rubies/ruby-3.1.0/lib -L. -fstack-protector-strong -rdynamic -Wl,-export-dynamic -Wl,--no-as-needed     -Wl,-rpath,/home/ubuntu/.rvm/rubies/ruby-3.1.0/lib -L/home/ubuntu/.rvm/rubies/ruby-3.1.0/lib -lruby  -lm  -lc" 
conftest.c: In function ‘t’:
conftest.c:14:57: error: ‘rb_wait_for_single_fd’ undeclared (first use in this function)
   14 | int t(void) { void ((*volatile p)()); p = (void ((*)()))rb_wait_for_single_fd; return !p; }
      |                                                         ^~~~~~~~~~~~~~~~~~~~~
conftest.c:14:57: note: each undeclared identifier is reported only once for each function it appears in
At top level:
cc1: note: unrecognized command-line option ‘-Wno-self-assign’ may have been intended to silence earlier diagnostics
cc1: note: unrecognized command-line option ‘-Wno-parentheses-equality’ may have been intended to silence earlier diagnostics
cc1: note: unrecognized command-line option ‘-Wno-constant-logical-operand’ may have been intended to silence earlier diagnostics
checked program was:
/* begin */
 1: #include "ruby.h" 
 2: 
 3: /*top*/
 4: extern int t(void);
 5: int main(int argc, char **argv)
 6: {
 7:   if (argc > 1000000) {
 8:     int (* volatile tp)(void)=(int (*)(void))&t;
 9:     printf("%d", (*tp)());
10:   }
11: 
12:   return !!argv[argc];
13: }
14: int t(void) { void ((*volatile p)()); p = (void ((*)()))rb_wait_for_single_fd; return !p; }
/* end */

LD_LIBRARY_PATH=.:/home/ubuntu/.rvm/rubies/ruby-3.1.0/lib "gcc -o conftest -I/home/ubuntu/.rvm/rubies/ruby-3.1.0/include/ruby-3.1.0/x86_64-linux -I/home/ubuntu/.rvm/rubies/ruby-3.1.0/include/ruby-3.1.0/ruby/backward -I/home/ubuntu/.rvm/rubies/ruby-3.1.0/include/ruby-3.1.0 -I.    -O3 -fno-fast-math -ggdb3 -Wall -Wextra -Wdeprecated-declarations -Wduplicated-cond -Wimplicit-function-declaration -Wimplicit-int -Wmisleading-indentation -Wpointer-arith -Wwrite-strings -Wimplicit-fallthrough=0 -Wmissing-noreturn -Wno-cast-function-type -Wno-constant-logical-operand -Wno-long-long -Wno-missing-field-initializers -Wno-overlength-strings -Wno-packed-bitfield-compat -Wno-parentheses-equality -Wno-self-assign -Wno-tautological-compare -Wno-unused-parameter -Wno-unused-value -Wsuggest-attribute=format -Wsuggest-attribute=noreturn -Wunused-variable -Wundef  -fPIC conftest.c  -L. -L/home/ubuntu/.rvm/rubies/ruby-3.1.0/lib -Wl,-rpath,/home/ubuntu/.rvm/rubies/ruby-3.1.0/lib -L. -fstack-protector-strong -rdynamic -Wl,-export-dynamic -Wl,--no-as-needed     -Wl,-rpath,/home/ubuntu/.rvm/rubies/ruby-3.1.0/lib -L/home/ubuntu/.rvm/rubies/ruby-3.1.0/lib -lruby  -lm  -lc" 
checked program was:
/* begin */
 1: #include "ruby.h" 
 2: 
 3: /*top*/
 4: extern int t(void);
 5: int main(int argc, char **argv)
 6: {
 7:   if (argc > 1000000) {
 8:     int (* volatile tp)(void)=(int (*)(void))&t;
 9:     printf("%d", (*tp)());
10:   }
11: 
12:   return !!argv[argc];
13: }
14: extern void rb_wait_for_single_fd();
15: int t(void) { rb_wait_for_single_fd(); return 0; }
/* end */

--------------------

have_func: checking for rb_enc_interned_str() in ruby.h... -------------------- yes

LD_LIBRARY_PATH=.:/home/ubuntu/.rvm/rubies/ruby-3.1.0/lib "gcc -o conftest -I/home/ubuntu/.rvm/rubies/ruby-3.1.0/include/ruby-3.1.0/x86_64-linux -I/home/ubuntu/.rvm/rubies/ruby-3.1.0/include/ruby-3.1.0/ruby/backward -I/home/ubuntu/.rvm/rubies/ruby-3.1.0/include/ruby-3.1.0 -I.    -O3 -fno-fast-math -ggdb3 -Wall -Wextra -Wdeprecated-declarations -Wduplicated-cond -Wimplicit-function-declaration -Wimplicit-int -Wmisleading-indentation -Wpointer-arith -Wwrite-strings -Wimplicit-fallthrough=0 -Wmissing-noreturn -Wno-cast-function-type -Wno-constant-logical-operand -Wno-long-long -Wno-missing-field-initializers -Wno-overlength-strings -Wno-packed-bitfield-compat -Wno-parentheses-equality -Wno-self-assign -Wno-tautological-compare -Wno-unused-parameter -Wno-unused-value -Wsuggest-attribute=format -Wsuggest-attribute=noreturn -Wunused-variable -Wundef  -fPIC conftest.c  -L. -L/home/ubuntu/.rvm/rubies/ruby-3.1.0/lib -Wl,-rpath,/home/ubuntu/.rvm/rubies/ruby-3.1.0/lib -L. -fstack-protector-strong -rdynamic -Wl,-export-dynamic -Wl,--no-as-needed     -Wl,-rpath,/home/ubuntu/.rvm/rubies/ruby-3.1.0/lib -L/home/ubuntu/.rvm/rubies/ruby-3.1.0/lib -lruby  -lm  -lc" 
conftest.c: In function ‘t’:
conftest.c:16:57: error: ‘rb_enc_interned_str’ undeclared (first use in this function); did you mean ‘rb_interned_str’?
   16 | int t(void) { void ((*volatile p)()); p = (void ((*)()))rb_enc_interned_str; return !p; }
      |                                                         ^~~~~~~~~~~~~~~~~~~
      |                                                         rb_interned_str
conftest.c:16:57: note: each undeclared identifier is reported only once for each function it appears in
At top level:
cc1: note: unrecognized command-line option ‘-Wno-self-assign’ may have been intended to silence earlier diagnostics
cc1: note: unrecognized command-line option ‘-Wno-parentheses-equality’ may have been intended to silence earlier diagnostics
cc1: note: unrecognized command-line option ‘-Wno-constant-logical-operand’ may have been intended to silence earlier diagnostics
checked program was:
/* begin */
 1: #include "ruby.h" 
 2: 
 3: #include <ruby.h>
 4: 
 5: /*top*/
 6: extern int t(void);
 7: int main(int argc, char **argv)
 8: {
 9:   if (argc > 1000000) {
10:     int (* volatile tp)(void)=(int (*)(void))&t;
11:     printf("%d", (*tp)());
12:   }
13: 
14:   return !!argv[argc];
15: }
16: int t(void) { void ((*volatile p)()); p = (void ((*)()))rb_enc_interned_str; return !p; }
/* end */

LD_LIBRARY_PATH=.:/home/ubuntu/.rvm/rubies/ruby-3.1.0/lib "gcc -o conftest -I/home/ubuntu/.rvm/rubies/ruby-3.1.0/include/ruby-3.1.0/x86_64-linux -I/home/ubuntu/.rvm/rubies/ruby-3.1.0/include/ruby-3.1.0/ruby/backward -I/home/ubuntu/.rvm/rubies/ruby-3.1.0/include/ruby-3.1.0 -I.    -O3 -fno-fast-math -ggdb3 -Wall -Wextra -Wdeprecated-declarations -Wduplicated-cond -Wimplicit-function-declaration -Wimplicit-int -Wmisleading-indentation -Wpointer-arith -Wwrite-strings -Wimplicit-fallthrough=0 -Wmissing-noreturn -Wno-cast-function-type -Wno-constant-logical-operand -Wno-long-long -Wno-missing-field-initializers -Wno-overlength-strings -Wno-packed-bitfield-compat -Wno-parentheses-equality -Wno-self-assign -Wno-tautological-compare -Wno-unused-parameter -Wno-unused-value -Wsuggest-attribute=format -Wsuggest-attribute=noreturn -Wunused-variable -Wundef  -fPIC conftest.c  -L. -L/home/ubuntu/.rvm/rubies/ruby-3.1.0/lib -Wl,-rpath,/home/ubuntu/.rvm/rubies/ruby-3.1.0/lib -L. -fstack-protector-strong -rdynamic -Wl,-export-dynamic -Wl,--no-as-needed     -Wl,-rpath,/home/ubuntu/.rvm/rubies/ruby-3.1.0/lib -L/home/ubuntu/.rvm/rubies/ruby-3.1.0/lib -lruby  -lm  -lc" 
checked program was:
/* begin */
 1: #include "ruby.h" 
 2: 
 3: #include <ruby.h>
 4: 
 5: /*top*/
 6: extern int t(void);
 7: int main(int argc, char **argv)
 8: {
 9:   if (argc > 1000000) {
10:     int (* volatile tp)(void)=(int (*)(void))&t;
11:     printf("%d", (*tp)());
12:   }
13: 
14:   return !!argv[argc];
15: }
16: extern void rb_enc_interned_str();
17: int t(void) { rb_enc_interned_str(); return 0; }
/* end */

--------------------

Thanks for your help !

[simogeo]

I did handle this by changing the value in the gemfile from :

gem "mysql2", "~> 0.5.0", :platforms => [:mri, :mingw, :x64_mingw]

to

gem "mysql2", "0.5.4", :platforms => [:mri, :mingw, :x64_mingw]

Seems to be ok ...

[gajet5]

I am installing a higher version "mysql2" -> "0.5.6".

The information I found says that the problem should be solved in 5.4.0, but in fact it is not.

[tenshiAMD]

I fixed it on my end after installing libmysqlclient-dev.

apt-get install -y libmysqlclient-dev