"pkg-config --exists libffi"
| pkg-config --libs libffi
=> "-lffi\n"
"gcc -o conftest -I/usr/include/x86_64-linux-gnu/ruby-2.5.0 -I/usr/include/ruby-2.5.0/ruby/backward -I/usr/include/ruby-2.5.0 -I. -Wdate-time -D_FORTIFY_SOURCE=2   -g -O2 -fdebug-prefix-map=/build/ruby2.5-F4mxqA/ruby2.5-2.5.5=. -fstack-protector-strong -Wformat -Werror=format-security -fPIC conftest.c  -L. -L/usr/lib/x86_64-linux-gnu -L. -Wl,-z,relro -Wl,-z,now -fstack-protector -rdynamic -Wl,-export-dynamic     -lruby-2.5  -lpthread -lgmp -ldl -lcrypt -lm   -lc"
checked program was:
/* begin */
1: #include "ruby.h"
2: 
3: int main(int argc, char **argv)
4: {
5:   return 0;
6: }
/* end */

"gcc -o conftest -I/usr/include/x86_64-linux-gnu/ruby-2.5.0 -I/usr/include/ruby-2.5.0/ruby/backward -I/usr/include/ruby-2.5.0 -I. -Wdate-time -D_FORTIFY_SOURCE=2   -g -O2 -fdebug-prefix-map=/build/ruby2.5-F4mxqA/ruby2.5-2.5.5=. -fstack-protector-strong -Wformat -Werror=format-security -fPIC conftest.c  -L. -L/usr/lib/x86_64-linux-gnu -L. -Wl,-z,relro -Wl,-z,now -fstack-protector -rdynamic -Wl,-export-dynamic     -lruby-2.5 -lffi -lpthread -lgmp -ldl -lcrypt -lm   -lc"
checked program was:
/* begin */
1: #include "ruby.h"
2: 
3: int main(int argc, char **argv)
4: {
5:   return 0;
6: }
/* end */

| pkg-config --cflags-only-I libffi
=> "\n"
| pkg-config --cflags-only-other libffi
=> "\n"
| pkg-config --libs-only-l libffi
=> "-lffi\n"
package configuration for libffi
cflags: 
ldflags: 
libs: -lffi

have_library: checking for ffi_prep_closure_loc() in -lffi... -------------------- yes

"gcc -o conftest -I/usr/include/x86_64-linux-gnu/ruby-2.5.0 -I/usr/include/ruby-2.5.0/ruby/backward -I/usr/include/ruby-2.5.0 -I.  -Wdate-time -D_FORTIFY_SOURCE=2   -g -O2 -fdebug-prefix-map=/build/ruby2.5-F4mxqA/ruby2.5-2.5.5=. -fstack-protector-strong -Wformat -Werror=format-security -fPIC  conftest.c  -L. -L/usr/lib/x86_64-linux-gnu -L. -Wl,-z,relro -Wl,-z,now -fstack-protector -rdynamic -Wl,-export-dynamic      -lffi -lruby-2.5 -lffi  -lffi -lpthread -lgmp -ldl -lcrypt -lm   -lc"
checked program was:
/* begin */
 1: #include "ruby.h"
 2: 
 3: #include <ffi.h>
 4: 
 5: /*top*/
 6: extern int t(void);
 7: int main(int argc, char **argv)
 8: {
 9:   if (argc > 1000000) {
10:     printf("%p", &t);
11:   }
12: 
13:   return 0;
14: }
15: int t(void) { void ((*volatile p)()); p = (void ((*)()))ffi_prep_closure_loc; return !p; }
/* end */

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

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

"gcc -o conftest -I/usr/include/x86_64-linux-gnu/ruby-2.5.0 -I/usr/include/ruby-2.5.0/ruby/backward -I/usr/include/ruby-2.5.0 -I.  -Wdate-time -D_FORTIFY_SOURCE=2   -g -O2 -fdebug-prefix-map=/build/ruby2.5-F4mxqA/ruby2.5-2.5.5=. -fstack-protector-strong -Wformat -Werror=format-security -fPIC  conftest.c  -L. -L/usr/lib/x86_64-linux-gnu -L. -Wl,-z,relro -Wl,-z,now -fstack-protector -rdynamic -Wl,-export-dynamic     -lffi  -lffi -lruby-2.5 -lffi  -lffi -lpthread -lgmp -ldl -lcrypt -lm   -lc"
conftest.c: In function ‘t’:
conftest.c:13:57: error: ‘ffi_prep_cif_var’ undeclared (first use in this function)
 int t(void) { void ((*volatile p)()); p = (void ((*)()))ffi_prep_cif_var; return !p; }
                                                         ^~~~~~~~~~~~~~~~
conftest.c:13:57: note: each undeclared identifier is reported only once for each function it appears in
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:     printf("%p", &t);
 9:   }
10: 
11:   return 0;
12: }
13: int t(void) { void ((*volatile p)()); p = (void ((*)()))ffi_prep_cif_var; return !p; }
/* end */

"gcc -o conftest -I/usr/include/x86_64-linux-gnu/ruby-2.5.0 -I/usr/include/ruby-2.5.0/ruby/backward -I/usr/include/ruby-2.5.0 -I.  -Wdate-time -D_FORTIFY_SOURCE=2   -g -O2 -fdebug-prefix-map=/build/ruby2.5-F4mxqA/ruby2.5-2.5.5=. -fstack-protector-strong -Wformat -Werror=format-security -fPIC  conftest.c  -L. -L/usr/lib/x86_64-linux-gnu -L. -Wl,-z,relro -Wl,-z,now -fstack-protector -rdynamic -Wl,-export-dynamic     -lffi  -lffi -lruby-2.5 -lffi  -lffi -lpthread -lgmp -ldl -lcrypt -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:     printf("%p", &t);
 9:   }
10: 
11:   return 0;
12: }
13: extern void ffi_prep_cif_var();
14: int t(void) { ffi_prep_cif_var(); return 0; }
/* end */

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

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

"gcc -o conftest -I/usr/include/x86_64-linux-gnu/ruby-2.5.0 -I/usr/include/ruby-2.5.0/ruby/backward -I/usr/include/ruby-2.5.0 -I.  -Wdate-time -D_FORTIFY_SOURCE=2   -g -O2 -fdebug-prefix-map=/build/ruby2.5-F4mxqA/ruby2.5-2.5.5=. -fstack-protector-strong -Wformat -Werror=format-security -fPIC  conftest.c  -L. -L/usr/lib/x86_64-linux-gnu -L. -Wl,-z,relro -Wl,-z,now -fstack-protector -rdynamic -Wl,-export-dynamic     -lffi  -lffi -lruby-2.5 -lffi  -lffi -lpthread -lgmp -ldl -lcrypt -lm   -lc"
conftest.c: In function ‘t’:
conftest.c:13:57: error: ‘ffi_raw_call’ undeclared (first use in this function); did you mean ‘rb_proc_call’?
 int t(void) { void ((*volatile p)()); p = (void ((*)()))ffi_raw_call; return !p; }
                                                         ^~~~~~~~~~~~
                                                         rb_proc_call
conftest.c:13:57: note: each undeclared identifier is reported only once for each function it appears in
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:     printf("%p", &t);
 9:   }
10: 
11:   return 0;
12: }
13: int t(void) { void ((*volatile p)()); p = (void ((*)()))ffi_raw_call; return !p; }
/* end */

"gcc -o conftest -I/usr/include/x86_64-linux-gnu/ruby-2.5.0 -I/usr/include/ruby-2.5.0/ruby/backward -I/usr/include/ruby-2.5.0 -I.  -Wdate-time -D_FORTIFY_SOURCE=2   -g -O2 -fdebug-prefix-map=/build/ruby2.5-F4mxqA/ruby2.5-2.5.5=. -fstack-protector-strong -Wformat -Werror=format-security -fPIC  conftest.c  -L. -L/usr/lib/x86_64-linux-gnu -L. -Wl,-z,relro -Wl,-z,now -fstack-protector -rdynamic -Wl,-export-dynamic     -lffi  -lffi -lruby-2.5 -lffi  -lffi -lpthread -lgmp -ldl -lcrypt -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:     printf("%p", &t);
 9:   }
10: 
11:   return 0;
12: }
13: extern void ffi_raw_call();
14: int t(void) { ffi_raw_call(); return 0; }
/* end */

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

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

"gcc -o conftest -I/usr/include/x86_64-linux-gnu/ruby-2.5.0 -I/usr/include/ruby-2.5.0/ruby/backward -I/usr/include/ruby-2.5.0 -I.  -Wdate-time -D_FORTIFY_SOURCE=2   -g -O2 -fdebug-prefix-map=/build/ruby2.5-F4mxqA/ruby2.5-2.5.5=. -fstack-protector-strong -Wformat -Werror=format-security -fPIC  conftest.c  -L. -L/usr/lib/x86_64-linux-gnu -L. -Wl,-z,relro -Wl,-z,now -fstack-protector -rdynamic -Wl,-export-dynamic     -lffi  -lffi -lruby-2.5 -lffi  -lffi -lpthread -lgmp -ldl -lcrypt -lm   -lc"
conftest.c: In function ‘t’:
conftest.c:13:57: error: ‘ffi_prep_raw_closure’ undeclared (first use in this function)
 int t(void) { void ((*volatile p)()); p = (void ((*)()))ffi_prep_raw_closure; return !p; }
                                                         ^~~~~~~~~~~~~~~~~~~~
conftest.c:13:57: note: each undeclared identifier is reported only once for each function it appears in
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:     printf("%p", &t);
 9:   }
10: 
11:   return 0;
12: }
13: int t(void) { void ((*volatile p)()); p = (void ((*)()))ffi_prep_raw_closure; return !p; }
/* end */

"gcc -o conftest -I/usr/include/x86_64-linux-gnu/ruby-2.5.0 -I/usr/include/ruby-2.5.0/ruby/backward -I/usr/include/ruby-2.5.0 -I.  -Wdate-time -D_FORTIFY_SOURCE=2   -g -O2 -fdebug-prefix-map=/build/ruby2.5-F4mxqA/ruby2.5-2.5.5=. -fstack-protector-strong -Wformat -Werror=format-security -fPIC  conftest.c  -L. -L/usr/lib/x86_64-linux-gnu -L. -Wl,-z,relro -Wl,-z,now -fstack-protector -rdynamic -Wl,-export-dynamic     -lffi  -lffi -lruby-2.5 -lffi  -lffi -lpthread -lgmp -ldl -lcrypt -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:     printf("%p", &t);
 9:   }
10: 
11:   return 0;
12: }
13: extern void ffi_prep_raw_closure();
14: int t(void) { ffi_prep_raw_closure(); return 0; }
/* end */

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

have_func: checking for rb_gc_mark_movable()... -------------------- no

"gcc -o conftest -I/usr/include/x86_64-linux-gnu/ruby-2.5.0 -I/usr/include/ruby-2.5.0/ruby/backward -I/usr/include/ruby-2.5.0 -I.  -Wdate-time -D_FORTIFY_SOURCE=2   -g -O2 -fdebug-prefix-map=/build/ruby2.5-F4mxqA/ruby2.5-2.5.5=. -fstack-protector-strong -Wformat -Werror=format-security -fPIC  conftest.c  -L. -L/usr/lib/x86_64-linux-gnu -L. -Wl,-z,relro -Wl,-z,now -fstack-protector -rdynamic -Wl,-export-dynamic     -lffi  -lffi -lruby-2.5 -lffi  -lffi -lpthread -lgmp -ldl -lcrypt -lm   -lc"
conftest.c: In function ‘t’:
conftest.c:13:57: error: ‘rb_gc_mark_movable’ undeclared (first use in this function); did you mean ‘rb_gc_mark_maybe’?
 int t(void) { void ((*volatile p)()); p = (void ((*)()))rb_gc_mark_movable; return !p; }
                                                         ^~~~~~~~~~~~~~~~~~
                                                         rb_gc_mark_maybe
conftest.c:13:57: note: each undeclared identifier is reported only once for each function it appears in
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:     printf("%p", &t);
 9:   }
10: 
11:   return 0;
12: }
13: int t(void) { void ((*volatile p)()); p = (void ((*)()))rb_gc_mark_movable; return !p; }
/* end */

"gcc -o conftest -I/usr/include/x86_64-linux-gnu/ruby-2.5.0 -I/usr/include/ruby-2.5.0/ruby/backward -I/usr/include/ruby-2.5.0 -I.  -Wdate-time -D_FORTIFY_SOURCE=2   -g -O2 -fdebug-prefix-map=/build/ruby2.5-F4mxqA/ruby2.5-2.5.5=. -fstack-protector-strong -Wformat -Werror=format-security -fPIC  conftest.c  -L. -L/usr/lib/x86_64-linux-gnu -L. -Wl,-z,relro -Wl,-z,now -fstack-protector -rdynamic -Wl,-export-dynamic     -lffi  -lffi -lruby-2.5 -lffi  -lffi -lpthread -lgmp -ldl -lcrypt -lm   -lc"
/usr/bin/ld: /tmp/cc5arXXP.o: in function `t':
/sdk/clients/client/ruby/vendor/bundle/ruby/2.5.0/gems/ffi-1.16.3/ext/ffi_c/conftest.c:14: undefined reference to `rb_gc_mark_movable'
collect2: error: ld returned 1 exit status
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:     printf("%p", &t);
 9:   }
10: 
11:   return 0;
12: }
13: extern void rb_gc_mark_movable();
14: int t(void) { rb_gc_mark_movable(); return 0; }
/* end */

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

block in append_ldflags: checking for whether -pthread is accepted as LDFLAGS... -------------------- yes

"gcc -o conftest -I/usr/include/x86_64-linux-gnu/ruby-2.5.0 -I/usr/include/ruby-2.5.0/ruby/backward -I/usr/include/ruby-2.5.0 -I.  -Wdate-time -D_FORTIFY_SOURCE=2   -g -O2 -fdebug-prefix-map=/build/ruby2.5-F4mxqA/ruby2.5-2.5.5=. -fstack-protector-strong -Wformat -Werror=format-security -fPIC  conftest.c  -L. -L/usr/lib/x86_64-linux-gnu -L. -Wl,-z,relro -Wl,-z,now -fstack-protector -rdynamic -Wl,-export-dynamic     -lffi  -lffi -lruby-2.5 -pthread -lpthread -lgmp -ldl -lcrypt -lm   -lc"
checked program was:
/* begin */
1: #include "ruby.h"
2: 
3: int main(int argc, char **argv)
4: {
5:   return 0;
6: }
/* end */

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

extconf.h is:
/* begin */
1: #ifndef EXTCONF_H
2: #define EXTCONF_H
3: #define HAVE_FFI_PREP_CIF_VAR 1
4: #define HAVE_FFI_RAW_CALL 1
5: #define HAVE_FFI_PREP_RAW_CLOSURE 1
6: #define HAVE_RAW_API 1
7: #endif
/* end */