"pkg-config --exists libffi"
| pkg-config --libs libffi
=> "-lffi \n"
"gcc -o conftest -I/usr/local/include/ruby-2.3.0/x86_64-linux -I/usr/local/include/ruby-2.3.0/ruby/backward -I/usr/local/include/ruby-2.3.0 -I.     -O3 -fno-fast-math -ggdb3 -Wall -Wextra -Wno-unused-parameter -Wno-parentheses -Wno-long-long -Wno-missing-field-initializers -Wunused-variable -Wpointer-arith -Wwrite-strings -Wdeclaration-after-statement -Wimplicit-function-declaration -Wdeprecated-declarations -Wno-packed-bitfield-compat  -fPIC conftest.c  -L. -L/usr/local/lib -Wl,-rpath,/usr/local/lib -L. -fstack-protector -rdynamic -Wl,-export-dynamic     -Wl,-rpath,/usr/local/lib -L/usr/local/lib -lruby  -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/local/include/ruby-2.3.0/x86_64-linux -I/usr/local/include/ruby-2.3.0/ruby/backward -I/usr/local/include/ruby-2.3.0 -I.     -O3 -fno-fast-math -ggdb3 -Wall -Wextra -Wno-unused-parameter -Wno-parentheses -Wno-long-long -Wno-missing-field-initializers -Wunused-variable -Wpointer-arith -Wwrite-strings -Wdeclaration-after-statement -Wimplicit-function-declaration -Wdeprecated-declarations -Wno-packed-bitfield-compat  -fPIC conftest.c  -L. -L/usr/local/lib -Wl,-rpath,/usr/local/lib -L. -fstack-protector -rdynamic -Wl,-export-dynamic     -Wl,-rpath,/usr/local/lib -L/usr/local/lib -lruby -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_call() in -lffi... -------------------- yes

"gcc -o conftest -I/usr/local/include/ruby-2.3.0/x86_64-linux -I/usr/local/include/ruby-2.3.0/ruby/backward -I/usr/local/include/ruby-2.3.0 -I.      -O3 -fno-fast-math -ggdb3 -Wall -Wextra -Wno-unused-parameter -Wno-parentheses -Wno-long-long -Wno-missing-field-initializers -Wunused-variable -Wpointer-arith -Wwrite-strings -Wdeclaration-after-statement -Wimplicit-function-declaration -Wdeprecated-declarations -Wno-packed-bitfield-compat  -fPIC  conftest.c  -L. -L/usr/local/lib -Wl,-rpath,/usr/local/lib -L. -fstack-protector -rdynamic -Wl,-export-dynamic      -lffi -Wl,-rpath,/usr/local/lib -L/usr/local/lib -lruby -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_call; return !p; }
/* end */

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

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

"gcc -o conftest -I/usr/local/include/ruby-2.3.0/x86_64-linux -I/usr/local/include/ruby-2.3.0/ruby/backward -I/usr/local/include/ruby-2.3.0 -I.      -O3 -fno-fast-math -ggdb3 -Wall -Wextra -Wno-unused-parameter -Wno-parentheses -Wno-long-long -Wno-missing-field-initializers -Wunused-variable -Wpointer-arith -Wwrite-strings -Wdeclaration-after-statement -Wimplicit-function-declaration -Wdeprecated-declarations -Wno-packed-bitfield-compat  -fPIC  conftest.c  -L. -L/usr/local/lib -Wl,-rpath,/usr/local/lib -L. -fstack-protector -rdynamic -Wl,-export-dynamic     -lffi  -lffi -Wl,-rpath,/usr/local/lib -L/usr/local/lib -lruby -lffi  -lffi -lpthread -lgmp -ldl -lcrypt -lm   -lc"
conftest.c: In function 't':
conftest.c:13:57: error: 'ffi_closure_alloc' undeclared (first use in this function)
 int t(void) { void ((*volatile p)()); p = (void ((*)()))ffi_closure_alloc; 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_closure_alloc; return !p; }
/* end */

"gcc -o conftest -I/usr/local/include/ruby-2.3.0/x86_64-linux -I/usr/local/include/ruby-2.3.0/ruby/backward -I/usr/local/include/ruby-2.3.0 -I.      -O3 -fno-fast-math -ggdb3 -Wall -Wextra -Wno-unused-parameter -Wno-parentheses -Wno-long-long -Wno-missing-field-initializers -Wunused-variable -Wpointer-arith -Wwrite-strings -Wdeclaration-after-statement -Wimplicit-function-declaration -Wdeprecated-declarations -Wno-packed-bitfield-compat  -fPIC  conftest.c  -L. -L/usr/local/lib -Wl,-rpath,/usr/local/lib -L. -fstack-protector -rdynamic -Wl,-export-dynamic     -lffi  -lffi -Wl,-rpath,/usr/local/lib -L/usr/local/lib -lruby -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_closure_alloc();
14: int t(void) { ffi_closure_alloc(); return 0; }
/* end */

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

have_header: checking for shlwapi.h... -------------------- no

"gcc -E -I/usr/local/include/ruby-2.3.0/x86_64-linux -I/usr/local/include/ruby-2.3.0/ruby/backward -I/usr/local/include/ruby-2.3.0 -I.      -O3 -fno-fast-math -ggdb3 -Wall -Wextra -Wno-unused-parameter -Wno-parentheses -Wno-long-long -Wno-missing-field-initializers -Wunused-variable -Wpointer-arith -Wwrite-strings -Wdeclaration-after-statement -Wimplicit-function-declaration -Wdeprecated-declarations -Wno-packed-bitfield-compat  -fPIC   conftest.c -o conftest.i"
conftest.c:3:21: fatal error: shlwapi.h: No such file or directory
 #include <shlwapi.h>
                     ^
compilation terminated.
checked program was:
/* begin */
1: #include "ruby.h"
2: 
3: #include <shlwapi.h>
/* end */

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

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

"gcc -o conftest -I/usr/local/include/ruby-2.3.0/x86_64-linux -I/usr/local/include/ruby-2.3.0/ruby/backward -I/usr/local/include/ruby-2.3.0 -I.      -O3 -fno-fast-math -ggdb3 -Wall -Wextra -Wno-unused-parameter -Wno-parentheses -Wno-long-long -Wno-missing-field-initializers -Wunused-variable -Wpointer-arith -Wwrite-strings -Wdeclaration-after-statement -Wimplicit-function-declaration -Wdeprecated-declarations -Wno-packed-bitfield-compat  -fPIC  conftest.c  -L. -L/usr/local/lib -Wl,-rpath,/usr/local/lib -L. -fstack-protector -rdynamic -Wl,-export-dynamic     -lffi  -lffi -Wl,-rpath,/usr/local/lib -L/usr/local/lib -lruby -lffi  -lffi -lpthread -lgmp -ldl -lcrypt -lm   -lc"
conftest.c: In function 't':
conftest.c:13:57: error: 'rb_thread_call_without_gvl' undeclared (first use in this function)
 int t(void) { void ((*volatile p)()); p = (void ((*)()))rb_thread_call_without_gvl; 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 ((*)()))rb_thread_call_without_gvl; return !p; }
/* end */

"gcc -o conftest -I/usr/local/include/ruby-2.3.0/x86_64-linux -I/usr/local/include/ruby-2.3.0/ruby/backward -I/usr/local/include/ruby-2.3.0 -I.      -O3 -fno-fast-math -ggdb3 -Wall -Wextra -Wno-unused-parameter -Wno-parentheses -Wno-long-long -Wno-missing-field-initializers -Wunused-variable -Wpointer-arith -Wwrite-strings -Wdeclaration-after-statement -Wimplicit-function-declaration -Wdeprecated-declarations -Wno-packed-bitfield-compat  -fPIC  conftest.c  -L. -L/usr/local/lib -Wl,-rpath,/usr/local/lib -L. -fstack-protector -rdynamic -Wl,-export-dynamic     -lffi  -lffi -Wl,-rpath,/usr/local/lib -L/usr/local/lib -lruby -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 rb_thread_call_without_gvl();
14: int t(void) { rb_thread_call_without_gvl(); return 0; }
/* end */

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

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

"gcc -o conftest -I/usr/local/include/ruby-2.3.0/x86_64-linux -I/usr/local/include/ruby-2.3.0/ruby/backward -I/usr/local/include/ruby-2.3.0 -I.      -O3 -fno-fast-math -ggdb3 -Wall -Wextra -Wno-unused-parameter -Wno-parentheses -Wno-long-long -Wno-missing-field-initializers -Wunused-variable -Wpointer-arith -Wwrite-strings -Wdeclaration-after-statement -Wimplicit-function-declaration -Wdeprecated-declarations -Wno-packed-bitfield-compat  -fPIC  conftest.c  -L. -L/usr/local/lib -Wl,-rpath,/usr/local/lib -L. -fstack-protector -rdynamic -Wl,-export-dynamic     -lffi  -lffi -Wl,-rpath,/usr/local/lib -L/usr/local/lib -lruby -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: int t(void) { void ((*volatile p)()); p = (void ((*)()))ruby_native_thread_p; return !p; }
/* end */

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

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

"gcc -o conftest -I/usr/local/include/ruby-2.3.0/x86_64-linux -I/usr/local/include/ruby-2.3.0/ruby/backward -I/usr/local/include/ruby-2.3.0 -I.      -O3 -fno-fast-math -ggdb3 -Wall -Wextra -Wno-unused-parameter -Wno-parentheses -Wno-long-long -Wno-missing-field-initializers -Wunused-variable -Wpointer-arith -Wwrite-strings -Wdeclaration-after-statement -Wimplicit-function-declaration -Wdeprecated-declarations -Wno-packed-bitfield-compat  -fPIC  conftest.c  -L. -L/usr/local/lib -Wl,-rpath,/usr/local/lib -L. -fstack-protector -rdynamic -Wl,-export-dynamic     -lffi  -lffi -Wl,-rpath,/usr/local/lib -L/usr/local/lib -lruby -lffi  -lffi -lpthread -lgmp -ldl -lcrypt -lm   -lc"
conftest.c: In function 't':
conftest.c:13:57: error: 'ruby_thread_has_gvl_p' undeclared (first use in this function)
 int t(void) { void ((*volatile p)()); p = (void ((*)()))ruby_thread_has_gvl_p; 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 ((*)()))ruby_thread_has_gvl_p; return !p; }
/* end */

"gcc -o conftest -I/usr/local/include/ruby-2.3.0/x86_64-linux -I/usr/local/include/ruby-2.3.0/ruby/backward -I/usr/local/include/ruby-2.3.0 -I.      -O3 -fno-fast-math -ggdb3 -Wall -Wextra -Wno-unused-parameter -Wno-parentheses -Wno-long-long -Wno-missing-field-initializers -Wunused-variable -Wpointer-arith -Wwrite-strings -Wdeclaration-after-statement -Wimplicit-function-declaration -Wdeprecated-declarations -Wno-packed-bitfield-compat  -fPIC  conftest.c  -L. -L/usr/local/lib -Wl,-rpath,/usr/local/lib -L. -fstack-protector -rdynamic -Wl,-export-dynamic     -lffi  -lffi -Wl,-rpath,/usr/local/lib -L/usr/local/lib -lruby -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 ruby_thread_has_gvl_p();
14: int t(void) { ruby_thread_has_gvl_p(); return 0; }
/* end */

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

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

"gcc -o conftest -I/usr/local/include/ruby-2.3.0/x86_64-linux -I/usr/local/include/ruby-2.3.0/ruby/backward -I/usr/local/include/ruby-2.3.0 -I.      -O3 -fno-fast-math -ggdb3 -Wall -Wextra -Wno-unused-parameter -Wno-parentheses -Wno-long-long -Wno-missing-field-initializers -Wunused-variable -Wpointer-arith -Wwrite-strings -Wdeclaration-after-statement -Wimplicit-function-declaration -Wdeprecated-declarations -Wno-packed-bitfield-compat  -fPIC  conftest.c  -L. -L/usr/local/lib -Wl,-rpath,/usr/local/lib -L. -fstack-protector -rdynamic -Wl,-export-dynamic     -lffi  -lffi -Wl,-rpath,/usr/local/lib -L/usr/local/lib -lruby -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/local/include/ruby-2.3.0/x86_64-linux -I/usr/local/include/ruby-2.3.0/ruby/backward -I/usr/local/include/ruby-2.3.0 -I.      -O3 -fno-fast-math -ggdb3 -Wall -Wextra -Wno-unused-parameter -Wno-parentheses -Wno-long-long -Wno-missing-field-initializers -Wunused-variable -Wpointer-arith -Wwrite-strings -Wdeclaration-after-statement -Wimplicit-function-declaration -Wdeprecated-declarations -Wno-packed-bitfield-compat  -fPIC  conftest.c  -L. -L/usr/local/lib -Wl,-rpath,/usr/local/lib -L. -fstack-protector -rdynamic -Wl,-export-dynamic     -lffi  -lffi -Wl,-rpath,/usr/local/lib -L/usr/local/lib -lruby -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/local/include/ruby-2.3.0/x86_64-linux -I/usr/local/include/ruby-2.3.0/ruby/backward -I/usr/local/include/ruby-2.3.0 -I.      -O3 -fno-fast-math -ggdb3 -Wall -Wextra -Wno-unused-parameter -Wno-parentheses -Wno-long-long -Wno-missing-field-initializers -Wunused-variable -Wpointer-arith -Wwrite-strings -Wdeclaration-after-statement -Wimplicit-function-declaration -Wdeprecated-declarations -Wno-packed-bitfield-compat  -fPIC  conftest.c  -L. -L/usr/local/lib -Wl,-rpath,/usr/local/lib -L. -fstack-protector -rdynamic -Wl,-export-dynamic     -lffi  -lffi -Wl,-rpath,/usr/local/lib -L/usr/local/lib -lruby -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)
 int t(void) { void ((*volatile p)()); p = (void ((*)()))ffi_raw_call; 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_raw_call; return !p; }
/* end */

"gcc -o conftest -I/usr/local/include/ruby-2.3.0/x86_64-linux -I/usr/local/include/ruby-2.3.0/ruby/backward -I/usr/local/include/ruby-2.3.0 -I.      -O3 -fno-fast-math -ggdb3 -Wall -Wextra -Wno-unused-parameter -Wno-parentheses -Wno-long-long -Wno-missing-field-initializers -Wunused-variable -Wpointer-arith -Wwrite-strings -Wdeclaration-after-statement -Wimplicit-function-declaration -Wdeprecated-declarations -Wno-packed-bitfield-compat  -fPIC  conftest.c  -L. -L/usr/local/lib -Wl,-rpath,/usr/local/lib -L. -fstack-protector -rdynamic -Wl,-export-dynamic     -lffi  -lffi -Wl,-rpath,/usr/local/lib -L/usr/local/lib -lruby -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/local/include/ruby-2.3.0/x86_64-linux -I/usr/local/include/ruby-2.3.0/ruby/backward -I/usr/local/include/ruby-2.3.0 -I.      -O3 -fno-fast-math -ggdb3 -Wall -Wextra -Wno-unused-parameter -Wno-parentheses -Wno-long-long -Wno-missing-field-initializers -Wunused-variable -Wpointer-arith -Wwrite-strings -Wdeclaration-after-statement -Wimplicit-function-declaration -Wdeprecated-declarations -Wno-packed-bitfield-compat  -fPIC  conftest.c  -L. -L/usr/local/lib -Wl,-rpath,/usr/local/lib -L. -fstack-protector -rdynamic -Wl,-export-dynamic     -lffi  -lffi -Wl,-rpath,/usr/local/lib -L/usr/local/lib -lruby -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/local/include/ruby-2.3.0/x86_64-linux -I/usr/local/include/ruby-2.3.0/ruby/backward -I/usr/local/include/ruby-2.3.0 -I.      -O3 -fno-fast-math -ggdb3 -Wall -Wextra -Wno-unused-parameter -Wno-parentheses -Wno-long-long -Wno-missing-field-initializers -Wunused-variable -Wpointer-arith -Wwrite-strings -Wdeclaration-after-statement -Wimplicit-function-declaration -Wdeprecated-declarations -Wno-packed-bitfield-compat  -fPIC  conftest.c  -L. -L/usr/local/lib -Wl,-rpath,/usr/local/lib -L. -fstack-protector -rdynamic -Wl,-export-dynamic     -lffi  -lffi -Wl,-rpath,/usr/local/lib -L/usr/local/lib -lruby -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 */

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

extconf.h is:
/* begin */
 1: #ifndef EXTCONF_H
 2: #define EXTCONF_H
 3: #define HAVE_FFI_CLOSURE_ALLOC 1
 4: #define HAVE_RB_THREAD_CALL_WITHOUT_GVL 1
 5: #define HAVE_RUBY_NATIVE_THREAD_P 1
 6: #define HAVE_RUBY_THREAD_HAS_GVL_P 1
 7: #define HAVE_FFI_PREP_CIF_VAR 1
 8: #define HAVE_FFI_RAW_CALL 1
 9: #define HAVE_FFI_PREP_RAW_CLOSURE 1
10: #define HAVE_RAW_API 1
11: #endif
/* end */