[rails] error: implicit declaration of function 'ffi_prep_closure_loc' is invalid in C99

error log

current directory: /Users//.rbenv/versions/2.6.6/lib/ruby/gems/2.6.0/gems/ffi-1.15.0/ext/ffi\_c  
/Users//.rbenv/versions/2.6.6/bin/ruby -I /Users//.rbenv/versions/2.6.6/lib/ruby/2.6.0 -r ./siteconf20210405-41671-1rcq3m7.rb extconf.rb  
checking for ffi\_prep\_closure\_loc() in -lffi... yes  
checking for ffi\_prep\_cif\_var()... yes  
checking for ffi\_raw\_call()... yes  
checking for ffi\_prep\_raw\_closure()... yes  
creating extconf.h  
creating Makefile  

current directory: /Users//.rbenv/versions/2.6.6/lib/ruby/gems/2.6.0/gems/ffi-1.15.0/ext/ffi\_c  
make "DESTDIR=" clean  

current directory: /Users//.rbenv/versions/2.6.6/lib/ruby/gems/2.6.0/gems/ffi-1.15.0/ext/ffi\_c  
make "DESTDIR="  
compiling AbstractMemory.c  
compiling ArrayType.c  
compiling Buffer.c  
compiling Call.c  
compiling ClosurePool.c  
compiling DynamicLibrary.c  
compiling Function.c  
Function.c:867:17: error: implicit declaration of function 'ffi\_prep\_closure\_loc' is invalid in C99 \[-Werror,-Wimplicit-function-declaration\]  
ffiStatus = ffi\_prep\_closure\_loc(closure->pcl, &fnInfo->ffi\_cif, callback\_invoke, closure, code);  
^  
Function.c:867:17: note: did you mean 'ffi\_prep\_closure'?  
/Library/Developer/CommandLineTools/SDKs/MacOSX10.14.sdk/usr/include/ffi/ffi.h:269:1: note: 'ffi\_prep\_closure' declared here  
ffi\_prep\_closure(  
^  
1 error generated.  
make: \*\*\* \[Function.o\] Error 1  

make failed, exit code 2

solution

gem install ffi -- --disable-system-libffi