gem install mailcatcher fails with - ERROR: Error installing mailcatcher: ERROR: Failed to build gem native extension

Question

I am on macOS Catalina 10.15.7, using rbenv (version rbenv 1.1.2-36-g60c9339 ) and ruby verion 2.6.3 (ruby 2.6.3p62 (2019-04-16 revision 67580) [x86_64-darwin19] is the output of ruby -v) for my project. I need to install mailcatcher to check the emails my application generates. On running gem install mailcatcher in my project folder, the command fails with the following error:

➜ gem install mailcatcher
Building native extensions. This could take a while...
ERROR:  Error installing mailcatcher:
    ERROR: Failed to build gem native extension.

    current directory: /Users/karansapolia/.rbenv/versions/2.6.3/lib/ruby/gems/2.6.0/gems/thin-1.5.1/ext/thin_parser
/Users/karansapolia/.rbenv/versions/2.6.3/bin/ruby -I /Users/karansapolia/.rbenv/versions/2.6.3/lib/ruby/2.6.0 -r ./siteconf20201103-23665-1tzqkaj.rb extconf.rb
checking for main() in -lc... yes
creating Makefile

current directory: /Users/karansapolia/.rbenv/versions/2.6.3/lib/ruby/gems/2.6.0/gems/thin-1.5.1/ext/thin_parser
make "DESTDIR=" clean

current directory: /Users/karansapolia/.rbenv/versions/2.6.3/lib/ruby/gems/2.6.0/gems/thin-1.5.1/ext/thin_parser
make "DESTDIR="
compiling parser.c
parser.rl:112:17: warning: comparison of integers of different signs: 'long' and 'unsigned long' [-Wsign-compare]
  assert(pe - p == len - off && "pointers aren't same distance");
         ~~~~~~ ^  ~~~~~~~~~
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/assert.h:93:25: note: expanded from macro 'assert'
    (__builtin_expect(!(e), 0) ? __assert_rtn(__func__, __FILE__, __LINE__, #e) : (void)0)
                        ^
parser.rl:142:7: error: implicit declaration of function 'thin_http_parser_has_error' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
  if (thin_http_parser_has_error(parser) ) {
      ^
parser.rl:142:7: note: did you mean 'http_parser_has_error'?
./parser.h:44:5: note: 'http_parser_has_error' declared here
int http_parser_has_error(http_parser *parser);
    ^
parser.rl:144:14: error: implicit declaration of function 'thin_http_parser_is_finished' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
  } else if (thin_http_parser_is_finished(parser) ) {
             ^
1 warning and 2 errors generated.
make: *** [parser.o] Error 1

make failed, exit code 2

Gem files will remain installed in /Users/karansapolia/.rbenv/versions/2.6.3/lib/ruby/gems/2.6.0/gems/thin-1.5.1 for inspection.
Results logged to /Users/karansapolia/.rbenv/versions/2.6.3/lib/ruby/gems/2.6.0/extensions/x86_64-darwin-19/2.6.0/thin-1.5.1/gem_make.out

Installing other gems is working perfectly. gem install mailman worked perfectly. Only fails for mailcatcher.

How do I install mailcatcher without the errors?

Answer 1

I ran the follow command and it worked to me

gem install mailcatcher -- --with-cflags="-Wno-error=implicit-function-declaration"

Answer 2

it seems that there is a problem at installing thin parser, i have found an already opened issue on github, and this contributor proposed a soultion, here.

make sure to install thin before mailcatcher.