无法在Windows上构建gem本机扩展

Question

I'm attempting to install the dandelion gem on on my Windows machine, but it keeps failing:

C:\Users\William>gem install dandelion --platform=ruby
Temporarily enhancing PATH to include DevKit...
Building native extensions.  This could take a while...
ERROR:  Error installing dandelion:
ERROR: Failed to build gem native extension.

C:/Ruby22/bin/ruby.exe -r ./siteconf20150623-7568-1ikffjg.rb extconf.rb
checking for gmake... no
checking for make... yes
checking for cmake... yes
checking for pkg-config... yes
-- cmake .. -DBUILD_CLAR=OFF -DTHREADSAFE=ON -DBUILD_SHARED_LIBS=OFF -DCMAKE_C_
FLAGS=-fPIC -DCMAKE_BUILD_TYPE=RelWithDebInfo -G "Unix Makefiles"
-- C:\DevKit\bin/make.exe
checking for main() in -lgit2... *** 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=C:/Ruby22/bin/$(RUBY_BASE_NAME)
--use-system-libraries
--with-git2-dir
--without-git2-dir
--with-git2-include
--without-git2-include=${git2-dir}/include
--with-git2-lib
--without-git2-lib=${git2-dir}/lib
--with-git2lib
--without-git2lib
C:/Ruby22/lib/ruby/2.2.0/mkmf.rb:456:in `try_do': The compiler failed to generate an executable file. (RuntimeError)
You have to install development tools first.
from C:/Ruby22/lib/ruby/2.2.0/mkmf.rb:541:in `try_link0'
from C:/Ruby22/lib/ruby/2.2.0/mkmf.rb:556:in `try_link'
from C:/Ruby22/lib/ruby/2.2.0/mkmf.rb:735:in `try_func'
from C:/Ruby22/lib/ruby/2.2.0/mkmf.rb:966:in `block in have_library'
from C:/Ruby22/lib/ruby/2.2.0/mkmf.rb:911:in `block in checking_for'
from C:/Ruby22/lib/ruby/2.2.0/mkmf.rb:351:in `block (2 levels) in postpone'
from C:/Ruby22/lib/ruby/2.2.0/mkmf.rb:321:in `open'
from C:/Ruby22/lib/ruby/2.2.0/mkmf.rb:351:in `block in postpone'
from C:/Ruby22/lib/ruby/2.2.0/mkmf.rb:321:in `open'
from C:/Ruby22/lib/ruby/2.2.0/mkmf.rb:347:in `postpone'
from C:/Ruby22/lib/ruby/2.2.0/mkmf.rb:910:in `checking_for'
from C:/Ruby22/lib/ruby/2.2.0/mkmf.rb:961:in `have_library'
from extconf.rb:89:in `<main>'

extconf failed, exit code 1

Gem files will remain installed in C:/Ruby22/lib/ruby/gems/2.2.0/gems/rugged-0.2
2.1b1 for inspection.
Results logged to C:/Ruby22/lib/ruby/gems/2.2.0/extensions/x86-mingw32/2.2.0/rug
ged-0.22.1b1/gem_make.out

The error that states "you have to install development tools first" is a head-scratcher. I have already installed DevKit.

Any ideas how to solve this error?

Answer 1

This is a fun one. I'm going to take a wild guess and say that you have a version of libgit2 located in C:/Program Files (x86)/libgit2/lib and that folder is somehow in your Path or possible some other environment variable.

The fix is to take that folder out of what environment variable that it could be in. That should let rugged build correctly.

The Problem

When gcc is trying to test for the libgit2 library it sees it could possibly be in C:/Program Files (x86)/libgit2/lib and uses -LC:/Program Files (x86)/libgit2/lib .

The problem is that it isn't properly escaped, which leads to

gcc: error: Files: No such file or directory
gcc: error: (x86)/libgit2/lib: No such file or directory

This is actually the same reason why Ruby can't be installed in folders with spaces.

As a side note: I'd like to point out that in addition to the regular DevKit you also have cmake and pkg-config somewhere installed and in your Path