Bug #16651
Updated by nobu (Nobuyoshi Nakada) about 3 years ago
When mkmf.rb creates a Makefile for an extension, it will generate something that looks like this: ```makefile srcdir = . topdir = C/MSYS64/USR/LOCAL/ruby-2.7.0/include/ruby-2.7.0 hdrdir = $(topdir) arch_hdrdir = C:/MSYS64/USR/LOCAL/ruby-2.7.0/include/ruby-2.7.0/x64-mingw32 ``` Notice the topdir path is c/ without the ":" Its only the topdir that does this, all other paths in the makefile use the "c:/" style. mkmf.rb intentionally does that, see line 1098: ```ruby def mkintpath(path) # mingw uses make from msys and it needs special care # converts from C:\some\path to /C/some/path path = path.dup path.tr!('\\', '/') path.sub!(/\A([A-Za-z]):(?=\/)/, '/\1') <-------- This line path end ``` But this is wrong, and causes errors like this (this is compiling the debase gem but it doesn't matter what c extension you use): ``` make: *** No rule to make target 'C/MSYS64/USR/LOCAL/ruby-2.7.0/include/ruby-2.7.0/ruby.h', needed by 'breakpoint.o'. Stop. ``` The fix is simple, just delete that line. The makefile should look like this: ```makefile srcdir = . topdir = C:/MSYS64/USR/LOCAL/ruby-2.7.0/include/ruby-2.7.0 hdrdir = $(topdir) arch_hdrdir = C:/MSYS64/USR/LOCAL/ruby-2.7.0/include/ruby-2.7.0/x64-mingw32 ``` Note I'm not the first person to see this, but I've just been manually fixing it over the years. Would be good to really fix it. https://github.com/oneclick/rubyinstaller2/issues/105 https://github.com/oneclick/rubyinstaller2/issues/47 https://github.com/tmm1/http_parser.rb/issues/55 Note some of those tickets put the blame on using mingw-make versus msys make. But on my system, neither work with the "c/" style path but both work with the "c:/" style path.