Hi Carl, On Thu, 17 Oct 2019 21:56:44 +0000 Carl Dong wrote: > Note that the reason mingw-w64-x86_64-6.0.0/include is in this list at all is > because of the 'fix-env phase I added, which plucked it from CPATH and plopped > it into CROSS_CPATH. Yeah, I did the same in sunxi-tools--which was also broken after the core-updates merge, but had been working fine before. It's using an x86_64->ARM cross compiler. But just changing it to CROSS_CPATH works, there. > 3. Does this reveal something more fundamentally wrong with how we build our > search paths in the first place that should be addressed I think so. I can't figure out why Guix is not just setting up CROSS_CPATH on its own in the first place. gnu/packages/cross-base.scm DOES have a search-path specification for CROSS_CPATH. Notes: * CPATH is something like "-I", but CPATH applies after all command-line "-I"s. * C_INCLUDE_PATH, CPLUS_INCLUDE_PATH and OBJC_INCLUDE_PATH are something like "-isystem", but they apply after all command-line "-isystem"s. Note that an empty (colon-separated) element in those environment variables means "current working directory". https://gcc.gnu.org/onlinedocs/gcc-6.2.0/gcc/Directory-Options.html : >If a standard system include directory, or a directory specified with >-isystem, is also specified with -I, the -I option is ignored. The >directory is still searched but as a system directory at its normal >position in the system include chain. This is to ensure that GCC's >procedure to fix buggy system headers and the ordering for the >include_next directive are not inadvertently changed. If you really >need to change the search order for system directories, use the >-nostdinc and/or -isystem options. https://gcc.gnu.org/onlinedocs/cpp/Invocation.html#Invocation : >The lookup order is as follows: > For the quote form of the include directive, the directory of the current file is searched first. > For the quote form of the include directive, the directories specified by -iquote options are searched in LTR order. > Directories specified with -I options are scanned in left-to-right order. > Directories specified with -isystem options are scanned in left-to-right order. > Standard system directories are scanned[, except if -nostdinc[++] is specified]. > Directories specified with -idirafter options are scanned in left-to-right order.