Hi, even after careful study of https://gcc.gnu.org/install/configure.html and looking around the internet I can't really find a satisfying answer to this question. When building native or cross compiler, it's quite easy, --with-sysroot points to the place where the new compiler should look for include and library files (i.e. <sysroot>/usr). >From the description of --with-build-sysroot I would say that if I wish to use different sysroot for building (i.e. during compilation of the new compiler) I should use this option and specify --with-sysroot with the path I'm interested to use when the new compiler is used. I struggle to understand how to use these two options when I want to build a compiler which is supposed to run on another machine. For example, I want to build a compiler which I will place in the target machine's /usr/bin. So, if "arm-linux-gnueabihf-gcc -print-sysroot" prints "/usr/arm-linux-gnueabihf", I would naively expect this to work: ./configure --host=arm-linux-gnueabihf --target=arm-linux-gnueabihf --prefix=/usr --with-build-sysroot=/usr/arm-linux-gnueabihf (other options omitted) I didn't specify --with-sysroot because I want it to use its default value (which is an empty string I believe, so the includes/libraries are searched in <sysroot>/usr = /usr by default). What happens however is that gcc's configure starts picking up stuff from my Linux's /usr folder, like detecting headers which are not in /usr/arm-linux-gnueabihf/usr/include (for example <sys/sdt.h>) or running the "fixing includes" process on includes from /usr/include instead of my build sysroot. Documentation for --with-build-sysroot says "This option is only useful when you are already using --with-sysroot" which could imply that I have to specify --with-sysroot to make it really work. So I did: ./configure --host=arm-linux-gnueabihf --target=arm-linux-gnueabihf --prefix=/usr --with-sysroot="" --with-build-sysroot=/usr/arm-linux-gnueabihf (other options omitted) Same result. Then I got an idea to specify --with-sysroot=/non-existent-dir and voila, it worked! However now the new gcc prints its sysroot as "/non-existent-dir" and is used as one of its search paths (what can be quite fatal if I wanted to have target's sysroot outside /usr -- and yes, I am aware of gcc's --sysroot command line parameter, I'm talking about its default setting). As a desperate attempt, I tried to specify --with-sysroot="/" and this worked, too. This leads to nearly perfect result, search paths are /lib, /usr/lib and so on however the new gcc naturally still prints its sysroot as "/" which I believe is wrong (paths then should look like //usr/include, //usr/lib etc what we clearly don't want). Plus it is a cosmetic bug, normally gcc doesn't print anything if it is configured with an empty sysroot. I guess my question is then: shouldn't --with-build-sysroot work autonomously from --with-sysroot? I.e. if I specify --with-build-sysroot, it should be used exactly as with --with-sysroot however the final gcc would use --with-sysroot value instead. Or is there something else I'm missing? Thanks, Miro
