As an old retired compiler-writer, I build gcc every few weeks for fun, and I like to benchmark the builds, examine generated code, etc. -> http://dkallen.org/BuildingGCC.htm This all ended a few months ago, as Apple’s Xcode 11 world on macOS 10.15 Catalina no longer has a /usr/include. With Xcode 11 one could in 10.14 Mojave install /usr/include, but this no longer works in Catalina. Apple moved lib and include into a new developer location. You can determine where /usr is via their xcrun tool, e.g., [~] 14:04:01 % xcrun --show-sdk-path /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk [~] 14:06:14 % ls /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr bin/ include/ lib/ libexec/ share/ You cannot create /usr anything, except within /usr/local, due to new read-only file systems around the OS and its folders. It is supposed to be more secure, but it is really a gigantic pain. So, with that background, building gcc works, but just for stage-1. This is because clang (used for the first build) knows all about the new developer tool path. Once a stage-1 gcc is built, gcc looks for /usr/include and dies, even with using -sysroot, or -isysroot, or a variety of other flags that I have tried. So gcc gurus, how does one fix this? I have tried bootstrap-building the latest snapshots of gcc 7, 8, 9, and 10, all with the same result: failure. Thanks, Dan Allen
