Building gn using itself to out/Release... DEBUG:root:Running: /x/portage/www-client/chromium-57.0.2979.0/work/temp/tmpxXl2wS/gn gen /x/portage/www-client/chromium-57.0.2979.0/work/chromium-57.0.2979.0/out/Release --args= is_debug=false is_component_build=false enable_nacl=false enable_hangout_services_extension=true enable_widevine=false use_cups=true use_gconf=false use_gnome_keyring=false use_gtk3=false use_kerberos=false use_pulseaudio=true fieldtrial_testing_like_official_build=true is_clang=true clang_base_path="/usr" clang_use_chrome_plugins=false use_gold=false use_sysroot=false linux_use_bundled_binutils=false proprietary_codecs=true ffmpeg_branding="Chrome" google_api_key="AIzaSyDEAOvatFo0eTgsV_ZlEzx0ObmepsMzfAc" google_default_client_id="329227923882.apps.googleusercontent.com" google_default_client_secret="vgKG0NNv7GoDpbtoFNLxCUXu" treat_warnings_as_errors=false fatal_linker_warnings=false custom_toolchain="/home/floppym/repos/gentoo/www-client/chromium/files/toolchain:default" use_allocator="none" is_debug=false [0115/222458.542906:FATAL:substitution_writer.cc(402)] Check failed: false. Unsupported substitution for this function: {{output}} /x/portage/www-client/chromium-57.0.2979.0/work/temp/tmpxXl2wS/gn() [0x4208ae] /x/portage/www-client/chromium-57.0.2979.0/work/temp/tmpxXl2wS/gn() [0x410e5f] /x/portage/www-client/chromium-57.0.2979.0/work/temp/tmpxXl2wS/gn() [0x525762] /x/portage/www-client/chromium-57.0.2979.0/work/temp/tmpxXl2wS/gn() [0x525d96] /x/portage/www-client/chromium-57.0.2979.0/work/temp/tmpxXl2wS/gn() [0x53df86] /x/portage/www-client/chromium-57.0.2979.0/work/temp/tmpxXl2wS/gn() [0x53d21d] /x/portage/www-client/chromium-57.0.2979.0/work/temp/tmpxXl2wS/gn() [0x4ec107] /x/portage/www-client/chromium-57.0.2979.0/work/temp/tmpxXl2wS/gn() [0x4d9fa1] /x/portage/www-client/chromium-57.0.2979.0/work/temp/tmpxXl2wS/gn() [0x4d643e] /x/portage/www-client/chromium-57.0.2979.0/work/temp/tmpxXl2wS/gn() [0x468aee] /x/portage/www-client/chromium-57.0.2979.0/work/temp/tmpxXl2wS/gn() [0x4680e8] /x/portage/www-client/chromium-57.0.2979.0/work/temp/tmpxXl2wS/gn() [0x46d125] /x/portage/www-client/chromium-57.0.2979.0/work/temp/tmpxXl2wS/gn() [0x425b55] /lib64/libpthread.so.0(+0x7546) [0x7f0667459546] /lib64/libc.so.6(clone+0x6d) [0x7f066719a16d]
I was able to repro. This is fixed in 57.0.2986.0 .