Trunk rev: 140188 (although this happened with several previous revisions)
Configure command: ../gcc/configure --disable-bootstrap --prefix=$HOME --program-prefix=current- --enable-languages=c,c++,objc,java
Build errors:
libtool: compile:  /home/lthode/gcc-build/./gcc/xgcc -shared-libgcc -B/home/lthode/gcc-build/./gcc -nostdinc++ -L/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/src -L/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/src/.libs -B/home/lthode/x86_64-unknown-linux-gnu/bin/ -B/home/lthode/x86_64-unknown-linux-gnu/lib/ -isystem /home/lthode/x86_64-unknown-linux-gnu/include -isystem /home/lthode/x86_64-unknown-linux-gnu/sys-include -I/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/x86_64-unknown-linux-gnu -I/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include -I/home/lthode/gcc/libstdc++-v3/libsupc++ -fno-implicit-templates -Wall -Wextra -Wwrite-strings -Wcast-qual -fdiagnostics-show-location=once -ffunction-sections -fdata-sections -g -O2 -D_GNU_SOURCE -c /home/lthode/gcc/libstdc++-v3/src/compatibility.cc  -fPIC -DPIC -o .libs/compatibility.o
In file included from /home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/fstream:48,
                 from /home/lthode/gcc/libstdc++-v3/src/compatibility.cc:51:
/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/cstdio:101: error: '::fpos_t' has not been declared
/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/cstdio:103: error: '::clearerr' has not been declared
/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/cstdio:104: error: '::fclose' has not been declared
/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/cstdio:105: error: '::feof' has not been declared
/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/cstdio:106: error: '::ferror' has not been declared
/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/cstdio:107: error: '::fflush' has not been declared
/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/cstdio:108: error: '::fgetc' has not been declared
/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/cstdio:109: error: '::fgetpos' has not been declared
/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/cstdio:110: error: '::fgets' has not been declared
/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/cstdio:111: error: '::fopen' has not been declared
/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/cstdio:112: error: '::fprintf' has not been declared
/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/cstdio:113: error: '::fputc' has not been declared
/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/cstdio:114: error: '::fputs' has not been declared
/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/cstdio:115: error: '::fread' has not been declared
/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/cstdio:116: error: '::freopen' has not been declared
/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/cstdio:117: error: '::fscanf' has not been declared
/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/cstdio:118: error: '::fseek' has not been declared
/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/cstdio:119: error: '::fsetpos' has not been declared
/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/cstdio:120: error: '::ftell' has not been declared
/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/cstdio:121: error: '::fwrite' has not been declared
/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/cstdio:122: error: '::getc' has not been declared
/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/cstdio:123: error: '::getchar' has not been declared
/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/cstdio:124: error: '::gets' has not been declared
/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/cstdio:125: error: '::perror' has not been declared
/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/cstdio:126: error: '::printf' has not been declared
/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/cstdio:127: error: '::putc' has not been declared
/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/cstdio:128: error: '::putchar' has not been declared
/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/cstdio:129: error: '::puts' has not been declared
/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/cstdio:130: error: '::remove' has not been declared
/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/cstdio:131: error: '::rename' has not been declared
/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/cstdio:132: error: '::rewind' has not been declared
/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/cstdio:133: error: '::scanf' has not been declared
/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/cstdio:134: error: '::setbuf' has not been declared
/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/cstdio:135: error: '::setvbuf' has not been declared
/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/cstdio:136: error: '::sprintf' has not been declared
/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/cstdio:137: error: '::sscanf' has not been declared
/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/cstdio:138: error: '::tmpfile' has not been declared
/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/cstdio:139: error: '::tmpnam' has not been declared
/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/cstdio:140: error: '::ungetc' has not been declared
/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/cstdio:141: error: '::vfprintf' has not been declared
/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/cstdio:142: error: '::vprintf' has not been declared
/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/cstdio:143: error: '::vsprintf' has not been declared
/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/cstdio:170: error: '::snprintf' has not been declared
/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/cstdio:171: error: '::vfscanf' has not been declared
/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/cstdio:172: error: '::vscanf' has not been declared
/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/cstdio:173: error: '::vsnprintf' has not been declared
/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/cstdio:174: error: '::vsscanf' has not been declared
/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/cstdio:181: error: '__gnu_cxx::snprintf' has not been declared
/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/cstdio:182: error: '__gnu_cxx::vfscanf' has not been declared
/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/cstdio:183: error: '__gnu_cxx::vscanf' has not been declared
/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/cstdio:184: error: '__gnu_cxx::vsnprintf' has not been declared
/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/cstdio:185: error: '__gnu_cxx::vsscanf' has not been declared
In file included from /home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/fstream:783,
                 from /home/lthode/gcc/libstdc++-v3/src/compatibility.cc:51:
/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/bits/fstream.tcc: In constructor 'std::basic_filebuf<_CharT, _Traits>::basic_filebuf()':
/home/lthode/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/bits/fstream.tcc:86: error: 'BUFSIZ' was not declared in this scope
make[4]: *** [compatibility.lo] Error 1

This looks somewhat like PR target/15065, just a ton worse and on a much more important platform. :|