https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66932
--- Comment #5 from Michael McWilliam <pilot.mm at gmail dot com> --- (In reply to Andrew Pinski from comment #4) > An empty : causes the current directory to be added. Thanks for explaining that... Including the current directory with an empty : makes sense (as it is in the documented). However that does not seem to be what is happening considering this causes ../bfd/ to take precedent over ./. Simply setting C_INCLUDE_PATH to any of the following will cause the error: C_INCLUDE_PATH=":" C_INCLUDE_PATH=":/usr/include/" C_INCLUDE_PATH="./" C_INCLUDE_PATH="/usr/include/:" According to the documentation the -I directives are included first, then those of C_INCLUDE_PATH, then the system headers. In this problem the local directory is included first with -I. So it seems that when the compiler sees a directory in C_INCLUDE_PATH it forgets any duplicates specified with -I and the include precedence is being broken. Stated simply I think gcc is failing to check if an include directory is already specified when it adds C_INCLUDE_PATH headers in lower precedence. So it seems it is a real bug... and a somewhat obscure bug...
