What does the gcc -R parameter do?

Question

I am trying to run an autotools configure script for the bson-cpp project, and it fails because it cannot determine what flags it needs to compile with boost_filesystem. A quick look at confg.log shows:

g++ -o conftest -g -O2   -pthread  -L/usr/local/lib -R/usr/local/lib -L/usr/local/libexec conftest.o -lboost_filesystem-mt  -lboost_system-mt >&5
g++: error: unrecognized option '-R'

So, naturally, I tried to find out what the R option does, but I can't seem to find it documented anywhere. I've checked here and here to no avail. What does the option do and how do I tell autotools not to use it?

Answer 1

-R does not seem to be an option for g++ or gcc anywhere. -R may be a linker option on some platforms that is equivalent of -rpath to gnu ld, ... This seems to be a known bug in boost builds ... have a look at Use -Wl to pass arguments to the linker.

It actually has the patch available there

I am re-posting it for convenience, however PLEASE PLEASE look at the original URL linked above for official patch!

--- ../gnote/m4/boost.m4    2011-01-25 14:30:18.000000000 +0200
+++ m4/boost.m4 2011-02-27 20:57:11.686221539 +0200
@@ -403,7 +403,7 @@
       LDFLAGS=$boost_save_LDFLAGS
       LIBS=$boost_save_LIBS
       if test x"$Boost_lib" = xyes; then
-        Boost_lib_LDFLAGS="-L$boost_ldpath -R$boost_ldpath"
+        Boost_lib_LDFLAGS="-L$boost_ldpath -Wl,-R$boost_ldpath"
         Boost_lib_LDPATH="$boost_ldpath"
         break 6
       else

Answer 2

It's an option similar to -rpath, but available only on some platforms. The script is maybe failing detecting your platform ?

Answer 3

It is not a valid option for GCC, so it does not do anything.

It is possibly a valid option for other compilers though, which could be why autoconf gives it a shot.

Not all errors in the config.log files are a problem. autoconf figures out a lot of things by "guessing", i.e. trying something and keeping that if it worked.