[Bug middle-end/54630] [4.8 Regression] GCC 4.8 --enable-languages=c build fails: Undefined symbols: ___cxa_guard_acquire and ___cxa_guard_release

["baker at usgs dot gov" <gcc-bugzilla@gcc.gnu.org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54630

--- Comment #17 from Larry Baker <baker at usgs dot gov> 2012-11-21 21:37:26 UTC ---
Jonathan,

Yes, I should have said "link with a C++ driver" instead of "link with a C++
compiler".

>No, it's not equivalent, -static-libstdcxx does not imply -lstdc++,
> which is why you get missing symbols.

-static-libstdcxx has nothing to do with why I get the missing symbols.  I get
the missing symbols because the LINKER changed from $(CC) to $(CXX).

>Why not just use the Sourcery configuration that works?

Why change the LINKER for a C++ program from $(CXX) to $(CC)?  That is what
causes the link to fail.  The g++ driver may have any number of built-in ld
options that differ from the gcc driver.  Why should I care?  The point of
using the g++ driver for a C++ program is that it takes care of all that for
me.

If I get everything working for my cross compiler without using
--with-host-libstdcxx, then the LINKER is $(CXX), which implies -lstdc++.  Now,
suppose I want to eliminate the dependencies of my cross compiler on the libc
and llibc++ shared libraries that happen to be on my Linux system, so that my
cross compiler will run on many Linux systems with possibly different libc's
and libc++'s.  In that case, I do not want to select different library (e.g., a
debug variant), I want to select the .a variant in place of the .so variant. 
If I were writing my own link command, I would use g++ to do the linking with
the options "-static-libgcc -static-libstdc++".  So, how to do the same when
building a GCC cross compiler?

The GCC installation notes, http://gcc.gnu.org/install/configure.html, offer
only one method to add linker options to build GCC: --with-host-libstdcxx.  The
example given there is `-Wl,-Bstatic,-lstdc++,-Bdynamic -lm', which is
equivalent to g++ -static-libstdc++ (plus -lm, which I have no idea why it is
there).  (As far as I can tell, Sourcery copied this example verbatim,
including the unnecessary -lm.)  This example was likely written before the g++
-static-libstdc++ options existed, and certainly was written before the GCC
implementation language was changed from C to C++.  What is not mentioned is
the side effect that the LINKER will change from $(CXX) to ($CC).

>To allow fine-tuning the libs, you need the
>additional libs to not be used, which implies not linking with g++.

Then they should specify CXX=gcc (since there is no way to specify the LINKER
directly).

All this will be moot, I think, when others start bumping into GCC builds that
fail as more of GCC is implemented in C++.