GCC-3.3.3 - Pass 2

Approximate build time:  11.0 SBU
Required disk space:     332.7 MB

The tools required to test GCC and Binutils are installed now: Tcl, Expect and DejaGnu. Therefore we can now rebuild GCC and Binutils, linking them against the new Glibc, and test them properly (if running the test suites in this chapter). One thing to note, however, is that these test suites are highly dependent on properly functioning pseudo terminals (PTYs) which are provided by your host. These days, PTYs are most commonly implemented via the devpts file system. You can quickly check if your host system is set up correctly in this regard by performing a simple test:

expect -c "spawn ls"

The response might be:

If you receive the above message, your host doesn't have its PTYs set up properly. In this case there is no point in running the test suites for GCC and Binutils until you are able to resolve the issue. You can consult the LFS Wiki at http://wiki.linuxfromscratch.org/ for more information on how to get PTYs working.

This time we will build both the C and the C++ compilers, so you'll have to unpack both the core and the g++ tarballs (and testsuite too, if you want to run the tests). Unpacking them in your working directory, they will all unfold into a single gcc-3.3.3/ subdirectory.

First correct a problem and make an essential adjustment:

patch -Np1 -i ../gcc-3.3.3-no_fixincludes-1.patch
patch -Np1 -i ../gcc-3.3.3-specs-1.patch

The first patch disables the GCC “fixincludes” script. We mentioned this briefly earlier, but a slightly more in-depth explanation of the fixincludes process is warranted here. Under normal circumstances, the GCC fixincludes script scans your system for header files that need to be fixed. It might find that some Glibc header files on your host system need to be fixed, fix them and put them in the GCC private include directory. Then, later on in Chapter 6, after we've installed the newer Glibc, this private include directory would be searched before the system include directory, resulting in GCC finding the fixed headers from the host system, which would most likely not match the Glibc version actually used for the LFS system.

The second patch changes GCC's default location of the dynamic linker (typically ld-linux.so.2). It also removes /usr/include from GCC's include search path. Patching now rather than adjusting the specs file after installation ensures that our new dynamic linker gets used during the actual build of GCC. That is, all the final (and temporary) binaries created during the build will link against the new Glibc.

Create a separate build directory again:

mkdir ../gcc-build
cd ../gcc-build

Before starting to build GCC, remember to unset any environment variables that override the default optimization flags.

Now prepare GCC for compilation:

../gcc-3.3.3/configure --prefix=/tools \
    --with-local-prefix=/tools \
    --enable-clocale=gnu --enable-shared \
    --enable-threads=posix --enable-__cxa_atexit \
    --enable-languages=c,c++

The meaning of the new configure options:

Compile the package:

make

There is no need to use the bootstrap target now, as the compiler we're using to compile this GCC was built from the exact same version of the GCC sources we used earlier.

Compilation is now complete. As mentioned earlier, we don't recommend running the test suites for the temporary tools here in this chapter. If you still want to run the GCC test suite anyway, the following command will do so:

make -k check

The -k flag is used to make the test suite run through to completion and not stop at the first failure. The GCC test suite is very comprehensive and is almost guaranteed to generate a few failures. To get a summary of the test suite results, run this:

../gcc-3.3.3/contrib/test_summary

(For just the summaries, pipe the output through grep -A7 Summ.)

You can compare your results to those posted to the gcc-testresults mailing list for similar configurations to your own. For an example of how current GCC-3.3.3 should look on i686-pc-linux-gnu, see http://gcc.gnu.org/ml/gcc-testresults/2004-01/msg00826.html.

Note that the results contain:

* 1 XPASS (unexpected pass) for g++
* 1 FAIL (unexpected failure) for gcc
* 24 XPASS's for libstdc++

The unexpected pass for g++ is due to the use of --enable-__cxa_atexit. Apparently not all platforms supported by GCC have support for “__cxa_atexit” in their C libraries, so this test is not always expected to pass.

The 24 unexpected passes for libstdc++ are due to the use of --enable-clocale=gnu. This option, which is the correct choice on Glibc-based systems of versions 2.2.5 and above, enables in the GNU C library a locale support that is superior to the otherwise selected generic model (which may be applicable if for instance you were using Newlibc, Sun-libc or whatever other libc). The libstdc++ test suite is apparently expecting the generic model, hence those tests are not always expected to pass.

Having a few unexpected failures often cannot be avoided. The GCC developers are usually aware of these, but haven't yet gotten around to fixing them. One particular case in point is the filebuf_members test in the C++ standard library testsuite. This test has been observed to fail in some situations, but succeeed in others. In short, unless your results are vastly different from those at the above URL, it is safe to continue.

And finally install the package:

make install

The details on this package are found in the section called “Contents of GCC”.