5.14. Installing GCC-3.3.1 - Pass 2

5.14.1.

5.14.2. Re-installation of GCC

The tools required to test GCC and Binutils are installed now (Tcl, Expect and DejaGnu). We can continue on rebuilding GCC and Binutils, link them against the new Glibc, and test them properly. 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 distribution. 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"

If you receive the message:

The system has no more ptys. Ask your system administrator to create more.

Your host distribution is not set up for proper PTY operation. 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.

Unpack all three GCC tarballs (-core, -g++, and -testsuite) in one and the same working directory. They will all unfold into a single gcc-3.3.1/ subdirectory.

First correct one problem and make an essential adjustment:

patch -Np1 -i ../gcc-3.3.1-no_fixincludes-2.patch
patch -Np1 -i ../gcc-3.3.1-specs-2.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 last 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.

These patches are critical in ensuring a successful overall build. Do not forget to apply them.

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-3.3.1/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:

• --enable-threads=posix: This enables C++ exception handling for multi-threaded code.

• --enable-__cxa_atexit: This option allows use of __cxa_atexit, rather than atexit, to register C++ destructors for local statics and global objects and is essential for fully standards-compliant handling of destructors. It also affects the C++ ABI and therefore results in C++ shared libraries and C++ programs that are interoperable with other Linux distributions.

• --enable-clocale=gnu: This option ensures the correct locale model is selected for the C++ libraries under all circumstances. If the configure script finds the de_DE locale installed, it will select the correct model of gnu. However, people who don't install the de_DE locale, run the risk of building ABI incompatible C++ libraries due to the wrong locale model of generic being selected.

• --enable-languages=c,c++: This option is needed to ensure that both C and C++ compilers are built.

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.

It's worth pointing out that running the GCC test suite here is considered not as important as running it in Chapter 6.

Test the results:

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-3.3.1/contrib/test_summary | more

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-3.3.1 should look on i686-pc-linux-gnu, see http://gcc.gnu.org/ml/gcc-testresults/2003-08/msg01612.html.

Note that the results contain:

* 1 XPASS (unexpected pass) for g++
* 1 FAIL (unexpected failure) for g++
* 2 FAIL for gcc
* 26 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 26 unexpected passes for libstdc++ are due to the use of --enable-clocale=gnu, which is the correct choice on Glibc-based systems of versions 2.2.5 and above. The underlying locale support in the GNU C library is superior to that of the otherwise selected "generic" model (which may be applicable if for instance you were using Newlibc, Sun-libc or whatever libc). The libstdc++ test suite is apparently expecting the "generic" model, hence those tests are not always expected to pass.

Unexpected failures often cannot be avoided. The GCC developers are usually aware of them but haven't yet gotten around to fixing them. In short, unless your results are vastly different from those at the above URL, it is safe to continue on.

And finally install the package:

make install

At this point it is strongly recommended to repeat the sanity check we performed earlier in the chapter. Refer back to Section 5.10 and repeat the check. If the results are wrong, then most likely you forgot to apply the above mentioned GCC Specs patch.