6.17.1. Installation of GCC
The GCC documentation recommends building GCC outside of the source
directory in a dedicated build directory:
mkdir -v ../gcc-build
cd ../gcc-build
Prepare GCC for compilation:
SED=sed \
../gcc-4.9.2/configure \
--prefix=/usr \
--enable-languages=c,c++ \
--disable-multilib \
--disable-bootstrap \
--with-system-zlib
Note that for other languages, there are some prerequisites that
are not yet available. See the BLFS
Book for instructions on how to build all of GCC's supported
languages.
The meaning of the new configure option:
-
SED=sed
-
Setting this environment variable prevents a hard-coded path
to /tools/bin/sed.
-
--with-system-zlib
-
This switch tells GCC to link to the system installed copy of
the Zlib library, rather than its own internal copy.
Compile the package:
make
![[Important]](../images/important.png)
Important
In this section, the test suite for GCC is considered critical.
Do not skip it under any circumstance.
One set of tests in the GCC test suite is known to exhaust the
stack, so increase the stack size prior to running the tests:
ulimit -s 32768
Test the results, but do not stop at errors:
make -k check
To receive a summary of the test suite results, run:
../gcc-4.9.2/contrib/test_summary
For only the summaries, pipe the output through grep -A7 Summ.
Results can be compared with those located at http://www.linuxfromscratch.org/lfs/build-logs/7.7/
and http://gcc.gnu.org/ml/gcc-testresults/.
A few unexpected failures cannot always be avoided. The GCC
developers are usually aware of these issues, but have not resolved
them yet. Unless the test results are vastly different from those
at the above URL, it is safe to continue.
Install the package:
make install
Some packages expect the C preprocessor to be installed in the
/lib directory. To support those
packages, create this symlink:
ln -sv ../usr/bin/cpp /lib
Many packages use the name cc to call the C compiler. To
satisfy those packages, create a symlink:
ln -sv gcc /usr/bin/cc
Add a compatibility symlink to enable building programs with Link
Time Optimization (LTO):
install -v -dm755 /usr/lib/bfd-plugins
ln -sfv ../../libexec/gcc/$(gcc -dumpmachine)/4.9.2/liblto_plugin.so /usr/lib/bfd-plugins/
Now that our final toolchain is in place, it is important to again
ensure that compiling and linking will work as expected. We do this
by performing the same sanity checks as we did earlier in the
chapter:
echo 'main(){}' > dummy.c
cc dummy.c -v -Wl,--verbose &> dummy.log
readelf -l a.out | grep ': /lib'
There should be no errors, and the output of the last command will
be (allowing for platform-specific differences in dynamic linker
name):
[Requesting program interpreter: /lib/ld-linux.so.2]
Now make sure that we're setup to use the correct startfiles:
grep -o '/usr/lib.*/crt[1in].*succeeded' dummy.log
The output of the last command should be:
/usr/lib/gcc/i686-pc-linux-gnu/4.9.2/../../../crt1.o succeeded
/usr/lib/gcc/i686-pc-linux-gnu/4.9.2/../../../crti.o succeeded
/usr/lib/gcc/i686-pc-linux-gnu/4.9.2/../../../crtn.o succeeded
Depending on your machine architecture, the above may differ
slightly, the difference usually being the name of the directory
after /usr/lib/gcc. If your machine
is a 64-bit system, you may also see a directory named lib64 towards the end of the string. The
important thing to look for here is that gcc has found all three
crt*.o files under the /usr/lib directory.
Verify that the compiler is searching for the correct header files:
grep -B4 '^ /usr/include' dummy.log
This command should return the following output:
#include <...> search starts here:
/usr/lib/gcc/i686-pc-linux-gnu/4.9.2/include
/usr/local/include
/usr/lib/gcc/i686-pc-linux-gnu/4.9.2/include-fixed
/usr/include
Again, note that the directory named after your target triplet may
be different than the above, depending on your architecture.
![[Note]](../images/note.png)
Note
As of version 4.3.0, GCC now unconditionally installs the
limits.h file into the private
include-fixed directory, and that
directory is required to be in place.
Next, verify that the new linker is being used with the correct
search paths:
grep 'SEARCH.*/usr/lib' dummy.log |sed 's|; |\n|g'
References to paths that have components with '-linux-gnu' should
be ignored, but otherwise the output of the last command should be:
SEARCH_DIR("/usr/i686-pc-linux-gnu/lib32")
SEARCH_DIR("/usr/local/lib32")
SEARCH_DIR("/lib32")
SEARCH_DIR("/usr/lib32")
SEARCH_DIR("/usr/i686-pc-linux-gnu/lib")
SEARCH_DIR("/usr/local/lib")
SEARCH_DIR("/lib")
SEARCH_DIR("/usr/lib");
A 64-bit system may see a few different directories. For example,
here is the output from an x86_64 machine:
SEARCH_DIR("/usr/x86_64-unknown-linux-gnu/lib64")
SEARCH_DIR("/usr/local/lib64")
SEARCH_DIR("/lib64")
SEARCH_DIR("/usr/lib64")
SEARCH_DIR("/usr/x86_64-unknown-linux-gnu/lib")
SEARCH_DIR("/usr/local/lib")
SEARCH_DIR("/lib")
SEARCH_DIR("/usr/lib");
Next make sure that we're using the correct libc:
grep "/lib.*/libc.so.6 " dummy.log
The output of the last command (allowing for a lib64 directory on
64-bit hosts) should be:
attempt to open /lib/libc.so.6 succeeded
Lastly, make sure GCC is using the correct dynamic linker:
grep found dummy.log
The output of the last command should be (allowing for
platform-specific differences in dynamic linker name and a lib64
directory on 64-bit hosts):
found ld-linux.so.2 at /lib/ld-linux.so.2
If the output does not appear as shown above or is not received at
all, then something is seriously wrong. Investigate and retrace the
steps to find out where the problem is and correct it. The most
likely reason is that something went wrong with the specs file
adjustment. Any issues will need to be resolved before continuing
on with the process.
Once everything is working correctly, clean up the test files:
rm -v dummy.c a.out dummy.log
Finally, move a misplaced file:
mkdir -pv /usr/share/gdb/auto-load/usr/lib
mv -v /usr/lib/*gdb.py /usr/share/gdb/auto-load/usr/lib