6.17. GCC-4.9.1

The GCC package contains the GNU compiler collection, which includes the C and C++ compilers.

Approximate build time: 83 SBU
Required disk space: 2.5 GB

6.17.1. Installation of GCC

As in Chapter 5, fix a problem identified upstream:

sed -i 's/if \((code.*))\)/if (\1 \&\& \!DEBUG_INSN_P (insn))/' gcc/sched-deps.c

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-4.9.1/configure        \
     --prefix=/usr            \
     --enable-languages=c,c++ \
     --disable-multilib       \
     --disable-bootstrap      \

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:


Setting this environment variable prevents a hard-coded path to /tools/bin/sed.


This switch tells GCC to link to the system installed copy of the Zlib library, rather than its own internal copy.

Compile the package:



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:


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/development/ 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)/4.9.1/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/4.9.1/../../../crt1.o succeeded
/usr/lib/gcc/i686-pc-linux-gnu/4.9.1/../../../crti.o succeeded
/usr/lib/gcc/i686-pc-linux-gnu/4.9.1/../../../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:

Again, note that the directory named after your target triplet may be different than the above, depending on your architecture.



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'

The output of the last command should be:


A 64-bit system may see a few different directories. For example, here is the output from an x86_64 machine:


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

6.17.2. Contents of GCC

Installed programs: c++, cc (link to gcc), cpp, g++, gcc, gcc-ar, gcc-nm, gcc-ranlib, and gcov
Installed libraries: libasan.{a,so}, libatomic.{a,so}, libgcc.a, libgcc_eh.a, libgcc_s.so, libgcov.a, libgomp.{a,so}, libiberty.a, libitm.{a,so}, liblto_plugin.so, libquadmath.{a,so}, libssp.{a,so}, libssp_nonshared.a, libstdc++.{a,so}, libsupc++.a and libtsan.{a,so}
Installed directories: /usr/include/c++, /usr/lib/gcc, /usr/libexec/gcc, /usr/share/gcc-4.9.1

Short Descriptions


The C++ compiler


The C compiler


The C preprocessor; it is used by the compiler to expand the #include, #define, and similar statements in the source files


The C++ compiler


The C compiler


A wrapper around ar that adds a plugin to the command line. This program is only used to add "link time optization" and is not useful with the default build options.


A wrapper around nm that adds a plugin to the command line. This program is only used to add "link time optization" and is not useful with the default build options.


A wrapper around ranlib that adds a plugin to the command line. This program is only used to add "link time optization" and is not useful with the default build options.


A coverage testing tool; it is used to analyze programs to determine where optimizations will have the most effect


The Address Sanitizer runtime library


Contains run-time support for gcc


This library is linked in to a program when GCC is instructed to enable profiling


GNU implementation of the OpenMP API for multi-platform shared-memory parallel programming in C/C++ and Fortran


Contains routines used by various GNU programs, including getopt, obstack, strerror, strtol, and strtoul


GCC's Link Time Optimization (LTO) plugin allows GCC to perform optimizations across compilation units.


GCC Quad Precision Math Library API


Contains routines supporting GCC's stack-smashing protection functionality


The standard C++ library


Provides supporting routines for the C++ programming language


The Thread Sanitizer runtime library