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<h1 class="settitle">Installing GCC: Building</h1>
+<a name="index-Installing-GCC_003a-Building-1"></a>
Now that GCC is configured, you are ready to build the compiler and
runtime libraries.
- <p>We <strong>highly</strong> recommend that GCC be built using GNU make;
-other versions may work, then again they might not.
-GNU make is required for compiling GNAT (the Ada compiler) and the Java
-runtime library.
-
- <p>(For example, many broken versions of make will fail if you use the
-recommended setup where <var>objdir</var> is different from <var>srcdir</var>.
-Other broken versions may recompile parts of the compiler when
-installing the compiler.)
-
<p>Some commands executed when making the compiler may fail (return a
-nonzero status) and be ignored by <code>make</code>. These failures, which
+nonzero status) and be ignored by <samp><span class="command">make</span></samp>. These failures, which
are often due to files that were not found, are expected, and can safely
be ignored.
<p>It is normal to have compiler warnings when compiling certain files.
Unless you are a GCC developer, you can generally ignore these warnings
-unless they cause compilation to fail.
+unless they cause compilation to fail. Developers should attempt to fix
+any warnings encountered, however they can temporarily continue past
+warnings-as-errors by specifying the configure flag
+<samp><span class="option">--disable-werror</span></samp>.
<p>On certain old systems, defining certain environment variables such as
-<code>CC</code> can interfere with the functioning of <code>make</code>.
+<samp><span class="env">CC</span></samp> can interfere with the functioning of <samp><span class="command">make</span></samp>.
<p>If you encounter seemingly strange errors when trying to build the
compiler in a directory other than the source directory, it could be
directory. Make sure you have done all the necessary preparations.
<p>If you build GCC on a BSD system using a directory stored in an old System
-V file system, problems may occur in running <code>fixincludes</code> if the
+V file system, problems may occur in running <samp><span class="command">fixincludes</span></samp> if the
System V file system doesn't support symbolic links. These problems
result in a failure to fix the declaration of <code>size_t</code> in
-<code>sys/types.h</code>. If you find that <code>size_t</code> is a signed type and
+<samp><span class="file">sys/types.h</span></samp>. If you find that <code>size_t</code> is a signed type and
that type mismatches occur, this could be the cause.
<p>The solution is not to use such a directory for building GCC.
- <p>When building from CVS or snapshots, or if you modify parser sources,
-you need the Bison parser generator installed. Any version 1.25 or
-later should work; older versions may also work. If you do not modify
-parser sources, releases contain the Bison-generated files and you do
-not need Bison installed to build them.
+ <p>Similarly, when building from SVN or snapshots, or if you modify
+<samp><span class="file">*.l</span></samp> files, you need the Flex lexical analyzer generator
+installed. If you do not modify <samp><span class="file">*.l</span></samp> files, releases contain
+the Flex-generated files and you do not need Flex installed to build
+them. There is still one Flex-based lexical analyzer (part of the
+build machinery, not of GCC itself) that is used even if you only
+build the C front end.
- <p>When building from CVS or snapshots, or if you modify Texinfo
-documentation, you need version 4.1 or later of Texinfo installed if you
+ <p>When building from SVN or snapshots, or if you modify Texinfo
+documentation, you need version 4.7 or later of Texinfo installed if you
want Info documentation to be regenerated. Releases contain Info
documentation pre-built for the unmodified documentation in the release.
<h3 class="section"><a name="TOC0"></a>Building a native compiler</h3>
- <p>For a native build issue the command <code>make bootstrap</code>. This
-will build the entire GCC system, which includes the following steps:
+<p>For a native build, the default configuration is to perform
+a 3-stage bootstrap of the compiler when ‘<samp><span class="samp">make</span></samp>’ is invoked.
+This will build the entire GCC system and ensure that it compiles
+itself correctly. It can be disabled with the <samp><span class="option">--disable-bootstrap</span></samp>
+parameter to ‘<samp><span class="samp">configure</span></samp>’, but bootstrapping is suggested because
+the compiler will be tested more completely and could also have
+better performance.
- <ul>
-<li>Build host tools necessary to build the compiler such as texinfo, bison,
-gperf.
+ <p>The bootstrapping process will complete the following steps:
- <li>Build target tools for use by the compiler such as binutils (bfd,
-binutils, gas, gprof, ld, and opcodes)
-if they have been individually linked
-or moved into the top level GCC source tree before configuring.
+ <ul>
+<li>Build tools necessary to build the compiler.
- <li>Perform a 3-stage bootstrap of the compiler.
+ <li>Perform a 3-stage bootstrap of the compiler. This includes building
+three times the target tools for use by the compiler such as binutils
+(bfd, binutils, gas, gprof, ld, and opcodes) if they have been
+individually linked or moved into the top level GCC source tree before
+configuring.
<li>Perform a comparison test of the stage2 and stage3 compilers.
</ul>
- <p>If you are short on disk space you might consider <code>make
-bootstrap-lean</code> instead. This is identical to <code>make
-bootstrap</code> except that object files from the stage1 and
+ <p>If you are short on disk space you might consider ‘<samp><span class="samp">make
+bootstrap-lean</span></samp>’ instead. The sequence of compilation is the
+same described above, but object files from the stage1 and
stage2 of the 3-stage bootstrap of the compiler are deleted as
soon as they are no longer needed.
- <p>If you want to save additional space during the bootstrap and in
-the final installation as well, you can build the compiler binaries
-without debugging information as in the following example. This will save
-roughly 40% of disk space both for the bootstrap and the final installation.
-(Libraries will still contain debugging information.)
-
-<pre class="example"> make CFLAGS='-O' LIBCFLAGS='-g -O2' \
- LIBCXXFLAGS='-g -O2 -fno-implicit-templates' bootstrap
- </pre>
-
- <p>If you wish to use non-default GCC flags when compiling the stage2 and
-stage3 compilers, set <code>BOOT_CFLAGS</code> on the command line when doing
-<code>make bootstrap</code>. Non-default optimization flags are less well
-tested here than the default of <code>-g -O2</code>, but should still work.
-In a few cases, you may find that you need to specify special flags such
-as <code>-msoft-float</code> here to complete the bootstrap; or, if the
-native compiler miscompiles the stage1 compiler, you may need to work
-around this, by choosing <code>BOOT_CFLAGS</code> to avoid the parts of the
-stage1 compiler that were miscompiled, or by using <code>make
-bootstrap4</code> to increase the number of stages of bootstrap.
-
- <p>If you used the flag <code>--enable-languages=...</code> to restrict
+ <p>If you wish to use non-default GCC flags when compiling the stage2
+and stage3 compilers, set <code>BOOT_CFLAGS</code> on the command line when
+doing ‘<samp><span class="samp">make</span></samp>’. For example, if you want to save additional space
+during the bootstrap and in the final installation as well, you can
+build the compiler binaries without debugging information as in the
+following example. This will save roughly 40% of disk space both for
+the bootstrap and the final installation. (Libraries will still contain
+debugging information.)
+
+<pre class="smallexample"> make BOOT_CFLAGS='-O' bootstrap
+</pre>
+ <p>You can place non-default optimization flags into <code>BOOT_CFLAGS</code>; they
+are less well tested here than the default of ‘<samp><span class="samp">-g -O2</span></samp>’, but should
+still work. In a few cases, you may find that you need to specify special
+flags such as <samp><span class="option">-msoft-float</span></samp> here to complete the bootstrap; or,
+if the native compiler miscompiles the stage1 compiler, you may need
+to work around this, by choosing <code>BOOT_CFLAGS</code> to avoid the parts
+of the stage1 compiler that were miscompiled, or by using ‘<samp><span class="samp">make
+bootstrap4</span></samp>’ to increase the number of stages of bootstrap.
+
+ <p><code>BOOT_CFLAGS</code> does not apply to bootstrapped target libraries.
+Since these are always compiled with the compiler currently being
+bootstrapped, you can use <code>CFLAGS_FOR_TARGET</code> to modify their
+compilation flags, as for non-bootstrapped target libraries.
+Again, if the native compiler miscompiles the stage1 compiler, you may
+need to work around this by avoiding non-working parts of the stage1
+compiler. Use <code>STAGE1_LIBCFLAGS</code> to this end.
+
+ <p>If you used the flag <samp><span class="option">--enable-languages=...</span></samp> to restrict
the compilers to be built, only those you've actually enabled will be
built. This will of course only build those runtime libraries, for
which the particular compiler has been built. Please note,
-that re-defining <code>LANGUAGES</code> when calling <code>make bootstrap</code>
+that re-defining <samp><span class="env">LANGUAGES</span></samp> when calling ‘<samp><span class="samp">make</span></samp>’
<strong>does not</strong> work anymore!
<p>If the comparison of stage2 and stage3 fails, this normally indicates
that the stage2 compiler has compiled GCC incorrectly, and is therefore
a potentially serious bug which you should investigate and report. (On
a few systems, meaningful comparison of object files is impossible; they
-always appear "different". If you encounter this problem, you will
-need to disable comparison in the <code>Makefile</code>.)
+always appear “different”. If you encounter this problem, you will
+need to disable comparison in the <samp><span class="file">Makefile</span></samp>.)
-<h3 class="section"><a name="TOC1"></a>Building a cross compiler</h3>
+ <p>If you do not want to bootstrap your compiler, you can configure with
+<samp><span class="option">--disable-bootstrap</span></samp>. In particular cases, you may want to
+bootstrap your compiler even if the target system is not the same as
+the one you are building on: for example, you could build a
+<code>powerpc-unknown-linux-gnu</code> toolchain on a
+<code>powerpc64-unknown-linux-gnu</code> host. In this case, pass
+<samp><span class="option">--enable-bootstrap</span></samp> to the configure script.
- <p>We recommend reading the
-<a href="http://www.objsw.com/CrossGCC/">crossgcc FAQ</a>
-for information about building cross compilers.
+<h3 class="section"><a name="TOC1"></a>Building a cross compiler</h3>
-
<p>When building a cross compiler, it is not generally possible to do a
+<p>When building a cross compiler, it is not generally possible to do a
3-stage bootstrap of the compiler. This makes for an interesting problem
as parts of GCC can only be built with GCC.
cross compiler. The installed native compiler needs to be GCC version
2.95 or later.
+ <p>If the cross compiler is to be built with support for the Java
+programming language and the ability to compile .java source files is
+desired, the installed native compiler used to build the cross
+compiler needs to be the same GCC version as the cross compiler. In
+addition the cross compiler needs to be configured with
+<samp><span class="option">--with-ecj-jar=...</span></samp>.
+
<p>Assuming you have already installed a native copy of GCC and configured
-your cross compiler, issue the command <code>make</code>, which performs the
+your cross compiler, issue the command <samp><span class="command">make</span></samp>, which performs the
following steps:
<ul>
-<li>Build host tools necessary to build the compiler such as texinfo, bison,
-gperf.
+<li>Build host tools necessary to build the compiler.
<li>Build target tools for use by the compiler such as binutils (bfd,
binutils, gas, gprof, ld, and opcodes)
<p>Note that if an error occurs in any step the make process will exit.
+ <p>If you are not building GNU binutils in the same source tree as GCC,
+you will need a cross-assembler and cross-linker installed before
+configuring GCC. Put them in the directory
+<samp><var>prefix</var><span class="file">/</span><var>target</var><span class="file">/bin</span></samp>. Here is a table of the tools
+you should put in this directory:
+
+ <dl>
+<dt><samp><span class="file">as</span></samp><dd>This should be the cross-assembler.
+
+ <br><dt><samp><span class="file">ld</span></samp><dd>This should be the cross-linker.
+
+ <br><dt><samp><span class="file">ar</span></samp><dd>This should be the cross-archiver: a program which can manipulate
+archive files (linker libraries) in the target machine's format.
+
+ <br><dt><samp><span class="file">ranlib</span></samp><dd>This should be a program to construct a symbol table in an archive file.
+</dl>
+
+ <p>The installation of GCC will find these programs in that directory,
+and copy or link them to the proper place to for the cross-compiler to
+find them when run later.
+
+ <p>The easiest way to provide these files is to build the Binutils package.
+Configure it with the same <samp><span class="option">--host</span></samp> and <samp><span class="option">--target</span></samp>
+options that you use for configuring GCC, then build and install
+them. They install their executables automatically into the proper
+directory. Alas, they do not support all the targets that GCC
+supports.
+
+ <p>If you are not building a C library in the same source tree as GCC,
+you should also provide the target libraries and headers before
+configuring GCC, specifying the directories with
+<samp><span class="option">--with-sysroot</span></samp> or <samp><span class="option">--with-headers</span></samp> and
+<samp><span class="option">--with-libs</span></samp>. Many targets also require “start files” such
+as <samp><span class="file">crt0.o</span></samp> and
+<samp><span class="file">crtn.o</span></samp> which are linked into each executable. There may be several
+alternatives for <samp><span class="file">crt0.o</span></samp>, for use with profiling or other
+compilation options. Check your target's definition of
+<code>STARTFILE_SPEC</code> to find out what start files it uses.
+
<h3 class="section"><a name="TOC2"></a>Building in parallel</h3>
- <p>If you have a multiprocessor system you can use <code>make bootstrap
-MAKE="make -j 2" -j 2</code> or just <code>make -j 2 bootstrap</code>
-for GNU Make 3.79 and above instead of just <code>make bootstrap</code>
-when building GCC. You can use a bigger number instead of two if
-you like. In most cases, it won't help to use a number bigger than
-the number of processors in your machine.
+<p>GNU Make 3.79 and above, which is necessary to build GCC, support
+building in parallel. To activate this, you can use ‘<samp><span class="samp">make -j 2</span></samp>’
+instead of ‘<samp><span class="samp">make</span></samp>’. You can also specify a bigger number, and
+in most cases using a value greater than the number of processors in
+your machine will result in fewer and shorter I/O latency hits, thus
+improving overall throughput; this is especially true for slow drives
+and network filesystems.
<h3 class="section"><a name="TOC3"></a>Building the Ada compiler</h3>
- <p>In order to build GNAT, the Ada compiler, you need a working GNAT
-compiler (GNAT version 3.13 or later, or GCC version 3.1 or later),
-since the Ada front end is written in Ada (with some
-GNAT-specific extensions), and GNU make.
-
- <p>However, you do not need a full installation of GNAT, just the GNAT
-binary <code>gnat1</code>, a copy of <code>gnatbind</code>, and a compiler driver
-which can deal with Ada input (by invoking the <code>gnat1</code> binary).
-You can specify this compiler driver by setting the <code>ADAC</code>
-environment variable at the configure step. <code>configure</code> can
-detect the driver automatically if it has got a common name such as
-<code>gcc</code> or <code>gnatgcc</code>. Of course, you still need a working
-C compiler (the compiler driver can be different or not).
-<code>configure</code> does not test whether the GNAT installation works
+<p>In order to build GNAT, the Ada compiler, you need a working GNAT
+compiler (GCC version 3.4 or later).
+This includes GNAT tools such as <samp><span class="command">gnatmake</span></samp> and
+<samp><span class="command">gnatlink</span></samp>, since the Ada front end is written in Ada and
+uses some GNAT-specific extensions.
+
+ <p>In order to build a cross compiler, it is suggested to install
+the new compiler as native first, and then use it to build the cross
+compiler.
+
+ <p><samp><span class="command">configure</span></samp> does not test whether the GNAT installation works
and has a sufficiently recent version; if too old a GNAT version is
-installed, the build will fail unless <code>--enable-languages</code> is
+installed, the build will fail unless <samp><span class="option">--enable-languages</span></samp> is
used to disable building the Ada front end.
- <p>Additional build tools (such as <code>gnatmake</code>) or a working GNAT
-run-time library installation are usually <em>not</em> required. However,
-if you want to bootstrap the compiler using a minimal version of GNAT,
-you have to issue the following commands before invoking <code>make
-bootstrap</code> (this assumes that you start with an unmodified and consistent
-source distribution):
-
-<pre class="example"> cd <var>srcdir</var>/gcc/ada
- touch treeprs.ads [es]info.h nmake.ad[bs]
- </pre>
-
- <p>At the moment, the GNAT library and several tools for GNAT are not built
-by <code>make bootstrap</code>. You have to invoke
-<code>make gnatlib_and_tools</code> in the <code></code><var>objdir</var><code>/gcc</code>
-subdirectory before proceeding with the next steps.
-
- <p>For example, you can build a native Ada compiler by issuing the
-following commands (assuming <code>make</code> is GNU make):
-
-<pre class="example"> cd <var>objdir</var>
- <var>srcdir</var>/configure --enable-languages=c,ada
- cd <var>srcdir</var>/gcc/ada
- touch treeprs.ads [es]info.h nmake.ad[bs]
- cd <var>objdir</var>
- make bootstrap
- cd gcc
- make gnatlib_and_tools
- cd ..
- </pre>
-
- <p>Currently, when compiling the Ada front end, you cannot use the parallel
-build feature described in the previous section.
-
- <hr />
-<p>
-<a href="./index.html">Return to the GCC Installation page</a>
-
- </body></html>
+ <p><samp><span class="env">ADA_INCLUDE_PATH</span></samp> and <samp><span class="env">ADA_OBJECT_PATH</span></samp> environment variables
+must not be set when building the Ada compiler, the Ada tools, or the
+Ada runtime libraries. You can check that your build environment is clean
+by verifying that ‘<samp><span class="samp">gnatls -v</span></samp>’ lists only one explicit path in each
+section.
+
+<h3 class="section"><a name="TOC4"></a>Building with profile feedback</h3>
+
+<p>It is possible to use profile feedback to optimize the compiler itself. This
+should result in a faster compiler binary. Experiments done on x86 using gcc
+3.3 showed approximately 7 percent speedup on compiling C programs. To
+bootstrap the compiler with profile feedback, use <code>make profiledbootstrap</code>.
+
+ <p>When ‘<samp><span class="samp">make profiledbootstrap</span></samp>’ is run, it will first build a <code>stage1</code>
+compiler. This compiler is used to build a <code>stageprofile</code> compiler
+instrumented to collect execution counts of instruction and branch
+probabilities. Then runtime libraries are compiled with profile collected.
+Finally a <code>stagefeedback</code> compiler is built using the information collected.
+
+ <p>Unlike standard bootstrap, several additional restrictions apply. The
+compiler used to build <code>stage1</code> needs to support a 64-bit integral type.
+It is recommended to only use GCC for this. Also parallel make is currently
+not supported since collisions in profile collecting may occur.
+
+ <p><hr />
+<p><a href="./index.html">Return to the GCC Installation page</a>
+
+<!-- ***Testing***************************************************************** -->
+<!-- ***Final install*********************************************************** -->
+<!-- ***Binaries**************************************************************** -->
+<!-- ***Specific**************************************************************** -->
+<!-- ***Old documentation****************************************************** -->
+<!-- ***GFDL******************************************************************** -->
+<!-- *************************************************************************** -->
+<!-- Part 6 The End of the Document -->
+</body></html>
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