diff options
Diffstat (limited to 'contrib/gcc/faq.html')
| -rw-r--r-- | contrib/gcc/faq.html | 698 |
1 files changed, 0 insertions, 698 deletions
diff --git a/contrib/gcc/faq.html b/contrib/gcc/faq.html deleted file mode 100644 index 9170647e31fb..000000000000 --- a/contrib/gcc/faq.html +++ /dev/null @@ -1,698 +0,0 @@ -<html> - -<head> -<title>GCC Frequently Asked Questions</title> -</head> - -<body> - -<h1>GCC Frequently Asked Questions</h1> - -<p>The latest version of this document is always available at -<a href="http://www.gnu.org/software/gcc/faq.html">http://www.gnu.org/software/gcc/faq.html</a>.</p> - -<p>This FAQ tries to answer specific questions concerning GCC. For -general information regarding C, C++, resp. Fortran please check the -<a href="http://www.eskimo.com/~scs/C-faq/top.html">comp.lang.c FAQ</a>, -<a href="http://www.research.att.com/~austern/csc/faq.html">comp.std.c++ -FAQ</a>, -and the <a href="http://www.fortran.com/fortran/info.html">Fortran -Information page</a>.</p> - -<p>Other GCC-related FAQs: - <a href="http://gcc.gnu.org/onlinedocs/libstdc++/faq/index.html"> - libstdc++-v3</a>, and - <a href="http://gcc.gnu.org/java/faq.html">GCJ</a>.</p> - -<hr /> -<h1>Questions</h1> -<ol> - <li><a href="#general">General information</a> - <ol> - <li><a href="#gcc">What is the relationship between GCC and EGCS?</a></li> - <li><a href="#cygnus">What is the relationship between GCC and Cygnus / Red Hat?</a></li> - <li><a href="#open-development">What is an open development model?</a></li> - <li><a href="#bugreport">How do I report a bug?</a></li> - <li><a href="#support">How do I get a bug fixed or a feature added?</a></li> - <li><a href="#platforms">Does GCC work on my platform?</a></li> - </ol></li> - - <li><a href="#installation">Installation</a> - <ol> - <li><a href="#multiple">How to install multiple versions of GCC</a></li> - <li><a href="#rpath">Dynamic linker is unable to find GCC libraries</a></li> - <li><a href="#rpath">libstdc++/libio tests fail badly with --enable-shared</a></li> - <li><a href="#gas">GCC can not find GNU as/GNU ld</a></li> - <li><a href="#environ">cpp: Usage:... Error</a></li> - <li><a href="#optimizing">Optimizing the compiler itself</a></li> - </ol></li> - - <li><a href="#testsuite">Testsuite problems</a> - <ol> - <li><a href="#dejagnu">Unable to run the testsuite</a></li> - <li><a href="#testoptions">How do I pass flags like - <code>-fnew-abi</code> to the testsuite?</a></li> - <li><a href="#multipletests">How can I run the test suite with multiple options?</a></li> - </ol></li> - - <li><a href="#old">Older versions of GCC</a> - <ol> - <li><a href="#2.95sstream">Is there a stringstream / sstream for GCC 2.95.2?</a></li> - </ol></li> - - <li><a href="#misc">Miscellaneous</a> - <ol> - <li><a href="#memexhausted">Virtual memory exhausted</a></li> - <li><a href="#friend">Friend Templates</a></li> - <li><a href="#dso"><code>dynamic_cast</code>, <code>throw</code>, <code>typeid</code> don't work with shared libraries</a></li> - <li><a href="#generated_files">Why do I need autoconf, bison, xgettext, automake, etc?</a></li> - <li><a href="#picflag-needed">Why can't I build a shared library?</a></li> - <li><a href="#squangle">How to work around too long C++ symbol names? - (<tt>-fsquangle</tt>)</a></li> - <li><a href="#vtables">When building C++, the linker says my constructors, destructors or virtual tables are undefined, but I defined them</a></li> - <li><a href="#incremental">Will GCC someday include an incremental linker?</a></li> - </ol></li> -</ol> - - -<hr /> -<a name="general"></a> -<h1>General information</h1> - -<h2><a name="gcc">What is the relationship between GCC and EGCS?</a></h2> - -<p>In 1990/1991 gcc version 1 had reached a point of stability. For the -targets it could support, it worked well. It had limitations inherent in -its design that would be difficult to resolve, so a major effort was made -to resolve those limitiations and gcc version 2 was the result.</p> - -<p>When we had gcc2 in a useful state, development efforts on gcc1 stopped -and we all concentrated on making gcc2 better than gcc1 could ever be. This -is the kind of step forward we wanted to make with the EGCS project when it -was formed in 1997.</p> - -<p>In April 1999 the Free Software Foundation officially halted -development on the gcc2 compiler and appointed the EGCS project as the -official GCC maintainers. The net result was a single project which -carries forward GCC development under the ultimate control of the -<a href="steering.html">GCC Steering Committee</a>.</p> - - -<hr /> -<h2><a name="cygnus">What is the relationship between GCC and Cygnus / Red Hat?</a></h2> - -<p>It is a common mis-conception that Red Hat controls GCC either -directly or indirectly.</p> - -<p>While Red Hat does donate hardware, network connections, code and -developer time to GCC development, Red Hat does not control GCC.</p> - -<p>Overall control of GCC is in the hands of the -<a href="steering.html">GCC Steering Committee</a> -which includes people from a variety of different organizations and -backgrounds. The purpose of the steering committee is to make -decisions in the best interest of GCC and to help ensure that no -individual or company has control over the project.</p> - -<p>To summarize, Red Hat contributes to the GCC project, but does not exert -a controlling influence over GCC.</p> - -<hr /> -<h2><a name="open-development">What is an open development model?</a></h2> - -<p>We are using a bazaar style -<a href="#cathedral-vs-bazaar"><b>[1]</b></a> -approach to GCC development: we make snapshots publicly available to -anyone who wants to try them; we welcome anyone to join -the development mailing list. All of the discussions on the -development mailing list are available via the web. We're going to be -making releases with a much higher frequency than they have been made -in the past.</p> - -<p>In addition to weekly snapshots of the GCC development sources, we -have the sources readable from a CVS server by anyone. Furthermore we -are using remote CVS to allow remote maintainers write access to the -sources.</p> - -<p>There have been many potential GCC developers who were not able to -participate in GCC development in the past. We want these people to -help in any way they can; we ultimately want GCC to be the best compiler -in the world.</p> - -<p>A compiler is a complicated piece of software, there will still be -strong central maintainers who will reject patches, who will demand -documentation of implementations, and who will keep the level of -quality as high as it is today. Code that could use wider testing may -be integrated--code that is simply ill-conceived won't be.</p> - -<p>GCC is not the first piece of software to use this open development -process; FreeBSD, the Emacs lisp repository, and the Linux kernel are -a few examples of the bazaar style of development.</p> - -<p>With GCC, we are adding new features and optimizations at a -rate that has not been done since the creation of gcc2; these -additions inevitably have a temporarily destabilizing effect. -With the help of developers working together with this bazaar style -development, the resulting stability and quality levels will be better -than we've had before.</p> - -<blockquote> -<a name="cathedral-vs-bazaar"><b>[1]</b></a> - We've been discussing different development models a lot over the - past few months. The paper which started all of this introduced two - terms: A <b>cathedral</b> development model versus a <b>bazaar</b> - development model. The paper is written by Eric S. Raymond, it is - called ``<a - href="http://www.tuxedo.org/~esr/writings/cathedral-bazaar/">The - Cathedral and the Bazaar</a>''. The paper is a useful starting point - for discussions. -</blockquote> - - -<hr /> -<h2><a name="bugreport">How do I report a bug?</a></h2> - -<p>There are complete instructions <a href="bugs.html">here</a>.</p> - - -<hr /> -<h2><a name="support">How do I get a bug fixed or a feature added?</a></h2> - -<p>There are lots of ways to get something fixed. The list below may be -incomplete, but it covers many of the common cases. These are listed -roughly in order of increasing difficulty for the average GCC user, -meaning someone who is not skilled in the internals of GCC, and where -difficulty is measured in terms of the time required to fix the bug. -No alternative is better than any other; each has its benefits and -disadvantages.</p> - -<ul> -<li>Hire someone to fix it for you. There are various companies and - individuals providing support for GCC. This alternative costs - money, but is relatively likely to get results.</li> - -<li><a href="bugs.html">Report the problem to the GCC GNATS bug tracking system</a> - and hope that someone will be kind - enough to fix it for you. While this is certainly possible, and - often happens, there is no guarantee that it will. You should - not expect the same response from this method that you would see - from a commercial support organization since the people who read - GCC bug reports, if they choose to help you, will be volunteering their - time. This alternative will work best if you follow the directions - on <a href="bugs.html">submitting bugreports</a>.</li> - -<li>Fix it yourself. This alternative will probably bring results, - if you work hard enough, but will probably take a lot of time, - and, depending on the quality of your work and the perceived - benefits of your changes, your code may or may not ever make it - into an official release of GCC.</li> -</ul> - -<hr /> - -<h2><a name="platforms">Does GCC work on my platform?</a></h2> - -<p>The host/target specific installation notes for GCC include information -about known problems with installing or using GCC on particular platforms. -These are included in the sources for a release in INSTALL/specific.html, -and the <a href="http://gcc.gnu.org/install/specific.html">latest version</a> -is always available at the GCC web site. -Reports of <a href="http://gcc.gnu.org/buildstat.html">successful builds</a> -for several versions of GCC are also available at the web site.</p> - -<hr /> -<a name="installation"></a> -<h1>Installation</h1> - -<h2><a name="multiple">How to install multiple versions of GCC</a></h2> - -<p>It may be desirable to install multiple versions of the compiler on -the same system. This can be done by using different prefix paths at -configure time and a few symlinks.</p> - -<p>Basically, configure the two compilers with different --prefix options, -then build and install each compiler. Assume you want "gcc" to be the latest -compiler and available in /usr/local/bin; also assume that you want "gcc2" -to be the older gcc2 compiler and also available in /usr/local/bin.</p> - -<p>The easiest way to do this is to configure the new GCC with -<code>--prefix=/usr/local/gcc</code> and the older gcc2 with -<code>--prefix=/usr/local/gcc2</code>. Build and install both -compilers. Then make a symlink from <code>/usr/local/bin/gcc</code> -to <code>/usr/local/gcc/bin/gcc</code> and from -<code>/usr/local/bin/gcc2</code> to -<code>/usr/local/gcc2/bin/gcc</code>. Create similar links for the -"g++", "c++" and "g77" compiler drivers.</p> - -<p>An alternative to using symlinks is to configure with a -<code>--program-transform-name</code> option. This option specifies a -sed command to process installed program names with. Using it you can, -for instance, have all the new GCC programs installed as "new-gcc" and -the like. You will still have to specify different -<code>--prefix</code> options for new GCC and old GCC, because it is -only the executable program names that are transformed. The difference -is that you (as administrator) do not have to set up symlinks, but -must specify additional directories in your (as a user) PATH. A -complication with <code>--program-transform-name</code> is that the -sed command invariably contains characters significant to the shell, -and these have to be escaped correctly, also it is not possible to use -"^" or "$" in the command. Here is the option to prefix "new-" to the -new GCC installed programs:</p> -<blockquote><code> ---program-transform-name='s,\\\\(.*\\\\),new-\\\\1,' -</code></blockquote> -<p>With the above <code>--prefix</code> option, that will install the new -GCC programs into <code>/usr/local/gcc/bin</code> with names prefixed -by "new-". You can use <code>--program-transform-name</code> if you -have multiple versions of GCC, and wish to be sure about which version -you are invoking.</p> - -<p>If you use <code>--prefix</code>, GCC may have difficulty locating a GNU -assembler or linker on your system, <a href="#gas">GCC can not find GNU -as/GNU ld</a> explains how to deal with this.</p> - -<p>Another option that may be easier is to use the -<code>--program-prefix=</code> or <code>--program-suffix=</code> -options to configure. So if you're installing GCC 2.95.2 and don't -want to disturb the current version of GCC in -<code>/usr/local/bin/</code>, you could do</p> -<blockquote><code> -configure --program-suffix=-2.95.2 <other configure options> -</code></blockquote> -<p>This should result in GCC being installed as -<code>/usr/local/bin/gcc-2.95.2</code> instead of -<code>/usr/local/bin/gcc</code>.</p> - -<hr /> -<h2><a name="rpath">Dynamic linker is unable to find GCC libraries</a></h2> - -<p>This problem manifests itself by programs not finding shared -libraries they depend on when the programs are started. Note this -problem often manifests itself with failures in the libio/libstdc++ -tests after configuring with <code>--enable-shared</code> and building GCC.</p> - -<p>GCC does not specify a runpath so that the dynamic linker can find -dynamic libraries at runtime.</p> - -<p>The short explanation is that if you always pass a -R option to the -linker, then your programs become dependent on directories which -may be NFS mounted, and programs may hang unnecessarily when an -NFS server goes down.</p> - -<p>The problem is not programs that do require the directories; those -programs are going to hang no matter what you do. The problem is -programs that do not require the directories.</p> - -<p>SunOS effectively always passed a <code>-R</code> option for every -<code>-L</code> option; this was a bad idea, and so it was removed for -Solaris. We should not recreate it.</p> - -<p>However, if you feel you really need such an option to be passed -automatically to the linker, you may add it to the GCC specs file. -This file can be found in the same directory that contains cc1 (run -<code>gcc -print-prog-name=cc1</code> to find it). You may add linker -flags such as <code>-R</code> or <code>-rpath</code>, depending on -platform and linker, to the <code>*link</code> or <code>*lib</code> -specs.</p> - -<p>Another alternative is to install a wrapper script around gcc, g++ -or ld that adds the appropriate directory to the environment variable -<code>LD_RUN_PATH</code> or equivalent (again, it's -platform-dependent).</p> - -<p>Yet another option, that works on a few platforms, is to hard-code -the full pathname of the library into its soname. This can only be -accomplished by modifying the appropriate <tt>.ml</tt> file within -<tt>libstdc++/config</tt> (and also <tt>libg++/config</tt>, if you are -building libg++), so that <code>$(libdir)/</code> appears just before -the library name in <code>-soname</code> or <code>-h</code> options.</p> - -<hr /> -<h2><a name="gas">GCC can not find GNU as/GNU ld</a></h2> -<p>GCC searches the PATH for an assembler and a loader, but it only -does so after searching a directory list hard-coded in the GCC -executables. Since, on most platforms, the hard-coded list includes -directories in which the system asembler and loader can be found, you -may have to take one of the following actions to arrange that GCC uses -the GNU versions of those programs.</p> - -<p>To ensure that GCC finds the GNU assembler (the GNU loader), which -are required by <a href="http://gcc.gnu.org/install/specific.html">some -configurations</a>, -you should configure these with the same --prefix option as you used -for GCC. Then build & install GNU as (GNU ld) and proceed with -building GCC.</p> - -<p>Another alternative is to create links to GNU as and ld in any of -the directories printed by the command `<tt>gcc -print-search-dirs | -grep '^programs:'</tt>'. The link to `<tt>ld</tt>' should be named -`<tt>real-ld</tt>' if `<tt>ld</tt>' already exists. If such links do -not exist while you're compiling GCC, you may have to create them in -the build directories too, within the <tt>gcc</tt> directory -<em>and</em> in all the <tt>gcc/stage*</tt> subdirectories.</p> - -<p>GCC 2.95 allows you to specify the full pathname of the assembler -and the linker to use. The configure flags are -`<tt>--with-as=/path/to/as</tt>' and `<tt>--with-ld=/path/to/ld</tt>'. -GCC will try to use these pathnames before looking for `<tt>as</tt>' -or `<tt>(real-)ld</tt>' in the standard search dirs. If, at -configure-time, the specified programs are found to be GNU utilities, -`<tt>--with-gnu-as</tt>' and `<tt>--with-gnu-ld</tt>' need not be -used; these flags will be auto-detected. One drawback of this option -is that it won't allow you to override the search path for assembler -and linker with command-line options <tt>-B/path/</tt> if the -specified filenames exist.</p> - -<hr /> -<h2><a name="environ">cpp: Usage:... Error</a></h2> - -<p>If you get an error like this when building GCC (particularly when building -__mulsi3), then you likely have a problem with your environment variables.</p> -<pre> - cpp: Usage: /usr/lib/gcc-lib/i586-unknown-linux-gnulibc1/2.7.2.3/cpp - [switches] input output -</pre> -<p>First look for an explicit '.' in either LIBRARY_PATH or GCC_EXEC_PREFIX -from your environment. If you do not find an explicit '.', look for -an empty pathname in those variables. Note that ':' at either the start -or end of these variables is an implicit '.' and will cause problems.</p> - -<p>Also note '::' in these paths will also cause similar problems.</p> - - -<hr /> -<h2><a name="optimizing">Optimizing the compiler itself</a></h2> - -<p>If you want to test a particular optimization option, it's useful to try -bootstrapping the compiler with that option turned on. For example, to -test the <code>-fssa</code> option, you could bootstrap like this:</p> - -<pre>make BOOT_CFLAGS="-O2 -fssa" bootstrap</pre> - - -<hr /> -<a name="testsuite"></a> -<h1>Testsuite problems</h1> - -<h2><a name="dejagnu">Unable to run the testsuite</a></h2> - -<p>If you get a message about unable to find "standard.exp" when trying to -run the GCC testsuites, then your dejagnu is too old to run the GCC tests. -You will need to get a newer version of dejagnu from -<a href="http://www.gnu.org/software/dejagnu/dejagnu.html"> - http://www.gnu.org/software/dejagnu/dejagnu.html</a>.</p> - -<hr /> -<h2><a name="testoptions">How do I pass flags like - <code>-fnew-abi</code> to the testsuite?</a></h2> - -<p>If you invoke <code>runtest</code> directly, you can use the -<code>--tool_opts</code> option, e.g:</p> -<pre> - runtest --tool_opts "-fnew-abi -fno-honor-std" <other options> -</pre> -<p>Or, if you use <code>make check</code> you can use the -<code>make</code> variable <code>RUNTESTFLAGS</code>, e.g:</p> -<pre> - make RUNTESTFLAGS="--tool_opts '-fnew-abi -fno-honor-std'" check-g++ -</pre> - -<hr /> -<h2><a name="multipletests"> How can I run the test suite with multiple options? </a></h2> - -<p>If you invoke <code>runtest</code> directly, you can use the -<code>--target_board</code> option, e.g:</p> -<pre> - runtest --target_board "unix{-fPIC,-fpic,}" <other options> -</pre> -<p>Or, if you use <code>make check</code> you can use the -<code>make</code> variable <code>RUNTESTFLAGS</code>, e.g:</p> -<pre> - make RUNTESTFLAGS="--target_board 'unix{-fPIC,-fpic,}'" check-gcc -</pre> -<p>Either of these examples will run the tests three times. Once -with <code>-fPIC</code>, once with <code>-fpic</code>, and once with -no additional flags.</p> - -<p>This technique is particularly useful on multilibbed targets.</p> - -<hr /> -<a name="old"></a> -<h1>Older versions of GCC and EGCS</h1> - -<h2><a name="2.95sstream">Is there a stringstream / sstream for GCC 2.95.2?</a></h2> - -<p>Yes, it's at: -<a href="http://gcc.gnu.org/ml/libstdc++/2000-q2/msg00700/sstream"> - http://gcc.gnu.org/ml/libstdc++/2000-q2/msg00700/sstream</a>.</p> - -<hr /> -<a name="misc"></a> -<h1>Miscellaneous</h1> - - - -<h2><a name="memexhausted">Virtual memory exhausted error</a></h2> - -<p> This error means your system ran out of memory; this can happen for large -files, particularly when optimizing. If you're getting this error you should -consider trying to simplify your files or reducing the optimization level.</p> - -<p>Note that using -pedantic or -Wreturn-type can cause an explosion in the -amount of memory needed for template-heavy C++ code, such as code that uses -STL. Also note that -Wall includes -Wreturn-type, so if you use -Wall you -will need to specify -Wno-return-type to turn it off.</p> - - -<hr /> -<h2><a name="friend">Friend Templates</a></h2> - -<p>In order to make a specialization of a template function a friend -of a (possibly template) class, you must explicitly state that the -friend function is a template, by appending angle brackets to its -name, and this template function must have been declared already. -Here's an example:</p> -<pre> -template <typename T> class foo { - friend void bar(foo<T>); -} -</pre> -<p>The above declaration declares a non-template function named -<code>bar</code>, so it must be explicitly defined for <b>each</b> -specialization of <code>foo</code>. A template definition of <code>bar</code> -won't do, because it is unrelated with the non-template declaration -above. So you'd have to end up writing:</p> -<pre> -void bar(foo<int>) { /* ... */ } -void bar(foo<void>) { /* ... */ } -</pre> -<p>If you meant <code>bar</code> to be a template function, you should -have forward-declared it as follows. Note that, since the template -function declaration refers to the template class, the template class -must be forward-declared too:</p> -<pre> -template <typename T> -class foo; - -template <typename T> -void bar(foo<T>); - -template <typename T> -class foo { - friend void bar<>(foo<T>); -}; - -template <typename T> -void bar(foo<T>) { /* ... */ } -</pre> -<p>In this case, the template argument list could be left empty, -because it can be implicitly deduced from the function arguments, but -the angle brackets must be present, otherwise the declaration will be -taken as a non-template function. Furthermore, in some cases, you may -have to explicitly specify the template arguments, to remove -ambiguity.</p> - -<p>An error in the last public comment draft of the ANSI/ISO C++ -Standard and the fact that previous releases of GCC would accept such -friend declarations as template declarations has led people to believe -that the forward declaration was not necessary, but, according to the -final version of the Standard, it is.</p> - - -<hr /> -<h2><a name="dso"><code>dynamic_cast</code>, <code>throw</code>, <code>typeid</code> don't work with shared libraries</a></h2> - -<p>The new C++ ABI in the GCC 3.0 series uses address comparisons, -rather than string compares, to determine type equality. This leads -to better performance. Like other objects that have to be present in the -final executable, these <code>std::typeinfo_t</code> objects have what -is called vague linkage because they are not tightly bound to any one -particular translation unit (object file). The compiler has to emit -them in any translation unit that requires their presence, and then -rely on the linking and loading process to make sure that only one of -them is active in the final executable. With static linking all of -these symbols are resolved at link time, but with dynamic linking, -further resolution occurs at load time. You have to ensure that -objects within a shared library are resolved against objects in the -executable and other shared libraries.</p> - -<ul> -<li>For a program which is linked against a shared library, no additional -precautions need taking.</li> - -<li>You cannot create a shared library with the "<code>-Bsymbolic</code>" -option, as that prevents the resolution described above.</li> - -<li>If you use <code>dlopen</code> to explicitly load code from a shared -library, you must do several things. First, export global symbols from -the executable by linking it with the "<code>-E</code>" flag (you will -have to specify this as "<code>-Wl,-E</code>" if you are invoking -the linker in the usual manner from the compiler driver, <code>g++</code>). -You must also make the external symbols in the loaded library -available for subsequent libraries by providing the <code>RTLD_GLOBAL</code> -flag to <code>dlopen</code>. The symbol resolution can be immediate or -lazy.</li> - -</ul> - -<p>Template instantiations are another, user visible, case of objects -with vague linkage, which needs similar resolution. If you do not take -the above precautions, you may discover that a template instantiation -with the same argument list, but instantiated in multiple translation -units, has several addresses, depending in which translation unit the -address is taken. (This is <em>not</em> an exhaustive list of the kind -of objects which have vague linkage and are expected to be resolved -during linking & loading.)</p> - -<p>If you are worried about different objects with the same name -colliding during the linking or loading process, then you should use -namespaces to disambiguate them. Giving distinct objects with global -linkage the same name is a violation of the One Definition Rule (ODR) -[basic.def.odr].</p> - -<p>For more details about the way that GCC implements these and other -C++ features, please read the <a -href="http://www.codesourcery.com/cxx-abi/">ABI specification</a>. -Note the <code>std::typeinfo_t</code> objects which <i>must</i> be -resolved all begin with "_ZTS". Refer to <code>ld</code>'s -documentation for a description of the "<code>-E</code>" & -"<code>-Bsymbolic</code>" flags.</p> - -<hr /> -<h2><a name="generated_files">Why do I need autoconf, bison, xgettext, automake, etc?</a></h2> - -<p>If you're using diffs up dated from one snapshot to the next, or -if you're using the CVS repository, you may need several additional programs -to build GCC.</p> - -<p>These include, but are not necessarily limited to autoconf, automake, -bison, and xgettext.</p> - -<p>This is necessary because neither diff nor cvs keep timestamps -correct. This causes problems for generated files as "make" may think -those generated files are out of date and try to regenerate them.</p> - -<p>An easy way to work around this problem is to use the <code>gcc_update -</code> script in the contrib subdirectory of GCC, which handles this -transparently without requiring installation of any additional tools. -(Note: Up to and including GCC 2.95 this script was called <code>egcs_update -</code>.)</p> - - -<p>When building from diffs or CVS or if you modified some sources, -you may also need to obtain development versions of some GNU tools, as -the production versions do not necessarily handle all features needed -to rebuild GCC.</p> - -<p>In general, the current versions of these tools from <a -href="ftp://ftp.gnu.org/gnu/">ftp://ftp.gnu.org/gnu/</a> will work. -At present, Autoconf 2.50 is not supported, and you will need to use -Autoconf 2.13; work is in progress to fix this problem. Also look at -<a href="ftp://gcc.gnu.org/pub/gcc/infrastructure/"> -ftp://gcc.gnu.org/pub/gcc/infrastructure/</a> for any special versions -of packages.</p> - - -<hr /> -<h2><a name="picflag-needed">Why can't I build a shared library?</a></h2> - -<p>When building a shared library you may get an error message from the -linker like `assert pure-text failed:' or `DP relative code in file'.</p> - -<p>This kind of error occurs when you've failed to provide proper flags -to gcc when linking the shared library. </p> - -<p>You can get this error even if all the .o files for the shared library were -compiled with the proper PIC option. When building a shared library, gcc will -compile additional code to be included in the library. That additional code -must also be compiled with the proper PIC option.</p> - -<p>Adding the proper PIC option (<tt>-fpic</tt> or <tt>-fPIC</tt>) to the link -line which creates the shared library will fix this problem on targets that -support PIC in this manner. For example:</p> -<pre> - gcc -c -fPIC myfile.c - gcc -shared -o libmyfile.so -fPIC myfile.o -</pre> - - -<hr /> -<h2><a name="squangle">How to work around too long C++ symbol names -(<tt>-fsquangle</tt>)</a></h2> - -<p>This question does not apply to GCC 3.0 or later versions, which -have a new C++ ABI with much shorter mangled names.</p> - -<p>If the standard assembler of your platform can't cope with the -large symbol names that the default g++ name mangling mechanism -produces, your best bet is to use GNU as, from the GNU binutils -package.</p> - -<p>Unfortunately, GNU as does not support all platforms supported by -GCC, so you may have to use an experimental work-around: the -<tt>-fsquangle</tt> option, that enables compression of symbol names.</p> - -<p>Note that this option is still under development, and subject to -change. Since it modifies the name mangling mechanism, you'll need to -build libstdc++ and any other C++ libraries with this option enabled. -Furthermore, if this option changes its behavior in the future, you'll -have to rebuild them all again. :-(</p> - -<p>This option can be enabled by default by initializing -`flag_do_squangling' with `1' in `gcc/cp/decl2.c' (it is not -initialized by default), then rebuilding GCC and any C++ libraries.</p> - - -<hr /> -<h2><a name="vtables">When building C++, the linker says my constructors, destructors or virtual tables are undefined, but I defined them</a></h2> - -<p>The ISO C++ Standard specifies that all virtual methods of a class -that are not pure-virtual must be defined, but does not require any -diagnostic for violations of this rule [class.virtual]/8. Based on -this assumption, GCC will only emit the implicitly defined -constructors, the assignment operator, the destructor and the virtual -table of a class in the translation unit that defines its first such -non-inline method.</p> - -<p>Therefore, if you fail to define this particular method, the linker -may complain about the lack of definitions for apparently unrelated -symbols. Unfortunately, in order to improve this error message, it -might be necessary to change the linker, and this can't always be -done.</p> - -<p>The solution is to ensure that all virtual methods that are not -pure are defined. Note that a destructor must be defined even if it -is declared pure-virtual [class.dtor]/7.</p> - - -<hr /> -<h2><a name="incremental">Will GCC someday include an incremental linker?</a></h2> - -<p>Incremental linking is part of the linker, not the compiler. As -such, GCC doesn't have anything to do with incremental linking. -Depending on what platform you use, it may be possible to tell GCC to -use the platform's native linker (e.g., Solaris' ild(1)).</p> - - -</body> -</html> |