X-Git-Url: https://oss.titaniummirror.com/gitweb?a=blobdiff_plain;f=FAQ;fp=FAQ;h=0000000000000000000000000000000000000000;hb=6fed43773c9b0ce596dca5686f37ac3fc0fa11c0;hp=632311b5b15eefd0bbe834795ac0c21c49e475da;hpb=27b11d56b743098deb193d510b337ba22dc52e5c;p=msp430-gcc.git diff --git a/FAQ b/FAQ deleted file mode 100644 index 632311b5..00000000 --- a/FAQ +++ /dev/null @@ -1,610 +0,0 @@ - - GCC Frequently Asked Questions - - The latest version of this document is always available at - [1]http://gcc.gnu.org/faq.html. - - This FAQ tries to answer specific questions concerning GCC. For - general information regarding C, C++, resp. Fortran please check the - [2]comp.lang.c FAQ, [3]comp.std.c++ FAQ, and the [4]Fortran - Information page. - - Other GCC-related FAQs: [5]libstdc++-v3, and [6]GCJ. - _________________________________________________________________ - - Questions - - 1. [7]General information - 1. [8]What is the relationship between GCC and EGCS? - 2. [9]What is the relationship between GCC and Cygnus / Red Hat? - 3. [10]What is an open development model? - 4. [11]How do I report a bug? - 5. [12]How do I get a bug fixed or a feature added? - 6. [13]Does GCC work on my platform? - 2. [14]Installation - 1. [15]How to install multiple versions of GCC - 2. [16]Dynamic linker is unable to find GCC libraries - 3. [17]libstdc++/libio tests fail badly with --enable-shared - 4. [18]GCC can not find GNU as/GNU ld - 5. [19]cpp: Usage:... Error - 6. [20]Optimizing the compiler itself - 3. [21]Testsuite problems - 1. [22]Unable to run the testsuite - 2. [23]How do I pass flags like -fnew-abi to the testsuite? - 3. [24]How can I run the test suite with multiple options? - 4. [25]Older versions of GCC - 1. [26]Is there a stringstream / sstream for GCC 2.95.2? - 5. [27]Miscellaneous - 1. [28]Friend Templates - 2. [29]dynamic_cast, throw, typeid don't work with shared - libraries - 3. [30]Why do I need autoconf, bison, xgettext, automake, etc? - 4. [31]Why can't I build a shared library? - 5. [32]When building C++, the linker says my constructors, - destructors or virtual tables are undefined, but I defined - them - 6. [33]Will GCC someday include an incremental linker? - _________________________________________________________________ - - General information - -What is the relationship between GCC and EGCS? - - 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. - - 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. - - 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 - [34]GCC Steering Committee. - _________________________________________________________________ - -What is the relationship between GCC and Cygnus / Red Hat? - - It is a common mis-conception that Red Hat controls GCC either - directly or indirectly. - - While Red Hat does donate hardware, network connections, code and - developer time to GCC development, Red Hat does not control GCC. - - Overall control of GCC is in the hands of the [35]GCC Steering - Committee 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. - - To summarize, Red Hat contributes to the GCC project, but does not - exert a controlling influence over GCC. - _________________________________________________________________ - -What is an open development model? - - We are using a bazaar style [36][1] 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. - - 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. - - 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. - - 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. - - 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. - - 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. - - [1] 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 cathedral development model versus a bazaar - development model. The paper is written by Eric S. Raymond, it is - called ``The Cathedral and the Bazaar''. The paper is a useful - starting point for discussions. - _________________________________________________________________ - -How do I report a bug? - - There are complete instructions [37]here. - _________________________________________________________________ - -How do I get a bug fixed or a feature added? - - 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. - * 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. - * [38]Report the problem to the GCC GNATS bug tracking system 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 - [39]submitting bugreports. - * 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. - _________________________________________________________________ - -Does GCC work on my platform? - - 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 [40]latest version is always - available at the GCC web site. Reports of [41]successful builds for - several versions of GCC are also available at the web site. - _________________________________________________________________ - - Installation - -How to install multiple versions of GCC - - 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. - - 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. - - The easiest way to do this is to configure the new GCC with - --prefix=/usr/local/gcc and the older gcc2 with - --prefix=/usr/local/gcc2. Build and install both compilers. Then make - a symlink from /usr/local/bin/gcc to /usr/local/gcc/bin/gcc and from - /usr/local/bin/gcc2 to /usr/local/gcc2/bin/gcc. Create similar links - for the "g++", "c++" and "g77" compiler drivers. - - An alternative to using symlinks is to configure with a - --program-transform-name 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 --prefix 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 --program-transform-name - 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: - - --program-transform-name='s,\\\\(.*\\\\),new-\\\\1,' - - With the above --prefix option, that will install the new GCC programs - into /usr/local/gcc/bin with names prefixed by "new-". You can use - --program-transform-name if you have multiple versions of GCC, and - wish to be sure about which version you are invoking. - - If you use --prefix, GCC may have difficulty locating a GNU assembler - or linker on your system, [42]GCC can not find GNU as/GNU ld explains - how to deal with this. - - Another option that may be easier is to use the --program-prefix= or - --program-suffix= options to configure. So if you're installing GCC - 2.95.2 and don't want to disturb the current version of GCC in - /usr/local/bin/, you could do - - configure --program-suffix=-2.95.2 - - This should result in GCC being installed as /usr/local/bin/gcc-2.95.2 - instead of /usr/local/bin/gcc. - _________________________________________________________________ - -Dynamic linker is unable to find GCC libraries - - 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 --enable-shared and building GCC. - - GCC does not specify a runpath so that the dynamic linker can find - dynamic libraries at runtime. - - 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. - - 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. - - SunOS effectively always passed a -R option for every -L option; this - was a bad idea, and so it was removed for Solaris. We should not - recreate it. - - 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 - gcc -print-prog-name=cc1 to find it). You may add linker flags such as - -R or -rpath, depending on platform and linker, to the *link or *lib - specs. - - Another alternative is to install a wrapper script around gcc, g++ or - ld that adds the appropriate directory to the environment variable - LD_RUN_PATH or equivalent (again, it's platform-dependent). - - 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 .ml file within - libstdc++/config (and also libg++/config, if you are building libg++), - so that $(libdir)/ appears just before the library name in -soname or - -h options. - _________________________________________________________________ - -GCC can not find GNU as/GNU ld - - 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 assembler 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. - - To ensure that GCC finds the GNU assembler (the GNU loader), which are - required by [43]some configurations, 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. - - Another alternative is to create links to GNU as and ld in any of the - directories printed by the command `gcc -print-search-dirs | grep - '^programs:''. The link to `ld' should be named `real-ld' if `ld' - 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 - gcc directory and in all the gcc/stage* subdirectories. - - GCC 2.95 allows you to specify the full pathname of the assembler and - the linker to use. The configure flags are `--with-as=/path/to/as' and - `--with-ld=/path/to/ld'. GCC will try to use these pathnames before - looking for `as' or `(real-)ld' in the standard search dirs. If, at - configure-time, the specified programs are found to be GNU utilities, - `--with-gnu-as' and `--with-gnu-ld' 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 -B/path/ if the specified filenames exist. - _________________________________________________________________ - -cpp: Usage:... Error - - If you get an error like this when building GCC (particularly when - building __mulsi3), then you likely have a problem with your - environment variables. - cpp: Usage: /usr/lib/gcc-lib/i586-unknown-linux-gnulibc1/2.7.2.3/cpp - [switches] input output - - 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. - - Also note '::' in these paths will also cause similar problems. - _________________________________________________________________ - -Optimizing the compiler itself - - 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 -fssa option, you could bootstrap like this: -make BOOT_CFLAGS="-O2 -fssa" bootstrap - _________________________________________________________________ - - Testsuite problems - -Unable to run the testsuite - - 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 - [44]http://www.gnu.org/software/dejagnu/dejagnu.html. - _________________________________________________________________ - -How do I pass flags like -fnew-abi to the testsuite? - - If you invoke runtest directly, you can use the --tool_opts option, - e.g: - runtest --tool_opts "-fnew-abi -fno-honor-std" - - Or, if you use make check you can use the make variable RUNTESTFLAGS, - e.g: - make RUNTESTFLAGS="--tool_opts '-fnew-abi -fno-honor-std'" check-g++ - _________________________________________________________________ - -How can I run the test suite with multiple options? - - If you invoke runtest directly, you can use the --target_board option, - e.g: - runtest --target_board "unix{-fPIC,-fpic,}" - - Or, if you use make check you can use the make variable RUNTESTFLAGS, - e.g: - make RUNTESTFLAGS="--target_board 'unix{-fPIC,-fpic,}'" check-gcc - - Either of these examples will run the tests three times. Once with - -fPIC, once with -fpic, and once with no additional flags. - - This technique is particularly useful on multilibbed targets. - _________________________________________________________________ - - Older versions of GCC and EGCS - -Is there a stringstream / sstream for GCC 2.95.2? - - Yes, it's at: - [45]http://gcc.gnu.org/ml/libstdc++/2000-q2/msg00700/sstream. - _________________________________________________________________ - - Miscellaneous - -Friend Templates - - 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: -template class foo { - friend void bar(foo); -} - - The above declaration declares a non-template function named bar, so - it must be explicitly defined for each specialization of foo. A - template definition of bar won't do, because it is unrelated with the - non-template declaration above. So you'd have to end up writing: -void bar(foo) { /* ... */ } -void bar(foo) { /* ... */ } - - If you meant bar 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: -template -class foo; - -template -void bar(foo); - -template -class foo { - friend void bar<>(foo); -}; - -template -void bar(foo) { /* ... */ } - - 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. - - 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. - _________________________________________________________________ - -dynamic_cast, throw, typeid don't work with shared libraries - - 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 std::typeinfo_t 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. - * For a program which is linked against a shared library, no - additional precautions need taking. - * You cannot create a shared library with the "-Bsymbolic" option, - as that prevents the resolution described above. - * If you use dlopen 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 "-E" flag (you will have to - specify this as "-Wl,-E" if you are invoking the linker in the - usual manner from the compiler driver, g++). You must also make - the external symbols in the loaded library available for - subsequent libraries by providing the RTLD_GLOBAL flag to dlopen. - The symbol resolution can be immediate or lazy. - - 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 not an exhaustive list of the kind of - objects which have vague linkage and are expected to be resolved - during linking & loading.) - - 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]. - - For more details about the way that GCC implements these and other C++ - features, please read the [46]ABI specification. Note the - std::typeinfo_t objects which must be resolved all begin with "_ZTS". - Refer to ld's documentation for a description of the "-E" & - "-Bsymbolic" flags. - _________________________________________________________________ - -Why do I need autoconf, bison, xgettext, automake, etc? - - 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. - - These include, but are not necessarily limited to autoconf, automake, - bison, and xgettext. - - 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. - - An easy way to work around this problem is to use the gcc_update - 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 egcs_update - .) - - 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. - - In general, the current versions of these tools from - [47]ftp://ftp.gnu.org/gnu/ 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 - [48]ftp://gcc.gnu.org/pub/gcc/infrastructure/ for any special versions - of packages. - _________________________________________________________________ - -Why can't I build a shared library? - - 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'. - - This kind of error occurs when you've failed to provide proper flags - to gcc when linking the shared library. - - 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. - - Adding the proper PIC option (-fpic or -fPIC) to the link line which - creates the shared library will fix this problem on targets that - support PIC in this manner. For example: - gcc -c -fPIC myfile.c - gcc -shared -o libmyfile.so -fPIC myfile.o - _________________________________________________________________ - -When building C++, the linker says my constructors, destructors or virtual -tables are undefined, but I defined them - - 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. - - 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. - - 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. - _________________________________________________________________ - -Will GCC someday include an incremental linker? - - 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)). - -References - - 1. http://gcc.gnu.org/faq.html - 2. http://www.eskimo.com/~scs/C-faq/top.html - 3. http://www.jamesd.demon.co.uk/csc/faq.html - 4. http://www.fortran.com/fortran/info.html - 5. http://gcc.gnu.org/onlinedocs/libstdc++/faq/index.html - 6. http://gcc.gnu.org/java/faq.html - 7. http://gcc.gnu.org/faq.html#general - 8. http://gcc.gnu.org/faq.html#gcc - 9. http://gcc.gnu.org/faq.html#cygnus - 10. http://gcc.gnu.org/faq.html#open-development - 11. http://gcc.gnu.org/faq.html#bugreport - 12. http://gcc.gnu.org/faq.html#support - 13. http://gcc.gnu.org/faq.html#platforms - 14. http://gcc.gnu.org/faq.html#installation - 15. http://gcc.gnu.org/faq.html#multiple - 16. http://gcc.gnu.org/faq.html#rpath - 17. http://gcc.gnu.org/faq.html#rpath - 18. http://gcc.gnu.org/faq.html#gas - 19. http://gcc.gnu.org/faq.html#environ - 20. http://gcc.gnu.org/faq.html#optimizing - 21. http://gcc.gnu.org/faq.html#testsuite - 22. http://gcc.gnu.org/faq.html#dejagnu - 23. http://gcc.gnu.org/faq.html#testoptions - 24. http://gcc.gnu.org/faq.html#multipletests - 25. http://gcc.gnu.org/faq.html#old - 26. http://gcc.gnu.org/faq.html#2.95sstream - 27. http://gcc.gnu.org/faq.html#misc - 28. http://gcc.gnu.org/faq.html#friend - 29. http://gcc.gnu.org/faq.html#dso - 30. http://gcc.gnu.org/faq.html#generated_files - 31. http://gcc.gnu.org/faq.html#picflag-needed - 32. http://gcc.gnu.org/faq.html#vtables - 33. http://gcc.gnu.org/faq.html#incremental - 34. http://gcc.gnu.org/steering.html - 35. http://gcc.gnu.org/steering.html - 36. http://gcc.gnu.org/faq.html#cathedral-vs-bazaar - 37. http://gcc.gnu.org/bugs.html - 38. http://gcc.gnu.org/bugs.html - 39. http://gcc.gnu.org/bugs.html - 40. http://gcc.gnu.org/install/specific.html - 41. http://gcc.gnu.org/buildstat.html - 42. http://gcc.gnu.org/faq.html#gas - 43. http://gcc.gnu.org/install/specific.html - 44. http://www.gnu.org/software/dejagnu/dejagnu.html - 45. http://gcc.gnu.org/ml/libstdc++/2000-q2/msg00700/sstream - 46. http://www.codesourcery.com/cxx-abi/ - 47. ftp://ftp.gnu.org/gnu/ - 48. ftp://gcc.gnu.org/pub/gcc/infrastructure/