INSTALL/faq.html

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   3 <title>egcs Frequently Asked Questions</title>
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   6 <h1 align="center">egcs Frequently Asked Questions</h1>
   7
   8 <ol>
   9   <li><a href="#gcc-2-diff">How is egcs be different from gcc2?</a>
  10   <li><a href="#open-development">What is an open development model?</a>
  11   <li><a href="#libc-lock">bits/libc-lock.h:  No such file or directory</a>
  12   <li><a href="#morelibc">`_IO_stdfile_0_lock' was not declared in this scope</a>
  13   <li><a href="#fortran">Problems building the Fortran compiler</a>
  14   <li><a href="#mips">Problems building on MIPS platforms</a>
  15   <li><a href="#x86eh">Problems with exception handling on x86 platforms</a>
  16   <li><a href="#hpcompare">Bootstrap comparison failures on HPs</a>
  17   <li><a href="#makebugs">Bootstrap loops rebuilding cc1 over and over</a>
  18   <li><a href="#rpath">Dynamic linker is unable to find GCC libraries</a>
  19   <li><a href="#rpath">libstdc++/libio tests fail badly with --enable-shared</a>
  20   <li><a href="#dejagnu">Unable to run the testsuite</a>
  21   <li><a href="#cross">How to build a cross compiler</a>
  22   <li><a href="#multiple">How to install both gcc2 and egcs</a>
  23   <li><a href="#snapshot">Snapshots, how, when, why</a>
  24   <li><a href="#linuxkernel">Problems building Linux kernels</a>
  25   <li><a href="#memexhausted">Virtual memory exhausted</a>
  26   <li><a href="#gas">GCC can not find GAS</a>
  27   <li><a href="#rh5.0">egcs does not work on Red Hat 5.0</a>
  28
  29 </ol>
  30
  31 <hr>
  32 <h2><a name="gcc-2-diff">How is egcs be different from gcc2?</a></h2>
  33
  34 <p>Six years ago, gcc version 1 had reached a point of stability.  For the
  35 targets it could support, it worked well.  It had limitations inherent in
  36 its design that would be difficult to resolve, so a major effort was made
  37 and gcc version 2 was the result.  When we had gcc2 in a useful state,
  38 development efforts on gcc1 stopped and we all concentrated on making
  39 gcc2 better than gcc1 could ever be.  This is the kind of step forward
  40 we want to make with egcs.
  41
  42 <p>In brief, the three biggest differences between egcs and gcc2 are
  43 these:
  44
  45 <ul>
  46   <li>More rexamination of basic architectual decisions of
  47     gcc and an interest in adding new optimizations;
  48
  49   <li>working with the groups who have fractured out from gcc2 (like
  50    the Linux folks, the Intel optimizations folks, Fortran folks)
  51    including more front-ends; and finally
  52
  53   <li>An open development model (<a
  54    href="#open-development">see below</a>) for the development process.
  55 </ul>
  56
  57 <p>These three differences will work together to result in a more
  58 useful compiler, a more stable compiler, a central compiler that works
  59 for more people, a compiler that generates better code.
  60
  61
  62 <p>There are a lot of exciting compiler optimizations that have come
  63 out.  We want them in gcc.  There are a lot of front ends out there for
  64 gcc for languages like Fortran or Pascal.  We want them easily
  65 installable by users.  After six years of working on gcc2, we've come
  66 to see problems and limitations in the way gcc is architected; it is
  67 time to address these again.
  68
  69 <hr>
  70 <h2><a name="open-development">What is an open development model?</a></h2>
  71
  72 <p>With egcs, we are going to try a bazaar style<a
  73 href="#cathedral-vs-bazaar"><b>[1]</b></a> approach to its
  74 development:  We're going to be making snapshots publically available
  75 to anyone who wants to try them; we're going to welcome anyone to join
  76 the development mailing list.  All of the discussions on the
  77 development mailing list are available via the web.  We're going to be
  78 making releases with a much higher frequency than they have been made
  79 in the past:  We're shooting for three by the end of 1997.
  80
  81 <p>In addition to weekly snapshots of the egcs development sources, we
  82 are going to look at making the sources readable from a CVS server by
  83 anyone.  We want to make it so external maintainers of parts of egcs
  84 are able to commit changes to their part of egcs directly into the
  85 sources without going through an intermediary.
  86
  87 <p>There have been many potential gcc developers who were not able to
  88 participate in gcc development in the past.  We these people to help in
  89 any way they can; we ultimately want gcc to be the best compiler in the
  90 world.
  91
  92 <p>A compiler is a complicated piece of software, there will still be
  93 strong central maintainers who will reject patches, who will demand
  94 documentation of implementations, and who will keep the level of
  95 quality as high as it is today.  Code that could use wider testing may
  96 be intergrated--code that is simply ill-conceived won't be.
  97
  98 <p>egcs is not the first piece of software to use this open development
  99 process; FreeBSD, the Emacs lisp repository, and Linux are a few
 100 examples of the bazaar style of development.
 101
 102 <p>With egcs, we will be adding new features and optimizations at a
 103 rate that has not been done since the creation of gcc2; these additions
 104 will inevitably have a temporarily destabilizing effect.  With the help
 105 of developers working together with this bazaar style development, the
 106 resulting stability and quality levels will be better than we've had
 107 before.
 108
 109 <blockquote>
 110 <a name="cathedral-vs-bazaar"><b>[1]</b></a>
 111   We've been discussing different development models a lot over the
 112   past few months.  The paper which started all of this introduced two
 113   terms:  A <b>cathedral</b> development model versus a <b>bazaar</b>
 114   development model.  The paper is written by Eric S. Raymond, it is
 115   called ``<a
 116   href="http://locke.ccil.org/~esr/writings/cathedral.html">The
 117   Cathedral and the Bazaar</a>''.  The paper is a useful starting point
 118   for discussions.
 119 </blockquote>
 120
 121
 122 <hr>
 123 <h2><a name="libc-lock">bits/libc-lock.h: No such file or directory</a></h2>
 124 <p>egcs includes a tightly integrated libio and libstdc++ implementation which
 125 can cause problems on hosts which have libio integrated into their C library
 126 (most notably Linux).
 127
 128 <p>We believe that we've solved the major technical problems for the most
 129 common versions of libc found on Linux systems.  However, some versions
 130 of Linux use pre-release versions of glibc2, which egcs has trouble detecting
 131 and correctly handling.
 132
 133 <p>If you're using one of these pre-release versions of glibc2, you may get
 134 a message "bits/libc-lock.h: No such file or directory" when building egcs.
 135 Unfortunately, to fix this problem you will need to update your C library to
 136 glibc2.0.5c.
 137
 138 <p>Late breaking news: we may have at least a partial solution for these
 139 problems.  So this FAQ entry may no longer be needed.
 140
 141 <hr>
 142 <h2><a name="morelibc">`_IO_stdfile_0_lock' was not declared in this scope</a></h2>
 143 <p>If you get this error, it means either egcs incorrectly guessed what version
 144 of libc is installed on your linux system, or you incorrectly specified a
 145 version of glibc when configuring egcs.
 146
 147 <p>If you did not provide a target name when configuring egcs, then you've
 148 found a bug which needs to be reported.  If you did provide a target name at
 149 configure time, then you should reconfigure without specifying a target name.
 150
 151 <hr>
 152 <h2><a name="fortran">Problems building the Fortran compiler</a></h2>
 153 <p>The Fortran front end can not be built with most vendor compilers; it must
 154 be built with gcc.  As a result, you may get an error if you do not follow
 155 the install instructions carefully.
 156
 157 <p>In particular, instead of using "make" to build egcs, you should use
 158 "make bootstrap" if you are building a native compiler or "make cross"
 159 if you are building a cross compiler.
 160
 161 <p>It has also been reported that the Fortran compiler can not be built
 162 on Red Hat 4.X linux for the Alpha.  Fixing this may require upgrading
 163 binutils or to Red Hat 5.0; we'll provide more information as it becomes
 164 available.
 165
 166 <hr>
 167 <h2><a name="mips">Problems building on MIPS platforms</a></h2>
 168 <p>egcs requires the use of GAS on all versions of Irix, except Irix 6 due
 169 to limitations in older Irix assemblers.
 170
 171 <p> Either of these messages indicates that you are using the MIPS assembler
 172 when instead you should be using GAS.
 173
 174 <pre>
 175     as0: Error: ./libgcc2.c, line 1:Badly delimited numeric literal
 176           .4byte $LECIE1-$LSCIE1
 177     as0: Error: ./libgcc2.c, line 1:malformed statement
 178 </pre>
 179
 180 <hr>
 181 <pre>
 182     as0: Error: /home/law/egcs_release/gcc/libgcc2.c, line 1:undefined symbol in expression
 183     .word $LECIE1-$LSCIE1
 184
 185 </pre>
 186
 187
 188 <p> For Irix 6, you should use the native assembler as GAS is not supported
 189 on Irix 6.
 190
 191 <hr>
 192 <h2> <a name="x86eh">Problems with exception handling on x86 platforms</a></h2>
 193 <p>If you are using the GNU assembler (aka gas) on an x86 platform and
 194 exception handling is not working correctly, then odds are you're using a
 195 buggy assembler.
 196
 197 <p>We recommend binutils-2.8.0.1.15 or newer.
 198 <br><a href="ftp://tsx-11.mit.edu/pub/linux/packages/GCC/binutils-2.8.1.0.15.tar.gz"> binutils-2.8.0.1.15 source</a>
 199 <br><a href="ftp://tsx-11.mit.edu/pub/linux/packages/GCC/binutils-2.8.1.0.15.bin.tar.gz"> binutils-2.8.0.1.15 x86 binary for libc5</a>
 200 <br><a href="ftp://tsx-11.mit.edu/pub/linux/packages/GCC/binutils-2.8.1.0.15.glibc.bin.tar.gz"> binutils-2.8.0.1.15 x86 binary for glibc2</a>
 201 Or, you can try a
 202 <a href="ftp://ftp.cygnus.com/pub/egcs/infrastructure/gas-970915.tar.gz"> binutils snapshot</a>; however, be aware that the binutils snapshot is untested
 203 and may not work (or even build).  Use it at your own risk.
 204
 205 <hr>
 206 <h2> <a name="hpcompare">Bootstrap comparison failures on HPs</a></h2>
 207 <p>If you bootstrap the compiler on hpux10 using the HP assembler instead of
 208 gas, every file will fail the comparison test.
 209
 210 <p>The HP asembler inserts timestamps into object files it creates, causing
 211 every file to be different.  The location of the timestamp varies for each
 212 object file, so there's no real way to work around this mis-feature.
 213
 214 <p>Odds are your compiler is fine, but there's no way to be certain.
 215
 216 <p>If you use GAS on HPs, then you will not run into this problem because
 217 GAS never inserts timestamps into object files.  For this and various other
 218 reasons we highly recommend using GAS on HPs.
 219
 220 <hr>
 221 <h2> <a name="makebugs">Bootstrap loops rebuilding cc1 over and over</a></h2>
 222 <p>When building egcs, the build process loops rebuilding cc1 over and
 223 over again.  This happens on mips-sgi-irix5.2, and possibly other platforms.
 224
 225 <p>This is probably a bug somewhere in the egcs Makefile.  Until we find and
 226 fix this bug we recommend you use GNU make instead of vendor supplied make
 227 programs.
 228
 229 <hr>
 230 <h2> <a name="rpath">Dynamic linker is unable to find GCC libraries</a></h2>
 231 <p>This problem manifests itself by programs not finding shared libraries
 232 they depend on when the programs are started.  Note this problem often manifests
 233 itself with failures in the libio/libstdc++ tests after configuring with
 234 --enable-shared and building egcs.
 235
 236 <p>GCC does not specify a runpath so that the dynamic linker can find dynamic
 237 libraries at runtime.
 238
 239 <p>The short explaination is that if you always pass a -R option to the
 240 linker, then your programs become dependent on directories which
 241 may be NFS mounted, and programs may hang unnecessarily when an
 242 NFS server goes down.
 243
 244 <p>The problem is not programs that do require the directories; those
 245 programs are going to hang no matter what you do.  The problem is
 246 programs that do not require the directories.
 247
 248 <p>SunOS effectively always passed a -R option for every -L option;
 249 this was a bad idea, and so it was removed for Solaris.  We should
 250 not recreate it.
 251
 252 <hr>
 253 <h2> <a name="dejagnu">Unable to run the testsuite</a></h2>
 254 <p>If you get a message about unable to find "standard.exp" when trying to
 255 run the egcs testsuites, then your dejagnu is too old to run the egcs tests.
 256 You will need to get a newer version of dejagnu; we've made a
 257 <a href="ftp://ftp.cygnus.com/pub/egcs/infrastructure/dejagnu-971028.tar.gz">
 258 dejagnu snapshot</a> available until a new version of dejagnu can be released.
 259
 260 <hr>
 261 <h2> <a name="cross">How to build a cross compiler</a></h2>
 262 <p> Building cross compilers is a rather complex undertaking because they
 263 usually need additional software (cross assembler, cross linker, target
 264 libraries, target include files, etc).
 265
 266 <p> We recommend reading the <a href="ftp://ftp.cygnus.com/pub/embedded/crossgcc/FAQ-0.8.1">
 267 crossgcc FAQ</a> for information about building cross compilers.
 268
 269 <p> If you have all the pieces available, then `make cross' should build a
 270 cross compiler.  `make LANGUAGES="c c++" install'will install the cross
 271 compiler.
 272
 273 <p> Note that if you're trying to build a cross compiler in a tree which
 274 includes binutils-2.8 in addition to egcs, then you're going to need to
 275 make a couple minor tweaks so that the cross assembler, linker and
 276 nm utilities will be found.
 277
 278 <p>binutils-2.8 builds those files as gas.new, ld.new and nm.new; egcs gcc
 279 looks for them using gas-new, ld-new and nm-new, so you may have to arrange
 280 for any symlinks which point to &ltfile&gt.new to be changed to &ltfile&gt-new.
 281
 282 <hr>
 283 <h2> <a name="snapshot">Snapshots, how, when, why</a></h2>
 284 <p> We make snapshots of the egcs sources about once a week; there is no
 285 predetermined schedule.  These snapshots are intended to give everyone
 286 access to work in progress.  Any given snapshot may generate incorrect code
 287 or even fail to build.
 288
 289 <p>If you plan on downloading and using snapshots, we highly recommend you
 290 subscribe to the egcs mailing lists.  See <a href="index.html#mailinglists">
 291 mailing lists</a> on the main egcs page for instructions on how to subscribe.
 292
 293 <p>When using the diff files to update from older snapshots to newer snapshots,
 294 make sure to use "-E" and "-p" arguments to patch so that empty files are
 295 deleted and full pathnames are provided to patch.  If your version of
 296 patch does not support "-E", you'll need to get a newer version.  Also note
 297 that you may need autoconf, autoheader and various other programs if you use
 298 diff files to update from one snapshot to the next.
 299
 300 <hr>
 301 <h2> <a name="multiple">How to install both egcs and gcc2</a></h2>
 302 <p>It may be desirable to install both egcs and gcc2 on the same system.  This
 303 can be done by using different prefix paths at configure time and a few
 304 symlinks.
 305
 306 <p>Basically, configure the two compilers with different --prefix options,
 307 then build and install each compiler.  Assume you want "gcc" to be the egcs
 308 compiler and available in /usr/local/bin; also assume that you want "gcc2"
 309 to be the gcc2 compiler and also available in /usr/local/bin.
 310
 311 <p>The easiest way to do this is to configure egcs with --prefix=/usr/local/egcs
 312 and gcc2 with --prefix=/usr/local/gcc2.  Build and install both compilers.
 313 Then make a symlink from /usr/local/bin/gcc to /usr/local/egcs/bin/gcc and
 314 from /usr/local/bin/gcc2 to /usr/local/gcc2/bin/gcc.  Create similar links
 315 for the "g++", "c++" and "g77" compiler drivers.
 316
 317 <hr>
 318 <h2> <a name="linuxkernel">Problems building Linux kernels</a></h2>
 319 <p>If you installed a recent binutils/gas snapshot on your Linux system,
 320 you may not be able to build the kernel because objdump does not understand
 321 the "-k" switch.  The solution for this problem is to remove /usr/bin/encaps.
 322
 323 <p>You may get an internal compiler error compiling process.c in newer
 324 versions of the Linux kernel on x86 machines.  This is a bug in an asm
 325 statement in process.c, not a bug in egcs.  XXX How to fix?!?
 326
 327 <p>You may get errors with the X driver of the form
 328 <pre>
 329 _X11TransSocketUNIXConnect: Can't connect: errno = 111
 330 </pre>
 331
 332 <p>It's a kernel bug. The function sys_iopl in arch/i386/kernel/process.c
 333 does an illegal hack which used to work but is now broken since GCC optimizes
 334 more aggressively . The newer 2.1.x kernels already have a fix which should
 335 also work in 2.0.32.
 336
 337 <hr>
 338 <h2> <a name="memexhausted">Virtual memory exhausted error</a></h2>
 339 <p> This error means your system ran out of memory; this can happen for large
 340 files, particularly when optimizing.  If you're getting this error you should
 341 consider trying to simplify your files or reducing the optimization level.
 342
 343 <p>Note that using -pedantic or -Wreturn-type can cause an explosion in the
 344 amount of memory needed for template-heavy C++ code, such as code that uses
 345 STL.  Also note that -Wall includes -Wreturn-type, so if you use -Wall you
 346 will need to specify -Wno-return-type to turn it off.
 347
 348 <hr>
 349 <h2> <a name="gas">GCC can not find GAS</a></h2>
 350 <p>Some configurations like irix4, irix5, hpux* require the use of the GNU
 351 assembler intead of the system assembler.  To ensure that egcs finds the GNU
 352 assembler, you should configure the GNU assembler with the same --prefix
 353 option as you used for egcs.  Then build & install the GNU assembler.
 354
 355 <hr>
 356 <h2> <a name="rh5.0">egcs does not work on Red Hat 5.0</a></h2>
 357 <p> egcs does not currently work with Red Hat 5.0; we'll update this
 358 entry with more information as it becomes available.
 359
 360 <hr>
 361 <p><a href="index.html">Return to the egcs home page</a>
 362 <p><i>Last modified:  December 2, 1997</i>
 363
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