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1 <?xml version='1.0' encoding="UTF-8"?>
2 <!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/gcc-upgrading.xml,v 1.21 2006/09/13 14:42:58 jkt Exp $ -->
3
4 <!DOCTYPE guide SYSTEM "/dtd/guide.dtd">
5
6 <guide link="/doc/en/gcc-upgrading.xml">
7 <title>Gentoo GCC Upgrade Guide</title>
8
9 <author title="Author">
10 <mail link="amne@gentoo.org">Wernfried Haas</mail>
11 </author>
12 <author title="Author">
13 <mail link="jkt@gentoo.org">Jan Kundrát</mail>
14 </author>
15 <author title="Editor">
16 <mail link="mark@halcy0n.com">Mark Loeser</mail>
17 </author>
18
19 <abstract>
20 This document will guide the user through the process of upgrading GCC on their
21 Gentoo machines.
22 </abstract>
23
24 <!-- The content of this document is licensed under the CC-BY-SA license -->
25 <!-- See http://creativecommons.org/licenses/by-sa/2.5 -->
26 <license/>
27
28 <version>19</version>
29 <date>2006-09-13</date>
30
31 <chapter id="intro">
32 <title>Introduction</title>
33 <section>
34 <title>GCC Upgrading</title>
35 <body>
36
37 <p>
38 Why should you upgrade? Well, GCC is quite similar to any other package on your
39 system, just a bit more critical. You should upgrade GCC whenever a new version
40 fixes some bug that annoys you, new functionality you need is introduced, or if
41 you want to keep your system up-to-date. If none of the previous cases apply to
42 you, you can safely postpone upgrade as long as your GCC version is supported by
43 Gentoo developers.
44 </p>
45
46 <p>
47 If you install a new major version of GCC (such as 3.3.6 to 3.4.5), the system
48 will not switch over to use it automatically. You'll have to explicitly request
49 the change because the migration process might require some additional steps.
50 If you decide not to switch, Portage will continue to use older version of your
51 compiler until you change your mind, or remove the old compiler from the system.
52 Non-major gcc upgrades are switched automatically for you (such as 3.4.5 to
53 3.4.6).
54 </p>
55
56 <p>
57 This guide will document the necessary steps required to perform a seamless
58 upgrade of the compiler used by your Gentoo box. A specific section is
59 dedicated to the <uri link="#upgrade-3.3-to-3.4">upgrade from GCC 3.3 to 3.4</uri>
60 and issues with <c>libstdc++</c>. A second specific
61 section is for users <uri link="#first-install">first installing</uri> Gentoo
62 using a stage3 tarball, after a new GCC major/minor version has been released.
63 </p>
64
65 <warn>
66 It should be noted that upgrading from GCC-3.4 to GCC-4.1 or greater still
67 requires you to follow the <uri link="#upgrade-general">general upgrading
68 instructions</uri>, as GCC-3.4 and GCC-4.1 use slightly different ABIs.
69 </warn>
70
71 </body>
72 </section>
73 </chapter>
74
75 <chapter id="upgrade-general">
76 <title>General Upgrade Instructions</title>
77 <section>
78 <title>Introduction</title>
79 <body>
80
81 <impo>
82 If you're looking for instructions specific to upgrades from GCC-3.3 to GCC-3.4,
83 please consult the <uri link="#upgrade-3.3-to-3.4">dedicated
84 section</uri>.
85 </impo>
86
87 <impo>
88 If you're looking for instructions specific to upgrades in GCC for new
89 installs, please consult the <uri link="#first-install">dedicated
90 section</uri>.
91 </impo>
92
93 <p>
94 Generally speaking, upgrades to <e>bug fix releases</e>, like from 3.3.5 to
95 3.3.6, should be quite safe -- just emerge new version, switch your system to
96 use it and rebuild the only affected package, <c>libtool</c>. However, some GCC
97 upgrades break binary compatibility; in such cases a rebuild of the affected
98 packages (or even whole toolchain and system) might be required.
99 </p>
100
101 <p>
102 When we spoke about the need to switch your compiler to the newer version by
103 hand, we said it won't happen automatically. However, there is one exception --
104 upgrades to bug fix releases, like from 3.3.5 to 3.3.6 in case you don't use the
105 "multislot" feature allowing them to coexist on one system. Multislot is
106 disabled by default as the majority of users won't benefit from it.
107 </p>
108
109 <pre caption="Upgrading GCC">
110 # <i>emerge -uav gcc</i>
111
112 <comment>(Please substitute "i686-pc-linux-gnu-4.1.1" with the GCC
113 version and CHOST settings you've upgraded to:)</comment>
114 # <i>gcc-config i686-pc-linux-gnu-4.1.1</i>
115 # <i>source /etc/profile</i>
116
117 <comment>If you upgraded from gcc 3 to 4 (e.g. from 3.4.6 to 4.1.1 in this
118 example) you will have to run fix_libtool_files.sh manually</comment>
119 # <i>fix_libtool_files.sh 3.4.6</i>
120
121 <comment>(Rebuilding libtool)</comment>
122 # <i>emerge --oneshot -av libtool</i>
123 </pre>
124
125 <p>
126 To be completely safe that your system is in a sane state, you <e>must</e>
127 rebuild the toolchain and then world to make use of the new compiler.
128 </p>
129
130 <pre caption="Rebuilding system">
131 # <i>emerge -eav system</i>
132 # <i>emerge -eav world</i>
133 </pre>
134
135 <p>
136 It is safe to remove the older GCC version at this time. If you feel the need,
137 please issue the following command (as usual, substitute
138 <c>=sys-devel/gcc-3.4*</c> with the version you want to uninstall):
139 </p>
140
141 <pre caption="Removing older GCC version">
142 # <i>emerge -aC =sys-devel/gcc-3.4*</i>
143 </pre>
144
145 <impo>
146 Please note that the GCC 4.1 and newer can't compile a 2.4 kernel. Don't remove
147 your old GCC version if you want to use an older kernel.
148 </impo>
149
150 </body>
151 </section>
152 </chapter>
153
154 <chapter id="upgrade-3.3-to-3.4">
155 <title>Upgrading from GCC-3.3 to 3.4</title>
156 <section>
157 <title>Introduction</title>
158 <body>
159
160 <p>
161 The upgrade from GCC-3.3 to 3.4 (or greater) is not seamless as the C++ ABI
162 changed between these two versions. There is an issue with the <c>libstdc++</c>
163 library which must be taken care of, as well.
164 </p>
165
166 </body>
167 </section>
168 <section id="upgrade-3.3-to-3.4-choices">
169 <title>The Choices</title>
170 <body>
171
172 <impo>
173 If you upgrade from gcc 3.4 to 4.1, please consult the <uri
174 link="#upgrade-general">General Update instructions</uri>.
175 </impo>
176
177 <impo>
178 If you're upgrading on a SPARC machine, you will have to take the way of
179 <uri link="#upgrade-3.3-to-3.4-emerge-e">complete system rebuild</uri> due to
180 some internal <uri link="http://gcc.gnu.org/gcc-3.4/sparc-abi.html">ABI
181 changes</uri> in GCC's parameter passing.
182 </impo>
183
184 <p>
185 If you upgrade from gcc 3.3 to 3.4, you have two possibilities on how to
186 upgrade your system. The <uri link="#upgrade-3.3-to-3.4-revdep-rebuild">first
187 method</uri> is faster and requires use of the <c>revdep-rebuild</c> tool from
188 package <c>gentoolkit</c> while the <uri
189 link="#upgrade-3.3-to-3.4-emerge-e">second one</uri> rebuilds the entire
190 system from scratch so it will make use of new GCC features. It's up to you to
191 decide which of these two ways you will choose. In most cases, the first
192 method is sufficient.
193 </p>
194
195 <p>
196 If you upgrade from gcc 3.3 to 4.1, do not use the method based on
197 revdep-rebuild, but do a <uri link="#upgrade-3.3-to-3.4-emerge-e">complete
198 system rebuild</uri>.
199 </p>
200
201 </body>
202 </section>
203 <section id="upgrade-3.3-to-3.4-revdep-rebuild">
204 <title>Using revdep-rebuild</title>
205 <body>
206
207 <p>
208 This method requires that you first install <c>gentoolkit</c> if you have not
209 already done so. Then we will upgrade GCC and switch to the new compiler. We
210 will also rebuild the <c>libtool</c> package to ensure that toolchain is in
211 healthy state.
212 </p>
213
214 <pre caption="Installing gentoolkit and upgrading GCC">
215 # <i>emerge -an gentoolkit</i>
216 # <i>emerge -uav gcc</i>
217 <comment>(Please substitute "i686-pc-linux-gnu-3.4.5" with the GCC
218 version and CHOST settings you've upgraded to:)</comment>
219 # <i>gcc-config i686-pc-linux-gnu-3.4.5</i>
220 # <i>source /etc/profile</i>
221
222 <comment>(Rebuilding libtool)</comment>
223 # <i>emerge --oneshot -av libtool</i>
224 </pre>
225
226 <p>
227 Now, we want to see which packages that revdep-rebuild will want to rebuild.
228 Then we will tell revdep-rebuild to actually rebuild the packages. This may take
229 some time, so have some patience.
230 </p>
231
232 <pre caption="Using revdep-rebuild">
233 # <i>revdep-rebuild --library libstdc++.so.5 -- -p -v</i>
234 # <i>revdep-rebuild --library libstdc++.so.5</i>
235 </pre>
236
237 <note>
238 It is possible that you might have problems with non-existing package versions
239 due to them being outdated or masked. If this is the case, you will want to use
240 the <c>--package-names</c> option to <c>revdep-rebuild</c>. This causes packages
241 to be recompiled based on the package name, rather than the exact name and
242 version.
243 </note>
244
245 <p>
246 To provide compatibility with older binary C++ applications and any packages
247 that revdep-rebuild might have missed, <c>sys-libs/libstdc++-v3</c> needs to be
248 merged before you unmerge GCC 3.3 from your system.
249 </p>
250
251 <pre caption="Installing libstdc++-v3 and cleaning up">
252 # <i>emerge --oneshot sys-libs/libstdc++-v3</i>
253 # <i>emerge -aC =sys-devel/gcc-3.3*</i>
254 </pre>
255
256 </body>
257 </section>
258 <section id="upgrade-3.3-to-3.4-emerge-e">
259 <title>Using emerge -e</title>
260 <body>
261
262 <p>
263 This method, while much slower, will rebuild your whole system to ensure that
264 everything has been rebuilt with your new compiler, and therefore safer. At
265 first, you will upgrade GCC and libtool and switch to your new compiler.
266 </p>
267
268 <pre caption="Upgrading GCC">
269 # <i>emerge -uav gcc</i>
270 <comment>(Please substitute "i686-pc-linux-gnu-3.4.5" with the GCC
271 version and CHOST settings you've upgraded to:)</comment>
272 # <i>gcc-config i686-pc-linux-gnu-3.4.5</i>
273 # <i>source /etc/profile</i>
274
275 <comment>If you upgraded from gcc 3 to 4 (e.g. from 3.3.6 to 4.1.1 in this
276 example) you will have to run fix_libtool_files.sh manually</comment>
277 # <i>fix_libtool_files.sh 3.3.6</i>
278
279 <comment>(Rebuilding libtool)</comment>
280 # <i>emerge --oneshot -av libtool</i>
281 </pre>
282
283 <p>
284 To provide compatibility with older binary C++ applications,
285 <c>sys-libs/libstdc++-v3</c> needs to be merged onto your system.
286 </p>
287
288 <pre caption="Installing libstdc++-v3">
289 # <i>emerge --oneshot sys-libs/libstdc++-v3</i>
290 </pre>
291
292 <p>
293 Now we will go about first rebuilding the system target, then the world target.
294 This will take a very long time, depending on the number of packages that you
295 have installed, as it will rebuild your entire toolchain and supporting system
296 files, followed by every package on your system, including the toolchain. This
297 is necessary to ensure that all packages have been compiled with the new
298 toolchain, including the toolchain itself.
299 </p>
300
301 <pre caption="Rebuilding system and world">
302 # <i>emerge -e system</i>
303 # <i>emerge -e world</i>
304 </pre>
305
306 <p>
307 It is also safe to remove older GCC versions at this time:
308 </p>
309
310 <pre caption="Cleaning up">
311 # <i>emerge -aC =sys-devel/gcc-3.3*</i>
312 </pre>
313
314 </body>
315 </section>
316 </chapter>
317
318 <chapter id="first-install">
319 <title>Upgrading to GCC on a First Install</title>
320 <section>
321 <title>Introduction</title>
322 <body>
323
324 <p>
325 A GCC upgrade on a system after installation from a stage3 tarball is a simple
326 affair. One advantage users of new installations have is they do not have a
327 plethora of software installed that links against the older version of GCC.
328 The following example is for a GCC-3.3 to 3.4 upgrade. Certain parts
329 will be different if upgrading from other versions of GCC. For example, the
330 library names used for <c>revdep-rebuild</c> below are GCC 3.3 specific, as
331 well as the need to install <c>libstdc++-v3</c>.
332 </p>
333
334 <p>
335 If a user has not made any customizations to their system yet, then there are
336 very few steps to get their system upgraded to a new GCC version. As with the
337 GCC-3.3 to 3.4 upgrade, the user has a couple options. However, unlike the
338 GCC-3.3 to 3.4 upgrade, this one is less complicated as there are fewer
339 differences between the methods. The <uri
340 link="#first-install-revdep-rebuild">first method</uri> is faster and makes use
341 of the <c>revdep-rebuild</c> tool from <c>gentoolkit</c>, similar to the above
342 procedure. Using revdep-rebuild causes only packages which actually link
343 against GCC libraries to be rebuilt, while the <uri
344 link="#first-install-emerge-e">second method</uri> causes your entire new
345 install to be recompiled with the new GCC version and takes much longer. This
346 second method is never required and only documented for completeness.
347 </p>
348
349 <p>
350 These first steps are common between both methods, and should be completed by
351 everyone.
352 </p>
353
354 <pre caption="Upgrading GCC">
355 # <i>emerge -uav gcc</i>
356 <comment>(Please substitute "i686-pc-linux-gnu-3.4.5" with the GCC
357 version and CHOST settings you've upgraded to:)</comment>
358 # <i>gcc-config i686-pc-linux-gnu-3.4.5</i>
359 # <i>source /etc/profile</i>
360
361 <comment>(Rebuilding libtool)</comment>
362 # <i>emerge --oneshot -av libtool</i>
363 </pre>
364
365 <p>
366 To provide compatibility with older binary C++ applications,
367 <c>sys-libs/libstdc++-v3</c> needs to be merged onto your system.
368 </p>
369
370 <pre caption="Installing libstdc++-v3">
371 # <i>emerge --oneshot sys-libs/libstdc++-v3</i>
372 </pre>
373
374 </body>
375 </section>
376
377 <section id="first-install-revdep-rebuild">
378 <title>Using revdep-rebuild</title>
379 <body>
380
381 <p>
382 This method requires that you first install <c>gentoolkit</c> if you have not
383 already done so. We will then run <c>revdep-rebuild</c> to actually scan the
384 installed packages for ones we need to rebuild, then rebuild them.
385 </p>
386
387 <pre caption="Installing gentoolkit and running revdep-rebuild">
388 # <i>emerge -an gentoolkit</i>
389 # <i>revdep-rebuild --library libstdc++.so.5 -- -p -v</i>
390 # <i>revdep-rebuild --library libstdc++.so.5</i>
391 </pre>
392
393 <note>
394 It is possible that you might have problems with non-existing package versions
395 due to them being outdated or masked. If this is the case, you will want to use
396 the <c>--package-names</c> option to <c>revdep-rebuild</c>. This causes packages
397 to be recompiled based on the package name, rather than the exact name and
398 version.
399 </note>
400
401 </body>
402 </section>
403 <section id="first-install-emerge-e">
404 <title>Using emerge -e</title>
405 <body>
406
407 <p>
408 This method, while much slower, will rebuild the system target to ensure that
409 everything has been rebuilt with your new compiler. This is not necessary, but
410 is valid if you are also making changes to CFLAGS or other make.conf variables
411 that will affect the system compile.
412 </p>
413
414 <p>
415 Since we are performing these actions after an initial installation, we do not
416 need to recompile the <c>world</c> target as we would when doing an upgrade on
417 an already installed system. However, you may choose to perform a world update
418 in place of the system update, to ensure that all packages are updated.
419 </p>
420
421 <pre caption="Rebuilding system">
422 # <i>emerge -e system</i>
423 </pre>
424
425 </body>
426 </section>
427 <section id="first-install-cleaning-up">
428 <title>Cleaning up</title>
429 <body>
430
431 <p>
432 It is also safe to remove older GCC versions at this time. Please substitute
433 <c>YOUR-NEW-GCC-VERSION</c> with the actual version you've upgraded to:
434 </p>
435
436 <pre caption="Cleaning up">
437 # <i>emerge -aC "&lt;sys-devel/gcc-YOUR-NEW-GCC-VERSION"</i>
438 </pre>
439
440 </body>
441 </section>
442 </chapter>
443
444 <chapter id="common-pitfalls">
445 <title>Common Pitfalls</title>
446 <section>
447 <body>
448
449 <p>
450 It's important to disable <c>distcc</c> during upgrade. Mixing compiler versions
451 on your nodes <e>will</e> cause build issues. This is not required for ccache,
452 as the cache objects will be invalidated anyway.
453 </p>
454
455 <p>
456 Always use same GCC version for your kernel and additional kernel modules. Once
457 you rebuild your world with new GCC, external modules (like
458 <c>app-emulation/qemu-softmmu</c>) will fail to load. Please rebuild your
459 kernel with the new GCC to fix that.
460 </p>
461
462 <p>
463 If you're upgrading on a SPARC machine, make sure to rerun <c>silo -f</c> after
464 re-emerging world to avoid possible issues.
465 </p>
466
467 </body>
468 </section>
469 <section>
470 <title>Frequent Error Messages</title>
471 <body>
472
473 <p>
474 If your system complains about something like <e>libtool: link:
475 `/usr/lib/gcc-lib/i686-pc-linux-gnu/3.3.6/libstdc++.la' is not a valid libtool
476 archive</e>, please run <c>/sbin/fix_libtool_files.sh 3.3.6</c> (substitute
477 "3.3.6" with the version numbers from the error message).
478 </p>
479
480 <p>
481 If you see <e>error: /usr/bin/gcc-config: line 632:
482 /etc/env.d/gcc/i686-pc-linux-gnu-3.3.5: No such file or directory</e>, then try
483 deleting <path>/etc/env.d/gcc/config-i686-pc-linux-gnu</path> and running
484 <c>gcc-config</c> again, followed by <c>source /etc/profile</c>. Only do this
485 if you do not have any cross-compilers set up, though.
486 </p>
487
488 <p>
489 If a package fails during <c>emerge -e system</c> or <c>emerge -e world</c>,
490 you can resume operation with <c>emerge --resume</c>. If a package fails
491 repeatedly, skip it with <c>emerge --resume --skipfirst</c>. Don't run any
492 other instances of emerge in between or you will lose the resume information.
493 </p>
494
495 <p>
496 If you get an error message <e>spec failure: unrecognized spec option</e> while
497 upgrading your compiler, try to switch back to your default compiler, unset the
498 <c>GCC_SPECS</c> variable and upgrade GCC again:
499 </p>
500
501 <pre caption="Restoring primary specs">
502 # <i>gcc-config 1</i>
503 # <i>source /etc/profile</i>
504 # <i>unset GCC_SPECS</i>
505 # <i>emerge -uav gcc</i>
506 </pre>
507
508 </body>
509 </section>
510 </chapter>
511 </guide>

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