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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 1.15 2006/09/02 04:16:58 vapier Exp $ -->
3
4 <!DOCTYPE guide SYSTEM "/dtd/guide.dtd">
5
6 <guide link="/doc/en/gcc-upgrading.xml">
7 <title>Gentoo Linux 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="halcy0n@gentoo.org">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 Linux 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>14</version>
29 <date>2006-09-01</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 or
60 greater versions</uri> 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 general upgrading instructions, as GCC-3.4 and
68 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 or greater, 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 </body>
146 </section>
147 </chapter>
148
149 <chapter id="upgrade-3.3-to-3.4">
150 <title>Upgrading from GCC-3.3 to 3.4 or greater</title>
151 <section>
152 <title>Introduction</title>
153 <body>
154
155 <p>
156 The upgrade from GCC-3.3 to 3.4 or greater is not seamless as the C++ ABI
157 changed between these two versions. There is an issue with the <c>libstdc++</c>
158 library which must be taken care of, as well.
159 </p>
160
161 </body>
162 </section>
163 <section id="upgrade-3.3-to-3.4-choices">
164 <title>The Choices</title>
165 <body>
166
167 <impo>
168 If you upgrade from gcc 3.4 to 4.1, please consult the General Update
169 instructions.
170 </impo>
171
172 <impo>
173 If you're upgrading on a SPARC machine, you will have to take the way of
174 <uri link="#upgrade-3.3-to-3.4-emerge-e">complete system rebuild</uri> due to
175 some internal <uri link="http://gcc.gnu.org/gcc-3.4/sparc-abi.html">ABI
176 changes</uri> in GCC's parameter passing.
177 </impo>
178
179 <p>
180 If you upgrade from gcc 3.3 to 3.4, you have two possibilities on how to
181 upgrade your system. The <uri link="#upgrade-3.3-to-3.4-revdep-rebuild">first
182 method</uri> is faster and requires use of the <c>revdep-rebuild</c> tool from
183 package <c>gentoolkit</c> while the <uri
184 link="#upgrade-3.3-to-3.4-emerge-e">second one</uri> rebuilds the entire
185 system from scratch so it will make use of new GCC features. It's up to you to decide which of these two ways you will choose. In most cases, the first
186 method is sufficient.</p>
187 <p>If you upgrade from gcc 3.3 to 4.1, do not use the method based on
188 revdep-rebuild, but do a <uri link="#upgrade-3.3-to-3.4-emerge-e">complete
189 system rebuild</uri>.
190 </p>
191
192 </body>
193 </section>
194 <section id="upgrade-3.3-to-3.4-revdep-rebuild">
195 <title>Using revdep-rebuild</title>
196 <body>
197
198 <p>
199 This method requires that you first install <c>gentoolkit</c> if you have not
200 already done so. Then we will upgrade GCC and switch to the new compiler. We
201 will also rebuild the <c>libtool</c> package to ensure that toolchain is in
202 healthy state.
203 </p>
204
205 <pre caption="Installing gentoolkit and upgrading GCC">
206 # <i>emerge -an gentoolkit</i>
207 # <i>emerge -uav gcc</i>
208 <comment>(Please substitute "i686-pc-linux-gnu-3.4.5" with the GCC
209 version and CHOST settings you've upgraded to:)</comment>
210 # <i>gcc-config i686-pc-linux-gnu-3.4.5</i>
211 # <i>source /etc/profile</i>
212
213 <comment>(Rebuilding libtool)</comment>
214 # <i>emerge --oneshot -av libtool</i>
215 </pre>
216
217 <p>
218 Now, we want to see which packages that revdep-rebuild will want to rebuild.
219 Then we will tell revdep-rebuild to actually rebuild the packages. This may take
220 some time, so have some patience.
221 </p>
222
223 <pre caption="Using revdep-rebuild">
224 # <i>revdep-rebuild --library libstdc++.so.5 -- -p -v</i>
225 # <i>revdep-rebuild --library libstdc++.so.5</i>
226 </pre>
227
228 <note>
229 It is possible that you might have problems with non-existing package versions
230 due to them being outdated or masked. If this is the case, you will want to use
231 the <c>--package-names</c> option to <c>revdep-rebuild</c>. This causes packages
232 to be recompiled based on the package name, rather than the exact name and
233 version.
234 </note>
235
236 <p>
237 To provide compatibility with older binary C++ applications and any packages
238 that revdep-rebuild might have missed, <c>sys-libs/libstdc++-v3</c> needs to be
239 merged before you unmerge GCC 3.3 from your system.
240 </p>
241
242 <pre caption="Installing libstdc++-v3 and cleaning up">
243 # <i>emerge --oneshot sys-libs/libstdc++-v3</i>
244 # <i>emerge -aC =sys-devel/gcc-3.3*</i>
245 </pre>
246
247 </body>
248 </section>
249 <section id="upgrade-3.3-to-3.4-emerge-e">
250 <title>Using emerge -e</title>
251 <body>
252
253 <p>
254 This method, while much slower, will rebuild your whole system to ensure that
255 everything has been rebuilt with your new compiler, and therefore safer. At
256 first, you will upgrade GCC and libtool and switch to your new compiler.
257 </p>
258
259 <pre caption="Upgrading GCC">
260 # <i>emerge -uav gcc</i>
261 <comment>(Please substitute "i686-pc-linux-gnu-3.4.5" with the GCC
262 version and CHOST settings you've upgraded to:)</comment>
263 # <i>gcc-config i686-pc-linux-gnu-3.4.5</i>
264 # <i>source /etc/profile</i>
265
266 <comment>If you upgraded from gcc 3 to 4 (e.g. from 3.3.6 to 4.1.1 in this
267 example) you will have to run fix_libtool_files.sh manually</comment>
268 # <i>fix_libtool_files.sh 3.3.6</i>
269
270 <comment>(Rebuilding libtool)</comment>
271 # <i>emerge --oneshot -av libtool</i>
272 </pre>
273
274 <p>
275 To provide compatibility with older binary C++ applications,
276 <c>sys-libs/libstdc++-v3</c> needs to be merged onto your system.
277 </p>
278
279 <pre caption="Installing libstdc++-v3">
280 # <i>emerge --oneshot sys-libs/libstdc++-v3</i>
281 </pre>
282
283 <p>
284 Now we will go about first rebuilding the system target, then the world target.
285 This will take a very long time, depending on the number of packages that you
286 have installed, as it will rebuild your entire toolchain and supporting system
287 files, followed by every package on your system, including the toolchain. This
288 is necessary to ensure that all packages have been compiled with the new
289 toolchain, including the toolchain itself.
290 </p>
291
292 <pre caption="Rebuilding system and world">
293 # <i>emerge -e system</i>
294 # <i>emerge -e world</i>
295 </pre>
296
297 <p>
298 It is also safe to remove older GCC versions at this time:
299 </p>
300
301 <pre caption="Cleaning up">
302 # <i>emerge -aC =sys-devel/gcc-3.3*</i>
303 </pre>
304
305 </body>
306 </section>
307 </chapter>
308
309 <chapter id="first-install">
310 <title>Upgrading to GCC on a First Install</title>
311 <section>
312 <title>Introduction</title>
313 <body>
314
315 <p>
316 A GCC upgrade on a system after installation from a stage3 tarball is a simple
317 affair. One advantage users of new installations have is they do not have a
318 plethora of software installed that links against the older version of GCC.
319 The following example is for a GCC-3.3 to 3.4 or greater upgrade. Certain parts
320 will be different if upgrading from other versions of GCC. For example, the
321 library names used for <c>revdep-rebuild</c> below are GCC 3.3 specific, as
322 well as the need to install <c>libstdc++-v3</c>.
323 </p>
324
325 <p>
326 If a user has not made any customizations to their system yet, then there are
327 very few steps to get their system upgraded to a new GCC version. As with the
328 GCC-3.3 to 3.4 upgrade, the user has a couple options. However, unlike the
329 GCC-3.3 to 3.4 upgrade, this one is less complicated as there are fewer
330 differences between the methods. The <uri
331 link="#first-install-revdep-rebuild">first method</uri> is faster and makes use
332 of the <c>revdep-rebuild</c> tool from <c>gentoolkit</c>, similar to the above
333 procedure. Using revdep-rebuild causes only packages which actually link
334 against GCC libraries to be rebuilt, while the <uri
335 link="#first-install-emerge-e">second method</uri> causes your entire new
336 install to be recompiled with the new GCC version and takes much longer. This
337 second method is never required and only documented for completeness.
338 </p>
339
340 <p>
341 These first steps are common between both methods, and should be completed by
342 everyone.
343 </p>
344
345 <pre caption="Upgrading GCC">
346 # <i>emerge -uav gcc</i>
347 <comment>(Please substitute "i686-pc-linux-gnu-3.4.5" with the GCC
348 version and CHOST settings you've upgraded to:)</comment>
349 # <i>gcc-config i686-pc-linux-gnu-3.4.5</i>
350 # <i>source /etc/profile</i>
351
352 <comment>(Rebuilding libtool)</comment>
353 # <i>emerge --oneshot -av libtool</i>
354 </pre>
355
356 <p>
357 To provide compatibility with older binary C++ applications,
358 <c>sys-libs/libstdc++-v3</c> needs to be merged onto your system.
359 </p>
360
361 <pre caption="Installing libstdc++-v3">
362 # <i>emerge --oneshot sys-libs/libstdc++-v3</i>
363 </pre>
364
365 </body>
366 </section>
367
368 <section id="first-install-revdep-rebuild">
369 <title>Using revdep-rebuild</title>
370 <body>
371
372 <p>
373 This method requires that you first install <c>gentoolkit</c> if you have not
374 already done so. We will then run <c>revdep-rebuild</c> to actually scan the
375 installed packages for ones we need to rebuild, then rebuild them.
376 </p>
377
378 <pre caption="Installing gentoolkit and running revdep-rebuild">
379 # <i>emerge -an gentoolkit</i>
380 # <i>revdep-rebuild --library libstdc++.so.5 -- -p -v</i>
381 # <i>revdep-rebuild --library libstdc++.so.5</i>
382 </pre>
383
384 <note>
385 It is possible that you might have problems with non-existing package versions
386 due to them being outdated or masked. If this is the case, you will want to use
387 the <c>--package-names</c> option to <c>revdep-rebuild</c>. This causes packages
388 to be recompiled based on the package name, rather than the exact name and
389 version.
390 </note>
391
392 </body>
393 </section>
394 <section id="first-install-emerge-e">
395 <title>Using emerge -e</title>
396 <body>
397
398 <p>
399 This method, while much slower, will rebuild the system target to ensure that
400 everything has been rebuilt with your new compiler. This is not necessary, but
401 is valid if you are also making changes to CFLAGS or other make.conf variables
402 that will affect the system compile.
403 </p>
404
405 <p>
406 Since we are performing these actions after an initial installation, we do not
407 need to recompile the <c>world</c> target as we would when doing an upgrade on
408 an already installed system. However, you may choose to perform a world update
409 in place of the system update, to ensure that all packages are updated.
410 </p>
411
412 <pre caption="Rebuilding system">
413 # <i>emerge -e system</i>
414 </pre>
415
416 </body>
417 </section>
418 <section id="first-install-cleaning-up">
419 <title>Cleaning up</title>
420 <body>
421
422 <p>
423 It is also safe to remove older GCC versions at this time. Please substitute
424 <c>YOUR-NEW-GCC-VERSION</c> with the actual version you've upgraded to:
425 </p>
426
427 <pre caption="Cleaning up">
428 # <i>emerge -aC "&lt;sys-devel/gcc-YOUR-NEW-GCC-VERSION"</i>
429 </pre>
430
431 </body>
432 </section>
433 </chapter>
434
435 <chapter id="common-pitfalls">
436 <title>Common Pitfalls</title>
437 <section>
438 <body>
439
440 <p>
441 It's important to disable <c>distcc</c> during upgrade. Mixing compiler versions
442 on your nodes <e>will</e> cause build issues. This is not required for ccache,
443 as the cache objects will be invalidated anyway.
444 </p>
445
446 <p>
447 Always use same GCC version for your kernel and additional kernel modules. Once
448 you rebuild your world with new GCC, external modules (like
449 <c>app-emulation/qemu-softmmu</c>) will fail to load. Please rebuild your
450 kernel with the new GCC to fix that.
451 </p>
452
453 <p>
454 If you're upgrading on a SPARC machine, make sure to rerun <c>silo -f</c> after
455 re-emerging world to avoid possible issues.
456 </p>
457
458 </body>
459 </section>
460 <section>
461 <title>Frequent Error Messages</title>
462 <body>
463
464 <p>
465 If your system complains about something like <e>libtool: link:
466 `/usr/lib/gcc-lib/i686-pc-linux-gnu/3.3.6/libstdc++.la' is not a valid libtool
467 archive</e>, please run <c>/sbin/fix_libtool_files.sh 3.3.6</c> (substitute
468 "3.3.6" with the version numbers from the error message).
469 </p>
470
471 <p>
472 If you see <e>error: /usr/bin/gcc-config: line 632:
473 /etc/env.d/gcc/i686-pc-linux-gnu-3.3.5: No such file or directory</e>, then try
474 deleting <path>/etc/env.d/gcc/config-i686-pc-linux-gnu</path> and running
475 <c>gcc-config</c> again, followed by <c>source /etc/profile</c>. Only do this
476 if you do not have any cross-compilers set up, though.
477 </p>
478
479 <p>
480 If a package fails during <c>emerge -e system</c> or <c>emerge -e world</c>,
481 you can resume operation with <c>emerge --resume</c>. If a package fails
482 repeatedly, skip it with <c>emerge --resume --skipfirst</c>. Don't run any
483 other instances of emerge in between or you will lose the resume information.
484 </p>
485
486 <p>
487 If you get an error message <e>spec failure: unrecognized spec option</e> while
488 upgrading your compiler, try to switch back to your default compiler, unset the
489 <c>GCC_SPECS</c> variable and upgrade GCC again:
490 </p>
491
492 <pre caption="Restoring primary specs">
493 # <i>gcc-config 1</i>
494 # <i>source /etc/profile</i>
495 # <i>unset GCC_SPECS</i>
496 # <i>emerge -uav gcc</i>
497 </pre>
498
499 </body>
500 </section>
501 </chapter>
502 </guide>

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