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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 1.11 2006/03/01 01:54:04 vanquirius 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>11</version>
29 <date>2006-03-01</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 newer version of GCC, the system will not switch over to use it
48 automatically. You'll have to explicitly request the change because the
49 migration process might require some additional steps. If you decide not to
50 switch, Portage will continue to use older version of your compiler until you
51 change your mind, or remove the old compiler from the system.
52 </p>
53
54 <p>
55 This guide will document the necessary steps required to perform a seamless
56 upgrade of the compiler used by your Gentoo box. A specific section is
57 dedicated to the <uri link="#upgrade-3.3-to-3.4">upgrade from GCC 3.3 to 3.4 or
58 greater versions</uri> and issues with <c>libstdc++</c>. A second specific
59 section is for users <uri link="#first-install">first installing</uri> Gentoo
60 using a stage3 tarball, after a new GCC major/minor version has been released.
61 </p>
62
63 <note>
64 It should be noted that upgrading from GCC-3.4 to GCC-4.0 or greater requires
65 no real changes to be made by the user, as GCC-3.4 and GCC-4.0 use the same
66 ABI. All that is required is that <c>gcc-config</c> is used to select the
67 compiler desired.
68 </note>
69
70 </body>
71 </section>
72 </chapter>
73
74 <chapter id="upgrade-general">
75 <title>General Upgrade Instructions</title>
76 <section>
77 <title>Introduction</title>
78 <body>
79
80 <impo>
81 If you're looking for instructions specific to upgrades from GCC-3.3 to GCC-3.4
82 or greater, please consult the <uri link="#upgrade-3.3-to-3.4">dedicated
83 section</uri>.
84 </impo>
85
86 <impo>
87 If you're looking for instructions specific to upgrades in GCC for new
88 installs, please consult the <uri link="#first-install">dedicated
89 section</uri>.
90 </impo>
91
92 <p>
93 Generally speaking, upgrades to <e>bug fix releases</e>, like from 3.3.5 to
94 3.3.6, should be quite safe -- just emerge new version, switch your system to
95 use it and rebuild the only affected package, <c>libtool</c>. However, some GCC
96 upgrades break binary compatibility; in such cases a rebuild of the affected
97 packages (or even whole toolchain and system) might be required.
98 </p>
99
100 <p>
101 When we spoke about the need to switch your compiler to the newer version by
102 hand, we said it won't happen automatically. However, there is one exception --
103 upgrades to bug fix releases, like from 3.3.5 to 3.3.6 in case you don't use the
104 "multislot" feature allowing them to coexist on one system. Multislot is
105 disabled by default as the majority of users won't benefit from it.
106 </p>
107
108 <pre caption="Upgrading GCC">
109 # <i>emerge -uav gcc</i>
110
111 <comment>(Please substitute "i686-pc-linux-gnu-3.4.5" with the GCC
112 version and CHOST settings you've upgraded to:)</comment>
113 # <i>gcc-config i686-pc-linux-gnu-3.4.5</i>
114 # <i>source /etc/profile</i>
115
116 <comment>(Rebuilding libtool)</comment>
117 # <i>emerge --oneshot -av libtool</i>
118 </pre>
119
120 <p>
121 Now let's rebuild toolchain and then world so we will make use of the new
122 compiler.
123 </p>
124
125 <pre caption="Rebuilding system">
126 # <i>emerge -eav system</i>
127 # <i>emerge -eav world</i>
128 </pre>
129
130 <p>
131 It is safe to remove the older GCC version at this time. If you feel the need,
132 please issue the following command (as usual, substitute
133 <c>=sys-devel/gcc-3.3*</c> with the version you want to uninstall):
134 </p>
135
136 <pre caption="Removing older GCC version">
137 # <i>emerge -aC =sys-devel/gcc-3.3*</i>
138 </pre>
139
140 </body>
141 </section>
142 </chapter>
143
144 <chapter id="upgrade-3.3-to-3.4">
145 <title>Upgrading from GCC-3.3 to 3.4 or greater</title>
146 <section>
147 <title>Introduction</title>
148 <body>
149
150 <p>
151 The upgrade from GCC-3.3 to 3.4 or greater is not seamless as the C++ ABI
152 changed between these two versions. There is an issue with the <c>libstdc++</c>
153 library which must be taken care of, as well.
154 </p>
155
156 </body>
157 </section>
158 <section id="upgrade-3.3-to-3.4-choices">
159 <title>The Choices</title>
160 <body>
161
162 <impo>
163 If you're upgrading on a SPARC machine, you will have to take the way of
164 <uri link="#upgrade-3.3-to-3.4-emerge-e">complete system rebuild</uri> due to
165 some internal <uri link="http://gcc.gnu.org/gcc-3.4/sparc-abi.html">ABI
166 changes</uri> in GCC's parameter passing.
167 </impo>
168
169 <p>
170 You have two possibilities on how to upgrade your system. The <uri
171 link="#upgrade-3.3-to-3.4-revdep-rebuild">first method</uri> is faster and
172 requires use of the <c>revdep-rebuild</c> tool from package <c>gentoolkit</c>
173 while the <uri link="#upgrade-3.3-to-3.4-emerge-e">second one</uri> rebuilds the
174 entire system from scratch so it will make use of new GCC features. It's up to
175 you to decide which of these two ways you will choose. In most cases, the first
176 method is sufficient.
177 </p>
178
179 </body>
180 </section>
181 <section id="upgrade-3.3-to-3.4-revdep-rebuild">
182 <title>Using revdep-rebuild</title>
183 <body>
184
185 <p>
186 This method requires that you first install <c>gentoolkit</c> if you have not
187 already done so. Then we will upgrade GCC and switch to the new compiler. We
188 will also rebuild the <c>libtool</c> package to ensure that toolchain is in
189 healthy state.
190 </p>
191
192 <pre caption="Installing gentoolkit and upgrading GCC">
193 # <i>emerge -an gentoolkit</i>
194 # <i>emerge -uav gcc</i>
195 <comment>(Please substitute "i686-pc-linux-gnu-3.4.5" with the GCC
196 version and CHOST settings you've upgraded to:)</comment>
197 # <i>gcc-config i686-pc-linux-gnu-3.4.5</i>
198 # <i>source /etc/profile</i>
199
200 <comment>(Rebuilding libtool)</comment>
201 # <i>emerge --oneshot -av libtool</i>
202 </pre>
203
204 <p>
205 Now, we want to see which packages that revdep-rebuild will want to rebuild.
206 Then we will tell revdep-rebuild to actually rebuild the packages. This may take
207 some time, so have some patience.
208 </p>
209
210 <pre caption="Using revdep-rebuild">
211 # <i>revdep-rebuild --library libstdc++.so.5 -- -p -v</i>
212 # <i>revdep-rebuild --library libstdc++.so.5</i>
213 </pre>
214
215 <note>
216 It is possible that you might have problems with non-existing package versions
217 due to them being outdated or masked. If this is the case, you will want to use
218 the <c>--package-names</c> option to <c>revdep-rebuild</c>. This causes packages
219 to be recompiled based on the package name, rather than the exact name and
220 version.
221 </note>
222
223 <p>
224 To provide compatibility with older binary C++ applications and any packages
225 that revdep-rebuild might have missed, <c>sys-libs/libstdc++-v3</c> needs to be
226 merged before you unmerge GCC 3.3 from your system.
227 </p>
228
229 <pre caption="Installing libstdc++-v3 and cleaning up">
230 # <i>emerge --oneshot sys-libs/libstdc++-v3</i>
231 # <i>emerge -aC =sys-devel/gcc-3.3*</i>
232 </pre>
233
234 </body>
235 </section>
236 <section id="upgrade-3.3-to-3.4-emerge-e">
237 <title>Using emerge -e</title>
238 <body>
239
240 <p>
241 This method, while much slower, will rebuild your whole system to ensure that
242 everything has been rebuilt with your new compiler, and therefore safer. At
243 first, you will upgrade GCC and libtool and switch to your new compiler.
244 </p>
245
246 <pre caption="Upgrading GCC">
247 # <i>emerge -uav gcc</i>
248 <comment>(Please substitute "i686-pc-linux-gnu-3.4.5" with the GCC
249 version and CHOST settings you've upgraded to:)</comment>
250 # <i>gcc-config i686-pc-linux-gnu-3.4.5</i>
251 # <i>source /etc/profile</i>
252
253 <comment>(Rebuilding libtool)</comment>
254 # <i>emerge --oneshot -av libtool</i>
255 </pre>
256
257 <p>
258 To provide compatibility with older binary C++ applications,
259 <c>sys-libs/libstdc++-v3</c> needs to be merged onto your system.
260 </p>
261
262 <pre caption="Installing libstdc++-v3">
263 # <i>emerge --oneshot sys-libs/libstdc++-v3</i>
264 </pre>
265
266 <p>
267 Now we will go about first rebuilding the system target, then the world target.
268 This will take a very long time, depending on the number of packages that you
269 have installed, as it will rebuild your entire toolchain and supporting system
270 files, followed by every package on your system, including the toolchain. This
271 is necessary to ensure that all packages have been compiled with the new
272 toolchain, including the toolchain itself.
273 </p>
274
275 <pre caption="Rebuilding system and world">
276 # <i>emerge -e system</i>
277 # <i>emerge -e world</i>
278 </pre>
279
280 <p>
281 It is also safe to remove older GCC versions at this time:
282 </p>
283
284 <pre caption="Cleaning up">
285 # <i>emerge -aC =sys-devel/gcc-3.3*</i>
286 </pre>
287
288 </body>
289 </section>
290 </chapter>
291
292 <chapter id="first-install">
293 <title>Upgrading to GCC on a First Install</title>
294 <section>
295 <title>Introduction</title>
296 <body>
297
298 <p>
299 A GCC upgrade on a system after installation from a stage3 tarball is a simple
300 affair. One advantage users of new installations have is they do not have a
301 plethora of software installed that links against the older version of GCC.
302 The following example is for a GCC-3.3 to 3.4 or greater upgrade. Certain parts
303 will be different if upgrading from other versions of GCC. For example, the
304 library names used for <c>revdep-rebuild</c> below are GCC 3.3 specific, as
305 well as the need to install <c>libstdc++-v3</c>.
306 </p>
307
308 <p>
309 If a user has not made any customizations to their system yet, then there are
310 very few steps to get their system upgraded to a new GCC version. As with the
311 GCC-3.3 to 3.4 upgrade, the user has a couple options. However, unlike the
312 GCC-3.3 to 3.4 upgrade, this one is less complicated as there are fewer
313 differences between the methods. The <uri
314 link="#first-install-revdep-rebuild">first method</uri> is faster and makes use
315 of the <c>revdep-rebuild</c> tool from <c>gentoolkit</c>, similar to the above
316 procedure. Using revdep-rebuild causes only packages which actually link
317 against GCC libraries to be rebuilt, while the <uri
318 link="#first-install-emerge-e">second method</uri> causes your entire new
319 install to be recompiled with the new GCC version and takes much longer. This
320 second method is never required and only documented for completeness.
321 </p>
322
323 <p>
324 These first steps are common between both methods, and should be completed by
325 everyone.
326 </p>
327
328 <pre caption="Upgrading GCC">
329 # <i>emerge -uav gcc</i>
330 <comment>(Please substitute "i686-pc-linux-gnu-3.4.5" with the GCC
331 version and CHOST settings you've upgraded to:)</comment>
332 # <i>gcc-config i686-pc-linux-gnu-3.4.5</i>
333 # <i>source /etc/profile</i>
334
335 <comment>(Rebuilding libtool)</comment>
336 # <i>emerge --oneshot -av libtool</i>
337 </pre>
338
339 <p>
340 To provide compatibility with older binary C++ applications,
341 <c>sys-libs/libstdc++-v3</c> needs to be merged onto your system.
342 </p>
343
344 <pre caption="Installing libstdc++-v3">
345 # <i>emerge --oneshot sys-libs/libstdc++-v3</i>
346 </pre>
347
348 </body>
349 </section>
350
351 <section id="first-install-revdep-rebuild">
352 <title>Using revdep-rebuild</title>
353 <body>
354
355 <p>
356 This method requires that you first install <c>gentoolkit</c> if you have not
357 already done so. We will then run <c>revdep-rebuild</c> to actually scan the
358 installed packages for ones we need to rebuild, then rebuild them.
359 </p>
360
361 <pre caption="Installing gentoolkit and running revdep-rebuild">
362 # <i>emerge -an gentoolkit</i>
363 # <i>revdep-rebuild --library libstdc++.so.5 -- -p -v</i>
364 # <i>revdep-rebuild --library libstdc++.so.5</i>
365 </pre>
366
367 <note>
368 It is possible that you might have problems with non-existing package versions
369 due to them being outdated or masked. If this is the case, you will want to use
370 the <c>--package-names</c> option to <c>revdep-rebuild</c>. This causes packages
371 to be recompiled based on the package name, rather than the exact name and
372 version.
373 </note>
374
375 </body>
376 </section>
377 <section id="first-install-emerge-e">
378 <title>Using emerge -e</title>
379 <body>
380
381 <p>
382 This method, while much slower, will rebuild the system target to ensure that
383 everything has been rebuilt with your new compiler. This is not necessary, but
384 is valid if you are also making changes to CFLAGS or other make.conf variables
385 that will affect the system compile.
386 </p>
387
388 <p>
389 Since we are performing these actions after an initial installation, we do not
390 need to recompile the <c>world</c> target as we would when doing an upgrade on
391 an already installed system. However, you may choose to perform a world update
392 in place of the system update, to ensure that all packages are updated.
393 </p>
394
395 <pre caption="Rebuilding system">
396 # <i>emerge -e system</i>
397 </pre>
398
399 </body>
400 </section>
401 <section id="first-install-cleaning-up">
402 <title>Cleaning up</title>
403 <body>
404
405 <p>
406 It is also safe to remove older GCC versions at this time. Please substitute
407 <c>YOUR-NEW-GCC-VERSION</c> with the actual version you've upgraded to:
408 </p>
409
410 <pre caption="Cleaning up">
411 # <i>emerge -aC "&lt;sys-devel/gcc-YOUR-NEW-GCC-VERSION"</i>
412 </pre>
413
414 </body>
415 </section>
416 </chapter>
417
418 <chapter id="common-pitfalls">
419 <title>Common Pitfalls</title>
420 <section>
421 <body>
422
423 <p>
424 It's important to disable <c>distcc</c> during upgrade. Mixing compiler versions
425 on your nodes <e>will</e> cause build issues. This is not required for ccache,
426 as the cache objects will be invalidated anyway.
427 </p>
428
429 <p>
430 Always use same GCC version for your kernel and additional kernel modules. Once
431 you rebuild your world with new GCC, external modules (like
432 <c>app-emulation/qemu-softmmu</c>) will fail to load. Please rebuild your kernel
433 with new GCC to fix that.
434 </p>
435
436 <p>
437 If you're upgrading on a SPARC machine, make sure to rerun <c>silo -f</c> after
438 re-emerging world to avoid possible issues.
439 </p>
440
441 </body>
442 </section>
443 <section>
444 <title>Frequent Error Messages</title>
445 <body>
446
447 <p>
448 If your system complains about something like <e>libtool: link:
449 `/usr/lib/gcc-lib/i686-pc-linux-gnu/3.3.6/libstdc++.la' is not a valid libtool
450 archive</e>, please run <c>/sbin/fix_libtool_files.sh 3.3.6</c> (substitute
451 "3.3.6" with the version numbers from the error message).
452 </p>
453
454 <p>
455 If you see the <e>error: /usr/bin/gcc-config: line 632:
456 /etc/env.d/gcc/i686-pc-linux-gnu-3.3.5: No such file or directory</e>, then try
457 deleting <path>/etc/env.d/gcc/config-i686-pc-linux-gnu</path> and running
458 <c>gcc-config</c> again, followed by <c>source /etc/profile</c>. Only do this if
459 you do not have any cross-compilers set up, though.
460 </p>
461
462 <p>
463 If a package fails during <c>emerge -e system</c> or <c>emerge -e world</c>,
464 you can resume operation with <c>emerge --resume</c>. If a package fails
465 repeatedly, skip it with <c>emerge --resume --skipfirst</c>. Don't run any
466 other instances of emerge in between or you will lose the resume information.
467 </p>
468
469 <p>
470 If you get an error message <e>spec failure: unrecognized spec option</e> while
471 upgrading your compiler, try to switch back to your default compiler, unset the
472 <c>GCC_SPECS</c> variable and upgrade GCC again:
473 </p>
474
475 <pre caption="Restoring primary specs">
476 # <i>gcc-config 1</i>
477 # <i>source /etc/profile</i>
478 # <i>unset GCC_SPECS</i>
479 # <i>emerge -uav gcc</i>
480 </pre>
481
482 </body>
483 </section>
484 </chapter>
485 </guide>

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