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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 1.12 2006/03/01 20:17:49 jkt 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>12</version>
29 <date>2006-05-26</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 <warn>
64 It should be noted that upgrading from GCC-3.4 to GCC-4.1 or greater still
65 requires you to follow the general upgrading instructions, as GCC-3.4 and
66 GCC-4.1 use slightly different ABIs.
67 </warn>
68
69 </body>
70 </section>
71 </chapter>
72
73 <chapter id="upgrade-general">
74 <title>General Upgrade Instructions</title>
75 <section>
76 <title>Introduction</title>
77 <body>
78
79 <impo>
80 If you're looking for instructions specific to upgrades from GCC-3.3 to GCC-3.4
81 or greater, please consult the <uri link="#upgrade-3.3-to-3.4">dedicated
82 section</uri>.
83 </impo>
84
85 <impo>
86 If you're looking for instructions specific to upgrades in GCC for new
87 installs, please consult the <uri link="#first-install">dedicated
88 section</uri>.
89 </impo>
90
91 <p>
92 Generally speaking, upgrades to <e>bug fix releases</e>, like from 3.3.5 to
93 3.3.6, should be quite safe -- just emerge new version, switch your system to
94 use it and rebuild the only affected package, <c>libtool</c>. However, some GCC
95 upgrades break binary compatibility; in such cases a rebuild of the affected
96 packages (or even whole toolchain and system) might be required.
97 </p>
98
99 <p>
100 When we spoke about the need to switch your compiler to the newer version by
101 hand, we said it won't happen automatically. However, there is one exception --
102 upgrades to bug fix releases, like from 3.3.5 to 3.3.6 in case you don't use the
103 "multislot" feature allowing them to coexist on one system. Multislot is
104 disabled by default as the majority of users won't benefit from it.
105 </p>
106
107 <pre caption="Upgrading GCC">
108 # <i>emerge -uav gcc</i>
109
110 <comment>(Please substitute "i686-pc-linux-gnu-3.4.5" with the GCC
111 version and CHOST settings you've upgraded to:)</comment>
112 # <i>gcc-config i686-pc-linux-gnu-3.4.5</i>
113 # <i>source /etc/profile</i>
114
115 <comment>(Rebuilding libtool)</comment>
116 # <i>emerge --oneshot -av libtool</i>
117 </pre>
118
119 <p>
120 Now let's rebuild toolchain and then world so we will make use of the new
121 compiler.
122 </p>
123
124 <pre caption="Rebuilding system">
125 # <i>emerge -eav system</i>
126 # <i>emerge -eav world</i>
127 </pre>
128
129 <p>
130 It is safe to remove the older GCC version at this time. If you feel the need,
131 please issue the following command (as usual, substitute
132 <c>=sys-devel/gcc-3.3*</c> with the version you want to uninstall):
133 </p>
134
135 <pre caption="Removing older GCC version">
136 # <i>emerge -aC =sys-devel/gcc-3.3*</i>
137 </pre>
138
139 </body>
140 </section>
141 </chapter>
142
143 <chapter id="upgrade-3.3-to-3.4">
144 <title>Upgrading from GCC-3.3 to 3.4 or greater</title>
145 <section>
146 <title>Introduction</title>
147 <body>
148
149 <p>
150 The upgrade from GCC-3.3 to 3.4 or greater is not seamless as the C++ ABI
151 changed between these two versions. There is an issue with the <c>libstdc++</c>
152 library which must be taken care of, as well.
153 </p>
154
155 </body>
156 </section>
157 <section id="upgrade-3.3-to-3.4-choices">
158 <title>The Choices</title>
159 <body>
160
161 <impo>
162 If you're upgrading on a SPARC machine, you will have to take the way of
163 <uri link="#upgrade-3.3-to-3.4-emerge-e">complete system rebuild</uri> due to
164 some internal <uri link="http://gcc.gnu.org/gcc-3.4/sparc-abi.html">ABI
165 changes</uri> in GCC's parameter passing.
166 </impo>
167
168 <p>
169 You have two possibilities on how to upgrade your system. The <uri
170 link="#upgrade-3.3-to-3.4-revdep-rebuild">first method</uri> is faster and
171 requires use of the <c>revdep-rebuild</c> tool from package <c>gentoolkit</c>
172 while the <uri link="#upgrade-3.3-to-3.4-emerge-e">second one</uri> rebuilds the
173 entire system from scratch so it will make use of new GCC features. It's up to
174 you to decide which of these two ways you will choose. In most cases, the first
175 method is sufficient.
176 </p>
177
178 </body>
179 </section>
180 <section id="upgrade-3.3-to-3.4-revdep-rebuild">
181 <title>Using revdep-rebuild</title>
182 <body>
183
184 <p>
185 This method requires that you first install <c>gentoolkit</c> if you have not
186 already done so. Then we will upgrade GCC and switch to the new compiler. We
187 will also rebuild the <c>libtool</c> package to ensure that toolchain is in
188 healthy state.
189 </p>
190
191 <pre caption="Installing gentoolkit and upgrading GCC">
192 # <i>emerge -an gentoolkit</i>
193 # <i>emerge -uav gcc</i>
194 <comment>(Please substitute "i686-pc-linux-gnu-3.4.5" with the GCC
195 version and CHOST settings you've upgraded to:)</comment>
196 # <i>gcc-config i686-pc-linux-gnu-3.4.5</i>
197 # <i>source /etc/profile</i>
198
199 <comment>(Rebuilding libtool)</comment>
200 # <i>emerge --oneshot -av libtool</i>
201 </pre>
202
203 <p>
204 Now, we want to see which packages that revdep-rebuild will want to rebuild.
205 Then we will tell revdep-rebuild to actually rebuild the packages. This may take
206 some time, so have some patience.
207 </p>
208
209 <pre caption="Using revdep-rebuild">
210 # <i>revdep-rebuild --library libstdc++.so.5 -- -p -v</i>
211 # <i>revdep-rebuild --library libstdc++.so.5</i>
212 </pre>
213
214 <note>
215 It is possible that you might have problems with non-existing package versions
216 due to them being outdated or masked. If this is the case, you will want to use
217 the <c>--package-names</c> option to <c>revdep-rebuild</c>. This causes packages
218 to be recompiled based on the package name, rather than the exact name and
219 version.
220 </note>
221
222 <p>
223 To provide compatibility with older binary C++ applications and any packages
224 that revdep-rebuild might have missed, <c>sys-libs/libstdc++-v3</c> needs to be
225 merged before you unmerge GCC 3.3 from your system.
226 </p>
227
228 <pre caption="Installing libstdc++-v3 and cleaning up">
229 # <i>emerge --oneshot sys-libs/libstdc++-v3</i>
230 # <i>emerge -aC =sys-devel/gcc-3.3*</i>
231 </pre>
232
233 </body>
234 </section>
235 <section id="upgrade-3.3-to-3.4-emerge-e">
236 <title>Using emerge -e</title>
237 <body>
238
239 <p>
240 This method, while much slower, will rebuild your whole system to ensure that
241 everything has been rebuilt with your new compiler, and therefore safer. At
242 first, you will upgrade GCC and libtool and switch to your new compiler.
243 </p>
244
245 <pre caption="Upgrading GCC">
246 # <i>emerge -uav gcc</i>
247 <comment>(Please substitute "i686-pc-linux-gnu-3.4.5" with the GCC
248 version and CHOST settings you've upgraded to:)</comment>
249 # <i>gcc-config i686-pc-linux-gnu-3.4.5</i>
250 # <i>source /etc/profile</i>
251
252 <comment>(Rebuilding libtool)</comment>
253 # <i>emerge --oneshot -av libtool</i>
254 </pre>
255
256 <p>
257 To provide compatibility with older binary C++ applications,
258 <c>sys-libs/libstdc++-v3</c> needs to be merged onto your system.
259 </p>
260
261 <pre caption="Installing libstdc++-v3">
262 # <i>emerge --oneshot sys-libs/libstdc++-v3</i>
263 </pre>
264
265 <p>
266 Now we will go about first rebuilding the system target, then the world target.
267 This will take a very long time, depending on the number of packages that you
268 have installed, as it will rebuild your entire toolchain and supporting system
269 files, followed by every package on your system, including the toolchain. This
270 is necessary to ensure that all packages have been compiled with the new
271 toolchain, including the toolchain itself.
272 </p>
273
274 <pre caption="Rebuilding system and world">
275 # <i>emerge -e system</i>
276 # <i>emerge -e world</i>
277 </pre>
278
279 <p>
280 It is also safe to remove older GCC versions at this time:
281 </p>
282
283 <pre caption="Cleaning up">
284 # <i>emerge -aC =sys-devel/gcc-3.3*</i>
285 </pre>
286
287 </body>
288 </section>
289 </chapter>
290
291 <chapter id="first-install">
292 <title>Upgrading to GCC on a First Install</title>
293 <section>
294 <title>Introduction</title>
295 <body>
296
297 <p>
298 A GCC upgrade on a system after installation from a stage3 tarball is a simple
299 affair. One advantage users of new installations have is they do not have a
300 plethora of software installed that links against the older version of GCC.
301 The following example is for a GCC-3.3 to 3.4 or greater upgrade. Certain parts
302 will be different if upgrading from other versions of GCC. For example, the
303 library names used for <c>revdep-rebuild</c> below are GCC 3.3 specific, as
304 well as the need to install <c>libstdc++-v3</c>.
305 </p>
306
307 <p>
308 If a user has not made any customizations to their system yet, then there are
309 very few steps to get their system upgraded to a new GCC version. As with the
310 GCC-3.3 to 3.4 upgrade, the user has a couple options. However, unlike the
311 GCC-3.3 to 3.4 upgrade, this one is less complicated as there are fewer
312 differences between the methods. The <uri
313 link="#first-install-revdep-rebuild">first method</uri> is faster and makes use
314 of the <c>revdep-rebuild</c> tool from <c>gentoolkit</c>, similar to the above
315 procedure. Using revdep-rebuild causes only packages which actually link
316 against GCC libraries to be rebuilt, while the <uri
317 link="#first-install-emerge-e">second method</uri> causes your entire new
318 install to be recompiled with the new GCC version and takes much longer. This
319 second method is never required and only documented for completeness.
320 </p>
321
322 <p>
323 These first steps are common between both methods, and should be completed by
324 everyone.
325 </p>
326
327 <pre caption="Upgrading GCC">
328 # <i>emerge -uav gcc</i>
329 <comment>(Please substitute "i686-pc-linux-gnu-3.4.5" with the GCC
330 version and CHOST settings you've upgraded to:)</comment>
331 # <i>gcc-config i686-pc-linux-gnu-3.4.5</i>
332 # <i>source /etc/profile</i>
333
334 <comment>(Rebuilding libtool)</comment>
335 # <i>emerge --oneshot -av libtool</i>
336 </pre>
337
338 <p>
339 To provide compatibility with older binary C++ applications,
340 <c>sys-libs/libstdc++-v3</c> needs to be merged onto your system.
341 </p>
342
343 <pre caption="Installing libstdc++-v3">
344 # <i>emerge --oneshot sys-libs/libstdc++-v3</i>
345 </pre>
346
347 </body>
348 </section>
349
350 <section id="first-install-revdep-rebuild">
351 <title>Using revdep-rebuild</title>
352 <body>
353
354 <p>
355 This method requires that you first install <c>gentoolkit</c> if you have not
356 already done so. We will then run <c>revdep-rebuild</c> to actually scan the
357 installed packages for ones we need to rebuild, then rebuild them.
358 </p>
359
360 <pre caption="Installing gentoolkit and running revdep-rebuild">
361 # <i>emerge -an gentoolkit</i>
362 # <i>revdep-rebuild --library libstdc++.so.5 -- -p -v</i>
363 # <i>revdep-rebuild --library libstdc++.so.5</i>
364 </pre>
365
366 <note>
367 It is possible that you might have problems with non-existing package versions
368 due to them being outdated or masked. If this is the case, you will want to use
369 the <c>--package-names</c> option to <c>revdep-rebuild</c>. This causes packages
370 to be recompiled based on the package name, rather than the exact name and
371 version.
372 </note>
373
374 </body>
375 </section>
376 <section id="first-install-emerge-e">
377 <title>Using emerge -e</title>
378 <body>
379
380 <p>
381 This method, while much slower, will rebuild the system target to ensure that
382 everything has been rebuilt with your new compiler. This is not necessary, but
383 is valid if you are also making changes to CFLAGS or other make.conf variables
384 that will affect the system compile.
385 </p>
386
387 <p>
388 Since we are performing these actions after an initial installation, we do not
389 need to recompile the <c>world</c> target as we would when doing an upgrade on
390 an already installed system. However, you may choose to perform a world update
391 in place of the system update, to ensure that all packages are updated.
392 </p>
393
394 <pre caption="Rebuilding system">
395 # <i>emerge -e system</i>
396 </pre>
397
398 </body>
399 </section>
400 <section id="first-install-cleaning-up">
401 <title>Cleaning up</title>
402 <body>
403
404 <p>
405 It is also safe to remove older GCC versions at this time. Please substitute
406 <c>YOUR-NEW-GCC-VERSION</c> with the actual version you've upgraded to:
407 </p>
408
409 <pre caption="Cleaning up">
410 # <i>emerge -aC "&lt;sys-devel/gcc-YOUR-NEW-GCC-VERSION"</i>
411 </pre>
412
413 </body>
414 </section>
415 </chapter>
416
417 <chapter id="common-pitfalls">
418 <title>Common Pitfalls</title>
419 <section>
420 <body>
421
422 <p>
423 It's important to disable <c>distcc</c> during upgrade. Mixing compiler versions
424 on your nodes <e>will</e> cause build issues. This is not required for ccache,
425 as the cache objects will be invalidated anyway.
426 </p>
427
428 <p>
429 Always use same GCC version for your kernel and additional kernel modules. Once
430 you rebuild your world with new GCC, external modules (like
431 <c>app-emulation/qemu-softmmu</c>) will fail to load. Please rebuild your kernel
432 with new GCC to fix that.
433 </p>
434
435 <p>
436 If you're upgrading on a SPARC machine, make sure to rerun <c>silo -f</c> after
437 re-emerging world to avoid possible issues.
438 </p>
439
440 </body>
441 </section>
442 <section>
443 <title>Frequent Error Messages</title>
444 <body>
445
446 <p>
447 If your system complains about something like <e>libtool: link:
448 `/usr/lib/gcc-lib/i686-pc-linux-gnu/3.3.6/libstdc++.la' is not a valid libtool
449 archive</e>, please run <c>/sbin/fix_libtool_files.sh 3.3.6</c> (substitute
450 "3.3.6" with the version numbers from the error message).
451 </p>
452
453 <p>
454 If you see the <e>error: /usr/bin/gcc-config: line 632:
455 /etc/env.d/gcc/i686-pc-linux-gnu-3.3.5: No such file or directory</e>, then try
456 deleting <path>/etc/env.d/gcc/config-i686-pc-linux-gnu</path> and running
457 <c>gcc-config</c> again, followed by <c>source /etc/profile</c>. Only do this if
458 you do not have any cross-compilers set up, though.
459 </p>
460
461 <p>
462 If a package fails during <c>emerge -e system</c> or <c>emerge -e world</c>,
463 you can resume operation with <c>emerge --resume</c>. If a package fails
464 repeatedly, skip it with <c>emerge --resume --skipfirst</c>. Don't run any
465 other instances of emerge in between or you will lose the resume information.
466 </p>
467
468 <p>
469 If you get an error message <e>spec failure: unrecognized spec option</e> while
470 upgrading your compiler, try to switch back to your default compiler, unset the
471 <c>GCC_SPECS</c> variable and upgrade GCC again:
472 </p>
473
474 <pre caption="Restoring primary specs">
475 # <i>gcc-config 1</i>
476 # <i>source /etc/profile</i>
477 # <i>unset GCC_SPECS</i>
478 # <i>emerge -uav gcc</i>
479 </pre>
480
481 </body>
482 </section>
483 </chapter>
484 </guide>

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