Gentoo Archives: gentoo-embedded

From: John Poole <jlpoole@×××.net>
To: gentoo-embedded@l.g.o
Subject: [gentoo-embedded] Embedded Handbook (5)(b) clarification
Date: Tue, 06 Oct 2009 02:18:12
1 I'd like to get some clarification on the Embedded Handbook,
2 particularly Chapter 5, subsection 5(b) "Filesystem Setup"
4 I'm trying to cross-compile on an AMD64 for two Marvel ARM architectures:
5 a) SheevaPlug which as the ARMv5TE without a numeric coprocessor "softfloat"
8 b) OpenRD Client which has the ARMv5TE
11 I previously had problems trying to install and work my cross compiler,
12 so I simply rebuilt my AMD box and see that the Embedded Handbook has
13 recently been updated in September, 2009. I had considerable help from
14 Mike Frysinger back in May and June on IRC, but I lost my chat logs due
15 to a crash on Windows which I was going to use to refer to and to
16 reconstruct what I had learned. I haven't had the time to devote to
17 this project until now and find myself not fully understanding the
18 instructions.
20 From
23 vvvvvvvvvv
24 5.b. Filesystem Setup
26 Cross-compiling a system generally involves two directory trees. The
27 first is where all development files are normally installed. This is
28 your sysroot. The other tree is where only your runtime files are
29 installed. You emerge all of your fun packages into your sysroot
30 (without trimming down any files), and then either install via binary
31 packages or copying files by hand all the stuff you need in your runtime
32 tree.
34 The common convention is to use your /usr/CTARGET/ tree as your sysroot
35 as the include/library directories in this tree are already encoded into
36 the gcc cross-compiler for searching. You could use another directory
37 and then add custom -I/-L paths to your CPPFLAGS/LDFLAGS, but this has
38 historically proven to be problematic. Yes, it works most of the time,
39 but the corner cases are why this method is discouraged. In the embedded
40 handbook, we'll assume you're using the sysroot as your development ROOT.
42 For your runtime system, you'll need a much slimmer/trimmed-down setup.
43 The files you remove from a normal installed package is why this tree is
44 not suitable for compiling against. If you build binary packages while
45 installing into your sysroot, then you can use those binary packages in
46 conjunction with the INSTALL_MASK variable to trim out most things. See
47 man make.conf for more information.
49 ^^^^^^^^^^
51 In my case, I have a CTARGET of "arm-softfloat-linux-gnueabi" so
52 "/usr/arm-softfloat-linux-gnueabi" is my sysroot. My
53 "arm-softfloat-linux-gnueabi-gcc" compiler knows to look under $CTARGET.
55 All questions below reference paragraph 3.
57 Question #1: What does "runtime system" mean? Is that the directory
58 tree underneath /usr/$CTARGET?
60 Question #2: I don't understand what you mean by "files you remove from
61 a normal installed package".
63 Question #3: "this tree is not suitable..." What tree?
65 I'm basically lost for the remainder of the paragraph.
67 When I find I have questions, I will read on past the problem part to
68 see if I can make sense of it by reading subsequent content.
69 Unfortunately, this tricky stuff (I apparently broke my previous
70 environment making assumptions and trying to follow the previous version
71 of the documentation) and I don't want to make any assumptions which
72 later cause me to taint, or "hose", my environments.
74 I do have several questions about subsection 5.c, but will reread that
75 subsection once I know I'm fully following subsection 5.b.
77 Thank you for you anticipated help/explanations.
79 A suggestion. You use an example in the previous chapters, e.g. Chapter
80 4 "sh4-unknown-linux-gnu". It would be really helpful if subsequent
81 discussions continued with that example to illustrate the point being
82 made. This would help provide continuity.
84 John
86 --
88 John Laurence Poole
89 P.O. Box 6566
90 Napa CA 94581-6566
91 Home: 707-265-7572
92 Office: 650-607-0853
93 Skype: JohnLPoole My status <skype:JohnLPoole?call>
94 email: jlpoole@×××.net


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Subject Author
Re: [gentoo-embedded] Embedded Handbook (5)(b) clarification Patrice Tisserand <ptisserand@××××××.com>