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[PATCH] doc: add Creating a New Cross Target.
From: |
Jan Nieuwenhuizen |
Subject: |
[PATCH] doc: add Creating a New Cross Target. |
Date: |
Wed, 07 Dec 2016 17:47:14 +0100 |
Hi,
Here's my doc draft on the cross build system. Suggestions/additions
welcome!
Greetings,
Jan
>From e887762bd07d77b68ff19b0ced3ab41c15faa1ac Mon Sep 17 00:00:00 2001
From: Jan Nieuwenhuizen <address@hidden>
Date: Wed, 7 Dec 2016 17:45:29 +0100
Subject: [PATCH] doc: add Creating a New Cross Target.
* doc/guix.texi: Add Creating a New Cross Target.
---
doc/guix.texi | 170 +++++++++++++++++++++++++++++++++++++++++++++++++
gnu/packages/mingw.scm | 6 +-
2 files changed, 171 insertions(+), 5 deletions(-)
diff --git a/doc/guix.texi b/doc/guix.texi
index 738b7fb..91a83e9 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -182,6 +182,7 @@ GNU Distribution
* Packaging Guidelines:: Growing the distribution.
* Bootstrapping:: GNU/Linux built from scratch.
* Porting:: Targeting another platform or kernel.
+* Creating a New Cross Target::
System Installation
@@ -259,6 +260,12 @@ Coding Style
* Data Types and Pattern Matching:: Implementing data structures.
* Formatting Code:: Writing conventions.
+Creating a New Cross Target
+
+* Rebuilding My World:: How to avoid rebuilding too often.
+* GCC and Cross Environment Paths:: Details on the cross build setup.
+* The MinGW Cross Target:: Some notes on MinGW.
+
@end detailmenu
@end menu
@@ -6457,6 +6464,7 @@ For information on porting to other architectures or
kernels,
* Packaging Guidelines:: Growing the distribution.
* Bootstrapping:: GNU/Linux built from scratch.
* Porting:: Targeting another platform or kernel.
+* Creating a New Cross Target::
@end menu
Building this distribution is a cooperative effort, and you are invited
@@ -14361,6 +14369,168 @@ Second, some of the required packages could fail to
build for that
platform. Lastly, the generated binaries could be broken for some
reason.
address@hidden Creating a New Cross Target
address@hidden Creating a New Cross Target
+
+As a first step of making a full port, you may want to start by creating
+a cross target. A cross target in essence is a cross compiler
address@hidden@var{<target>}}, which depends on
address@hidden@var{<target>}} a @address@hidden<target>}} and
+possibly @address@hidden<target>}}. Several cross targets
+are available, such as @code{i586-pc-hurd}, @code{armhf-linux},
address@hidden, @code{i686-w64-mingw32} and @code{mips64el-linux}.
+
+Building a full gcc cross compiler depends on a c-library for the
+target. We can build a c-library for the target once we have a cross
+compiler. To break this loop a minimal gcc compiler can be built
+without a c-library; we call this
address@hidden@var{<target>}}. With this minimal gcc
+compiler we cross compile the c-library and then we build the full cross
+gcc.
+
+In @code{gnu/packages/cross-base.scm} are functions to create these
+cross packages. Also, Guix needs to know the name of the dynamic
+linker, see @var{glibc-dynamic-linker} in
address@hidden/packages/bootstrap.scm}.
+
address@hidden
+* Rebuilding My World:: How to avoid rebuilding too often.
+* GCC and Cross Environment Paths:: Details on the cross build setup.
+* The MinGW Cross Target:: Some notes on MinGW.
address@hidden menu
+
address@hidden Rebuilding My World
address@hidden Rebuilding My World
+
+Why is it that we all tend love to rebuild our world, yet like it
+somewhat less when others decide do it for us? One of the great things
+of Guix is that it tracks all dependencies and will rebuild any package
+that is out of date: We never have to worry that doing a fresh, clean
+build does not reproduce.
+
+However, if we make the tiniest change for our cross build to the
address@hidden package then Guix will first rebuild world before starting
+the cross-build. If we made a silly typo in the cross-build recipe, it
+takes a long time to get feedback on that.
+
+Say our target is to cross-build @var{Guile} which needs a cross-built
address@hidden which requires making a change to the @var{ncurses}
+package. What we can do is create a temporary alternative package
+hierarchy. We copy @var{ncurses} to @var{cross-ncurses}
+
address@hidden
+(define-public cross-ncurses
+ @dots{}
+ (name "cross-ncurses")
+ @dots{})
address@hidden example
+
address@hidden
+and because we are really aiming for @var{readline}, we copy that too
+
address@hidden
+(define-public cross-readline
+ @dots{}
+ (name "cross-readline")
+ @dots{}
+ (propagated-inputs `(("ncurses" ,cross-ncurses)))
+ @dots{})
address@hidden example
+
address@hidden
+which we then use in our copied @var{cross-guile} package. We replace
+the original packages descriptions with the @var{cross-} variants and
+remove the @var{cross-} prefixes.
+
+Now it is time to check what the impact of our changes in @var{ncurses}
+
address@hidden
+$ ./pre-inst-env guix refresh -l ncurses
+Building the following 1056 packages would ensure 2658 dependent packages are
rebuilt: @dots{}
address@hidden smallexample
+
+When we are satisfied with our changes, we can enjoy our favorite
+beverage while we having our worlds rebuild. If we decide the impact is
+too great we can rewrite our changes in a way so that they do not change
+the regular package recipe, e.g.
+
address@hidden
+ (patches (search-patches "ncurses-mingw.patch"))))
+ @dots{}
+ (inputs
+ `(;; breaks with MinGW...not needed? ("coreutils" ,coreutils)
+ ("zlib" ,zlib)))
address@hidden smallexample
+
+can be written as
+
address@hidden
+ (patches (if (target-mingw?)
+ (search-patches "ncurses-mingw.patch")
+ '()))))
+ @dots{}
+ (inputs
+ `(;; fails with MinGW and could be removed unconditionally
+ ;; but that triggers a rebuild
+ ,@@(if (target-mingw?)
+ '()
+ `(("coreutils" ,coreutils)))
+ ("zlib" ,zlib))
address@hidden smallexample
+
+and the original non-cross build recipe remains identical to the
+builder.
+
address@hidden GCC and Cross Environment Paths
address@hidden GCC and Cross Environment Paths
+
address@hidden See <http://gcc.gnu.org/ml/gcc/2013-02/msg00124.html>
address@hidden <http://bugs.gnu.org/22186> and
address@hidden
<https://lists.gnu.org/archive/html/guix-devel/2016-04/msg00533.html>
address@hidden for a discussion of what follows.
+Some build systems compile and run programs at build time to generate
+host-specific data. This means we usually have two compilers installed:
address@hidden and @code{<target>-gcc}. Guix does not use
address@hidden/usr/include} and @file{/usr/lib} to install additional headers
+and libraries, instead it adds to environment path variables such as
address@hidden and @var{LIBRARY_PATH}.
+
+To distinguish between native build-time headers and libraries and
+cross-built target system headers and libraries, we use a patched gcc as
+cross compiler. The cross compiler instead looks at
address@hidden and @var{CROSS_LIBRARY_PATH}.
+
address@hidden The MinGW Cross Target
address@hidden The MinGW Cross Target
+
+The MinGW target is somewhat special in that it does not support
address@hidden @var{Gcc} needs to be passed the @code{--with-newlib} flag
+and instead we use the combined c-library and free reïmplementation of
+Windows kernel-headers and system-libraries provided by the MinGW-w64
+project. Also, it's not POSIX so it often needs explicit support,
+sometimes we need to create a patch ourselves.
+
+For standard libc headers and libraries that are missing in MinGW such
+as @var{libiconv} and @var{gettext} helper functions are available
+
address@hidden
+ (inputs
+ @dots{}
+ ,@@(libiconv-if-needed)
+ ,@@(gnu-gettext-if-needed))
address@hidden example
+
+Finally, a simple example of how MinGW can be used/tested
+
address@hidden
+$ guix build --target=i686-w64-mingw32 hello
address@hidden
+/gnu/store/@dots{}-hello-2.10
+$ guix environment --ad-hoc wine
+$ wine /gnu/store/@dots{}-hello-2.10/bin/hello.exe
+Hello, world!
address@hidden example
+
@c *********************************************************************
@include contributing.texi
diff --git a/gnu/packages/mingw.scm b/gnu/packages/mingw.scm
index 4eb2c8f..dd9b597 100644
--- a/gnu/packages/mingw.scm
+++ b/gnu/packages/mingw.scm
@@ -21,14 +21,10 @@
#:use-module (gnu packages)
#:use-module (gnu packages base)
#:use-module (gnu packages cross-base)
- #:use-module (gnu packages gcc)
- #:use-module (gnu packages compression)
- #:use-module (gnu packages multiprecision)
#:use-module (guix build-system gnu)
#:use-module (guix packages)
#:use-module (guix download)
- #:use-module (guix utils)
- #:use-module (ice-9 match))
+ #:use-module (guix utils))
(define-public mingw-w64
(package
--
2.10.2
--
Jan Nieuwenhuizen <address@hidden> | GNU LilyPond http://lilypond.org
Freelance IT http://JoyofSource.com | Avatar® http://AvatarAcademy.nl
- [PATCH] doc: add Creating a New Cross Target.,
Jan Nieuwenhuizen <=