Qt的sysroot和prefix选项的实用示例 [英] What would be a pratical example of sysroot and prefix options for Qt
问题描述
我正在查看Qt随附的配置脚本可以运行的所有选项。 （特别是qt-everywhere-opensource-src-5.2.0）。
经过大量搜索之后，我确定这些东西充其量是文献记录不足的，所以我希望可以获得一些帮助。当我查看前缀和 sysroot 配置选项的描述时：
〜/ qt-everywhere-opensource-src-5.2.0 $ ./configure -help | grep sysroot
-extprefix< dir>...使用-sysroot时，将所有内容安装到< dir>，
-sysroot< dir>......设置< ; dir>作为目标编译器和qmake的sysroot，还设置pkg-config路径。
-no-gcc-sysroot .....使用-sysroot时，它将禁用--sysroot传递给编译器
〜/ qt-everywhere-opensource-src-5.2.0 $ ./configure -help | grep prefix
-prefix< dir>......这将安装与相关的所有内容。 dir>
-extprefix< dir>...使用-sysroot时，将所有内容安装到< dir>，
-hostprefix [dir] ..开发时所需的工具和库
所以我以前用过-前缀，它的功能完全符合所述。它将所有内容放置在提供的< dir> 中，然后当我使用< prefix_dir> / bin / qmake 并将其安装在目标平台上，它想在< prefix_dir> / lib 中找到所有共享库。
我的印象是，如果我使用 -sysroot ，它将安装所有内容到< sysroot_dir> 然后，当我在目标平台上安装应用程序时，它将在 / lib 中搜索。至少我希望这是真的。
现在，如果我的假设是正确的...那么 -extprefix ？他们是说如果我同时使用 -sysroot 和 -extprefix 可以重定向到哪里好吗？
为什么我要使用 -no-gcc-sysroot 是什么原因？如果我希望将Qt库安装在 sysroot上，为什么我不希望 gcc 使用/知道相同的sysroot？
其中一些解释将是很好的，如果我能得到一些如何正确使用这些选项的实际例子，那就更好了。
这些是在构建嵌入式平台时使用的选项。
是的，它们是一团糟。因此，这里只是部分答案：
前缀
- 尝试并证明了方式在为Qt的当前运行平台构建Qt时，对整个Qt安装说/ usr / lib而不是/ usr / local / lib或类似版本
-sysroot / path
- 打算为未安装在/
- 上的系统构建Qt，例如-sysroot〜/ mysystem，其中〜/ myssytem包含
/ lib / bin等... - 将--sysroot传递给其他工具，例如gcc和pkg-config，因此它们将在〜/ mysystem / lib而不是/ lib中搜索其依赖项
-extprefix / b
- 使用-sysroot / a时，不要t实际上写到/ a
- 写qt到/ b代替
- 这旨在针对只读sysroots进行交叉编译
-no-gcc-sysroot
- 非常对于无法在--sysroot
- 中找到自己的crt的编译器的特定黑客，将sysroot传递给pkgconfig和其他人，而不传递给gcc
- so可以使用-L / sysroot / lib /正确地调用gcc，但不会在此处尝试找到隐式路径（crt）。
< h3> -hostprefix / path
- 在为与我们当前运行的目标不同的目标进行编译时
- qmake将是主机体系结构（例如x86），而qt本身将是目标体系结构（让我们说arm）
- 因此将qmake放在/ path而不是-指定的目标系统中sysroot。在目标系统上没有任何作用
要增加混乱：
-R / path
- 设置链接程序运行路径-例如QtGui查找QtCore的位置-与其他所有路径无关options
在为目标而不是主机进行编译时要使用的标志取决于configure内的大量硬编码假设。 / p>
通常-sysroot加-prefix在大多数情况下都可以使用。
ie当您拥有以下内容时：
$ ls〜/ mytarget
lib bin share dev
您可以只使用-sysroot〜/ mytarget -prefix /
I'm looking at all the options that can be run for the configure script provided with Qt. (specifically qt-everywhere-opensource-src-5.2.0).
After considerable searching, I've determined this stuff is poorly documented at best so I was hoping I could get some help. When I look at the descriptions for prefix and sysroot configuration options:
~/qt-everywhere-opensource-src-5.2.0$ ./configure -help | grep "sysroot"
-extprefix<dir>... When -sysroot is used, install everything to<dir>,
-sysroot<dir>...... Sets<dir>as the target compiler's and qmake's sysroot and also sets pkg-config paths.
-no-gcc-sysroot ..... When using -sysroot, it disables the passing of --sysroot to the compiler
~/qt-everywhere-opensource-src-5.2.0$ ./configure -help | grep "prefix"
-prefix<dir>...... This will install everything relative to<dir>
-extprefix<dir>... When -sysroot is used, install everything to<dir>,
-hostprefix [dir] .. Tools and libraries needed when developing
So I've used -prefix before, and it did exactly as described. It placed everything at the provided <dir>, then when I built my application using <prefix_dir>/bin/qmake and installed that on my target platform it wanted to find all the shared object libraries at <prefix_dir>/lib.
I'm under the impressions that if I use -sysroot it will install everything at <sysroot_dir> then when I install my application on the target platform it will search in /lib. At least I hope that's true.
Now if my assumption is correct... then what's the point of -extprefix? Are they saying that if I can redirect where things good if I use both -sysroot and -extprefix?
And what would be a reason why I would want to use -no-gcc-sysroot? If I wanted my Qt libs to be installed at "sysroot" why wouldn't I want gcc to use/know the same sysroot?
An explanation of some of these would be great, even better if I can get some practical examples of how to correctly use these options.
These are options that are used when building embedded platforms. Yes they are a royal mess. So here's only a partial answer:
-prefix
- tried and proven way to say /usr/lib instead of /usr/local/lib or similar for the entire installation of Qt
- when Qt is built for the platform it is currently running on (typical for desktop)
-sysroot /path
- intends to build Qt for a system which isn't installed at /
- for example -sysroot ~/mysystem where ~/myssytem contains /lib /bin etc...
- will pass --sysroot to other tools, like gcc and pkg-config, so they will search for their dependencies in ~/mysystem/lib rather than /lib
-extprefix /b
- when using -sysroot /a, don't actually write to /a
- write qt to /b instead
- this is intended for cross-compiling against read-only sysroots
-no-gcc-sysroot
- very specific hack for compilers that can't find their own crt inside --sysroot
- passes sysroot to pkgconfig and others, but not to gcc
- so that gcc will be called with -L/sysroot/lib/ correctly, but doesn't try to find implicit paths (crt) here.
-hostprefix /path
- when compiling for a different target than we are currently running on
- qmake will be the host architecture (for example x86) and qt itself will be the target architecture (lets say arm)
- so put qmake in /path instead of the target system specified by -sysroot. it won't be any useful on the target system
To add to the confusion:
-R /path
- sets the linkers runpath - which is where QtGui finds QtCore for example - independant of all the other options
Which flags you want to use when compiling for a target not your host, depends on a boatload of hardcoded assumptions inside configure.
generally -sysroot plus -prefix should work for most use cases.
i.e. when you have:
$ ls ~/mytarget
lib bin share dev
you could just use -sysroot ~/mytarget -prefix /
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