标题依赖在automake [英] Header dependency in automake

问题描述

我想创建一个 Makefile.am 文件，它生成一个 xxx.c中提到的头文件。文件

我们假设 xxx.c 包含：

  #include< version.h> 
 ... 
  

而且我有一个规则在 Makefile.am ：

  version.h：
 echo' #define VERSION'`hg id`'''> version.h.tmp 
 cmp version.h.tmp version.h || mv version.h.tmp version.h 
  

我必须更改哪些才能使 xxx.c 编译取决于 version.h ？我试过 nodist_progname_SOURCES = version.h ，但似乎没有这样做。

解决方案

  BUILT_SOURCES = version.h 
  

全部提交的文件 BUILT_SOURCES 将在任何正常编译规则运行之前构建。

但是，这将创建一个轻微的问题：由于 version.h 将需要在每个 make 调用中重建，每次 foo.c 文件，其中 #include s version.h 将被触发再次在每个 make 运行。如果重新编译仅在实际发生变化的情况下才会发生。

要解决此问题，请使用 BUILT_SOURCES 依赖于每次都创建的邮票文件（它从未实际创建，因此构建规则每次运行）。该邮票文件的构建规则创建一个新的 version.h 文件作为 version.h.tmp ，只有副本 version.h.tmp to version.h if version.h.tmp 实际上不同于 version.h （就像你的 version.h 规则一样）。所以如果 version.h 中没有变化，它的时间戳（mtime）保持不变，并且根据 version.h 被触发：

  BUILT_SOURCES = version.stamp 
 
 version.stamp：
 echo'#define VERSION'`hg id`'''> version.h.tmp 
 cmp version.h.tmp version.h || mv version.h.tmp version.h 
  

这个解决方案会做你所要求的。 p>

不幸的是，当您从dist tarball构建时，会有一个小问题：然后 hg id 会给你伪造的信息，并且您的压缩包中可能没有 version.h ，因此构建将失败或包含虚假版本信息。

我已经解决了此问题，以获取 xf86-video-radeonhd 项目正在使用 git 。此解决方案中生成的 git-version.h 文件包含的版本信息不仅仅是一个版本号。您可以在只有更新的解决方案tree / git_version.shrel =noreferrer> git_version.sh 和 BUILT_SOURCES 连接（包括处理希望所有源代码在和 from-dist-tarball 构建案例） RadeonHD.amrel =noreferrer> RadeonHD.am 如果你有兴趣。

I'd like to create a Makefile.am file which generates one header file mentioned in a xxx.c file.

Let's say that xxx.c contains:

#include <version.h>
...

and that I have a rule to create it at the end of Makefile.am:

version.h:
       echo '#define VERSION "'`hg id`'"' > version.h.tmp
       cmp version.h.tmp version.h || mv version.h.tmp version.h

What do I have to change to make the xxx.c compilation depend on version.h? I tried nodist_progname_SOURCES=version.h, but that doesn't seem to do it.

解决方案

BUILT_SOURCES = version.h

All files mentioned as BUILT_SOURCES will be built before any of the normal compilation rules run.

However, this will create a slight problem: As version.h will need to be rebuilt on every make invocation, the recompilation of every foo.c file which #includes version.h will be triggered again on every make run. We would prefer if the recompilation only happens when there is actually something that has changed.

To get around this problem, use a BUILT_SOURCES dependency on a stamp file which is "created" every time (it never is actually created, so the build rule runs every time). The build rule for that stamp file creates a new version.h file as version.h.tmp, and only copies version.h.tmp to version.h if version.h.tmp is actually different from version.h (just like your version.h rule does). So if nothing has changed in version.h, its timestamp (mtime) remains the same, and no build of objects depending on version.h is triggered:

BUILT_SOURCES = version.stamp

version.stamp:
        echo '#define VERSION "'`hg id`'"' > version.h.tmp
        cmp version.h.tmp version.h || mv version.h.tmp version.h

This solution will do what you are asking for.

Unfortunately though, there will be a slight problem when you are building from a dist tarball: Then hg id will give you bogus information, and there probably is no version.h in your tarball, so the build will fail or contain bogus version information.

I have solved this issue for a the xf86-video-radeonhd project which is using git. The git-version.h file generated in this solution contains some more version information than just a single version number. You can see this update-only-if-different solution of mine at the end of git_version.sh and the BUILT_SOURCES hookup (including handling of hopefully all out-of-source-tree and from-dist-tarball build cases) in RadeonHD.am if you are interested.

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