如何在不编辑makefile的情况下附加到makefile中的cxxflags？
我正在为QT应用程序编写构建脚本。脚本首先调用.pro文件上的 qmake ，然后运行make cxxflags = -dswversion = xxxx。
问题在于，它覆盖了Makefile中已经定义的CXXFLAG。当前，我知道解决此问题的唯一方法是编辑Makefile并更改此问题：
CXXFLAGS = <flags>
对此：
CXXFLAGS += <flags>
我希望有一个更简单的解决方案。有什么办法可以简单地将命令行中的cxxflag附加到而无需重写makefile的情况下？
另外，我的真正问题是在构建时间定义swversion（因为它取决于构建时间戳）。您是否知道在运行时定义此问题而不是将其传递给CXXFLAGS的更好方法？
I'm writing a build script for a Qt application. The script first calls qmake on the .pro file and then runs make CXXFLAGS=-DSWVERSION=xxxx.
The problem with this is that it overwrites the CXXFLAGS already defined in the Makefile. Currently, the only method I know to solve this problem is to edit the Makefile and change this:
CXXFLAGS = <flags>
To this:
CXXFLAGS += <flags>
I was hoping there would be a simpler solution. Is there any way I can simply append to CXXFLAGS from the command line WITHOUT rewriting the Makefile?
Alternatively, my real problem is defining SWVERSION at build-time (because it is dependent on the build timestamp). Do you know of a better way to define this at runtime instead of passing it to CXXFLAGS?
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您建议的更改无论如何都无法正常工作：即使将值附加到
+=的情况下，命令行上设置的值也完全覆盖了Makefile中的值。您可以做到这一点，并且可以工作：但是，它的方式通常是 的方式是，makefile提供了专门保留的变量，这些变量专门为用户覆盖命令行。例如，在自动化生成的makefiles中，保留
cxxflags，cflags等的常见变量，请保留使用命令行或环境设置的用户，并且内部makefile标志被放入其他变量中，例如am_cflags。 编译对象的配方使用两个变量然后， 一组类似的保留makefile变量，但您可以检查QT文档或生成的Makefile配方。
The change you suggest won't work anyway: a value set on the command line completely overrides the value set in the makefile, even if the value is appended to with
+=. You could do this and it would work:However, the way it's normally done is that the makefile provides variables which are reserved specifically for users to override on the command line. For example in automake-generated makefiles, the common variables like
CXXFLAGS,CFLAGS, etc. are reserved for users to set via the command line or environment, and the internal makefile flags are put into a different variable, likeAM_CFLAGS. Then the recipes to compile objects uses both variable, like$(CC) $(AM_CFLAGS) $(CFLAGS) ...I don't know anything about qt so I can't say whether they have a similar set of reserved makefile variables but you might check the qt docs, or your generated makefile recipes, to see.
对于将来阅读本文的任何人，我发现的解决方案是调用
qmake＆lt; project file＆gt;定义+=“ swversion = xxxx”。希望有人能发现这个有用。For anyone reading this in the future, the solution I found was to call
qmake <project file> DEFINES+="SWVERSION=xxxx". Hope someone finds this helpful.