英文:
How to make a CMake custom command depends on a target being built but without rerunning on relink?
问题
我有一个可执行文件用于生成一个“cache”文件。在CMake中，我有类似这样的内容：
add_executable(Generator ...)
add_custom_target(OUTPUT cache
DEPENDS Generator OtherDep1 OtherDep2
COMMAND Generator --input OtherDep1 OtherDep2 --output cache)
然而，因为它大约需要10分钟，我不关心cache在Generator更改时是否不同，我不希望每当出于任何原因重新链接Generator时都重新计算cache。但如果我从依赖关系中移除Generator，则在自定义命令需要时可能无法使用它。
我知道这与通常的Make/CMake工作流程有点不同，但是否有办法要求在运行自定义命令之前必须先编译Generator？
英文:
I have a executable used to generate a "cache" file. In CMake, I have something like this:
add_executable(Generator ...)
add_custom_target(OUTPUT cache
DEPENDS Generator OtherDep1 OtherDep2
COMMAND Generator --input OtherDep1 OtherDep2 --output cache)
However, because it takes about 10 minutes and I do not care of the cache differs when Generator changes, I do not want cache to be re-computed whenever Generator is re-linked for whatever reason. But if I remove Generator from the dependencies, it may not be available when the custom commands needs it.
I know this is a bit far from the usual Make/CMake workflow, but is there something I can do to require Generator to have been compiled before running the custom command?
答案1
得分: 2
我不希望每当“Generator”由于任何原因重新链接时都重新计算“cache”。
那么，您需要定义目标级别的依赖关系，而不是文件级别的依赖关系。目标级别的依赖关系是使用add_dependencies命令定义的：
add_executable(Generator ...)
# 用于**文件级**依赖关系的自定义命令。
# 只有当输出文件比其某个依赖项旧时，输出文件才会被重新构建。
add_custom_command(OUTPUT cache
DEPENDS OtherDep1 OtherDep2
COMMAND Generator --input OtherDep1 OtherDep2 --output cache)
# 自定义目标。
# 它只确保其依赖项是最新的。
add_custom_target(create_cache
DEPENDS cache
)
# **目标级**的目标之间的依赖关系。
# 它们仅确保顺序，但不会因为另一个目标已被重新构建而导致一个目标重新构建。
add_dependencies(create_cache Generator)
英文:
> I do not want cache to be re-computed whenever Generator is re-linked for whatever reason.
Then you need to define target-level dependencies instead of file-level ones. Target-level dependencies are defined with add_dependencies command:
add_executable(Generator ...)
# Custom command for **file-level** dependencies.
# The output will be rebuilt whenever it will be found older than one of its dependencies.
add_custom_command(OUTPUT cache
DEPENDS OtherDep1 OtherDep2
COMMAND Generator --input OtherDep1 OtherDep2 --output cache)
# Custom target.
# It just makes sure, that its dependencies are up-to-date.
add_custom_target(create_cache
DEPENDS cache
)
# **target-level** dependencies between the targets.
# They ensures only order, but do not cause rebuilding of one target
# because of another target has been rebuilt
add_dependencies(create_cache Generator)
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