bazel - 在 bazel 构建中使用生成的代码

Question

$ python gencpp.py 

此命令生成一个 cpp 文件 foo.cpp在工作目录中。

我想在 bazel 中运行此命令建之前可以包含 foo.cpp在 cc_binary的 srcs属性。

我试过的:

genrule(
    name = 'foo',
    outs = ['foo.cpp'],
    cmd = 'python gencpp.py',
)

cc_library(
    srcs = ['foo.cpp'], # tried also with :foo
    ...
)

declared output 'external/somelib/foo.cpp' was not created by genrule. This is probably because the genrule actually didn't create this output, or because the output was a directory and the genrule was run remotely (note that only the contents of declared file outputs are copied from genrules run remotely).

我知道有一个解决方案需要 gencpp.py稍作修改，但这不是我要找的。

Answer 1

This command generates a cpp file foo.cpp in the working directory.

我建议您更改此设置，以便:

您将输出写入由命令行标志指定的文件

您将输出写入标准输出，并将标准输出重定向到文件

那么您的 genrule 命令可以是:

python gencpp.py --outputFile=$@

或者

python gencpp.py > $@

(我个人的一般偏好是后者，尽管在需要写入多个输出的情况下不能使用。)

分别。

如 Ulf Adams指出:

Bazel runs multiple actions in parallel, and if the same rule is a dependency of a tool as well as of an app, it may try to run both at the same time, and they'd overwrite each other, with potentially very bad results.

因此，最好避免编写 bazel 不直接了解的输出文件。