英文:

How do you get stack to pass custom flags to ghc (and the cpp preprocessor)?

问题

以下是您提供的代码的翻译部分：

我在我的文件中有一些条件编译，比如

```haskell
#if FLAG
bogus1 x = x + 1
#else
bogus2 x = x + 2
#endif

然后我尝试将package.yaml文件设置为在构建时将标志传递给ghc。因此，我将以下内容添加到文件中：

executables:
  my_maim:
    main:                Main.hs
    source-dirs:         app
    ghc-options:
    - "-DFLAG"
    - -main-is Main
    dependencies:
    - MyPackage

这不起作用（我仍然看到bogus2），但它给了我一个有用的警告：“警告：请改用cpp-options: -DFGLAG，而不是ghc-options: -DFGLAG”。好吧，于是我尝试了：

executables:
  my_maim:
    main:                Main.hs
    source-dirs:         app
    cpp-options:
    - "-DFLAG"
    ghc-options:
    - -main-is Main
    dependencies:
    - MyPackage

然后使用stack build构建不会传递正确的标志（我仍然看到bogus2）。

另一方面，我可以执行stack build -ghc-options --DFLAG，这样可以正常工作！（最终我看到bogus1）。

我做错了什么，如何设置Stack以传递正确的标志？

请注意，翻译是基于您提供的内容进行的，不包括任何附加信息。如果您需要进一步的帮助或有其他问题，请随时提出。

<details>
<summary>英文:</summary>

I have some conditional compilation in my files, say

#if FLAG
bogus1 x = x + 1
#else
bogus2 x = x + 2
#endif

Then I'm trying to set my `package.yaml` to pass the flag to `ghc` on build. So I added the following to the file:

executables:
my_maim:
main: Main.hs
source-dirs: app
ghc-options:
- "-DFLAG"
- -main-is Main
dependencies:
- MyPackage

This does not work (I still see `bogus2`) but it gives me a useful warning `Warning: Instead of 'ghc-options: -DFGLAG' use 'cpp-options: -DFGLAG'`. Fair enough, so I tried:

executables:
my_maim:
main: Main.hs
source-dirs: app
cpp-options:
- "-DFLAG"
ghc-options:
- -main-is Main
dependencies:
- MyPackage

Then building with `stack build` does not pass the right flags (I still see `bogus2`). 

On the other hand, I can do `stack build -ghc-options --DFLAG`, which works! (I finally see `bogus1`). 

What am I doing wrong, and how do you set stack to pass the right flags?

</details>


# 答案1
**得分**: 1

我猜你可能在除了 Main.hs 之外的文件中使用了该标志。executables: 下的选项仅影响 app/Main.hs。你可以将你的 cpp-options: 配置放在顶层或者在 library: 下。

顶层 (缩进为0)

cpp-options:

• -DFLAG

library:

... (其他字段)

cpp-options:

• -DFLAG

<details>
<summary>英文:</summary>

I&#39;m guessing that you are using that flag in files other than `Main.hs`. The options under `executables:` only affect `app/Main.hs`. You can put your `cpp-options:` config at the toplevel or under `library:` instead.

Toplevel (indentation 0)

cpp-options:

• -DFLAG

library:

... (other fields)

cpp-options:

• -DFLAG

</details>