# Escape hell, and how to escape it

**URL:** https://discourse.cmake.org/t/escape-hell-and-how-to-escape-it/13737
**Category:** Code
**Created:** [March 12, 2025, 9:54pm UTC](https://discourse.cmake.org/t/escape-hell-and-how-to-escape-it/13737 "2025-03-12T21:54:10Z")
**Posts on this page:** 3
**Page:** 1

<div class="post-metadata">

### Author: ![w3sip](https://discourse.cmake.org/user_avatar/discourse.cmake.org/w3sip/32/5405_2.png) [@w3sip](https://discourse.cmake.org/u/w3sip)
#### Post date: [March 12, 2025, 9:54pm UTC](https://discourse.cmake.org/t/escape-hell-and-how-to-escape-it/13737/1 "2025-03-12T21:54:10Z")

</div>

I’m trying to make the following code work:

```auto
    foreach(module ${CXXMODULES})
        set(MODULE_MAP_FLAGS "")
        string(APPEND MODULE_MAP_FLAGS ";-Xcc;-fmodule-map-file=${MODULE_SOURCE_DIR}/module.modulemap")
      endif()
    endforeach()

    message(STATUS "MODULE_MAP_FLAGS: ${_NAME} ${MODULE_MAP_FLAGS}")
    target_compile_options(${_NAME} PRIVATE
      $<$<COMPILE_LANGUAGE:Swift>:-cxx-interoperability-mode=default>
      $<$<COMPILE_LANGUAGE:Swift>:-Xcc;-std=c++${CXX_STANDARD};${MODULE_MAP_FLAGS}>
      $<$<COMPILE_LANGUAGE:Swift>:-I${INTERFACE_INCLUDE_DIRS}>
    )

```

However, as presented above, while the output of message looks valid:

```auto
-- MODULE_MAP_FLAGS: Session ;-Xcc;-fmodule-map-file=dir1/module.modulemap;-Xcc;-fmodule-map-file=dir2/module.modulemap

```

The actual command during build looks like

```auto
-Xcc -std\=c++20 -fmodule-map-file\=dir1/module.modulemap -fmodule-map-file\=dir2/module.modulemap

```

In other words, all the repeat occurrences of `-Xcc` are being eliminated. Most of the alternatives tried result in spaces being escaped with backslash, which is a different problem.

Any advice on how to make this work and keep all of my `-Xcc`’s intact?

---

<div class="post-metadata">

### Author: ![w3sip](https://discourse.cmake.org/user_avatar/discourse.cmake.org/w3sip/32/5405_2.png) [@w3sip](https://discourse.cmake.org/u/w3sip)
#### Post date: [March 12, 2025, 10:12pm UTC](https://discourse.cmake.org/t/escape-hell-and-how-to-escape-it/13737/2 "2025-03-12T22:12:38Z")

</div>

Using

```auto
        target_compile_options(${_NAME} PRIVATE
          $<$<COMPILE_LANGUAGE:Swift>:-Xcc;-fmodule-map-file=${MODULE_SOURCE_DIR}/module.modulemap>
        )

```

multiple times in the loop results in the same behavior (only the first `-Xcc` makes it through)

---

<div class="post-metadata">

### Author: ![w3sip](https://discourse.cmake.org/user_avatar/discourse.cmake.org/w3sip/32/5405_2.png) [@w3sip](https://discourse.cmake.org/u/w3sip)
#### Post date: [March 12, 2025, 10:46pm UTC](https://discourse.cmake.org/t/escape-hell-and-how-to-escape-it/13737/3 "2025-03-12T22:46:12Z")

</div>

Found this in the docs for `target_compile_options`: [https://cmake.org/cmake/help/latest/command/target\_compile\_options.html#option-de-duplication](https://cmake.org/cmake/help/latest/command/target_compile_options.html#option-de-duplication)

Building a list of options with it, like so, works:

```auto
      if(EXISTS "${MODULE_SOURCE_DIR}/module.modulemap")
        list(APPEND LOCAL_CXX_FLAGS "SHELL:-Xcc -fmodule-map-file=${MODULE_SOURCE_DIR}/module.modulemap")
      endif()

```