# Source doesn't exist yet for target depending on custom target using source generated by add\_custom\_command

**URL:** <https://discourse.cmake.org/t/source-doesnt-exist-yet-for-target-depending-on-custom-target-using-source-generated-by-add-custom-command/1218>\
**Category:** Code\
**Tags:** os:linux\
**Created:** [May 14, 2020, 5:47pm UTC](https://discourse.cmake.org/t/source-doesnt-exist-yet-for-target-depending-on-custom-target-using-source-generated-by-add-custom-command/1218 "2020-05-14T17:47:10Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![Smit\_Patil](https://discourse.cmake.org/user_avatar/discourse.cmake.org/smit_patil/32/602_2.png) [@Smit\_Patil](https://discourse.cmake.org/u/Smit_Patil)\
**Post date:** [May 14, 2020, 5:47pm UTC](https://discourse.cmake.org/t/source-doesnt-exist-yet-for-target-depending-on-custom-target-using-source-generated-by-add-custom-command/1218/1 "2020-05-14T17:47:10Z")

</div>

> **[VioletSith/qtlayershell](https://github.com/VioletSith/qtlayershell)**
>
> Qt support for the Wayland layer-shell extension. Contribute to VioletSith/qtlayershell development by creating an account on GitHub.

I am trying to port a meson project to CMake. I have the following subdirectories in my main CMake file:

```
add_subdirectory(protos)
add_subdirectory(qtlayershell)
add_subdirectory(demo)

```

and the following in `protos/CMakeLists.txt`:

```
set(PROTOCOLS
    ${WAYLAND_PROTOCOL_DIR}/stable/xdg-shell/xdg-shell.xml
    wlr-layer-shell-unstable-v1.xml'
)

foreach(XML ${PROTOCOLS})
    get_filename_component(BASENAME ${XML} NAME_WE)
    add_custom_command(
        OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/wayland-protos/wayland-${BASENAME}-protocol.c
        COMMAND wayland-scanner private-code ${XML} @OUTPUT@
    )
    add_custom_command(
        OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/wayland-protos/wayland-${BASENAME}-protocol.h
        COMMAND wayland-scanner client-header ${XML} @OUTPUT@
    )

    add_custom_command(
        OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/wayland-protos/qwayland-${BASENAME}.h
        COMMAND qtwaylandscanner client-header ${XML} @OUTPUT@
    )
    add_custom_command(
        OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/wayland-protos/${BASENAME}-protocol.cpp
        COMMAND qtwaylandscanner client-code ${XML} @OUTPUT@
    )

    list(APPEND PROTOCOL_SRC
        ${CMAKE_CURRENT_BINARY_DIR}/wayland-protos/wayland-${BASENAME}-protocol.c
        ${CMAKE_CURRENT_BINARY_DIR}/wayland-protos/${BASENAME}-protocol.cpp
    )

    list(APPEND PROTOCOL_HEADERS
        ${CMAKE_CURRENT_BINARY_DIR}/wayland-protos/qwayland-${BASENAME}.h
        ${CMAKE_CURRENT_BINARY_DIR}/wayland-protos/wayland-${BASENAME}-protocol.h
    )
endforeach()

set(WAYLAND_PROTOCOL_SRC ${PROTOCOL_SRC} PARENT_SCOPE)
set(WAYLAND_PROTOCOL_HEADERS ${PROTOCOL_HEADERS} PARENT_SCOPE)

add_custom_target(wayland_protocols DEPENDS ${WAYLAND_PROTOCOL_SRC} ${WAYLAND_PROTOCOL_HEADERS})

```

and in `qtlayershell/CMakeLists.txt`, a target like this:

```
add_library(qtlayershell SHARED
    ${QTLAYERSHELL_SRC}
    ${WAYLAND_PROTOCOL_SRC}
    DEPENDS wayland_protocols
)

```

But I am getting an error that `somelongbuildpath/protos/wayland-protos/wayland-xdg-shell-protocol.c` doesn’t exist yet. Here is full error:

```
  Cannot find source file:

    /home/noone/KDE/my/build-qtlayershell-Desktop-Debug/protos/wayland-protos/wayland-xdg-shell-protocol.c

  Tried extensions .c .C .c++ .cc .cpp .cxx .cu .m .M .mm .h .hh .h++ .hm
  .hpp .hxx .in .txx

CMake Error at qtlayershell/CMakeLists.txt:9 (add_library):
  No SOURCES given to target: qtlayershell
CMake Generate step failed. Build files cannot be regenerated correctly.
CMake process exited with exit code 1.

```

here is the full project on github [https://github.com/VioletSith/qtlayershell](https://github.com/VioletSith/qtlayershell)

---

<div class="post-metadata">

**Author:** ![ben.boeckel](https://discourse.cmake.org/letter_avatar_proxy/v4/letter/b/ea5d25/32.png) [@ben.boeckel](https://discourse.cmake.org/u/ben.boeckel)\
**Post date:** [November 9, 2020, 7:53pm UTC](https://discourse.cmake.org/t/source-doesnt-exist-yet-for-target-depending-on-custom-target-using-source-generated-by-add-custom-command/1218/2 "2020-11-09T19:53:48Z")

</div>

Scope visibility between `add_custom_command` and targets can be a bit weird. I’d recommend moving the `add_custom_command` calls to be beside the target (not made by `add_custom_target`) that will use them.

[This discussion](https://discourse.cmake.org/t/automatically-detecting-generated-dependencies/1183) has some relevant details for that.