[cmake-developers] Possible Bug With "add_custom_command()" and the Visual Studio Generator for CMake

[Timothy Wrona]

Ha that actually seems like a totally separate bug.

>From what I understand - if "add_custom_command()" is not associated with
any target and is just given a command it is supposed to run at build time
every time the build is initiated, but with the Visual Studio generator it
seems to just skip over it unless CMake has something else it needs to do.

On Fri, Feb 8, 2019 at 8:44 PM frodak17 <frodak17 at gmail.com> wrote:

> I haven't tried it out but I'm not exactly surprised it wouldn't work with
> Visual Studio 2017.
>
> It seems to be similar to the issue mentioned here:
> https://stackoverflow.com/q/54557801/1028434
>
> The problem I noticed in the case of the StackOverflow question,
> "add_custom_target(testcmake2 ALL)" doesn't have a "command" so it doesn't
> generate an output.
>
> When performing a build Visual Studio prints a message like "all outputs
> up to date" and skips over it.  So any associated custom commands with the
> target are never run.
> Adding a "command" that is even an echo, like add_custom_target(testcmake1
> COMMAND ${CMAKE_COMMAND} -E echo "Running testcmake1 step 1"), and the
> problem goes away.
>
>
>
> On Fri, Feb 8, 2019 at 6:08 PM Timothy Wrona <tjwrona1992 at gmail.com>
> wrote:
>
>> I have been following the examples in the "CMake Cookbook" by Radovan
>> Bast and Roberto Di Remigio and came across one example that doesn't appear
>> to work right on Windows.
>>
>> The source code for these example can be found here:
>> https://github.com/dev-cafe/cmake-cookbook
>>
>> Chapter-06/Recipe-07 is supposed to update the Git commit hash referenced
>> by the version header file every time the project is built. According to
>> the book, "add_custom_command()" is supposed to execute on every build
>> regardless of whether any files are changed. This example seems to work
>> correctly in a Linux environment, but not in Windows with the Visual Studio
>> Generator. When a new commit is created (an empty commit created with "git
>> commit --allow-empty") the custom command is never called and the commit
>> hash is not updated correctly.
>>
>> For specific instructions to reproduce the issue, see this bug report I
>> opened for the example in the book:
>> https://github.com/dev-cafe/cmake-cookbook/issues/506
>>
>> I assumed this was an issue with the example, but it looks like the
>> Visual Studio Generator may not be handling "add_custom_command()"
>> correctly and may be the source of the problem.
>>
>> System info:
>> CMake version 3.13.3
>> Windows 10
>> Visual Studio 2017
>> --
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