Proper method to update templated "git-version.h.in" file

[tabedzki]

Hi there,
I am trying to get the git hash of a project written to a header file for c++. I have a template src/git-version.h.in and a intended target src/git-version.h.
I've read the documentation for vcs_tag and I've looked at a few StackOverflows but I am unable to get it working. The current error I get is
src/meson.build:56:0: ERROR: vcs_tag keyword argument "output" Output 'src/git_version.h' must not contain a path segment.

Thanks in advance for your help/suggestions.

./meson.build
./src/meson.build
./src/main.cpp (this has the command to include the header file)
./src/git-version.h

meson.build

project('cuda-example', ['cuda', 'cpp'],
    version         : '0.1.0',
    license         : 'MIT',
    meson_version   : '>=0.58.0',
    default_options : ['warning_level=2','cuda_std=c++11','c_std=c11', 'cpp_std=c++11'])

nvcc = meson.get_compiler('cuda')

cuda = import('unstable-cuda')

subdir('src')
...
executable(
  target_exec,
  gpu_files,
 dependencies : [dep, vcs_dep], install : true, cuda_args: [myargs] 
 )

src/meson.build

gpu_files=['src/main.cpp']


vcs_dep=vcs_tag(command: ['git', 'describe', '--tags', '--always', '--dirty', '--abbrev=9'], 
      input:'src/git_version.h.in',
      output:'src/git_version.h',
      replace_string:'@GIT_VERSION@')

src/main.cu

#include "git-version.h"
int main(int argc, char** argv)
{
	printf("Git Version hash: %s\n", MY_GIT_VERSION);
        return 0;
}

src/git-version.h.in

#define MY_GIT_VERSION "@GIT_VERSION@"

[eli-schwartz]

Specify the output file as

output: 'git_version.h'

Meson will automatically treat that as relative to the current build directory context, which is src/ because it is defined in src/meson.build.

You should also do this for the input file as well, though, because otherwise it won't find the input file.

The source file defined as a list of strings can be defined instead with files('main.cpp') and it will remember the directory it was defined in, but if you leave it as a plain string then it's "defined" at the time of use, which is in the root meson.build

[tabedzki]

thanks very much!
Also, the ./meson.build should be

executable(
  target_exec,
  gpu_files,
 dependencies : dep, install : true, cuda_args: [myargs] 
 )

and ./src/meson.build should be

vcs_dep = vcs_tag(command: ['git', 'describe', '--tags', '--always', '--dirty', '--abbrev=9'], 
     input: 'git_version.h.in',
     output:'git_version.h',
     replace_string:'@GIT_VERSION@')

gpu_files=files(['main.cpp'])
gpu_files += vcs_dep

[tabedzki]

@eli-schwartz I have a follow up question. How do I get meson to (1) check if the vcs_tag is old, and if it is old (2) update git_version.h and (2.1) force recompilation of main.cpp?