Dependency compile_args cannot carry language-specific arguments

[mitchgrout]

Currently, a dep object created via declare_dependency can supply compilation arguments through the compile_args: field. These appear to be applied the same regardless of the language of the build target. This can be a problem in mixed C/C++ builds for example:

foo_dep = declare_dependency(
  link_with: foo_lib,
  compile_args: [
    '-Wno-register', # Valid for `g++` where `register` isn't a keyword; invalid for `gcc` though
  ],
)

c_lib   = library(..., dependency: foo_dep) # Breaks due to `-Wregister`
cpp_lib = library(..., dependency: foo_dep) # No problems

What's the motivation behind compile_args? Would it be possible to introduce a per-language version of compile_args, e.g. by using the same <lang>_args syntax available to build-target calls? Or, is it simply recommended to avoid the use of compile_args itself?

[dcbaker]

There is an issue open somewhere about this that I'm assigned to...

Long story short this is known and I'm going to fix it.

[dcbaker]

The longer story is this is a leaky abstraction over pkg-config

[bruchar1]

#5723

[rgommers]

Perhaps close this as a duplicate of gh-5723?