On Wed, Dec 21, 2022 at 19:33:48 +0100, Alejandro Colomar via Gcc wrote:
> I've long had this wish: an option similar to -std, but which would not
> specify
> the standard. Rather, mark a requirement that the standard be at least a
> version.
>
> This would be especially useful for libraries, which might for example
> require
> C99 or C11 to work. They would be able to specify -minstd=c11 in their pc(5)
> file (for use with pkgconf(1)). That way, a program using such library,
> would
> be free to use -std to specify the C version that the project should be
> compiled
> with; maybe gnu17, maybe even gnu2x. But if the program tries to compile
> under,
> say gnu89, the compiler would report an error.
(FD: CMake developer, ISO C++ SG15 committee member)
I'd like to see us move away from "flag soup" and instead towards more
structured information here. This request corresponds to CMake's
`C_STANDARD` target property[1] which CMake then puts together to mean
something.
Note that there are real hazards with just putting the flags like this
into `.pc` files directly. If you have a C library and say "-minstd=c99"
and I'm C++, what is supposed to happen with this flag for a C++
compilre? Does it translate to C++11 (which is the first C++ standard to
"fully contain" C99)? What if there is no answer (e.g., `-minstd=c23`)?
FWIW, my idea is to broaden the concept CMake has of "usage
requirements" to not be so CMake-centered and to encompass things like
"you need an rpath to X to use my libraries" or even "here's an entry
for `PYTHONPATH` to use my Python code". ISO C++'s SG15 has started
discussion of such things with an eye towards standardization here:
https://github.com/isocpp/pkg-fmt
--Ben
[1]https://cmake.org/cmake/help/latest/prop_tgt/C_STANDARD.html
