Since version 9.1, GCC provides support for the D programming language. Thus it
is easy to build a cross-compiler for D, such as aarch64-unknown-linux-gnu-gdc.
However to cross-compile a Meson project using D, using a cross build definition
such as the following is not enough:
```
[binaries]
d = '/path/to/aarch64-unknown-linux-gnu-gdc'
exe_wrapper = '/path/to/qemu-aarch64-static'
[properties]
needs_exe_wrapper = true
[host_machine]
system = 'linux'
cpu_family = 'aarch64'
cpu = 'cortex-a53'
endian = 'little'
```
Indeed, "exe_wrapper" is not be taken into account. Build will fail with:
```
Executables created by D compiler /path/to/aarch64-uknown-linux-gnu-gdc are not runnable.
```
This patch fixes this by reworking:
- detect_d_compiler() to properly get exe_wrapper and D compilers and detect the
one available.
- Dcompiler to properly handle exe_wrapper.
It would be very challenging if not futile to make has_function work for Fortran.
The meson.get_compiler('fortran').links() works very well instead.
As a reference, CMake's check_fortran_function_exists is completely broken in general.
This change raises a useful MesonException instead of giving bizarre errors.
These compilers invoke external linkers and have the appropriate .linker
property set. Therefore, BasicLinkerIsCompilerMixin appears to be
misplaced.
It used to work by chance, because BasicLinkerIsCompilerMixin failed to
override the get_allow_undefined_link_args method. The D compilers do
not provide their own get_allow_undefined_link_args, because they expect
to inherit it from Compiler, which simply delegates it to the linker.
Now that BasicLinkerIsCompilerMixin correctly overrides that method with
a stub, it broke compilers that relied on the buggy behavior.
Commit ff4a17dbef modified the version
requirements wrongly. AppleClangC should be the one with higher version
numbers. Exchange them to fix the check.
compiler.get_supported_arguments reports success for certain unsupported
flags when using the gnu C/ObjC, C++/ObjC++ compilers. This fix reads
the stderr on the has_arguments check to ensure the arguments really are
supported and not valid for the language selection
Now that the linkers are split out of the compilers this enum is
only used to know what platform we're compiling for. Which is
what the MachineInfo class is for