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For the reference Rust did consider a similar style of C++ FFI back then [1] [2] [3], but to my knowledge it went nowhere due to the sheer amount of work requir

For the reference Rust did consider a similar style of C++ FFI back then [1] [2] [3], but to my knowledge it went nowhere due to the sheer amount of work required and the inability to future-proof. Inline assembly is another similar feature that D is substantially different from Rust, and the rationale for Rust [4] was also similar: D's inline assembly DSL only works in x86 and x86-64. [1] https://github.com/rust-lang/rust/issues/5853 https://github.com/rust-lang/rust/issues/5853 [2] https://github.com/rust-lang/rfcs/issues/602 https://github.com/rust-lang/rfcs/issues/602 [3] https://internals.rust-lang.org/t/better-c-interoperability/2650 https://internals.rust-lang.org/t/better-c-interoperability/... [4] https://rust-lang.github.io/rfcs/2873-inline-asm.html#implement-an-embedded-dsl https://rust-lang.github.io/rfcs/2873-inline-asm.html#implem...

nicwilson 5y ago
> D's inline assembly DSL only works in x86 and x86-64. You're conflating DMD (the reference compiler) with the language here. LDC and GDC (the LLVM and GCC based D compilers) both support GCC style "extended" inline assembly[0] and LDC even allows you to write inline LLVM IR. [0]: https://gcc.gnu.org/onlinedocs/gcc/Extended-Asm.html https://gcc.gnu.org/onlinedocs/gcc/Extended-Asm.html
- WalterBright 5y ago
  You're quite right, the D language leaves the inline assembler as implementation defined. DMD has a quite nice assembler that was lifted and updated from the older Digital Mars C++ inline assembler. Each of the D compilers supports inline assembler for each of the targets the particular compiler supports.
- lifthrasiir 5y ago
  I might not have been clear (sorry!) but the DSL here refers to the integrated assembly syntax as opposed to LLVM/GCC's textual approaches. Both syntaxes are officially documented in the D Language Reference [1], which is arguably the specification for D the language, but since DMD came much earlier than other implementations, I think it's fair to consider the DSL to be designed alongside with D. Anyway LDC and GCD's inability to support the DSL strengthens my original point. [1] https://dlang.org/spec/iasm.html https://dlang.org/spec/iasm.html
  - mhh__ 5y ago
    LDC also supports most of the extended inline asm. GDC used to support it (long story but that code is now the LDC impl), but it was removed a long time ago. GDC isn't that much younger than dmd.
WalterBright 5y ago
As for the amount of work required, we just rolled up our sleeves and did it :-) To improve interactivity with C, we even went so far as to build a C compiler into the D compiler. It was officially released this week.
- lifthrasiir 5y ago
  It seems that the C reimplementation is becoming a preferred approach for C FFI in recent languages---at least ones that can afford the cost. Not just D's ImportC but there are other examples like Python cffi. C++ FFI is another story though.
  - melony 5y ago
    Zig has C++ FFI
    - lifthrasiir 5y ago
      Zig's C and C++ FFI is basically based on embedding clang, which seems the only way for its level of FFI in case of C++. For C it is much more doable to make a new C compiler specifically for FFI.
      - WalterBright 5y ago
        D's ImportC also allows the C code to be extended with D-ish features, like forward references, compile time function execution, and modules.

nicwilson 5y ago

> D's inline assembly DSL only works in x86 and x86-64. You're conflating DMD (the reference compiler) with the language here. LDC and GDC (the LLVM and GCC based D compilers) both support GCC style "extended" inline assembly[0] and LDC even allows you to write inline LLVM IR. [0]: https://gcc.gnu.org/onlinedocs/gcc/Extended-Asm.html https://gcc.gnu.org/onlinedocs/gcc/Extended-Asm.html

WalterBright 5y ago
You're quite right, the D language leaves the inline assembler as implementation defined. DMD has a quite nice assembler that was lifted and updated from the older Digital Mars C++ inline assembler. Each of the D compilers supports inline assembler for each of the targets the particular compiler supports.
lifthrasiir 5y ago
I might not have been clear (sorry!) but the DSL here refers to the integrated assembly syntax as opposed to LLVM/GCC's textual approaches. Both syntaxes are officially documented in the D Language Reference [1], which is arguably the specification for D the language, but since DMD came much earlier than other implementations, I think it's fair to consider the DSL to be designed alongside with D. Anyway LDC and GCD's inability to support the DSL strengthens my original point. [1] https://dlang.org/spec/iasm.html https://dlang.org/spec/iasm.html
- mhh__ 5y ago
  LDC also supports most of the extended inline asm. GDC used to support it (long story but that code is now the LDC impl), but it was removed a long time ago. GDC isn't that much younger than dmd.

WalterBright 5y ago

As for the amount of work required, we just rolled up our sleeves and did it :-) To improve interactivity with C, we even went so far as to build a C compiler into the D compiler. It was officially released this week.

lifthrasiir 5y ago
It seems that the C reimplementation is becoming a preferred approach for C FFI in recent languages---at least ones that can afford the cost. Not just D's ImportC but there are other examples like Python cffi. C++ FFI is another story though.
- melony 5y ago
  Zig has C++ FFI
  - lifthrasiir 5y ago
    Zig's C and C++ FFI is basically based on embedding clang, which seems the only way for its level of FFI in case of C++. For C it is much more doable to make a new C compiler specifically for FFI.
    - WalterBright 5y ago
      D's ImportC also allows the C code to be extended with D-ish features, like forward references, compile time function execution, and modules.