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GCC did already exist when the C-- project was started, so that part didn't really change. The C-- team's hypothesis was that some kinds of languages (especiall

GCC did already exist when the C-- project was started, so that part didn't really change. The C-- team's hypothesis was that some kinds of languages (especially functional languages) would benefit from a cross-platform layer that is a better compilation target than C, partly through being a bit more low-level. The previous two popular routes were native-code compilers and compile-via-C compilers. Native-code compilers have the disadvantage that porting them and maintaining them on N architectures is significant work, and compile-via-C compilers have the disadvantage that C isn't a very convenient compilation target for many language features, especially to efficiently compile some common FP language features. The hope was that C-- would be a nice middle ground between compiling via C and compiling to native code, producing a target that was nicer than C as a target. Imo, that hypothesis did have some legs, but people are now instead usually using LLVM in various ways to accomplish it. LLVM's intermediate representation isn't really properly cross-platform, but it can be sort of hacked to be used for that purpose.

mattgreenrocks 13y ago
Do you think LLVM IR covers this ground adequately, despite not being cross-platform?
- _delirium 13y ago
  I'm not really a language implementor, more of a spectator of language implementations, so someone with more experience would give a better answer. My impression is that the GHC people, at least, still think that C-- is a nicer IR than LLVM-IR for their purposes. But they are slowly moving more things to LLVM anyway, because the LLVM project as a project has, in the meantime, built up a lot more momentum and infrastructure. In the early 2000s this wasn't obvious, but in 2013 it's clear that LLVM has an ecosystem, institutional support, resources to maintain ports, etc., while C-- didn't manage to get the same traction.
- thinkmoore 13y ago
  From my personal experience, LLVM is tied a bit to closely to the C ABI, which makes it difficult to implement some FP features cleanly. One example is forgoing C's stack discipline to implement double-barreled continuations.

mattgreenrocks 13y ago

Do you think LLVM IR covers this ground adequately, despite not being cross-platform?

_delirium 13y ago
I'm not really a language implementor, more of a spectator of language implementations, so someone with more experience would give a better answer. My impression is that the GHC people, at least, still think that C-- is a nicer IR than LLVM-IR for their purposes. But they are slowly moving more things to LLVM anyway, because the LLVM project as a project has, in the meantime, built up a lot more momentum and infrastructure. In the early 2000s this wasn't obvious, but in 2013 it's clear that LLVM has an ecosystem, institutional support, resources to maintain ports, etc., while C-- didn't manage to get the same traction.
thinkmoore 13y ago
From my personal experience, LLVM is tied a bit to closely to the C ABI, which makes it difficult to implement some FP features cleanly. One example is forgoing C's stack discipline to implement double-barreled continuations.