Re: C and Java, was Compilers :)

gah4 <>
Fri, 13 Jan 2023 12:39:41 -0800 (PST)

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From: gah4 <>
Newsgroups: comp.compilers
Date: Fri, 13 Jan 2023 12:39:41 -0800 (PST)
Organization: Compilers Central
References: 23-01-001 23-01-007 23-01-051 23-01-053
Injection-Info:; posting-host=""; logging-data="18371"; mail-complaints-to=""
Keywords: C, Java
Posted-Date: 13 Jan 2023 16:19:24 EST
In-Reply-To: 23-01-053

On Friday, January 13, 2023 at 11:10:37 AM UTC-8, gah4 wrote:


> Some time ago, I was trying to figure out if you could make a C compiler
> that generated JVM code. I would run much closer to the C standard
> than much C code does, especially regarding casting of pointers.

> [So what did you conclude? I'd think C type casts would be hard to
> turn into Java unless you made all of storage an opaque block. -John]

Someone else might have thought about the "opaque block" method.
But that wouldn't work if you wanted to call between Java and C.

As well as I know it, C only requires assignment to work for
pointers cast to (unsigned char *). And once they are cast,
usually (though I suppose not always), it is done with memcpy(),
or compared with memcmp().

So, all the complication of figuring out what is actually being
done, can be done inside one of those.

C pointers, then, are an object with a reference to the actual
array, and current offset within the array, and bounds for
the array. Pointer arithmetic only changes the offset.

Scalar variables that can be pointed to, compile as arrays
dimensioned [1].

I didn't get as far as figuring out varargs functions, but someone
must have done that, as System.out.format() works.
You can call it with the usual different argument types,
and it figures out everything.

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