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Show HN: My C compiler compiled itself

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Re: Show HN: My C compiler compiled itself

#71

Post by nar001 »

unwind wrote: post #59
keyvank wrote: post #55

Earlier quoted context omitted.

thanks man! yes that makes sense. unfortunately 30cc is not able to compile that syntax, and will probably give type-checker errors when passing a void* to pointer of another type. but will implement it sometime soon!

Aha, so it doesn't know about void* being compatible with all (object) pointers, but so far just requires the pointers to match exactly? I see. Not sure why I was down-voted, I think that is ... not nice. :(

I don't think you can be downvoted, there's no downvote button

Re: Show HN: My C compiler compiled itself

#72

Post by dataflow »

unwind wrote: post #59
keyvank wrote: post #55

Earlier quoted context omitted.

thanks man! yes that makes sense. unfortunately 30cc is not able to compile that syntax, and will probably give type-checker errors when passing a void* to pointer of another type. but will implement it sometime soon!

Aha, so it doesn't know about void* being compatible with all (object) pointers, but so far just requires the pointers to match exactly? I see. Not sure why I was down-voted, I think that is ... not nice. :(

I downvoted just because I thought it wasn't great advice. It makes the code incompatible with C++ compilers, and being able to compile C with C++ compiler is often useful.

Also... it felt kind of... unnecessary? to tell someone who is making a compiler how to write basic code in the language they're writing a compiler for. It almost felt like telling an overweight medical student/doctor that he should avoid eating fatty foods.

Re: Show HN: My C compiler compiled itself

#73

Post by hollerith »

nar001 wrote: post #71
unwind wrote: post #59

Earlier quoted context omitted.

Aha, so it doesn't know about void* being compatible with all (object) pointers, but so far just requires the pointers to match exactly? I see. Not sure why I was down-voted, I think that is ... not nice. :(

I don't think you can be downvoted, there's no downvote button

Users with enough karma can downvote comments.

Re: Show HN: My C compiler compiled itself

#75

Post by solarengineer »

unwind wrote: post #65
gizmo wrote: post #57

Earlier quoted context omitted.

This kind of condescending advice doesn't help anybody. Redundant casts, like redundant braces, white space, and a plethora of similar choices are stylistic more than anything else. If you really feel the need to give unsolicited coding style feedback maybe at least spend more than a few seconds looking at the code before you do so. Otherwise it's just rude.

Really? Wow. I had no idea, and I really tried to sound non-condescending. I simply don't agree that redundant casts are something to be ignored, since they can be harmful and hide actual errors (the cast is a bit like `sudo make me a sandwich`, it makes the compiler do what you say which is not always a good idea). I guess I believe that publicly posting code, and even writing a compiler for the language in question…

FWIW, I liked your suggestion, the author’s explanation, And your follow on written understanding.

If someone’s technical article is submitted and they are themselves participating in a discussion out feeling insulted, then accusations of unsolicited advice are unfounded.

Re: Show HN: My C compiler compiled itself

#76

Post by peterfirefly »

gizmo wrote: post #57
unwind wrote: post #54

Very cool, congratulations! I took a 2-second peek at the code, and just wanted to offer a small piece of advice that I think makes it better. Or two, really. Counting is hard. Instead of (this is from parser.c): apply_result *ret = (apply_result*)malloc(sizeof(apply_result)); apply the two common principles of DRY [1] and "don't cast the return value of malloc()" [2] and you get: apply_result *ret = malloc(sizeof *r…

This kind of condescending advice doesn't help anybody. Redundant casts, like redundant braces, white space, and a plethora of similar choices are stylistic more than anything else. If you really feel the need to give unsolicited coding style feedback maybe at least spend more than a few seconds looking at the code before you do so. Otherwise it's just rude.

Redundant casts are really, really good at hiding errors...

(And few people know that sizeof is a unary operator so the parentheses are rarely necessary. Dropping them reduces the visual noise => improves readability.)

Re: Show HN: My C compiler compiled itself

#77

Post by williamdclt »

unwind wrote: post #65
gizmo wrote: post #57

Earlier quoted context omitted.

This kind of condescending advice doesn't help anybody. Redundant casts, like redundant braces, white space, and a plethora of similar choices are stylistic more than anything else. If you really feel the need to give unsolicited coding style feedback maybe at least spend more than a few seconds looking at the code before you do so. Otherwise it's just rude.

Really? Wow. I had no idea, and I really tried to sound non-condescending. I simply don't agree that redundant casts are something to be ignored, since they can be harmful and hide actual errors (the cast is a bit like `sudo make me a sandwich`, it makes the compiler do what you say which is not always a good idea). I guess I believe that publicly posting code, and even writing a compiler for the language in question…

I didn't find your tone condescending at all, it was a perfectly fine comment (esp with sources)

Re: Show HN: My C compiler compiled itself

#78

Post by williamdclt »

dbcurtis wrote: post #13
yjftsjthsd-h wrote: post #8

> Then run ./build.py. This will use the bootstrapped 30cc-compiler to compile 30cc itself. It then again uses the 30cc-compiled compiler to compile 30cc once again. The final compiler is then stored as ./30cc. Why isn't that also done by the Makefile? The only catch I could see is that you'd need to have it build to different output names, but that seems fine for what it is? --- Also, I'm curious - did you find your…

> Also, I'm curious - did you find yourself having to constrain your use of C in order to make sure that the compiler could compile itself? Or does it implement everything you would use naturally anyways? That would be the "bootstrapping" process. Nearly a half-century ago I took a compiler lab class where we were given a working, but slightly lame, compiler, and were tasked with adding new, less lame, language featu…

I guess the full bootstrapping process would start with writing a basic compiler in assembly?

Re: Show HN: My C compiler compiled itself

#79

Post by peterfirefly »

saghm wrote: post #42
anyfoo wrote: post #26

Earlier quoted context omitted.

It is so trivial, it takes you 10 minutes to learn. Less even, here is an attempt: foo.o: foo.c clang -c -o foo.o foo.c This builds a file called foo.o, if foo.c is newer than foo.o. Imagine that there is an identical bar.o as well, that builds it from bar.c. fooexec: foo.o bar.o clang -o fooexec foo.o bar.o This links together foo.o and bar.o into a file called fooexec, if at least one of foo.o or bar.o is newer (wh…

> Do $@ and $ And yet, I still don't actually know what `$@` and `$ The problem is that "simple" is not the same as "intuitive" or "discoverable". Yes, I could probably put in the effort to go and find out these things, but why would you expect someone to be motivated to do that by someone telling you that it's "trivial" and it "pains" them as they explain things in a way that doesn't actually clarify things in a way…

$@ is the name of the target -- the @looks a bit like an old-fashioned target for practice and competition shooting.

$$^ is the names of all the files the rule depends on. Think of it as a large hat above all the input file names.

Many things in make are clumsy and GNU make is a behemoth that does so much more than the original make that it is really hard to learn -- but these shortcuts have really good names!

(They are GNU make extensions, btw.)

Re: Show HN: My C compiler compiled itself

#80

Post by atq2119 »

williamdclt wrote: post #78
dbcurtis wrote: post #13

Earlier quoted context omitted.

> Also, I'm curious - did you find yourself having to constrain your use of C in order to make sure that the compiler could compile itself? Or does it implement everything you would use naturally anyways? That would be the "bootstrapping" process. Nearly a half-century ago I took a compiler lab class where we were given a working, but slightly lame, compiler, and were tasked with adding new, less lame, language featu…

I guess the full bootstrapping process would start with writing a basic compiler in assembly?

The full bootstrapping process starts with entering instructions in binary (or hex or octal) to build an assembler in the first place :)
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