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Show HN: My C compiler compiled itself

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Re: Show HN: My C compiler compiled itself

#31

Post by akira2501 »

unclad5968 wrote: post #23
anyfoo wrote: post #16

Earlier quoted context omitted.

Or just take a few moments to learn the basics about Makefiles. The thing about Makefiles is that simples ones at least are really easy to write, and read. Much simpler and quicker than a cumbersome python script, that will most likely do less with much more boilerplate code (e.g. dependencies), and be much harder to read. Of course, you may hit a point where you stretch your Makefile so much beyond its common capabi…

As someone that learned C# and python before C and C++, to this day I couldn't explain to you how make rules work. Make is so unlike build tools from other languages that it doesn't surprise me someone would rather use python to bootstrap their compiler.

    output: dependencies
If any "dependencies" are newer than "output" or if "output" does not exist the commands run. Otherwise they don't.

Re: Show HN: My C compiler compiled itself

#32

Post by fuhsnn »

CJefferson wrote: post #29
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…

Saying this is an 'incremental makefile' isn't really correct, as changes to header files aren't going to lead to rebuilding. So, either you need to manually keep references to which .h files you include in your Makefiles up to date, or start worrying about M / MM / MG / MP, and of course you'd like those to be re-run when you change your files, and suddenly your Makefile is an awful lot less simple. This is the main…

Yes, this is quite important for C projects as it leads to subtle bugs. I also long for a way to let make detect a change of $CC (new build of the compiler itself) in the context of debugging a compiler against third party makefile projects.

Re: Show HN: My C compiler compiled itself

#33

Post by anyfoo »

CJefferson wrote: post #29
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…

Saying this is an 'incremental makefile' isn't really correct, as changes to header files aren't going to lead to rebuilding. So, either you need to manually keep references to which .h files you include in your Makefiles up to date, or start worrying about M / MM / MG / MP, and of course you'd like those to be re-run when you change your files, and suddenly your Makefile is an awful lot less simple. This is the main…

It is correct to call it an incremental Makefile, it merely doesn’t name the dependencies for you. A Makefile has exactly the dependencies you specify. It’s that simple.

That is not necessarily the most useful. Especially as your project gets larger, you probably will not want to specify every header file as a manual dependency, or alternatively rebuild everything every time you change a header file. (Though for me personally, either approach often works for surprisingly long.)

Then you can do things like letting the C preprocessor create the dependencies that get included in your Makefile (yes, common C compilers can create Makefile fragments). Or do something more complicated. Or switch to another build system, if your project really outgrew, or really mismatches, make.

But at its core, Makefiles follow a simple concept, are entirely language agnostic, and even with just the simpler concepts they remain useful for a long time.

Re: Show HN: My C compiler compiled itself

#34

Post by anyfoo »

fuhsnn wrote: post #32
CJefferson wrote: post #29

Earlier quoted context omitted.

Saying this is an 'incremental makefile' isn't really correct, as changes to header files aren't going to lead to rebuilding. So, either you need to manually keep references to which .h files you include in your Makefiles up to date, or start worrying about M / MM / MG / MP, and of course you'd like those to be re-run when you change your files, and suddenly your Makefile is an awful lot less simple. This is the main…

Yes, this is quite important for C projects as it leads to subtle bugs. I also long for a way to let make detect a change of $CC (new build of the compiler itself) in the context of debugging a compiler against third party makefile projects.

Have a step that takes the SHA256 or similar of $CC, make that a dependency. You’d need slightly more advanced make features if you want to make it “pretty” (and not just, say, touch a file through some shell code comparison), but this is a slightly more advanced request.

Or potentially just specify the path to $CC itself as dependency? Presumably, if the C compiler changes, the timestamp of its executable does too. (Bad if it goes backwards, though.)

Re: Show HN: My C compiler compiled itself

#35

Post by anyfoo »

downboots wrote: post #30
anyfoo wrote: post #25

Earlier quoted context omitted.

Ah, thanks. My brain actually did not see that second "compiler" when reading, now it makes sense.

How could you tell the difference between missing it and your brain filtering it out?

Isn’t that the same now?

By the way, I dislike the term “compiler compiler”, because that’s not really what it does. I like “parser generator” for tax/bison, and “lexer generator” for flex.

Re: Show HN: My C compiler compiled itself

#36

Post by ModernMech »

Koshkin wrote: post #22
anyfoo wrote: post #17

Earlier quoted context omitted.

> if you want more of a challenge try a compiler compiler that can compile itself... :) Is that not what OP did?

No (if the parent really meant ‘compiler compiler’ which, I think, would be what yacc/bison is).

yacc calls it's a compiler compiler, but it's a parser compiler.

Re: Show HN: My C compiler compiled itself

#37

Post by yjftsjthsd-h »

anyfoo wrote: post #34
fuhsnn wrote: post #32

Earlier quoted context omitted.

Yes, this is quite important for C projects as it leads to subtle bugs. I also long for a way to let make detect a change of $CC (new build of the compiler itself) in the context of debugging a compiler against third party makefile projects.

Have a step that takes the SHA256 or similar of $CC, make that a dependency. You’d need slightly more advanced make features if you want to make it “pretty” (and not just, say, touch a file through some shell code comparison), but this is a slightly more advanced request. Or potentially just specify the path to $CC itself as dependency? Presumably, if the C compiler changes, the timestamp of its executable does too.…

> Have a step that takes the SHA256 or similar of $CC, make that a dependency.

Careful, one more step and we'll start recreating nix in Makefiles;)

(Wait, could we? Should we?)

Re: Show HN: My C compiler compiled itself

#38

Post by 3836293648 »

aleph_minus_one wrote: post #19
anyfoo wrote: post #16

Earlier quoted context omitted.

Or just take a few moments to learn the basics about Makefiles. The thing about Makefiles is that simples ones at least are really easy to write, and read. Much simpler and quicker than a cumbersome python script, that will most likely do less with much more boilerplate code (e.g. dependencies), and be much harder to read. Of course, you may hit a point where you stretch your Makefile so much beyond its common capabi…

> The thing about Makefiles is that simples ones at least are really easy to write, and read. Much simpler and quicker than a cumbersome python script, that will most likely do less with much more boilerplate code (e.g. dependencies), and be much harder to read. Whether this is true or not depends a lot on from which programming culture/background you come.

It's is absolutely objectively true. Whether you already know it or not depends on your background

Re: Show HN: My C compiler compiled itself

#39

Post by CJefferson »

fuhsnn wrote: post #32
CJefferson wrote: post #29

Earlier quoted context omitted.

Saying this is an 'incremental makefile' isn't really correct, as changes to header files aren't going to lead to rebuilding. So, either you need to manually keep references to which .h files you include in your Makefiles up to date, or start worrying about M / MM / MG / MP, and of course you'd like those to be re-run when you change your files, and suddenly your Makefile is an awful lot less simple. This is the main…

Yes, this is quite important for C projects as it leads to subtle bugs. I also long for a way to let make detect a change of $CC (new build of the compiler itself) in the context of debugging a compiler against third party makefile projects.

I often use a Python program called 'fabricate', which basically checks every file a command opens, and re-runs the command if any touched file changes.

I love it, and I hoped this would become the future of how build-systems are built -- you could automatically parallelise, rebuild, make clean, everything, just by tracking which files are read, and written.

It does add a bit of overhead, but I'd be willing to pay that for simplicity. Unfortunately, it doesn't seem to have caught on.

Re: Show HN: My C compiler compiled itself

#40

Post by saghm »

anyfoo wrote: post #16
__alexander wrote: post #11

Earlier quoted context omitted.

> Why isn't that also done by the Makefile? My guess is that some people would rather write Python code than dig into Make’s documentation. That said, ChatGPT is excellent at creating valid make files.

Or just take a few moments to learn the basics about Makefiles. The thing about Makefiles is that simples ones at least are really easy to write, and read. Much simpler and quicker than a cumbersome python script, that will most likely do less with much more boilerplate code (e.g. dependencies), and be much harder to read. Of course, you may hit a point where you stretch your Makefile so much beyond its common capabi…

On the other hand, I'd argue that the point where you've stretched it so far that it's more trouble than it's worth is basically impossible to see until you've gone beyond it.
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