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git rebase I pretty much understand. Make will forever be a mystery to me. Mostly just how after the third or fourth version of it they didn't take a step back

git rebase I pretty much understand. Make will forever be a mystery to me. Mostly just how after the third or fourth version of it they didn't take a step back and think, "Hey, wait, maybe we should just make a language that spits out a shell file and ditch having it sort of kind of look like a shell file itself."

GauntletWizard 12y ago
Because a shell file would be an inefficient and imprecise way of describing the state and logic that Make uses.
- DannoHung 12y ago
  Really? I mean, it pretty much just runs commands in sequence and/or parallel, right? Sorry, like I said, I don't think I really understand make. I mean, I can understand that it's doing some checks to determine what commands to emit, but doesn't it all end up falling out as pretty much a straight "Yes? Do this. No? Do that. Do this and then this and then this. Do all these at the same time." That's my mental model at the moment anyway.
  - GauntletWizard 12y ago
    Ultimately, make represents a dependency graph; Something that a shell language is not well prepared to represent. Yes, it's doing X, Y, and Z at the same time, but when X is done it can launch A and B, when Z finishes then C can also be started, but you don't want to run them all at the same time because of a max subprocesses limit. You don't know if X or Z will finish first, so you can't just launch C as soon as Z is done, nor do you want to waste time waiting for A and B to finish to launch C if Z is done. How do you express that in pure shell?
  - barrkel 12y ago
    x: y z x depends on y (meaning, if x is missing, or is a file that is older than y where y is also a file, it needs to be recreated). z is how to recreate x. Makefiles are programs that construct a dependency graph. The rest of makefile syntax is mostly about ways of generating variants of the above without being overly verbose, or reducing gruntwork when e.g. adding new header includes to existing source files. But this is the heart of it. Root the dependency graph somewhere, and as long as the dependencies are complete and correct, the minimal set of commands, and potential parallelism, can be calculated.
hamstergene 12y ago
The point of make is to avoid doing what does not need to be done. Don't recompile binary whose sources didn't change, don't copy file which is already there, and so on. Because those operations add up to hours as the project grows. If we didn't mind waiting for hours each time we build, then of course, a shell script that does `rm -rf target` then assembles everything from scratch would be significantly more straightforward and readable.

GauntletWizard 12y ago

Because a shell file would be an inefficient and imprecise way of describing the state and logic that Make uses.

DannoHung 12y ago
Really? I mean, it pretty much just runs commands in sequence and/or parallel, right? Sorry, like I said, I don't think I really understand make. I mean, I can understand that it's doing some checks to determine what commands to emit, but doesn't it all end up falling out as pretty much a straight "Yes? Do this. No? Do that. Do this and then this and then this. Do all these at the same time." That's my mental model at the moment anyway.
- GauntletWizard 12y ago
  Ultimately, make represents a dependency graph; Something that a shell language is not well prepared to represent. Yes, it's doing X, Y, and Z at the same time, but when X is done it can launch A and B, when Z finishes then C can also be started, but you don't want to run them all at the same time because of a max subprocesses limit. You don't know if X or Z will finish first, so you can't just launch C as soon as Z is done, nor do you want to waste time waiting for A and B to finish to launch C if Z is done. How do you express that in pure shell?
- barrkel 12y ago
  x: y z x depends on y (meaning, if x is missing, or is a file that is older than y where y is also a file, it needs to be recreated). z is how to recreate x. Makefiles are programs that construct a dependency graph. The rest of makefile syntax is mostly about ways of generating variants of the above without being overly verbose, or reducing gruntwork when e.g. adding new header includes to existing source files. But this is the heart of it. Root the dependency graph somewhere, and as long as the dependencies are complete and correct, the minimal set of commands, and potential parallelism, can be calculated.

hamstergene 12y ago

The point of make is to avoid doing what does not need to be done. Don't recompile binary whose sources didn't change, don't copy file which is already there, and so on. Because those operations add up to hours as the project grows. If we didn't mind waiting for hours each time we build, then of course, a shell script that does `rm -rf target` then assembles everything from scratch would be significantly more straightforward and readable.