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Knowing C has made me a better and much more versatile programmer than I would be without it. For instance, a while back I had to diagnose a JVM core dumping sp

by sreque 9y ago

Knowing C has made me a better and much more versatile programmer than I would be without it. For instance, a while back I had to diagnose a JVM core dumping sporadically, and I was able to use my knowledge of C to try to recover valid return addresses from a corrupted stack, figure out there was a signal handler block on the stack, then further unwind from there to find out the whole story of what likely caused the crash. Knowing C also helps me write more performant code. Fast Java code ends up looking like C code written in Java. For instance, netty 4 implemented their own custom memory allocator to avoid heap pressure. Cassandra also has their own manual memory pools to try to improve performance, and VoltDB ended up implementing much of their database in C++. I've been able to speed up significant chunks of Java code by putting my "C" hat on. I would recommend every college student learn C, and learn it from the perspective of an "abstract machine" language, how your C code will interact with the OS and underlying hardware, and what assembly a compiler may generate. I would consider learning C for pedagogical purposes to be much more important than C++.

tomsmeding 9y ago
> I would recommend every college student learn C, and learn it from the perspective of an "abstract machine" language, how your C code will interact with the OS and underlying hardware, and what assembly a compiler may generate. Do note that these are two very different things. The C abstract machine as defined by the standard is sometimes so different from the actual machines you're going to run your code on, that you get these fine undefined behaviour things that everybody's on about. Please learn both, indeed, and stress the differences; then highlight the advantages of C. C is a dangerous, but powerful tool, and the necessity of warning students about things should not inhibit learning C.
- fao_ 9y ago
  > C is a dangerous, but powerful tool, and the necessity of warning students about things should not inhibit learning C. C is sharp, yes. It's also a universal interface. Almost every language has bindings for C, and C has bindings for almost everything.
  - AlexandrB 9y ago
    > Almost every language has bindings for C, and C has bindings for almost everything. In my mind this is the #1 reason to learn C. And it's unlikely that C++ will replace C in this role anytime soon as C++ has many more ways for an ABI to go wrong.
    - bobbyi_settv 9y ago
      It often works to implement well to implement your code in C++ and have a C interface (using extern "C") wrapped around it to be consumed be interfaced with by other languages.
kovrik 9y ago
Can it be replaced with Rust nowadays? Is it low-level enough? Or borrow checker and lifetimes defeat the whole purpose?
- oconnor663 9y ago
  My guess is that for this author's purposes, Rust is in the same place as C++. It can do the low level things, but you tend to spend more of your time working with higher level libraries that hide the nuts-and-blots details like allocation.
  - pcwalton 9y ago
    Rust libraries don't really hide allocation any more than modern C libraries do. (And if you aren't using modern libraries for stuff like string handling in C, you should be.)
    - notriddle 9y ago
      Isn't the point of this whole argument about avoiding abstraction?
      - pcwalton 9y ago
        I don't see any way in which string.h is less abstract in the "close to metal" sense than a real string or vector library (or Rust) is. The standard C library offers abstractions, just poor ones.
        kibwen 9y ago
        Not sure why this is being downvoted. Whether or not anyone out there likes Rust, dislikes Rust, or is completely apathetic to Rust, we can unanimously agree that the standard string-handling routines in C are quite poor. This isn't a controversial statement.
    - mwcampbell 9y ago
ZenoArrow 9y ago
> "For instance, a while back I had to diagnose a JVM core dumping sporadically, and I was able to use my knowledge of C to try to recover valid return addresses from a corrupted stack, figure out there was a signal handler block on the stack, then further unwind from there to find out the whole story of what likely caused the crash." Okay, but is that knowledge coming from coding in C, or it coming from debugging low-level code? I don't know what tool(s) you used to do that debugging, but if I assume for a second that you were using GDB, wasn't the main benefit of your past C experience (in this case) the exposure to tools like GDB, rather than your C knowledge being key in enabling you to dissect that JVM issue?
- maxxxxx 9y ago
  I think it's the C knowledge. I assume JVM is written in C or C++ so with C knowledge you can understand better how it works.
maxxxxx 9y ago
I feel the same. Even when debugging JavaScript or C# performance problems I often have insights from a C perspective that people who have only learned Java or JavaScript don't have. I haven't learned much assembly but I think some level of it would also be a very good thing. Once whole operating systems are written in Rust maybe Rust will be the most important language but until then it's C. C++ doesn't really count. I don't think you can do any serious C++ without knowing C really well.
- vvanders 9y ago
  I was with you until the part about C++. I spent very little part of my career writing C(mostly embedded hobbies) but still managed to pick up all the important bits(memory layout, CPU caches, allocation costs, processor pipelines and the like) from C++. Really it wasn't too long ago that the STL just wasn't good enough for high performance code and we rolled our own containers/pooling/everything. Modern C++ is a very much a different beast these days.
  - maxxxxx 9y ago
    I think I expressed my thoughts wrong. I didn't mean to say that you need to learn C to use C++ but that if you do any serious C++ work you will know a lot about the way C works. I don't think you will go very far in C++ if you don't understand pointers, heap vs. stack, when to allocate and release memory and a lot of other stuff.
    - vvanders 9y ago
      Ah, I think we're just arguing semantics then. I see that as very much a part of C++(new vs malloc only has some small subtle differences for instance). I will say if you don't understand pointers you're in for a world of pain in C++.
    - mikepurvis 9y ago
      Another important thing is understanding what's going on under the hood with C++ features— like, how you'd compile C++ into C. I don't put a ton of weight in it, but I enjoy engaging interview candidates about what's going on with virtual methods, casting classes, specialization with polymorphism vs templates, "public virtual" and multiple inheritance, etc etc. Like I say, no one thing is super interesting on its own, and its not a textbook answer I'm looking for, more just a sign that someone was curious enough to dig in at some point and figure out how the sausage was made.

by sreque 9y ago

tomsmeding 9y ago

> I would recommend every college student learn C, and learn it from the perspective of an "abstract machine" language, how your C code will interact with the OS and underlying hardware, and what assembly a compiler may generate. Do note that these are two very different things. The C abstract machine as defined by the standard is sometimes so different from the actual machines you're going to run your code on, that you get these fine undefined behaviour things that everybody's on about. Please learn both, indeed, and stress the differences; then highlight the advantages of C. C is a dangerous, but powerful tool, and the necessity of warning students about things should not inhibit learning C.

fao_ 9y ago
> C is a dangerous, but powerful tool, and the necessity of warning students about things should not inhibit learning C. C is sharp, yes. It's also a universal interface. Almost every language has bindings for C, and C has bindings for almost everything.
- AlexandrB 9y ago
  > Almost every language has bindings for C, and C has bindings for almost everything. In my mind this is the #1 reason to learn C. And it's unlikely that C++ will replace C in this role anytime soon as C++ has many more ways for an ABI to go wrong.
  - bobbyi_settv 9y ago
    It often works to implement well to implement your code in C++ and have a C interface (using extern "C") wrapped around it to be consumed be interfaced with by other languages.

kovrik 9y ago

Can it be replaced with Rust nowadays? Is it low-level enough? Or borrow checker and lifetimes defeat the whole purpose?

oconnor663 9y ago
My guess is that for this author's purposes, Rust is in the same place as C++. It can do the low level things, but you tend to spend more of your time working with higher level libraries that hide the nuts-and-blots details like allocation.
- pcwalton 9y ago
  Rust libraries don't really hide allocation any more than modern C libraries do. (And if you aren't using modern libraries for stuff like string handling in C, you should be.)
  - notriddle 9y ago
    Isn't the point of this whole argument about avoiding abstraction?
    - pcwalton 9y ago
      I don't see any way in which string.h is less abstract in the "close to metal" sense than a real string or vector library (or Rust) is. The standard C library offers abstractions, just poor ones.
      - kibwen 9y ago
        Not sure why this is being downvoted. Whether or not anyone out there likes Rust, dislikes Rust, or is completely apathetic to Rust, we can unanimously agree that the standard string-handling routines in C are quite poor. This isn't a controversial statement.
  - mwcampbell 9y ago

ZenoArrow 9y ago

> "For instance, a while back I had to diagnose a JVM core dumping sporadically, and I was able to use my knowledge of C to try to recover valid return addresses from a corrupted stack, figure out there was a signal handler block on the stack, then further unwind from there to find out the whole story of what likely caused the crash." Okay, but is that knowledge coming from coding in C, or it coming from debugging low-level code? I don't know what tool(s) you used to do that debugging, but if I assume for a second that you were using GDB, wasn't the main benefit of your past C experience (in this case) the exposure to tools like GDB, rather than your C knowledge being key in enabling you to dissect that JVM issue?

maxxxxx 9y ago
I think it's the C knowledge. I assume JVM is written in C or C++ so with C knowledge you can understand better how it works.

maxxxxx 9y ago

I feel the same. Even when debugging JavaScript or C# performance problems I often have insights from a C perspective that people who have only learned Java or JavaScript don't have. I haven't learned much assembly but I think some level of it would also be a very good thing. Once whole operating systems are written in Rust maybe Rust will be the most important language but until then it's C. C++ doesn't really count. I don't think you can do any serious C++ without knowing C really well.

vvanders 9y ago
I was with you until the part about C++. I spent very little part of my career writing C(mostly embedded hobbies) but still managed to pick up all the important bits(memory layout, CPU caches, allocation costs, processor pipelines and the like) from C++. Really it wasn't too long ago that the STL just wasn't good enough for high performance code and we rolled our own containers/pooling/everything. Modern C++ is a very much a different beast these days.
- maxxxxx 9y ago
  I think I expressed my thoughts wrong. I didn't mean to say that you need to learn C to use C++ but that if you do any serious C++ work you will know a lot about the way C works. I don't think you will go very far in C++ if you don't understand pointers, heap vs. stack, when to allocate and release memory and a lot of other stuff.
  - vvanders 9y ago
    Ah, I think we're just arguing semantics then. I see that as very much a part of C++(new vs malloc only has some small subtle differences for instance). I will say if you don't understand pointers you're in for a world of pain in C++.
  - mikepurvis 9y ago
    Another important thing is understanding what's going on under the hood with C++ features— like, how you'd compile C++ into C. I don't put a ton of weight in it, but I enjoy engaging interview candidates about what's going on with virtual methods, casting classes, specialization with polymorphism vs templates, "public virtual" and multiple inheritance, etc etc. Like I say, no one thing is super interesting on its own, and its not a textbook answer I'm looking for, more just a sign that someone was curious enough to dig in at some point and figure out how the sausage was made.