4 ms·

Truthfully, C does what you tell it to do. As it turns out, most people don't want it to do what they tell it to do, they want it to do what is in their head. T

Truthfully, C does what you tell it to do. As it turns out, most people don't want it to do what they tell it to do, they want it to do what is in their head. Those warnings are "did you really mean what you just told me to do?". For some people, the answer is "no, what, wait!" -- those are what they are for. Not that the behavior is insane, just "less common". I don't think people fully grasp the idea that C does what you tell it to do when they first start using it. If you told C "make me a sandwich", it'd give a warning about not having enough mustard to cover your entire body and an error about not have a large enough bun type to fit you in.

JoachimSchipper 14y ago
This is facile; there is no good reason why C couldn't have a less-dangerous switch statement, or why compilers don't have nicer defaults. (If you run gcc without -W -Wall -O2, you either really know what you're doing or you're doing it wrong; in either case, having those options as defaults makes sense.)
- figglesonrails 14y ago
  Since the context is "C" not "C compilers", then I'd say C could have a less dangerous switch statement by requiring break/continue to indicate this. Agreed. Why people don't document/annotate for static analysis intentional fallthroughs is beyond me. OK, so we can eliminate one type of bug if we make that change (assuming we fixed all legacy code) -- what about the other legitimate uses of potentially suspect constructs? Compiler writers can do whatever the heck they want, and if dumping ALL THE WARNINGS was the priority, you'd need three lines of command line switches to turn off the "noise" warnings. Clearly, the a bunch of people see it as "noise" or don't care about writing clean code. That's more systemic of programmers.
- joshAg 14y ago
  There are many cases where fall through switch statements are preferable, but that's almost beside the point. C is basically just portable assembler with syntactic sugar sprinkled on top. Assembler doesn't have less dangerous switch statements and switch statments. Assembler has branching and jumping. That break statement in c is almost literally telling the assembler to jump out of a chain of branch statements after probably returning from a jal of the function within the same case block. Adding an extra switch statement just takes the language farther away from assembler and makes compiling more complicated, which is silly since the unsafe switch statement with break statements will/should produce the exact same assembler (this is different from the difference between using if{}else{ if...} chains and using switch, which will produce different assembler code). To make it even more fun, there are many use cases for fall through switch statements. My personal favorite is duff's device, which is an unwrapped version of a serial copy that will run faster on certain architectures than a more typical serial copy will run: send(to, from, count) register short to, from; register count; { register n = (count + 7) / 8; switch(count % 8) { case 0: do { to = from++; //this is for a memory mapped register. case 7: to = from++; // use to++ for non memory mapped registers case 6: to = from++; case 5: to = from++; case 4: to = from++; case 3: to = from++; case 2: to = from++; case 1: to = *from++; } while(--n > 0); } }
  - shurane 14y ago
    I thought duff's device was one of the few examples that use fall through switch statements. I was taught to use switches with blocks, because otherwise unexpected things happen.

JoachimSchipper 14y ago

This is facile; there is no good reason why C couldn't have a less-dangerous switch statement, or why compilers don't have nicer defaults. (If you run gcc without -W -Wall -O2, you either really know what you're doing or you're doing it wrong; in either case, having those options as defaults makes sense.)

figglesonrails 14y ago
Since the context is "C" not "C compilers", then I'd say C could have a less dangerous switch statement by requiring break/continue to indicate this. Agreed. Why people don't document/annotate for static analysis intentional fallthroughs is beyond me. OK, so we can eliminate one type of bug if we make that change (assuming we fixed all legacy code) -- what about the other legitimate uses of potentially suspect constructs? Compiler writers can do whatever the heck they want, and if dumping ALL THE WARNINGS was the priority, you'd need three lines of command line switches to turn off the "noise" warnings. Clearly, the a bunch of people see it as "noise" or don't care about writing clean code. That's more systemic of programmers.
joshAg 14y ago
There are many cases where fall through switch statements are preferable, but that's almost beside the point. C is basically just portable assembler with syntactic sugar sprinkled on top. Assembler doesn't have less dangerous switch statements and switch statments. Assembler has branching and jumping. That break statement in c is almost literally telling the assembler to jump out of a chain of branch statements after probably returning from a jal of the function within the same case block. Adding an extra switch statement just takes the language farther away from assembler and makes compiling more complicated, which is silly since the unsafe switch statement with break statements will/should produce the exact same assembler (this is different from the difference between using if{}else{ if...} chains and using switch, which will produce different assembler code). To make it even more fun, there are many use cases for fall through switch statements. My personal favorite is duff's device, which is an unwrapped version of a serial copy that will run faster on certain architectures than a more typical serial copy will run: send(to, from, count) register short to, from; register count; { register n = (count + 7) / 8; switch(count % 8) { case 0: do { to = from++; //this is for a memory mapped register. case 7: to = from++; // use to++ for non memory mapped registers case 6: to = from++; case 5: to = from++; case 4: to = from++; case 3: to = from++; case 2: to = from++; case 1: to = *from++; } while(--n > 0); } }
- shurane 14y ago
  I thought duff's device was one of the few examples that use fall through switch statements. I was taught to use switches with blocks, because otherwise unexpected things happen.