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> the generalized "for" of C was a mistake, because it complicates the frequent use cases in order to simplify seldom encountered use cases The worst offender

> the generalized "for" of C was a mistake, because it complicates the frequent use cases in order to simplify seldom encountered use cases The worst offender is the quasi-obligatory "break" statement in "case" blocks. Fall-through cases are useful for things like lexers but probably not needed in 99.999% of other programs. I wonder how many millions of (wo)man hours have been wasted on debugging missing breaks. (yes, I know that linters exist)

bluecalm 3y ago
You don't really need a linter. It's just a warning setting, see: -Wimplicit-fallthrough From the compiler docs. It's just not a problem. If you waste time once and learn about warning options in the compiler you will be better off anyway. It's like with assignment being an expression panic - something that maybe bites you once and then you learn to read the compiler warnings and it never causes problems again. If you don't want to read then there is: -Werror Available.
kps 3y ago
That (also) came from BCPL. (BCPL had a separate `endcase` statement; `break` applied only to loops. It also had `docase ‹expr›`, which is the equivalent of a loop `continue`, re-entering the `switchon`.)
- vincent-manis 3y ago
  As I recall, B was modelled on an early BCPL compiler that didn't have an ENDCASE statement, hence the overloading of break for exiting a switch block.
cassepipe 3y ago
Note that gcc and clang will warn you about fallthrough statements i you use -Wextra and that you have to either have insert a /fallthrough/ comment to make your intent clear. Pity the (wo)man who does not use -Wall -Wextra for (s)he is truly mistaken
- flohofwoe 3y ago
  Clang actually doesn't warn in -Wextra: https://www.godbolt.org/z/99ejvY9Pc https://www.godbolt.org/z/99ejvY9Pc It requires the separate option -Wimplicit-fallthrough: https://www.godbolt.org/z/GP576zG9h https://www.godbolt.org/z/GP576zG9h (which tbh sounds like a bug, because usually Clang tries to emulate GCC behaviour)
- a_e_k 3y ago
  C++17 now has standardized the [[fallthrough]] attribute: https://en.cppreference.com/w/cpp/language/attributes/fallthrough https://en.cppreference.com/w/cpp/language/attributes/fallth... (For backwards compatibility, it still must fallthrough with or without the attribute; the attribute just signals programmer intention and silences the warning.)
pjmlp 3y ago
Incidently lint was invented exactly because of improving the way C was, they decided it was better in the UNIX tradition to add yet another tool, which those millions rather not use.
deleted 3y ago
[deleted]
flohofwoe 3y ago
No separate linters needed, but details differ between compilers. GCC has a warning in the '-Wextra' warning set, Clang requires the explicit option `-Wimplicit-fallthrough', MSVC is completely silent (apparently it's in the CppCoreCheck rules though). This should really be in the default warning set with an annotation that the fallthrough is intended (unless the case-branch is completely empty).
lisper 3y ago
> The worst offender is the quasi-obligatory "break" statement in "case" blocks. This was (almost certainly) done to simplify the compiler. CASE in C is not actually a structured control construct despite its syntactic appearance, it's just a computed GOTO. This is what makes things like Duff's device [1] possible. [1] https://en.wikipedia.org/wiki/Duff%27s_device https://en.wikipedia.org/wiki/Duff%27s_device
- itsphilos 3y ago
  I didn't know about Duff's device, which looks pretty interesting! Thanks for sharing
  - lisper 3y ago
    Sure, but just for the record IMHO duffs device is an abomination and an illustration of how badly broken C is. No one should ever actually use it.
    - commandersaki 3y ago
      I think I've come across Duff's device in Go internals for zero-ing memory.
- codr7 3y ago
  Yeah, I remember having my mind blown when I first discovered Duff's Device. My mental picture of what C-compilers are up to turned out to be a lot more sophisticated than reality. But having written a few Forth-interpreters, it makes total sense to me. Treating the input as a mostly unstructured stream of tokens is very convenient.
- bxparks 3y ago
  I think computed-GOTO is easier to understand and more flexible than Duff's device, but computed-GOTO is not part of the C standard. It is sometimes available as a non-portable extension, e.g. https://gcc.gnu.org/onlinedocs/gcc/Labels-as-Values.html https://gcc.gnu.org/onlinedocs/gcc/Labels-as-Values.html. Anyone know why it is not included in C?
reactordev 3y ago
break; has a special color value in my IDE’s. Just so it’s loud. Strictly because of what you describe.
- AnimalMuppet 3y ago
  That's not a bad idea, but it still leaves you having to notice when the loudness is silently missing. (It's easier when it's loud, but still...)
WalterBright 3y ago
In D, if there are no intervening statements: case 1: case 2: ... code ... the fallthrough is allowed. case 1: ... code ... case 2: ... code ... Is an error. But `goto case` can be used: case 1: ... code ... goto case; case 2: ... code ... which makes it clear. No new keywords are needed. C could adopt this easily. All those /* fallthrough */ comments and warnings and compiler switches will just go away. Oh, and obviously: case 1: ... code ... goto default; default: ... code ... also works!

bluecalm 3y ago

You don't really need a linter. It's just a warning setting, see: -Wimplicit-fallthrough From the compiler docs. It's just not a problem. If you waste time once and learn about warning options in the compiler you will be better off anyway. It's like with assignment being an expression panic - something that maybe bites you once and then you learn to read the compiler warnings and it never causes problems again. If you don't want to read then there is: -Werror Available.

kps 3y ago

That (also) came from BCPL. (BCPL had a separate `endcase` statement; `break` applied only to loops. It also had `docase ‹expr›`, which is the equivalent of a loop `continue`, re-entering the `switchon`.)

vincent-manis 3y ago
As I recall, B was modelled on an early BCPL compiler that didn't have an ENDCASE statement, hence the overloading of break for exiting a switch block.

cassepipe 3y ago

Note that gcc and clang will warn you about fallthrough statements i you use -Wextra and that you have to either have insert a /fallthrough/ comment to make your intent clear. Pity the (wo)man who does not use -Wall -Wextra for (s)he is truly mistaken

flohofwoe 3y ago
Clang actually doesn't warn in -Wextra: https://www.godbolt.org/z/99ejvY9Pc https://www.godbolt.org/z/99ejvY9Pc It requires the separate option -Wimplicit-fallthrough: https://www.godbolt.org/z/GP576zG9h https://www.godbolt.org/z/GP576zG9h (which tbh sounds like a bug, because usually Clang tries to emulate GCC behaviour)
a_e_k 3y ago
C++17 now has standardized the [[fallthrough]] attribute: https://en.cppreference.com/w/cpp/language/attributes/fallthrough https://en.cppreference.com/w/cpp/language/attributes/fallth... (For backwards compatibility, it still must fallthrough with or without the attribute; the attribute just signals programmer intention and silences the warning.)

pjmlp 3y ago

Incidently lint was invented exactly because of improving the way C was, they decided it was better in the UNIX tradition to add yet another tool, which those millions rather not use.

deleted 3y ago

[deleted]

flohofwoe 3y ago

No separate linters needed, but details differ between compilers. GCC has a warning in the '-Wextra' warning set, Clang requires the explicit option `-Wimplicit-fallthrough', MSVC is completely silent (apparently it's in the CppCoreCheck rules though). This should really be in the default warning set with an annotation that the fallthrough is intended (unless the case-branch is completely empty).

lisper 3y ago

> The worst offender is the quasi-obligatory "break" statement in "case" blocks. This was (almost certainly) done to simplify the compiler. CASE in C is not actually a structured control construct despite its syntactic appearance, it's just a computed GOTO. This is what makes things like Duff's device [1] possible. [1] https://en.wikipedia.org/wiki/Duff%27s_device https://en.wikipedia.org/wiki/Duff%27s_device

itsphilos 3y ago
I didn't know about Duff's device, which looks pretty interesting! Thanks for sharing
- lisper 3y ago
  Sure, but just for the record IMHO duffs device is an abomination and an illustration of how badly broken C is. No one should ever actually use it.
  - commandersaki 3y ago
    I think I've come across Duff's device in Go internals for zero-ing memory.
codr7 3y ago
Yeah, I remember having my mind blown when I first discovered Duff's Device. My mental picture of what C-compilers are up to turned out to be a lot more sophisticated than reality. But having written a few Forth-interpreters, it makes total sense to me. Treating the input as a mostly unstructured stream of tokens is very convenient.
bxparks 3y ago
I think computed-GOTO is easier to understand and more flexible than Duff's device, but computed-GOTO is not part of the C standard. It is sometimes available as a non-portable extension, e.g. https://gcc.gnu.org/onlinedocs/gcc/Labels-as-Values.html https://gcc.gnu.org/onlinedocs/gcc/Labels-as-Values.html. Anyone know why it is not included in C?

reactordev 3y ago

break; has a special color value in my IDE’s. Just so it’s loud. Strictly because of what you describe.

AnimalMuppet 3y ago
That's not a bad idea, but it still leaves you having to notice when the loudness is silently missing. (It's easier when it's loud, but still...)

WalterBright 3y ago

In D, if there are no intervening statements: case 1: case 2: ... code ... the fallthrough is allowed. case 1: ... code ... case 2: ... code ... Is an error. But `goto case` can be used: case 1: ... code ... goto case; case 2: ... code ... which makes it clear. No new keywords are needed. C could adopt this easily. All those /* fallthrough */ comments and warnings and compiler switches will just go away. Oh, and obviously: case 1: ... code ... goto default; default: ... code ... also works!