5 ms·

I still hope that modules become mature and safe for production code. Initially I coded in C/C++ and this header #include/#ifndef approach seemed OK at that ti

by senfiaj 9mo ago

I still hope that modules become mature and safe for production code. Initially I coded in C/C++ and this header #include/#ifndef approach seemed OK at that time. But after using other programming languages, this approach started to feel too boilerplate and archaic. No sane programming language should require a duplication in order to export something (for example, the full function and its prototype), you should write something once and easily export.

kccqzy 9mo ago
> No sane programming language should require a duplication in order to export something (for example, the full function and its prototype) You are spoiled by the explosive growth of open source and the ease of accessing source code. Lots of closed source commercial libraries provide some .h files and a .so file. And even when open source, when you install a library from a package from a distribution or just a tarball, it usually installs some .h files and a .so file. The separation between interface and implementation into separate files was a good idea. The idea seemed to be going out of vogue but it’s still a good idea.
- senfiaj 9mo ago
  > Lots of closed source commercial libraries provide some .h files and a .so file. I'm mostly talking about modules for internal implementation, which is likely to be the bulk of the exports. Yes, it's understandable that for dll / so files exporting something for external executables is more complicated also because of ABI compatibility concerns (we use things like extern "C"). So, yes header approach might be justified in this case, but as I stated, such exports are probably a fraction of all exports (if they are needed at all). I'll still prefer modules when it's possible to avoid them.
- AgentME 9mo ago
  In most situations, auto-generating the equivalent of .h files for a library based on export statements in the source code would be fine and a useful simplification.
- johannes1234321 9mo ago
  > The separation between interface and implementation into separate files was a good idea. The idea seemed to be going out of vogue but it’s still a good idea. However as soon as you do C++ that goes away. With C++ you need implementation of templates available to the consumer (except cases with limited set of types where you can extern them), wmin many cases you get many small functions (basic operator implementations, begin()/end() for iterators in all variations etc.) which benefit from inking, thus need to be in the header. Oh and did I mention class declarations tonthe the class size ... or more generic and even with plain C: As soon as the client should know about the size of a type (for being able to allocate it, have an array of those etc) you can't provide the size by itself, but you have to provide the full type declaration with all types down the rabbit hole. Till you somewhere introduce a pointer to opaque type indirection. And then there macros ... Modules attempt to do that better, by providing just the interface in a file. But hey, C++ standard doesn't "know" about those, so module interface files aren't a portable thing ...
- nextaccountic 9mo ago
  The .h could have been a compiler output, like the .so
  - kccqzy 9mo ago
    The C language is too complicated and too flexible to allow that. If you are starting from scratch and creating a new language, this could be a design goal from the beginning.
    - quuxplusone 9mo ago
      > The C language is too complicated and too flexible to allow that. I disagree. In fact, I would expect the following could be a pretty reasonable exercise in a book like "Software Tools"[1]: "Write a program to extract all the function declarations from a C header file that does not contain any macro-preprocessor directives." This requires writing a full C lexer; a parser for function declarations (but for function and struct bodies you can do simple brace-matching); and nothing else. To make this tool useful in production, you must either write a full C preprocessor, or else use a pipeline to compose your tool with `cpp` or `gcc -E`. Which is the better choice? However, I do see that the actual "Software Tools" book doesn't get as advanced as lexing/parsing; it goes only as far as the tools we today call `grep` and `sed`. I certainly agree that doing the same for C++ would require a full-blown compiler, because of context-dependent constructs like `decltype(arbitrary-expression)::x < y > (z)`; but there's nothing like that in K&R-era C, or even in C89. No, I think the only reason such a declaration-extracting tool wasn't disseminated widely at the time (say, the mid-to-late 1970s) is that the cost-benefit ratio wouldn't have been seen as very rewarding. It would automate only half the task of writing a header file: the other and more difficult half is writing the accompanying code comments, which cannot be automated. Also, programmers of that era might be more likely to start with the header file (the interface and documentation), and proceed to the implementation only afterward. [1] - K&P's "Software Tools" was originally published in 1976, with exercises in Ratfor. "Software Tools in Pascal" (1981) is here: https://archive.org/details/softwaretoolsinp00kern/ https://archive.org/details/softwaretoolsinp00kern/
      - 9mo ago
Maxatar 9mo ago
I think everyone hopes/hoped for a sane and useful version of modules, one that would provide substantial improvements to compilation speed and make things like packaging libraries and dealing with dependencies a lot more sane. The version of modules that got standardized is anything but that. It's an incredibly convoluted mess that requires an enormous amount of effort for little benefit.
- senfiaj 9mo ago
  > It's an incredibly convoluted mess that requires an enormous amount of effort for little benefit. I'd say C++ as a whole is a complete mess. While it's powerful (including OOP), it's complicated and inconsistent language with a lot of historical baggage (40+ years). That's why people and companies still search for (or even already use) viable replacements for C++, such as Rust, Zig, etc.

by senfiaj 9mo ago

kccqzy 9mo ago

> No sane programming language should require a duplication in order to export something (for example, the full function and its prototype) You are spoiled by the explosive growth of open source and the ease of accessing source code. Lots of closed source commercial libraries provide some .h files and a .so file. And even when open source, when you install a library from a package from a distribution or just a tarball, it usually installs some .h files and a .so file. The separation between interface and implementation into separate files was a good idea. The idea seemed to be going out of vogue but it’s still a good idea.

senfiaj 9mo ago
> Lots of closed source commercial libraries provide some .h files and a .so file. I'm mostly talking about modules for internal implementation, which is likely to be the bulk of the exports. Yes, it's understandable that for dll / so files exporting something for external executables is more complicated also because of ABI compatibility concerns (we use things like extern "C"). So, yes header approach might be justified in this case, but as I stated, such exports are probably a fraction of all exports (if they are needed at all). I'll still prefer modules when it's possible to avoid them.
AgentME 9mo ago
In most situations, auto-generating the equivalent of .h files for a library based on export statements in the source code would be fine and a useful simplification.
johannes1234321 9mo ago
> The separation between interface and implementation into separate files was a good idea. The idea seemed to be going out of vogue but it’s still a good idea. However as soon as you do C++ that goes away. With C++ you need implementation of templates available to the consumer (except cases with limited set of types where you can extern them), wmin many cases you get many small functions (basic operator implementations, begin()/end() for iterators in all variations etc.) which benefit from inking, thus need to be in the header. Oh and did I mention class declarations tonthe the class size ... or more generic and even with plain C: As soon as the client should know about the size of a type (for being able to allocate it, have an array of those etc) you can't provide the size by itself, but you have to provide the full type declaration with all types down the rabbit hole. Till you somewhere introduce a pointer to opaque type indirection. And then there macros ... Modules attempt to do that better, by providing just the interface in a file. But hey, C++ standard doesn't "know" about those, so module interface files aren't a portable thing ...
nextaccountic 9mo ago
The .h could have been a compiler output, like the .so
- kccqzy 9mo ago
  The C language is too complicated and too flexible to allow that. If you are starting from scratch and creating a new language, this could be a design goal from the beginning.
  - quuxplusone 9mo ago
    > The C language is too complicated and too flexible to allow that. I disagree. In fact, I would expect the following could be a pretty reasonable exercise in a book like "Software Tools"[1]: "Write a program to extract all the function declarations from a C header file that does not contain any macro-preprocessor directives." This requires writing a full C lexer; a parser for function declarations (but for function and struct bodies you can do simple brace-matching); and nothing else. To make this tool useful in production, you must either write a full C preprocessor, or else use a pipeline to compose your tool with `cpp` or `gcc -E`. Which is the better choice? However, I do see that the actual "Software Tools" book doesn't get as advanced as lexing/parsing; it goes only as far as the tools we today call `grep` and `sed`. I certainly agree that doing the same for C++ would require a full-blown compiler, because of context-dependent constructs like `decltype(arbitrary-expression)::x < y > (z)`; but there's nothing like that in K&R-era C, or even in C89. No, I think the only reason such a declaration-extracting tool wasn't disseminated widely at the time (say, the mid-to-late 1970s) is that the cost-benefit ratio wouldn't have been seen as very rewarding. It would automate only half the task of writing a header file: the other and more difficult half is writing the accompanying code comments, which cannot be automated. Also, programmers of that era might be more likely to start with the header file (the interface and documentation), and proceed to the implementation only afterward. [1] - K&P's "Software Tools" was originally published in 1976, with exercises in Ratfor. "Software Tools in Pascal" (1981) is here: https://archive.org/details/softwaretoolsinp00kern/ https://archive.org/details/softwaretoolsinp00kern/
    - 9mo ago

Maxatar 9mo ago

I think everyone hopes/hoped for a sane and useful version of modules, one that would provide substantial improvements to compilation speed and make things like packaging libraries and dealing with dependencies a lot more sane. The version of modules that got standardized is anything but that. It's an incredibly convoluted mess that requires an enormous amount of effort for little benefit.

senfiaj 9mo ago
> It's an incredibly convoluted mess that requires an enormous amount of effort for little benefit. I'd say C++ as a whole is a complete mess. While it's powerful (including OOP), it's complicated and inconsistent language with a lot of historical baggage (40+ years). That's why people and companies still search for (or even already use) viable replacements for C++, such as Rust, Zig, etc.