10 ms·

If it's not that complicated please explain why OpenSSL, the linux kernel, Curl a multitude of very popular C libraries don't do what you describe. Clearly it's

by simias 7y ago

If it's not that complicated please explain why OpenSSL, the linux kernel, Curl a multitude of very popular C libraries don't do what you describe. Clearly it's complicated enough that even talented C coders try to cut some corners when given the chance. C error handling ergonomics are non-existent which means that everybody bakes ad-hoc library-specific conventions that are extremely error-prone. You could argue that they're doing it wrong and you might have a point but if almost everybody gets it wrong maybe it's fair to blame the language itself a little bit.

robert_foss 7y ago
The kernel very much returns sentinel values, if something more complicated has to be transmitted error codes are commonly used. I see nothing wrong with it.
- simias 7y ago
  I'm not arguing that the kernel devs are doing it wrong. I'm only pointing out that, in my opinion, the way C deals with error handling (that is, by not doing anything at all) is far from reasonable and the cause of many bugs. It's terrible ergonomics. If you have a kernel function returning a pointer and you think that you're supposed to check for NULL when it actually returns a ERR_PTR in case of errors you will not only fail to do the check but on top of that end up with a garbage pointer somewhere in your program. If you have a MMU and you try to de-reference the pointer you'll have a violent crash, which at least shouldn't be too hard to debug. If you feed the pointer to some hardware module or if you're working on an MMU-less system then Good Luck; Have Fun. C doesn't have your back here. It doesn't let you signal how a function reports errors, it doesn't even let you tag nullable pointers.
Crinus 7y ago
I already gave an example of APIs that do this - pretty much all COM APIs use HRESULT. I do not know why not everyone does this as i'm not everyone and as such i cannot tell what sort of considerations (if any) were going on. At best i can make some guesses. BTW curl does seem to do what i wrote above, for example `curl_easy_init` returns a `CURL` object on success or NULL if there was an error [1] and `curl_easy_perform` returns a `CURLcode` value [2] that looks like it is used across the API to indicate errors. [1] https://curl.haxx.se/libcurl/c/curl_easy_init.html https://curl.haxx.se/libcurl/c/curl_easy_init.html [2] https://curl.haxx.se/libcurl/c/curl_easy_perform.html https://curl.haxx.se/libcurl/c/curl_easy_perform.html

by simias 7y ago

robert_foss 7y ago

The kernel very much returns sentinel values, if something more complicated has to be transmitted error codes are commonly used. I see nothing wrong with it.

simias 7y ago
I'm not arguing that the kernel devs are doing it wrong. I'm only pointing out that, in my opinion, the way C deals with error handling (that is, by not doing anything at all) is far from reasonable and the cause of many bugs. It's terrible ergonomics. If you have a kernel function returning a pointer and you think that you're supposed to check for NULL when it actually returns a ERR_PTR in case of errors you will not only fail to do the check but on top of that end up with a garbage pointer somewhere in your program. If you have a MMU and you try to de-reference the pointer you'll have a violent crash, which at least shouldn't be too hard to debug. If you feed the pointer to some hardware module or if you're working on an MMU-less system then Good Luck; Have Fun. C doesn't have your back here. It doesn't let you signal how a function reports errors, it doesn't even let you tag nullable pointers.

Crinus 7y ago

I already gave an example of APIs that do this - pretty much all COM APIs use HRESULT. I do not know why not everyone does this as i'm not everyone and as such i cannot tell what sort of considerations (if any) were going on. At best i can make some guesses. BTW curl does seem to do what i wrote above, for example `curl_easy_init` returns a `CURL` object on success or NULL if there was an error [1] and `curl_easy_perform` returns a `CURLcode` value [2] that looks like it is used across the API to indicate errors. [1] https://curl.haxx.se/libcurl/c/curl_easy_init.html https://curl.haxx.se/libcurl/c/curl_easy_init.html [2] https://curl.haxx.se/libcurl/c/curl_easy_perform.html https://curl.haxx.se/libcurl/c/curl_easy_perform.html