{"id":6216,"date":"2024-01-27T00:01:20","date_gmt":"2024-01-27T08:01:20","guid":{"rendered":"https:\/\/c-for-dummies.com\/blog\/?p=6216"},"modified":"2024-01-20T13:00:09","modified_gmt":"2024-01-20T21:00:09","slug":"the-c23-deprecated-and-removed-collection","status":"publish","type":"post","link":"https:\/\/c-for-dummies.com\/blog\/?p=6216","title":{"rendered":"The C23 Deprecated and Removed Collection"},"content":{"rendered":"

As with all language updates, things change. Some of these items are deprecated while others are outright removed. Here’s the list.
\n
\nAccording to the cppreference.com<\/a> website, the following items are removed from the C language with the C23 standard:<\/p>\n

• Old-style function declarations and definitions you’ve probably never used, but which are defined in the original K&R. For example:<\/p>\n

int swap(a,b)
\n    int *a, b;
\n{
\n    \/* stuff *\/
\n}<\/code><\/p>\n

I don’t know anyone who declares a function with the variable list presented as above. The current form was introduced with C89.<\/p>\n

• Representations for signed integers other than two’s complement.<\/p>\n

Without getting too geeky, signed integer values typically range from -2n-1<\/sup> to +2n-1<\/sup>-1. For example, -128 through 127 for a signed char<\/em> data type. Some obscure compilers set these values as -127 through 127, which isn’t supported in the C23 standard.<\/p>\n

• Permission that u\/U-prefixed character constants and string literals may be not UTF-16\/32
\n• Mixed wide string literal concatenation<\/p>\n

Both of these items can be confusing, but they’re cleaning up definitions for wide and multibyte characters. The C23 standard brings consistency to expressing wide character and multibyte literals by removing the old definitions for the u<\/code> and U<\/code> character prefixes that were inconsistent or ill-defined.<\/p>\n

• Support for calling realloc()<\/em> with zero size<\/p>\n

The realloc()<\/em> function can reallocate a memory chunk to zero bytes. When you do so, different things can happen depending on the compiler, e.g., is the memory block freed? In the C23 standard, the behavior of reallocating memory to zero bytes is officially flagged as “undefined.”<\/p>\n

• __alignof_is_defined<\/em> and __alignas_is_defined<\/em><\/p>\n

These macros are removed in C23. If used, they return constant 1 (TRUE).<\/p>\n

• static_assert<\/em> is not provided as a macro defined in <\/code>
\n• thread_local<\/em> is not provided as a macro defined in <\/code><\/p>\n

The old static_assert<\/em> macro is now the new keyboard _Static_assert<\/em>; thread_local<\/em> becomes keyword _Thread_local<\/em>.<\/p>\n

The list of Deprecated items is rather long but contains a few things you may recognize. Before showing the list, remember that deprecated doesn’t mean that the function or feature is no longer available. It means that you should avoid using the functions in future code as a better, stronger way to do the task is available.<\/p>\n

Two functions being deprecated as asctime()<\/em> and ctime()<\/em>.<\/p>\n

The asctime()<\/em> function converts a time\/date value stored in a tm<\/code> structure into a string. The string isn’t the issue, but rather that values in the tm<\/code> structure can be out of range. The function’s behavior for dealing with out of range values is undefined, which is probably why this function is being deprecated. The asctime_s()<\/em> function can be used as a substitute.<\/p>\n

The ctime()<\/em> function converts a clock tick (time_t<\/em>) value into a string. If I’m reading the docs correctly, this function works by calling the asctime()<\/em> function internally, which would explain why it’s also being deprecated. The substitute function is ctime_s()<\/em>.<\/p>\n

The deprecated list also includes the stdnoreturn.h<\/code> header file plus a few macros I’m unfamiliar with. The math.h<\/code> defined constants\/macros INFINITY<\/code>, DEC_INFINITY<\/code>, NAN<\/code>, and DEC_NAN<\/code> are now found in the float.h<\/code> header file.<\/p>\n

You can view more details at the cppreference.com<\/a> website. The site also features a table that shows current compilers and their C23 status.<\/p>\n","protected":false},"excerpt":{"rendered":"

Review what’s gone bye-bye and what’s about to leave the C language as defined in the new C23 standard. Continue reading →<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[2],"tags":[],"class_list":["post-6216","post","type-post","status-publish","format-standard","hentry","category-main"],"_links":{"self":[{"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/6216","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=6216"}],"version-history":[{"count":6,"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/6216\/revisions"}],"predecessor-version":[{"id":6223,"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/6216\/revisions\/6223"}],"wp:attachment":[{"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=6216"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=6216"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=6216"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}