Which parts of the C standard library are not covered by (the rest of) the C++ standard library?

Question

The C++ library includes the same definitions as the C language library

But the C++ library seems to duplicate (/extend) some of the functionality of the C library in non-C-library headers. For example, the C library has <string.h>, and the C++ library has both <cstring> and <string>; the C library has <time.h>, and the C+ library has both <ctime> and <chrono>.

If I need a string class, I assume that I am better off using <string> instead of <cstring>, because <string> can benefit from all the non-C functionality in C++ (e.g. exceptions). But there is functionality in the C library that doesn't exist in any other form in the C++ library. For example, I couldn't find anything like memcpy and memcmp outside <cstring>.

Which parts of the C library have no analogue in the non-C-library headers?

(If the version of the C++ standard matters for this, I am interested in C++11.)

note: http://stackoverflow.com/questions/4707012/c-memcpy-vs-stdcopy — Karoly Horvath, Mar 08 '14 at 12:40
The reason there's nothing like memcpy and memcmp in `` is that `` isn't a re-implementation of ``, it's an entirely separate approach to the abstract problem space "text manipulation". One that happens to differ significantly from the approach taken by ``, partly because it used a different language and partly for language-agnostic reasons (e.g. nul termination vs. length). — , Mar 08 '14 at 12:41

Mike Seymour · Accepted Answer · 2014-03-09T01:55:57.560

There aren't that many headers, so lets just list them. Some could be replaced by language facilities, rather than libraries. (I haven't enumerated every function in each header, so I might have missed the odd function that doesn't have a C++ alternative when most of its colleagues do.)

C library         C++ alternatives
assert.h          Exceptions
complex.h         <complex>
ctype.h           None (or maybe <locale>, if you want to jump down that rabbit-hole)
errno.h           None (but only applies to C functions)
fenv.h            None
float.h           <limits>
inttypes.h        (See breakdown)
   formatting     <iostream>
   strto...       <string> (C++11), <sstream>
   imaxabs        std::abs overloads
   imaxdiv        std::div overloads
iso646.h          Language
locale.h          <locale>
math.h            None (extended with C++ overloads)
setjmp.h          Exceptions
signal.h          None
stdarg.h          Variadic templates (C++11)
stdbool.h         Language
stddef.h          None
stdint.h          None
stdio.h           <iostream> etc.
stdlib.h          (See breakdown)
   atof etc.      <sstream>, <string> (C++11)
   rand etc.      <random> (C++11)
   malloc etc.    new, containers
   abort etc.     None
   bsearch etc.   <algorithm>
   abs etc.       None (extended with C++ overloads)
   mb strings     None
string.h          <string>, <algorithm>
tgmath.h          <cmath> (C++ overloads)
time.h            <chrono> (C++11)
wchar.h           <iostream> etc.
wctype.h          None

To summarise:

Which parts of the C library have no analogue in the non-C-library headers?

[w]ctype.h, errno.h, fenv.h, fenv.h, math.h, signal.h, stddef.h, stdint.h, some of stdlib.h. Before C++11, also stdarg.h, time.h and more of stdlib.h

The features from `ctype.h` are covered by the facet `std::ctype` in ``. — Morwenn, Mar 08 '14 at 19:16
@timwoj: Yes, that's the C++ wrapper for the C library header, just as for example is the wrapper for — Mike Seymour, Mar 08 '14 at 21:47
@MikeSeymour No wonder. I think that it is one of the less "documented" parts of the standard. There are very few articles on the internet about `` compared to the rest of the standard :) — Morwenn, Mar 08 '14 at 22:26

Which parts of the C standard library are not covered by (the rest of) the C++ standard library?

1 Answers1