It depends on what you mean by ‘truly standards compliant’. However, the short answer is “it is a good idea to ensure that all functions have a prototype in scope before being used”. A more qualified answer notes that if the function accepts variable arguments (notably the printf() family of functions), then a prototype must … Read more
In C99, it’s technically undefined behavior. C99 ยง6.5.6 says: 7) For the purposes of these operators, a pointer to an object that is not an element of an array behaves the same as a pointer to the first element of an array of length one with the type of the object as its element type. … Read more
For a very resource constrained target such as 4KB of RAM, I’d test the waters with some samples before committing a lot of effort that can’t be easily ported back into a pure ANSI C implementation. The Embedded C++ working group did propose a standard subset of the language and a standard subset of the … Read more
You can find nice HTML versions of C89, C99, and C11, as well as some of the official draft PDF files they’re generated from, here: http://port70.net/~nsz/c/ Some other useful direct links to free PDF files of the C89/C90, C99 and C11 standards are listed below: C89/C90: https://www.pdf-archive.com/2014/10/02/ansi-iso-9899-1990-1/ansi-iso-9899-1990-1.pdf C99: http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1256.pdf C11: http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1570.pdf
The strncpy() function was designed with a very particular problem in mind: manipulating strings stored in the manner of original UNIX directory entries. These used a short fixed-sized array (14 bytes), and a nul-terminator was only used if the filename was shorter than the array. That’s what’s behind the two oddities of strncpy(): It doesn’t … Read more
As the C FAQ says: It’s not clear if it’s legal or portable, but it is rather popular. and: … an official interpretation has deemed that it is not strictly conforming with the C Standard, although it does seem to work under all known implementations. (Compilers which check array bounds carefully might issue warnings.) The … Read more
C99 allows //-style comments, C89 does not. So, to translate: C99: printf(“C%d\n”,(int)(90-(-4.5 /*Some comment stuff*/ -4.5))); // Outputs: 99 C89: printf(“C%d\n”,(int)(90-(-4.5/ -4.5))); /* so we get 90-1 or 89 */
It compiles successfully because GCC allows the declaration of s as a GNU extension, even though it’s not part of the C89 or ANSI standard. If you want to adhere strictly to those standards, you must pass the -pedantic flag. The declaration of c at the start of a { } block is part of … Read more
Everything before standardization is generally called “K&R C”, after the famous book (1st edition and 2nd edition), with Dennis Ritchie, the inventor of the C language, as one of the authors. This was “the C language” from 1972-1989. The first C standard was released 1989 nationally in USA, by their national standard institute ANSI. This … Read more
Will result always be the floor of the division? What is the defined behavior? Not quite. It rounds toward 0, rather than flooring. 6.5.5 Multiplicative operators 6 When integers are divided, the result of the / operator is the algebraic quotient with any fractional part discarded.88) If the quotient a/b is representable, the expression (a/b)*b … Read more