Instead of calling /usr/bin/gcc, use /usr/bin/c99. This is the Single-Unix-approved way of invoking a C99 compiler. On an Ubuntu system, this points to a script which invokes gcc after having added the -std=c99 flag, which is precisely what you want.
A C code can be optimized in two ways: For Code size and for Execution Time. inline functions: gcc.gnu.org says, By declaring a function inline, you can direct GCC to make calls to that function faster. One way GCC can achieve this is to integrate that function’s code into the code for its callers. This … Read more
This is explained in depth in the gcc manual, available (if it’s installed) by typing info gcc or online here. The relevant section of the current manual is here, but it may or may not correspond to the version you’re using. Some of this information has changed since I posted this answer in 2013, and … Read more
Digraphs were created for programmers that didn’t have a keyboard which supported the ISO 646 character set. http://en.wikipedia.org/wiki/C_trigraph
I’m so used to typing for (int i = 0; i < n; ++i) { … } in C++ that it’s a pain to use a non-C99 compiler where I am forced to say int i; for (i = 0; i < n; ++i ) { … }
In C99, it’s technically undefined behavior. C99 §6.5.6 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
State machines are very simple in C if you use function pointers. Basically you need 2 arrays – one for state function pointers and one for state transition rules. Every state function returns the code, you lookup state transition table by state and return code to find the next state and then just execute it. … Read more
Here is my homework of the day, it’s based on macro tricks and today I particularly learnt about __VA_NARG__ invented by Laurent Deniau. Anyway, the following sample code works up to 8 fields for the sake of clarity. Just extend the code by duplicating if you need more (this is because the preprocessor doesn’t feature … Read more
uint_least8_t is the smallest type that has at least 8 bits. uint_fast8_t is the fastest type that has at least 8 bits. You can see the differences by imagining exotic architectures. Imagine a 20-bit architecture. Its unsigned int has 20 bits (one register), and its unsigned char has 10 bits. So sizeof(int) == 2, but … Read more
This is one of those weird corner cases where we’re subject to the limitations of the English language and inconsistent structure in the standard. So at best, I can make a compelling counter-argument, as it’s impossible to prove it 🙂1 The code in the question exhibits well-defined behaviour. As [7.1.4] is the basis of the … Read more