This is a simple function which performs the desired operation. But it requires the + operator, so all you have left to do is to add the values with bit-operators: // replaces the + operator int add(int x, int y) { while (x) { int t = (x & y) << 1; y ^= x; … Read more
make defines a tab is required to start each recipe. All actions of every rule are identified by tabs. If you prefer to prefix your recipes with a character other than tab, you can set the .RECIPEPREFIX variable to an alternate character. To check, I use the command cat -e -t -v makefile_name. It shows … Read more
From Wikipedia: According to the 1999 ISO C standard (C99), size_t is an unsigned integer type of at least 16 bit (see sections 7.17 and 7.18.3). size_tis an unsigned data type defined by several C/C++ standards, e.g. the C99 ISO/IEC 9899 standard, that is defined in stddef.h.1 It can be further imported by inclusion of … Read more
Declaration A prototype for a function which takes a function parameter looks like the following: void func ( void (*f)(int) ); This states that the parameter f will be a pointer to a function which has a void return type and which takes a single int parameter. The following function (print) is an example of … Read more
From best to worse: Option 1 (C99 and newer) #include <stdbool.h> Option 2 typedef enum { false, true } bool; Option 3 typedef int bool; enum { false, true }; Option 4 typedef int bool; #define true 1 #define false 0 Explanation Option 1 will work only if you use C99 (or newer) and it’s … Read more
C has the concept of undefined behavior, i.e. some language constructs are syntactically valid but you can’t predict the behavior when the code is run. As far as I know, the standard doesn’t explicitly say why the concept of undefined behavior exists. In my mind, it’s simply because the language designers wanted there to be … Read more
calloc() gives you a zero-initialized buffer, while malloc() leaves the memory uninitialized. For large allocations, most calloc implementations under mainstream OSes will get known-zeroed pages from the OS (e.g. via POSIX mmap(MAP_ANONYMOUS) or Windows VirtualAlloc) so it doesn’t need to write them in user-space. This is how normal malloc gets more pages from the OS … Read more
One unit testing framework in C is Check; a list of unit testing frameworks in C can be found here and is reproduced below. Depending on how many standard library functions your runtime has, you may or not be able to use one of those. AceUnit AceUnit (Advanced C and Embedded Unit) bills itself as … Read more
[*] The common idiom is using both: typedef struct S { int x; } S; They are different definitions. To make the discussion clearer I will split the sentence: struct S { int x; }; typedef struct S S; In the first line you are defining the identifier S within the struct name space (not … Read more
A declaration introduces an identifier and describes its type, be it a type, object, or function. A declaration is what the compiler needs to accept references to that identifier. These are declarations: extern int bar; extern int g(int, int); double f(int, double); // extern can be omitted for function declarations class foo; // no extern … Read more