He who is Shy* gave you the germ of an answer, but only the germ. The basic technique for converting a value into a string in the C pre-processor is indeed via the ‘#’ operator, but a simple transliteration of the proposed solution gets a compilation error: #define TEST_FUNC test_func #define TEST_FUNC_NAME #TEST_FUNC #include <stdio.h> … Read more
Assuming what you need is a simple byte swap, try something like Unsigned 16 bit conversion: swapped = (num>>8) | (num<<8); Unsigned 32-bit conversion: swapped = ((num>>24)&0xff) | // move byte 3 to byte 0 ((num<<8)&0xff0000) | // move byte 1 to byte 2 ((num>>8)&0xff00) | // move byte 2 to byte 1 ((num<<24)&0xff000000); // … Read more
The program will not work properly because at Line 1, when the user presses Enter, it will leave in the input buffer 2 character: Enter key (ASCII code 13) and \n (ASCII code 10). Therefore, at Line 2, it will read the \n and will not wait for the user to enter a character. The … Read more
Using floating point numbers, 0.0 / 0.0 isn’t a “divide by zero” error; it results in NaN. This C program prints -nan: #include <stdio.h> int main() { float x = 0.0 / 0.0; printf(“%f\n”, x); return 0; } In terms what NaN looks like to the computer, two “invalid” numbers are reserved for “signaling” and … Read more
A very simple implementation, expressed in C. Implements a circular buffer style FIFO queue. Could be made more generic by creating a structure containing the queue size, queue data, and queue indexes (in and out), which would be passed in with the data to add or remove from the queue. These same routines could then … Read more
The comma operator evaluates all its operands and yields the value of the last one. So basically whichever condition you write first, it will be disregarded, and the second one will be significant only. for (i = 0; j >= 0, i <= 5; i++) is thus equivalent with for (i = 0; i <= … Read more
If you don’t declare a function and it only appears after being called, it is automatically assumed to be int, so in your case, you didn’t declare void my_print (char *); void my_print2 (char *); before you call it in main, so the compiler assume there are functions which their prototypes are int my_print2 (char … Read more
It is well defined behavior. In C11 a new clause 6.8.5 ad 6 has been added An iteration statement whose controlling expression is not a constant expression,156) that performs no input/output operations, does not access volatile objects, and performs no synchronization or atomic operations in its body, controlling expression, or (in the case of a … Read more
Just as a brief answer, there are two usages for the static keyword when defining variables: 1- Variables defined in the file scope with static keyword, i.e. defined outside functions will be visible only within that file. Any attempt to access them from other files will result in unresolved symbol at link time. 2- Variables … Read more
const char *opt; opt = “eth0”; const len = strnlen(opt, IFNAMSIZ); if (len == IFNAMSIZ) { fprintf(stderr, “Too long iface name”); return 1; } setsockopt(sd, SOL_SOCKET, SO_BINDTODEVICE, opt, len); First line: set up your variable Second line: tell the program which interface to bind to Lines 3-5: get length of interface name and check if … Read more