c – Page 235 – IT Nursery

How to static assert to disallow “mixed endianness” in a non-templated member function

March 10, 2022 by IT Nursery

I suggest asserting that it’s either big or little endian: [code]#include <bit> #include <compare> struct pawned_pw { std::strong_ordering operator<=>(const pawned_pw& rhs) const { static_assert(std::endian::native == std::endian::big || std::endian::native == std::endian::little, "mixed-endianess architectures are not supported"); if constexpr (std::endian::native == std::endian::little) { return …; } else { // big return …; } } };[/code]

scanf() Leaves the Newline Character in the Buffer

May 20, 2022March 4, 2022 by IT Nursery

I have the following program: [c]int main(int argc, char *argv[]) { int a, b; char c1, c2; printf("Enter something: "); scanf("%d",&a); // line 1 printf("Enter other something: "); scanf("%d", &b); // line 2 printf("Enter a char: "); scanf("%c",&c1); // line 3 printf("Enter another char: "); scanf("%c", &c2); // line 4 printf("Done"); // line 5 system("PAUSE"); … Read more

Why Gets Function So Dangerous That It Should Not Be Used

May 19, 2022March 4, 2022 by IT Nursery

When I try to compile C code that uses the gets() function with GCC, I get this warning: (.text+0x34): warning: the `gets’ function is dangerous and should not be used. I remember this has something to do with stack protection and security, but I’m not sure exactly why. How can I remove this warning and why is … Read more

Why in C Constructs Using Pre and Post-Increment Undefined Behavior?

May 19, 2022March 4, 2022 by IT Nursery

[c]#include <stdio.h> int main(void) { int i = 0; i = i++ + ++i; printf("%d\n", i); // 3 i = 1; i = (i++); printf("%d\n", i); // 2 Should be 1, no ? volatile int u = 0; u = u++ + ++u; printf("%d\n", u); // 1 u = 1; u = (u++); printf("%d\n", u); … Read more

Why is “while ( !feof (file) )” always wrong

May 19, 2022March 4, 2022 by IT Nursery

What is wrong with using feof() to control a read loop? For example: [c]#include <stdio.h> #include <stdlib.h> int main(int argc, char **argv) { char *path = "stdin"; FILE *fp = argc > 1 ? fopen(path=argv[1], "r") : stdin; if( fp == NULL ){ perror(path); return EXIT_FAILURE; } while( !feof(fp) ){ /* THIS IS WRONG */ /* Read … Read more

Undefined, unspecified and implementation-defined behavior

May 20, 2022March 4, 2022 by IT Nursery

What is undefined behavior (UB) in C and C++? What about unspecified behavior and implementation-defined behavior? and What is the difference between them? Best Answer Undefined behavior is one of those aspects of the C and C++ language that can be surprising to programmers coming from other languages (other languages try to hide it better). Basically, it is possible to write … Read more

Do I cast the result of malloc?

May 19, 2022March 3, 2022 by IT Nursery

TL;DR int *sieve = (int *) malloc(sizeof(int) * length); Has two problems in result of malloc. The cast and that you’re using the type instead of variable as argument for sizeof. Instead, do like this: int *sieve = malloc(sizeof *sieve * length); Long version No; you don’t cast the result, since: It is unnecessary, as void * is automatically … Read more