Read Char From File Portability Bugs + Fix | C Programming Example

[kazkylheku]

The type char is an integer type, like int. The problem is that on most machines it is smaller than int, and so cannot represent all of the values. If a function returns an int value, then unless you know that the value is between CHAR_MIN and CHAR_MAX, you are potentially converting the value to a different value if you force it to char. If a function returns int, then it behooves you to capture its value into a variable of that same type, or else some type which is a guaranteed superset like long.

In the case of fgets, the range of values it returns is a byte value in the range 0 to UCHAR_MAX, or else EOF which is negative. So right off the bat we have a problem. Let's assume bytes are 8 bits, and arithmetic is two's complement. The fgets function therefore returns 257 different values: 256 possible byte values or else EOF. An 8 bit char cannot represent 257 different values, so something has to give. If char is signed, then the byte value 255 will get converted to -1, which may look like a false positive for EOF. If char is unsigned, then none of its values are equal to EOF; the loop will not terminate. Either situation is a bug.

[nemoo]

yesterday, i was googling this problem with getting a char from user, and i found that you have to use space before %c in scanf, like that scanf(" %c", &ch);, and i know that there are getchar and getch/getche but they didn't help, so now i'm using scanf(" %c", &ch) always

[RoockYou]

i want to ask if you can explain "detached threads",
your way of explaining really help us

[ionguzun]

can u please explain in a video about runtime complexity in C please