If this is what you are asking, %p and %Fp print out a pointer, specifically the address to which the pointer refers, and since it is printing out a part of your computer’s architecture, it does so in Hexadecimal. In C, you can cast between a pointer and an int, since a pointer is just … Read more
Use the ll (el-el) long-long modifier with the u (unsigned) conversion. (Works in windows, GNU).
You are failing to access a field of the indexed union array: mydata[0] is a value of type union data, and can’t be cast to uint64_t. You need to access the proper union member: to select the uint64_t value. No need for the cast. Also: Use PRIu64 to portably print 64-bit values, you can’t assume … Read more
You can use an asterisk (*) to pass the width specifier/precision to printf(), rather than hard coding it into the format string, i.e.
%lu is the correct format for unsigned long. Sounds like there are other issues at play here, such as memory corruption or an uninitialized variable. Perhaps show us a larger picture?
“%f” is the (or at least one) correct format for a double. There is no format for a float, because if you attempt to pass a float to printf, it’ll be promoted to double before printf receives it1. “%lf” is also acceptable under the current standard — the l is specified as having no effect … Read more