Using floats with sprintf() in embedded C

Question

Guys, I want to know if float variables can be used in sprintf() function.

Like, if we write:

sprintf(str,"adc_read = %d \n",adc_read);

where adc_read is an integer variable, it will store the string

"adc_read = 1023 \n"

in str (assuming that adc_read = 1023)

How can I use a float variable in place of integer?

Answer 1

Yes, and no. Despite what some other replies have said, the C compiler is required to perform conversions for sprintf(), and all other variadic functions, as follows:

• char => int
• short => int
• float => double

(and signed/unsigned variants of the above integral types)

It does this precisely because sprintf() (and the other print()-family functions) would be unusable without it. (Of course, they're pretty unusable as it is.)

But you cannot assume any other conversions, and your code will have undefined behaviour - read: crash! - if you do it.