IAR for MSP430 function printf

Radoslav Marinov

Hi everyone,

Why

uint8_t c;
 c = ~0x0A;
printf("%u", (unsigned int)c);

outputs value greater than 8bit variable can hold? for example the output might be something like this: 65525.

Is there is an approach to print 8bit variable's values using printf function?

over 8 years ago

0 Clemens Ladisch over 8 years ago

Guru 243920 points

With %u, you are telling printf() that you have a value of type unsigned int. However, with a variadic function like this, the actual type used by the compiler is signed int (this is where the sign extension comes from).

You must explicitly cast the value to unsigned:

printf("%u", (unsigned int)c);

0 Radoslav Marinov over 8 years ago in reply to Clemens Ladisch

Intellectual 1000 points

I just changed the code accordingly, unfortunately I get the same outcomes. In the original post you will be able to see the changes I have made.

0 Anders Lindgren over 8 years ago

Expert 2070 points

When I run the code you have provided, the IAR tools print "245". Did you include the standard header file `stdio.h' in your application? If not, the printf function would look for the argument in the wrong location.

-- Anders Lindgren, IAR Systems

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IAR for MSP430 function printf