Unexpected Output

Question

Why does this outputs 3?

int a = 3;
float b = 5.89f;
printf("%d", b);

The output is always the value of the latest defined int variable (here 'a') and remains unchanged:

- After interchanging the positions of the definitions.
- Also if datatype of b is double.
- If b is uninitialized.
- If there's simply printf("%d", 24.8)

Answer 1

"The output is always the value of the latest int variable ..."
Actually not, it outputs varying value on each run, not value of <a>.

Use of inappropriate format specifier leads to undefined behaviour (unexpected output).

In Code Playground you will see a warning about wrong format specifier.

Answer 2

Thanks Ipang. I was running it on a different platform (Cxxdroid). So it can be concluded that this undefined behaviour is specific to platform.

Answer 3

Yes Abhinav,
I tested your snippet in C4Droid and also Code Playground, and also get different outputs 👌

Answer 4

Ipang But anyway, the float format specifier reads 4 bytes from the integer data block, which is obviously not in the same format. So what makes the output unpredictable?