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printf of an indexed array

Topic last updated 16 Mar 2010, by Igor Skochinsky. 1 reply
tim owen
16 Mar 2010

Hi

If you printf an indexed array on MBED it comes out backwards;-i.e.

int a[3],ind = 0; etc etc

pc.printf("%d %d %d", a[ind++],a[ind++],a[ind++]);

it prints  a[2] a[1] a[0]   - i.e. it evaluates  the index from the far end inwards. I haven't checked fprintf yet.

I don't remember it being like that when I did a lot of C programming on other systems and I don't have another compiler to hand. Is this normal C++ or is it a anomaly in the compiler?  You can obviously get round it, but it just seems strange.

Igor Skochinsky
16 Mar 2010

The order of evaluation of function's arguments is not specified in the C standard:

http://stackoverflow.com/questions/376278/parameter-evaluation-order-before-a-function-calling-in-c

Most C compilers push (and evaluate) arguments from the last to first, thus the result you get. To get deterministic behavior, don't use the increment operators in the arguments.