A customer recently performed static analysis of my employer’s C codebase and gave us the results. Among useful patches was the request to change the famous do { ... } while(0) macro to do { ... } while(0,0). I understand what their patch is doing (using the sequence operator to return evaluate to the value of the second “0”, so the effect is the same) but it’s not clear why they’d favor the second form over the first form.
Is there a legitimate reason why one should prefer the second form of the macro, or is our customer’s static analysis being overly pedantic?
Well, I’ll go for an answer:
No. There is no legitimate reason. Both always evaluate to false, and any decent compiler will probably turn the second one into the first in the assembly anyway. If there was any reason for it to be invalid in some cases, C’s been around far long enough for that reason to be discovered by greater gurus than I.
If you like your code making owl-y eyes at you, use
while(0,0). Otherwise, use what the rest of the C programming world uses and tell your customer’s static analysis tool to shove it.