Implementation of the switch statement in C

Asked Mar 23 '17 at 20:17

Active Mar 23 '17 at 20:28

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How is a switch-case statement compiled/implemented in C.

Is it a linear lookup? Is it a hash table? Some other option?

If the specific compiler changes the answer, assume recent gcc version with no build flags.

In my situation the data is more that 50 sequential enums, so dense data.

edited Mar 23 '17 at 20:28

asked Mar 23 '17 at 20:17

OrangePeel52

6

Look at the compiled code. It probably depends on whether the case values are dense or sparse. – Barmar Mar 23 '17 at 20:19
It's unlikely to be a hash table. For sparse values it's probably linear `if/else`, for dense values it's probably an indexed goto. – Barmar Mar 23 '17 at 20:20
What@Barmar says.Plus: gcc sometimes generates a tree-like decision chain. – wildplasser Mar 23 '17 at 20:25
@FredLarson thanks for finding that. – OrangePeel52 Mar 23 '17 at 20:26

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