[BUG] Checkpatch reports what appears to be a false error

[stolx]

Describe the bug Checkpatch spawns an error on switch case statement in the situation when there is intentional fallthrough from case to default, indicated by COMPILER_FALLTHROUGH macro, defined in sof/compiler_attributes.h.

Consider following code:

    switch (n) {
    case 1:
        res = 1;
        break;
    case 2:
        COMPILER_FALLTHROUGH
    default:
        res = 2;
        break;
    }

Checkpatch will report an error:

> ERROR: spaces required around that ':' (ctx:VxE)
> +       default:

To Reproduce Run checkpatch on commit ee4539b

Reproduction Rate All the time

Expected behavior Checkpatch reports no errors

Impact False errors prevent automatic checks from passing during PR review.

Environment 1) Branch name and commit hash of the 2 repositories: sof (firmware/topology) and linux (kernel driver).

• Kernel: N/A
• SOF: b0faccc 2) Name of the topology file
• Topology: N/A 3) Name of the platform(s) on which the bug is observed.
• Platform: N/A

Screenshots or console output

ERROR: spaces required around that ':' (ctx:VxE)
#44: FILE: src/include/sof/audio/format.h:191:
+       default:
               ^

[plbossart]

it's probably fooled because there's a missing ';' at the end of COMPILER_FALLTHROUGH.

Actually in this case there is no need for a fallthrough at all?

this could be

case 2: default: res = 2; break;

[stolx]

@plbossart I agree that fallthrough in this example is not needed. Even more so, case 2 is not needed, since

case 2:
default:
   res = 2;
   break;

is the effectively the same as

default:
   res = 2;
   break;

So I extended the example, added slightly more complicated "logic" to illustrate the error that I got:

    int res = 0;

    switch (a) {
    case 0:
        res += 1;
        break;
    case 1:
        res += 2;
        COMPILER_FALLTHROUGH
    default:
        res += 3;
        break;
    }

checkpatch on this code will spawn the same error

ERROR: spaces required around that ':' (ctx:VxE)
+       default:
               ^

new commit with example 6c7131c

[lgirdwood]

@stolx care to send a fix and remove case 2