[Cocci] [bug-cocci] deadcode detection

[Cocci] [bug-cocci] deadcode detection

[Akihiro Sagawa]

Hello, julia and folks,
I found the following source code (deadcode.c) isn't updated by semantic
patch (deadcode.cooci) with spatch version 1.0.4.

[deadcode.c]
int deadcode(const char* c)
{
    do {
        if (c) {
            foo(*c);
            break;
        }
        break;
    } while (0);
}

[deadcode.cocci]
@@
expression E;
@@
-foo(E)
+bar(E)

With `--debug` option, spatch shows `FLOW: deadcode detected: File
"./deadcode.c", line 3`. But, I think there is no deadcode. There is
just a redundant `break` at the end of the loop. In my opinion, although
it's a bit strange, `break` keyword is harmless like the last `break`
keyword in the last label block in a `switch` statement, e.g.

switch (*c) {
  case 'x': x++; break;
  case 'y': y++; break;
  default:
    warn("Invalid input: %c\n", *c);
    break; // <-- this is harmless, not a deadcode
}

Practical issue is seen in Wine 2.7's dlls/shlwapi/url.c from line 707
to 874. I tried to replace isalnum() to isalnumW(), a WCHAR version of
isalnum(),@line 812. However, spatch missed it without warnings. You
can see https://source.winehq.org/source/dlls/shlwapi/url.c?v=wine-2.7#0707
for the source code.

I'll be happy if spatch finds out the above case and makes a patch for it.
Deadcode.{c,cocci} are available in the Github pull requests.

Thanks in advance,
Akihiro Sagawa

[Cocci] [bug-cocci] deadcode detection

[Michael Stefaniuc]

On 05/13/2017 02:40 PM, Akihiro Sagawa wrote:
> Hello, julia and folks,
> I found the following source code (deadcode.c) isn't updated by semantic
> patch (deadcode.cooci) with spatch version 1.0.4.
This fails also with coccinelle-1.0.6-111-g8996213 which is the latest
one from git.

bye
	michael

> 
> [deadcode.c]
> int deadcode(const char* c)
> {
>     do {
>         if (c) {
>             foo(*c);
>             break;
>         }
>         break;
>     } while (0);
> }
> 
> [deadcode.cocci]
> @@
> expression E;
> @@
> -foo(E)
> +bar(E)
> 
> With `--debug` option, spatch shows `FLOW: deadcode detected: File
> "./deadcode.c", line 3`. But, I think there is no deadcode. There is
> just a redundant `break` at the end of the loop. In my opinion, although
> it's a bit strange, `break` keyword is harmless like the last `break`
> keyword in the last label block in a `switch` statement, e.g.
> 
> switch (*c) {
>   case 'x': x++; break;
>   case 'y': y++; break;
>   default:
>     warn("Invalid input: %c\n", *c);
>     break; // <-- this is harmless, not a deadcode
> }
> 
> Practical issue is seen in Wine 2.7's dlls/shlwapi/url.c from line 707
> to 874. I tried to replace isalnum() to isalnumW(), a WCHAR version of
> isalnum(), at line 812. However, spatch missed it without warnings. You
> can see https://source.winehq.org/source/dlls/shlwapi/url.c?v=wine-2.7#0707
> for the source code.
> 
> I'll be happy if spatch finds out the above case and makes a patch for it.
> Deadcode.{c,cocci} are available in the Github pull requests.
> 
> Thanks in advance,
> Akihiro Sagawa
> 
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