2014-06-01 17:47:45

by Peter Senna Tschudin

Subject: [PATCH] coccicheck: Add unneeded return variable test

This semantic patch looks for variables that are initialized with a
constant, are never updated, and are only used as parameter of return.
Return the constant instead of using a variable.

There are 8 patches accepted reported by this semantic patch and more
than 300 fixes to be applied.

Signed-off-by: Peter Senna Tschudin <[email protected]>
---
scripts/coccinelle/misc/returnvar.cocci | 66 +++++++++++++++++++++++++++++++++
1 file changed, 66 insertions(+)
create mode 100644 scripts/coccinelle/misc/returnvar.cocci

diff --git a/scripts/coccinelle/misc/returnvar.cocci b/scripts/coccinelle/misc/returnvar.cocci
new file mode 100644
index 0000000..605955a
--- /dev/null
+++ b/scripts/coccinelle/misc/returnvar.cocci
@@ -0,0 +1,66 @@
+///
+/// Removes unneeded variable used to store return value.
+///
+// Confidence: Moderate
+// Copyright: (C) 2012 Peter Senna Tschudin, INRIA/LIP6. GPLv2.
+// URL: http://coccinelle.lip6.fr/
+// Comments: Comments on code can be deleted if near code that is removed.
+// "when strict" can be removed to get more hits, but adds false
+// positives
+// Options: --no-includes --include-headers
+
+virtual patch
+virtual report
+virtual context
+virtual org
+
+@depends on patch@
+type T;
+constant C;
+identifier ret;
+@@
+- T ret = C;
+... when != ret
+ when strict
+return
+- ret
++ C
+;
+
+@depends on context@
+type T;
+constant C;
+identifier ret;
+@@
+* T ret = C;
+... when != ret
+ when strict
+* return ret;
+
+@r1 depends on report || org@
+type T;
+constant C;
+identifier ret;
+position p1, p2;
+@@
+T ret@p1 = C;
+... when != ret
+ when strict
+return ret@p2;
+
+@script:python depends on report@
+p1 << r1.p1;
+p2 << r1.p2;
+C << r1.C;
+ret << r1.ret;
+@@
+coccilib.report.print_report(p1[0], "Unneeded variable: \"" + ret + "\". Return \"" + C + "\" on line " + p2[0].line)
+
+@script:python depends on org@
+p1 << r1.p1;
+p2 << r1.p2;
+C << r1.C;
+ret << r1.ret;
+@@
+cocci.print_main("unneeded \"" + ret + "\" variable", p1)
+cocci.print_sec("return " + C + " here", p2)
--
1.8.3.1

2014-06-01 17:52:29

by Julia Lawall

Subject: Re: [PATCH] coccicheck: Add unneeded return variable test

On Sun, 1 Jun 2014, Peter Senna Tschudin wrote:

> This semantic patch looks for variables that are initialized with a
> constant, are never updated, and are only used as parameter of return.
> Return the constant instead of using a variable.
>
> There are 8 patches accepted reported by this semantic patch and more
> than 300 fixes to be applied.

I think that this comment should go below the ---. Five years from now,
it will not be meaningful.

julia


> Signed-off-by: Peter Senna Tschudin <[email protected]>
> ---
> scripts/coccinelle/misc/returnvar.cocci | 66 +++++++++++++++++++++++++++++++++
> 1 file changed, 66 insertions(+)
> create mode 100644 scripts/coccinelle/misc/returnvar.cocci
>
> diff --git a/scripts/coccinelle/misc/returnvar.cocci b/scripts/coccinelle/misc/returnvar.cocci
> new file mode 100644
> index 0000000..605955a
> --- /dev/null
> +++ b/scripts/coccinelle/misc/returnvar.cocci
> @@ -0,0 +1,66 @@
> +///
> +/// Removes unneeded variable used to store return value.
> +///
> +// Confidence: Moderate
> +// Copyright: (C) 2012 Peter Senna Tschudin, INRIA/LIP6. GPLv2.
> +// URL: http://coccinelle.lip6.fr/
> +// Comments: Comments on code can be deleted if near code that is removed.
> +// "when strict" can be removed to get more hits, but adds false
> +// positives
> +// Options: --no-includes --include-headers
> +
> +virtual patch
> +virtual report
> +virtual context
> +virtual org
> +
> +@depends on patch@
> +type T;
> +constant C;
> +identifier ret;
> +@@
> +- T ret = C;
> +... when != ret
> + when strict
> +return
> +- ret
> ++ C
> +;
> +
> +@depends on context@
> +type T;
> +constant C;
> +identifier ret;
> +@@
> +* T ret = C;
> +... when != ret
> + when strict
> +* return ret;
> +
> +@r1 depends on report || org@
> +type T;
> +constant C;
> +identifier ret;
> +position p1, p2;
> +@@
> +T ret@p1 = C;
> +... when != ret
> + when strict
> +return ret@p2;
> +
> +@script:python depends on report@
> +p1 << r1.p1;
> +p2 << r1.p2;
> +C << r1.C;
> +ret << r1.ret;
> +@@
> +coccilib.report.print_report(p1[0], "Unneeded variable: \"" + ret + "\". Return \"" + C + "\" on line " + p2[0].line)
> +
> +@script:python depends on org@
> +p1 << r1.p1;
> +p2 << r1.p2;
> +C << r1.C;
> +ret << r1.ret;
> +@@
> +cocci.print_main("unneeded \"" + ret + "\" variable", p1)
> +cocci.print_sec("return " + C + " here", p2)
> --
> 1.8.3.1
>
>