Am 30.01.2017 um 17:16 schrieb Johannes Schindelin:
Hi René,
On Sat, 28 Jan 2017, René Scharfe wrote:
Exchange the values of graph->columns and graph->new_columns using the
macro SWAP instead of hand-rolled code. The result is shorter and
easier to read.
This transformation was not done by the semantic patch swap.cocci
because there's an unrelated statement between the second and the last
step of the exchange, so it didn't match the expected pattern.
Is it really true that Coccinelle cannot be told to look for a code block
that declares a variable that is then used *only* in the lines we want to
match and replace?
Hope I parsed your question correctly; my answer would be that it can't
be true because that's basically what the proposed semantic patch does:
@ swap @
type T;
T tmp, a, b;
@@
- tmp = a;
- a = b;
- b = tmp;
+ SWAP(a, b);
@ extends swap @
identifier unused;
@@
{
...
- T unused;
... when != unused
}
The first part (up to the "+") looks for a opportunities to use SWAP,
and the second part looks for blocks where that transformation was done
and we declare identifiers that are/became unused.
It did not match the code in graph.c because the pattern was basically:
tmp = a;
a = b;
something = totally_different;
b = tmp;
Coccinelle can be told to ignore such unrelated code by adding "... when
!= tmp" etc. (which matches context lines that don't reference tmp), but
that's slooow. (Perhaps I just did it wrong, though.)
René
