On Fri, 27 Mar 2020, George McCollister wrote:
> Hello,
>
> I'm working with an old code base that makes excessive use of the
> following sort of construct:
>
> char display[128];
>
> ...
>
> snprintf(display, sizeof(display), "example log message %d", i);
> log_buffer(level, strlen(display)+1, display);
>
> I'd like to replace this mess with a single call to a function named
> log_formatted(). This involves moving the format string and arguments
> passed to snprintf into the log_formatted() call, removing snprintf
> call and (here's where it gets a bit tricky) remove the buffer if it
> isn't used for anything else.
>
> I have this all working with the following script with the caveat that
> running it on moderately complicated source files makes it never
> finish (after an hour or so the spatch process crashes with a stack
> overflow error).
> I've tried --no-loops which seem to speed things up but complicated
> source files still result in it never finishing.
>
> @r1@
> type T;
> identifier disp;
> expression level;
> expression list prnt;
> @@
>
> {
> ... when any
The above is not necessary. YOu don't have to start the match from a
block. You can just start it from the declaration.
On the other hand, the declaration may not be needed either. After your
metavariable type T, you can put
local idexpression T[] disp2;
Then the match should be:
snprintf(disp2@disp, sizeof(disp), prnt);
... when != disp
- log_buffer(level, strlen(disp)+1, disp);
+ log_formatted(level, prnt);
The notation disp2@disp will match both disp2 (idexpression of a
particular type) and disp (identifier) against the first argument of
snprintf. This is needed because 1) you want to give a type, which
requires and idexpression, and 2) in later rules you want to change a
variable declaration, which requires an identifier.
> (
> T disp[...];
> |
> T disp[...]="";
> )
> <+...
> snprintf(disp, sizeof(disp), prnt);
> ... when != disp
> - log_buffer(level, strlen(disp)+1, disp);
> + log_formatted(level, prnt);
> ...+>
> }
>
> // Only remove the display variable and snprintf if there are no
> // other references to the variable.
>
> @r2 depends on r1@
> type r1.T;
> identifier r1.disp;
> expression list r1.prnt;
> @@
>
> {
> ... when any
> (
> - T disp[...];
> |
> - T disp[...]="";
> )
> <+... when != disp
> - snprintf(disp, sizeof(disp), prnt);
> ...+>
> }
Here you could try considering the problem from the opposite point of
view.
@r2 exists@ // exists is what helps you drop the complexity, by needing to
type r1.T; // find only one matching path
identifier r1.disp;;
expression list r1.prnt;
position p;
@@
(
T@p disp[...];
|
T@p disp[...]="";
)
...
snprintf(disp, sizeof(disp), prnt);
@r3@
position p != r2.p;
type r1.T;
identifier r1.disp;;
@@
(
- T@p disp[...];
|
- T@p disp[...]="";
)
Does it matter that the initial value of disp is ""? In the proposed
first rule I have dropped that constraint.
julia
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