`0i32 != 0` vs `false`

[samuela]

I'm looking through the c2rust translation of a bit of C code and I'm seeing statements like

bool nonempty = false;

translated into

let mut nonempty: bool = 0i32 != 0;

which seems like a pretty roundabout way to simply say false.

[rinon]

The transpiler does not currently look at the integer value it needs to convert to a boolean (which in this case is 0), it just compares the value with 0 to convert it to a boolean. This could be fixed by a simple constant folding pass during refactoring, or we can special case it in the transpiler.

[ahomescu]

In this particular case, running the rewrite_expr '0i32 != 0' 'false' refactoring command should fix all instances.

[robinmoussu]

@ahomescu Is there an easy way to run all common refactoring pass easily? Something like

c2rust transpile compile_commands.json
c2rust refactor --default
cargo fmt **/*.rs

Or even better

c2rust transpile compile_command.json --refactor=default

If yes, then this re-write could be added to the list of refactoring pass that are run by default.

[ahomescu]

@robinmoussu Not currently, but it is on our TODO list.

What you can do right now is save all the commands you want to run to a file and pass it to c2rust-refactor using -f (the format of the file is roughly shell syntax, we parse it using shlex). It would look something like:

rewrite_expr 'a' 'b' ;
rewrite_expr 'b' 'c' ;
save_crate