Adds a flag to `ClangTidyContext` that is used to indicate to checks that fixes will only be applied one at a time.
This is to indicate to checks that each fix emitted should not depend on any other fixes emitted across the translation unit.
I've currently implemented the `IncludeInserter`, `LoopConvertCheck` and `PreferMemberInitializerCheck` to use these support these modes.
Reasoning behind this is in use cases like `clangd` it's only possible to apply one fix at a time.
For include inserter checks, the include is only added once for the first diagnostic that requires it, this will result in subsequent fixes not having the included needed.
A similar issue is seen in the `PreferMemberInitializerCheck` where the `:` will only be added for the first member that needs fixing.
Fixes emitted in `StandaloneDiagsMode` will likely result in malformed code if they are applied all together, conversely fixes currently emitted may result in malformed code if they are applied one at a time.
For this reason invoking `clang-tidy` from the binary will always with `StandaloneDiagsMode` disabled, However using it as a library its possible to select the mode you wish to use, `clangd` always selects `StandaloneDiagsMode`.
This is an example of the current behaviour failing
```lang=c++
struct Foo {
int A, B;
Foo(int D, int E) {
A = D;
B = E; // Fix Here
}
};
```
Incorrectly transformed to:
```lang=c++
struct Foo {
int A, B;
Foo(int D, int E), B(E) {
A = D;
// Fix Here
}
};
```
In `StandaloneDiagsMode`, it gets transformed to:
```lang=c++
struct Foo {
int A, B;
Foo(int D, int E) : B(E) {
A = D;
// Fix Here
}
};
```
Reviewed By: sammccall
Differential Revision: https://reviews.llvm.org/D97121
Overflows are never fun.
In most cases (in most of the code), they are rare,
because usually you e.g. don't have as many elements.
However, it's exceptionally easy to fall into this pitfail
in code that deals with images, because, assuming 4-channel 32-bit FP data,
you need *just* ~269 megapixel image to case an overflow
when computing at least the total byte count.
In [[ https://github.com/darktable-org/darktable | darktable ]], there is a *long*, painful history of dealing with such bugs:
* https://github.com/darktable-org/darktable/pull/7740
* https://github.com/darktable-org/darktable/pull/7419
* eea1989f2c
* 70626dd95b
* https://github.com/darktable-org/darktable/pull/670
* 38c69fb1b2
and yet they clearly keep resurfacing still.
It would be immensely helpful to have a diagnostic for those patterns,
which is what this change proposes.
Currently, i only diagnose the most obvious case, where multiplication
is directly widened with no other expressions inbetween,
(i.e. `long r = (int)a * (int)b` but not even e.g. `long r = ((int)a * (int)b)`)
however that might be worth relaxing later.
Reviewed By: aaron.ballman
Differential Revision: https://reviews.llvm.org/D93822
Nathan James