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# Clang IteratorChecker
> Note for developers:
> FlowSensitive is a fast evolving framework, and thus some breaking changes
> are regularly introduced. The current state of this plugin works against
> `llvmorg-18.0.0`.
This clang plugin aims at detecting iterator use-after-invalidation bugs using
the clang-tidy dataflow framework FlowSensitive.
For instance:
```cpp
for (auto* it = container->begin(); it != container->end();) {
if (it->block_end <= block_offset) {
// should be it = container->erase(it);
container->erase(it);
} else {
++it;
}
}
}
```
It is not valid using `++it` in the second branch of the loop after if
`container->erase(it)` was called on the first branch. See real code
[example](https://chromium-review.googlesource.com/c/chromium/src/+/4306699).
## Build
Clang is built using CMake. To run cmake, this script can be used:
```bash
./tools/clang/scripts/build.py \
--without-android \
--without-fuchsia \
--extra-tools iterator_checker
```
The build directory is created into: `third_party/llvm-build/Release+Asserts/`
and you can build it again using:
```bash
ninja -C third_party/llvm-build/Release+Asserts/
```
## Run the tests
```bash
./tools/clang/iterator_checker/tests/test.py \
$(pwd)/third_party/llvm-build/Release+Asserts/bin/clang
```
## Using the plugin
The procedure is mostly the same as for the other clang plugins in chrome. What
you need to do is to basically add the following [in a GN file](https://source.chromium.org/chromium/chromium/src/+/main:build/config/clang/BUILD.gn)
(depending what you want the plugin to be used for).
```bash
cflags += [
"-Xclang",
"-add-plugin",
"-Xclang",
"iterator-checker",
]
```
|
