[clang] [clang-tools-extra] [clang-tidy] Add new check `modernize-use-designated-initializers` (PR #80541)

[Piotr Zegar via cfe-commits]

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In-Reply-To: <llvm.org/llvm/llvm-project/pull/80541 at github.com>


PiotrZSL wrote:

@SimplyDanny 

There is a bug, when run (locally) with:
`../.build-llvm-project/bin/clang-tidy --checks="-*,modernize-use-designated-initializers" clang/lib/Basic/Module.cpp --header-filter=".*" --fix`

It inserts some random characters into Module.h:

```
-      return Header{UmbrellaAsWritten, UmbrellaRelativeToRootModuleDirectory,
-                    *Hdr};
+      return Header{.NameAsWritten=UmbrellaAsWritten, .<E1><E2>[<EA>U^@^@<B2>GI<AD><89>}<95><DA>ootModuleDirectory=UmbrellaRelativeToRootModuleDirectory,
+                    .Entry=*Hdr};
```

Looks like "use after free" error.
Probably that was a reason why tests were toggling.

Valgrind detect this as:
```
==41359== Invalid read of size 1
==41359==    at 0x6A03309: memmove (vg_replace_strmem.c:1398)
==41359==    by 0x2E039EB: llvm::raw_svector_ostream::write_impl(char const*, unsigned long) (in /fpwork/.build-llvm-project/bin/clang-tidy)
==41359==    by 0x2E01C2F: llvm::raw_ostream::write(char const*, unsigned long) (in /fpwork/.build-llvm-project/bin/clang-tidy)
==41359==    by 0x2E122C1: llvm::Twine::toStringRef(llvm::SmallVectorImpl<char>&) const (in /fpwork/.build-llvm-project/bin/clang-tidy)
==41359==    by 0x2E1214E: llvm::Twine::str[abi:cxx11]() const (in /fpwork/.build-llvm-project/bin/clang-tidy)
==41359==    by 0x3C8B2B7: clang::tidy::modernize::UseDesignatedInitializersCheck::check(clang::ast_matchers::MatchFinder::MatchResult const&) 
```



https://github.com/llvm/llvm-project/pull/80541