aaron.ballman added inline comments.
================
Comment at:
clang-tools-extra/test/clang-tidy/checkers/modernize-use-using.cpp:305
};
+
+extern "C" {
----------------
steveire wrote:
> njames93 wrote:
> > steveire wrote:
> > > Can you add tests for typedefs in other scopes like
> > >
> > > ```
> > >
> > > extern "C" {
> > > typedef int CType;
> > >
> > > struct CAnother {
> > > };
> > >
> > > typedef struct {
> > > int b;
> > > typedef struct CAnother AStruct;
> > > } CStruct;
> > >
> > > void foo()
> > > {
> > > typedef struct CAnother AStruct;
> > > }
> > > }
> > >
> > > ```
> > I'm not sure those tests add any value. For the struct, you can't have a
> > typedef in a struct in c. The function typedef is valid in c, but I still
> > can't see a reason to use extern C when defining a function in c++
> Fair enough - Clang accepts the typedef in the struct with a warning, but it
> doesn't get transformed by the check anyway. The one in the function doesn't
> get transformed either, and if functions are so unlikely to appear in extern
> C, that it doesn't need to be covered, that's fine with me.
> I still can't see a reason to use extern C when defining a function in c++
There are a few reasons.
1) You're defining an extern linkage function with C language linkage and not
providing the declaration or you're being consistent between the declaration
and the definition.
2) You have an `extern "C"` block that contains function definitions.
3) Pedantically, if the function declaration is `extern "C"`, the function
definition must be as well (http://eel.is/c++draft/dcl.link#1.sentence-5,
http://eel.is/c++draft/dcl.link#6), however, many compilers ignore these
requirements because otherwise the STL has issues.
So it definitely does happen in the wild. As some examples:
https://codesearch.isocpp.org/actcd19/main/b/bali-phy/bali-phy_3.4+dfsg-1/src/builtins/SModel.cc
https://codesearch.isocpp.org/actcd19/main/o/openjdk-11/openjdk-11_11.0.3+1-1/test/hotspot/jtreg/vmTestbase/nsk/jvmti/AttachOnDemand/attach015/attach015Agent00.c
https://codesearch.isocpp.org/actcd19/main/m/mp3fs/mp3fs_0.91-1/src/transcode.cc
https://codesearch.isocpp.org/actcd19/main/t/theano/theano_0.8.2-6/theano/sandbox/cuda/cnmem.cpp
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D96725/new/
https://reviews.llvm.org/D96725
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