[clang-tidy] misc-confusable-identifiers ignores -header-filter option

[ottml]

When using the clang tidy check misc-confusable-identifiers the option -header-filter is ignored. The warnings from the files not matching the header-filter are always displayed and not suppressed. This works perfectly for the check google-explicit-constructor shown by the example below.

Ubuntu LLVM version 18.1.3

The problem can be reproduced by the following example:

main.cpp:

#include "header1.h"

namespace AI{
  const int val = 10;
}

int main(int c, char** v)
{
    return 0;
}

header1.h:

class A { A(int); };

namespace A1
{
void printi();
}

Output from clang-tidy with misc-confusable-identifiers:

clang-tidy-18 -checks='-*,misc-confusable-identifiers' -header-filter='ignore_all' main.cpp -p=../build/

1 warning generated.
/home/...../example/main/main.cpp:3:11: warning: 'AI' is confusable with 'A1' [misc-confusable-identifiers]
    3 | namespace AI{
      |           ^
/home/...../example/main/header1.h:3:11: note: other declaration found here
    3 | namespace A1
      |           ^

Output from clang-tidy with google-explicit-constructor:

clang-tidy-18 -checks='-*,google-explicit-constructor' -header-filter='ignore_all' m
ain.cpp -p=../build/

1 warning generated.
Suppressed 1 warnings (1 in non-user code).
Use -header-filter=.* to display errors from all non-system headers. Use -system-headers to display errors from system headers as well.

[llvmbot]

@llvm/issue-subscribers-clang-tidy

Author: Sunrise (ottml)

When using the clang tidy check **misc-confusable-identifiers** the option -header-filter is ignored. The warnings from the files not matching the header-filter are always displayed and not suppressed. This works perfectly for the check **google-explicit-constructor** shown by the example below.

Ubuntu LLVM version 18.1.3

The problem can be reproduced by the following example:

main.cpp:

#include "header1.h"

namespace AI{
  const int val = 10;
}

int main(int c, char** v)
{
    return 0;
}

header1.h:

class A { A(int); };

namespace A1
{
void printi();
}

Output from clang-tidy with misc-confusable-identifiers:

clang-tidy-18 -checks='-*,misc-confusable-identifiers' -header-filter='ignore_all' main.cpp -p=../build/

1 warning generated.
/home/...../example/main/main.cpp:3:11: warning: 'AI' is confusable with 'A1' [misc-confusable-identifiers]
    3 | namespace AI{
      |           ^
/home/...../example/main/header1.h:3:11: note: other declaration found here
    3 | namespace A1
      |           ^

Output from clang-tidy with google-explicit-constructor:

clang-tidy-18 -checks='-*,google-explicit-constructor' -header-filter='ignore_all' m
ain.cpp -p=../build/

1 warning generated.
Suppressed 1 warnings (1 in non-user code).
Use -header-filter=.* to display errors from all non-system headers. Use -system-headers to display errors from system headers as well.

[vbvictor]

With misc-confusable-identifiers the main diagnostics is emitted in main.cpp, which is not excluded by header filter.
main.cpp:3:11: warning: 'AI' is confusable with 'A1' [misc-confusable-identifiers] - this warning is the main one.

If you would put both confusable namespaces in header like this:

class A { A(int); };

namespace AI
{
void printi();
}

namespace A1 {
  const int val = 10;
}

You would not get any diagnostics because both identifiers are in ignored header

[ottml]

Thanks for the fast response. This explains the different output. So everything works as expected.

But what is the preferred way when i am including headers from system libraries like boost. And i get a warning about misc-confusable-identifiers in the system libray headers of boost. In general i do not want to see this warnings because i can not change this headers. Is thera a possibilty to suppress this warnings without rewritting our code? Because we have exactly this problem with boost in our codebase. The -header-filter option will as you explained above not work to solve this problem

See the following example:

main.cpp

#include <boost/bind/bind.hpp>

namespace AI
{
int f(int const)
{
    return 0;
};
}

int main(int c, char** v)
{
    boost::bind(AI::f, 1);
    return 0;
}

Output:

clang-tidy-20 -checks='-*,misc-confusable-identifiers' -header-filter='ignore_all' main.cpp -p=../build/
387 warnings generated.
/home/........../example/main/main.cpp:3:11: warning: 'AI' is confusable with 'A1' [misc-confusable-identifiers]
    3 | namespace AI
      |           ^
/usr/include/boost/bind/mem_fn_template.hpp:136:34: note: other declaration found here
  136 | template<class R, class T, class A1 BOOST_MEM_FN_CLASS_F> class BOOST_MEM_FN_NAME(mf1)
      |                                  ^
Suppressed 114 warnings (114 in non-user code).
Use -header-filter=.* to display errors from all non-system headers. Use -system-headers to display errors from system headers as well.

[vbvictor]

As for now, you can suppress this with a // NOLINT(misc-confusable-identifiers) or // NOLINTNEXTLINE(misc-confusable-identifiers).
I suppose this check need an option called IgnoreSystemIdentifiers if you want only to check confusions among your code.