Как объяснить AC_CHECK_LIB что библиотека экспортирует C++-символы?

info automake:

- Macro: AC_CHECK_LIB (LIBRARY, FUNCTION, [ACTION-IF-FOUND], [ACTION-IF-NOT-FOUND], [OTHER-LIBRARIES]) Depending on the current language(*note Language Choice::), try to ensure that the C, C++, or Fortran function FUNCTION is available by checking whether a test program can be linked with the library LIBRARY to get the function. LIBRARY is the base name of the library; e.g., to check for `-lmp', use `mp' as the LIBRARY argument

- Macro: AC_LANG (LANGUAGE) Do compilation tests using the compiler, preprocessor, and file extensions for the specified LANGUAGE.

Supported languages are:

`C' Do compilation tests using `CC' and `CPP' and use extension `.c' for test programs. Use compilation flags: `CPPFLAGS' with `CPP', and both `CPPFLAGS' and `CFLAGS' with `CC'.

`C++' Do compilation tests using `CXX' and `CXXCPP' and use extension `.C' for test programs. Use compilation flags: `CPPFLAGS' with `CXXPP', and both `CPPFLAGS' and `CXXFLAGS' with `CXX'.