AC_CHECK_LIB failures with AC_LANG(C++)

[Jani Välimaa]

Hello,

Looks like AC_CHECK_LIB(foo, main, [foo="yes"]) calls fails after
https://git.savannah.gnu.org/cgit/autoconf.git/commit/?id=326c9a547423d25c621bc5c0ef76edbf6eda8c92
if AC_LANG(C++) is also used.

Running configure fails to find libraries and config.log shows the
following.

conftest.cpp:38:14: error: '::main' must return 'int'
   38 |   extern "C" void main ();
      |              ^~~~       

Problem disappears if I revert the commit. gcc version is 10.2.0.

pgp8m4luCIJKi.pgp
Description: OpenPGP-allekirjoitus