Fix compilation errors in a testdir created with --with-c++-tests

[Bruno Haible]

In a testdir created through
  ./gnulib-tool --create-testdir --dir=... --single-configure --with-c++-tests 
lchmod fchmodat
I'm getting compilation errors, such as:

In file included from test-string-c++.cc:22:
../gllib/string.h:707: error: type of 'memrchr' is unknown
../gllib/string.h:707: error: invalid type in declaration before ';' token
../gllib/string.h:707: error: 'int memrchr' redeclared as different kind of 
symbol
/usr/include/string.h:114: error: previous declaration of 'const void* 
memrchr(const void*, int, size_t)'

This patch fixes it, unfortunately at the cost of disabling useful warnings.


2020-02-08  Bruno Haible  <br...@clisp.org>

        Fix compilation errors in a testdir created with --with-c++-tests.
        * lib/c++defs.h (_GL_CXXALIASWARN1_2): Do not use __typeof__ (func),
        since it does not work any more with g++ >= 4.4.

diff --git a/lib/c++defs.h b/lib/c++defs.h
index 5d5da71..402cae4 100644
--- a/lib/c++defs.h
+++ b/lib/c++defs.h
@@ -301,9 +301,6 @@
     _GL_WARN_ON_USE_CXX (func, rettype, parameters_and_attributes, \
                          "The symbol ::" #func " refers to the system 
function. " \
                          "Use " #namespace "::" #func " instead.")
-# elif __GNUC__ >= 3 && GNULIB_STRICT_CHECKING
-#  define 
_GL_CXXALIASWARN1_2(func,rettype,parameters_and_attributes,namespace) \
-     extern __typeof__ (func) func
 # else
 #  define 
_GL_CXXALIASWARN1_2(func,rettype,parameters_and_attributes,namespace) \
      _GL_EXTERN_C int _gl_cxxalias_dummy