Make the don't-use-nm symbol table probes work under C++.

p4raw-id: //depot/perl@30897

diff --git a/Configure b/Configure
index dd3cd92..b317e44 100755 (executable)
--- a/Configure
+++ b/Configure
@@ -7582,18 +7582,21 @@ true-*) tx=no; eval "tval=\$$4"; case "$tval" in "") tx=yes;; esac;;
 esac;
 case "$tx" in
 yes)
+       case "$d_cplusplus" in
+               $define) extern_C=\"C\";;
+       esac;
        tval=false;
        if $test "$runnm" = true; then
                if $contains $tlook $tf >/dev/null 2>&1; then
                        tval=true;
                elif $test "$mistrustnm" = compile -o "$mistrustnm" = run; then
-                       echo "void *(*(p()))$tdc { extern void *$1$tdc; return &$1; } int main() { if(p()) return(0); else return(1); }"> try.c;
+                       echo "extern $extern_C void *$1$tdc; void *(*(p()))$tdc { return &$1; } int main() { if(p()) return(0); else return(1); }"> try.c;
                        $cc -o try $optimize $ccflags $ldflags try.c >/dev/null 2>&1 $libs && tval=true;
                        $test "$mistrustnm" = run -a -x try && { $run ./try$_exe >/dev/null 2>&1 || tval=false; };
                        $rm -f try$_exe try.c core core.* try.core;
                fi;
        else
-               echo "void *(*(p()))$tdc { extern void *$1$tdc; return &$1; } int main() { if(p()) return(0); else return(1); }"> try.c;
+               echo "extern $extern_C void *$1$tdc; void *(*(p()))$tdc { return &$1; } int main() { if(p()) return(0); else return(1); }"> try.c;
                $cc -o try $optimize $ccflags $ldflags try.c $libs >/dev/null 2>&1 && tval=true;
                $rm -f try$_exe try.c;
        fi;