+sub compiler_predefined {
+ state %predefined;
+ my $default_compiler = shift;
+
+ return () if $^O eq 'VMS';
+
+ die 'compiler_predefines called without a default compiler'
+ unless $default_compiler;
+
+ if (! $predefined{$default_compiler}) {
+ my $cc = "$config{cross_compile_prefix}$default_compiler";
+
+ $predefined{$default_compiler} = {};
+
+ # collect compiler pre-defines from gcc or gcc-alike...
+ open(PIPE, "$cc -dM -E -x c /dev/null 2>&1 |");
+ while (my $l = <PIPE>) {
+ $l =~ m/^#define\s+(\w+(?:\(\w+\))?)(?:\s+(.+))?/ or last;
+ $predefined{$default_compiler}->{$1} = $2 // '';
+ }
+ close(PIPE);
+ }
+
+ return %{$predefined{$default_compiler}};
+}
+