Bug 260955 - add an #includesubst instruction r=Hixie

config/preprocessor.pl

@@ -427,6 +427,19 @@ sub include {
     }
 }
 
+sub includesubst {
+    my ($stack, $filename) = @_;
+    return if $stack->disabled;
+    die "argument expected\n" unless $filename;
+    $filename =~ s/@(\w+)@/$stack->get($1, 1)/gose;
+    $filename = File::Spec::_0_8::catpath(File::Spec::_0_8::splitpath($filename));
+    if ($stack->{'dependencies'}) {
+        $stack->visit($filename);
+    } else {
+        main::include($stack, $filename);
+    }
+}
+
 sub filter {
     my $stack = shift;
     return if $stack->disabled;

config/preprocessor.txt

@@ -33,6 +33,7 @@ The following preprocessor instructions are recognised.
    #endif
    #error STRING
    #include FILENAME
+   #includesubst @VAR@FILENAME
    #expand STRING
    #literal STRING
    #filter FILTER1 FILTER2 ... FILTERn
@@ -115,6 +116,9 @@ There is no predefined limit to the depth of #includes, and there is
 no restriction on self-inclusion, so care should be taken to avoid
 infinite loops.
 
+The #includesubst instruction behaves like #include, except that any
+variables in @ATSIGNS@ are expanded, like the substitution filter.
+
 The #expand instruction will print the given STRING with variable
 substitutions. See the substitution section below.