sys/fuchsia: prune unused structs in syscall description generated by fidlgen

After generating syscall description for fidl files using fidlgen, prune
all unused structs using the exact same mechanism used by the compiler's
check for unused structs. This allows the FIDL compiler to support
modular compilation; it does not need to have global knowledge of
whether each struct is used or not.

1 files changed, 46 insertions, 29 deletions

diff --git a/pkg/compiler/check.go b/pkg/compiler/check.go
index 7b4b63fa8..087075a12 100644
--- a/pkg/compiler/check.go
+++ b/pkg/compiler/check.go
@@ -11,6 +11,7 @@ import (
 
 	"github.com/google/syzkaller/pkg/ast"
 	"github.com/google/syzkaller/prog"
+	"github.com/google/syzkaller/sys/targets"
 )
 
 func (comp *compiler) typecheck() {
@@ -371,6 +372,48 @@ func (comp *compiler) checkLenTarget(t *ast.Type, name, target string, fields []
 	comp.error(t.Pos, "%v target %v does not exist", t.Ident, target)
 }
 
+func CollectUnused(desc *ast.Description, target *targets.Target) []ast.Node {
+	comp := createCompiler(desc, target, nil)
+	comp.typecheck()
+	return comp.collectUnused()
+}
+
+func (comp *compiler) collectUnused() []ast.Node {
+	var unused []ast.Node
+
+	comp.used, _, _ = comp.collectUsed(false)
+	structs, flags, strflags := comp.collectUsed(true)
+	_, _, _ = structs, flags, strflags
+
+	for name, n := range comp.intFlags {
+		if !flags[name] {
+			unused = append(unused, n)
+		}
+	}
+	for name, n := range comp.strFlags {
+		if !strflags[name] && builtinStrFlags[name] == nil {
+			unused = append(unused, n)
+		}
+	}
+	for name, n := range comp.resources {
+		if !structs[name] {
+			unused = append(unused, n)
+		}
+	}
+	for name, n := range comp.structs {
+		if !structs[name] {
+			unused = append(unused, n)
+		}
+	}
+	for name, n := range comp.typedefs {
+		if !comp.usedTypedefs[name] {
+			unused = append(unused, n)
+		}
+	}
+
+	return unused
+}
+
 func (comp *compiler) collectUsed(all bool) (structs, flags, strflags map[string]bool) {
 	structs = make(map[string]bool)
 	flags = make(map[string]bool)
@@ -432,35 +475,9 @@ func (comp *compiler) collectUsedType(structs, flags, strflags map[string]bool,
 }
 
 func (comp *compiler) checkUnused() {
-	comp.used, _, _ = comp.collectUsed(false)
-	structs, flags, strflags := comp.collectUsed(true)
-	_, _, _ = structs, flags, strflags
-
-	for name, n := range comp.intFlags {
-		if !flags[name] {
-			comp.error(n.Pos, "unused flags %v", name)
-		}
-	}
-	for name, n := range comp.strFlags {
-		if !strflags[name] && builtinStrFlags[name] == nil {
-			comp.error(n.Pos, "unused string flags %v", name)
-		}
-	}
-	for name, n := range comp.resources {
-		if !structs[name] {
-			comp.error(n.Pos, "unused resource %v", name)
-		}
-	}
-	for name, n := range comp.structs {
-		if !structs[name] {
-			_, typ, _ := n.Info()
-			comp.error(n.Pos, "unused %v %v", typ, name)
-		}
-	}
-	for name, n := range comp.typedefs {
-		if !comp.usedTypedefs[name] {
-			comp.error(n.Pos, "unused type %v", name)
-		}
+	for _, n := range comp.collectUnused() {
+		pos, typ, name := n.Info()
+		comp.error(pos, fmt.Sprintf("unused %v %v", typ, name))
 	}
 }