ir,build: pragma support (#97)

Adds support for arbitrary compiler directives.

Fixes #15

printer/stubs.go

@@ -28,7 +28,18 @@ func (s *stubs) Print(f *ir.File) ([]byte, error) {
 	for _, fn := range f.Functions() {
 		s.NL()
 		s.Comment(fn.Doc...)
+		for _, pragma := range fn.Pragmas {
+			s.pragma(pragma)
+		}
 		s.Printf("%s\n", fn.Stub())
 	}
 	return s.Result()
 }
+
+func (s *stubs) pragma(p ir.Pragma) {
+	s.Printf("//go:%s", p.Directive)
+	for _, arg := range p.Arguments {
+		s.Printf(" %s", arg)
+	}
+	s.NL()
+}

printer/stubs_test.go

@@ -0,0 +1,28 @@
+package printer_test
+
+import (
+	"testing"
+
+	"github.com/mmcloughlin/avo/build"
+	"github.com/mmcloughlin/avo/printer"
+)
+
+func TestStubsPragmas(t *testing.T) {
+	ctx := build.NewContext()
+	ctx.Function("f")
+	ctx.Pragma("noescape")
+	ctx.Pragma("linkname f remote.f")
+	ctx.SignatureExpr("func(x *uint64)")
+	ctx.RET()
+
+	AssertPrintsLines(t, ctx, printer.NewStubs, []string{
+		"// Code generated by avo. DO NOT EDIT.",
+		"",
+		"package printer",
+		"",
+		"//go:noescape",
+		"//go:linkname f remote.f",
+		"func f(x *uint64)",
+		"",
+	})
+}

printer/util_test.go

@@ -15,6 +15,7 @@ func AssertPrintsLines(t *testing.T, ctx *build.Context, pb printer.Builder, exp
 	lines := strings.Split(output, "\n")
 
 	if len(expect) != len(lines) {
+		t.Logf("output:\n%s", output)
 		t.Fatalf("have %d lines of output; expected %d", len(lines), len(expect))
 	}