compiler: accept cgo_import_dynamic directives only in column 1

The gc compiler rejects a directive that shares a line with code. It
accepts an indented directive on a line of its own. TinyGo uses a
simple column 1 check, which is more strict for indented directives.
Add tests for the trailing, function line, and indented cases.

Author: neomantra

compiler/compiler_test.go

@@ -402,6 +402,18 @@ func TestDarwinCgoImportDynamic(t *testing.T) {
 	if strings.Contains(ir, "@bad_remote") {
 		t.Error("a declaration was created for the remote symbol of a non-uintptr trampoline global")
 	}
+	if !strings.Contains(ir, "load i64, ptr @main.libc_misplaced_trampoline_addr") {
+		t.Error("a directive that shares a line with code was honored")
+	}
+	if strings.Contains(ir, "@misplaced_remote") {
+		t.Error("a declaration was created for the remote symbol of a misplaced directive")
+	}
+	if strings.Contains(ir, "@indented_remote") {
+		t.Error("an indented directive was honored")
+	}
+	if strings.Contains(ir, "@brace_remote") {
+		t.Error("a directive after code on a function line was honored")
+	}
 }
 
 // normalizeIR canonicalizes LLVM-version-specific IR spellings for comparison

compiler/symbol.go

@@ -779,13 +779,19 @@ func (c *compilerContext) loadASTComments(pkg *loader.Package) {
 		for _, group := range file.Comments {
 			for _, comment := range group.List {
 				parts := strings.Fields(comment.Text)
-				if len(parts) >= 2 && parts[0] == "//go:cgo_import_dynamic" {
-					local, remote := parts[1], parts[1]
-					if len(parts) >= 3 {
-						remote = parts[2]
-					}
-					c.cgoImportDynamic[local] = remote
+				if len(parts) < 2 || parts[0] != "//go:cgo_import_dynamic" {
+					continue
+				}
+				// Accept a directive only in column 1. The gc compiler also
+				// accepts an indented directive on a line of its own.
+				if c.program.Fset.Position(comment.Slash).Column != 1 {
+					continue
+				}
+				local, remote := parts[1], parts[1]
+				if len(parts) >= 3 {
+					remote = parts[2]
 				}
+				c.cgoImportDynamic[local] = remote
 			}
 		}
 

compiler/testdata/cgo-import-dynamic.go

@@ -8,6 +8,9 @@ var libc_fcntl_trampoline_addr uintptr
 var libc_nolib_trampoline_addr uintptr
 var libc_self_trampoline_addr uintptr
 var libc_badtype_trampoline_addr uint32
+var libc_misplaced_trampoline_addr uintptr //go:cgo_import_dynamic libc_misplaced misplaced_remote "/usr/lib/libSystem.B.dylib"
+var libc_indented_trampoline_addr uintptr
+var libc_brace_trampoline_addr uintptr
 
 //go:cgo_import_dynamic libc_test remote$INODE64 "/usr/lib/libSystem.B.dylib"
 //go:cgo_import_dynamic libc_ioctl ioctl "/usr/lib/libSystem.B.dylib"
@@ -49,3 +52,16 @@ func loadImportedSelfAddress() uintptr {
 func loadImportedBadTypeAddress() uint32 {
 	return libc_badtype_trampoline_addr
 }
+
+func loadMisplacedAddress() uintptr {
+	return libc_misplaced_trampoline_addr
+}
+
+func loadIndentedAddress() uintptr {
+	//go:cgo_import_dynamic libc_indented indented_remote "/usr/lib/libSystem.B.dylib"
+	return libc_indented_trampoline_addr
+}
+
+func loadBraceAddress() uintptr { //go:cgo_import_dynamic libc_brace brace_remote "/usr/lib/libSystem.B.dylib"
+	return libc_brace_trampoline_addr
+}