From 482c5633dd34af850d384a74559ed9d977417c7c Mon Sep 17 00:00:00 2001
From: Ayke van Laethem <aykevanlaethem@gmail.com>
Date: Sat, 6 Oct 2018 23:50:35 +0200
Subject: [PATCH] compiler: put debug information on package initializer
 functions

Make sure package initializers show up in backtraces, as they should. In
practice, it doesn't actually break backtraces as these functions are
usually inlined anyway, but it may help to debug an error in
initialization code.
---
 compiler/compiler.go | 29 +++++++++++++++++++++--------
 1 file changed, 21 insertions(+), 8 deletions(-)

diff --git a/compiler/compiler.go b/compiler/compiler.go
index 6794511a..4cac848a 100644
--- a/compiler/compiler.go
+++ b/compiler/compiler.go
@@ -815,7 +815,13 @@ func (c *Compiler) parseFuncDecl(f *ir.Function) (*Frame, error) {
 		frame.fn.LLVMFn = llvm.AddFunction(c.mod, name, fnType)
 	}
 
-	if c.Debug && f.Syntax() != nil && len(f.Blocks) != 0 {
+	if c.Debug && f.Synthetic == "package initializer" {
+		difunc, err := c.attachDebugInfoRaw(f, "", 0)
+		if err != nil {
+			return nil, err
+		}
+		frame.difunc = difunc
+	} else if c.Debug && f.Syntax() != nil && len(f.Blocks) != 0 {
 		// Create debug info file if needed.
 		difunc, err := c.attachDebugInfo(f)
 		if err != nil {
@@ -829,9 +835,16 @@ func (c *Compiler) parseFuncDecl(f *ir.Function) (*Frame, error) {
 
 func (c *Compiler) attachDebugInfo(f *ir.Function) (llvm.Metadata, error) {
 	pos := c.ir.Program.Fset.Position(f.Syntax().Pos())
-	if _, ok := c.difiles[pos.Filename]; !ok {
-		dir, file := filepath.Split(pos.Filename)
-		c.difiles[pos.Filename] = c.dibuilder.CreateFile(file, dir[:len(dir)-1])
+	return c.attachDebugInfoRaw(f, pos.Filename, pos.Line)
+}
+
+func (c *Compiler) attachDebugInfoRaw(f *ir.Function, filename string, line int) (llvm.Metadata, error) {
+	if _, ok := c.difiles[filename]; !ok {
+		dir, file := filepath.Split(filename)
+		if dir != "" {
+			dir = dir[:len(dir)-1]
+		}
+		c.difiles[filename] = c.dibuilder.CreateFile(file, dir)
 	}
 
 	// Debug info for this function.
@@ -844,15 +857,15 @@ func (c *Compiler) attachDebugInfo(f *ir.Function) (llvm.Metadata, error) {
 		diparams = append(diparams, ditype)
 	}
 	diFuncType := c.dibuilder.CreateSubroutineType(llvm.DISubroutineType{
-		File:       c.difiles[pos.Filename],
+		File:       c.difiles[filename],
 		Parameters: diparams,
 		Flags:      0, // ?
 	})
-	difunc := c.dibuilder.CreateFunction(c.difiles[pos.Filename], llvm.DIFunction{
+	difunc := c.dibuilder.CreateFunction(c.difiles[filename], llvm.DIFunction{
 		Name:         f.RelString(nil),
 		LinkageName:  f.LinkName(),
-		File:         c.difiles[pos.Filename],
-		Line:         pos.Line,
+		File:         c.difiles[filename],
+		Line:         line,
 		Type:         diFuncType,
 		LocalToUnit:  true,
 		IsDefinition: true,