first-commit

modules/log/stack.go

@@ -0,0 +1,80 @@
+// Copyright 2019 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package log
+
+import (
+	"bytes"
+	"fmt"
+	"os"
+	"runtime"
+)
+
+var unknown = []byte("???")
+
+// Stack will skip back the provided number of frames and return a stack trace with source code.
+// Although we could just use debug.Stack(), this routine will return the source code and
+// skip back the provided number of frames - i.e. allowing us to ignore preceding function calls.
+// A skip of 0 returns the stack trace for the calling function, not including this call.
+// If the problem is a lack of memory of course all this is not going to work...
+func Stack(skip int) string {
+	buf := new(bytes.Buffer)
+
+	// Store the last file we opened as its probable that the preceding stack frame
+	// will be in the same file
+	var lines [][]byte
+	var lastFilename string
+	for i := skip + 1; ; i++ { // Skip over frames
+		programCounter, filename, lineNumber, ok := runtime.Caller(i)
+		// If we can't retrieve the information break - basically we're into go internals at this point.
+		if !ok {
+			break
+		}
+
+		// Print equivalent of debug.Stack()
+		_, _ = fmt.Fprintf(buf, "%s:%d (0x%x)\n", filename, lineNumber, programCounter)
+		// Now try to print the offending line
+		if filename != lastFilename {
+			data, err := os.ReadFile(filename)
+			if err != nil {
+				// can't read this source file
+				// likely we don't have the sourcecode available
+				continue
+			}
+			lines = bytes.Split(data, []byte{'\n'})
+			lastFilename = filename
+		}
+		_, _ = fmt.Fprintf(buf, "\t%s: %s\n", functionName(programCounter), source(lines, lineNumber))
+	}
+	return buf.String()
+}
+
+// functionName converts the provided programCounter into a function name
+func functionName(programCounter uintptr) []byte {
+	function := runtime.FuncForPC(programCounter)
+	if function == nil {
+		return unknown
+	}
+	name := []byte(function.Name())
+
+	// Because we provide the filename we can drop the preceding package name.
+	if lastslash := bytes.LastIndex(name, []byte("/")); lastslash >= 0 {
+		name = name[lastslash+1:]
+	}
+	// And the current package name.
+	if period := bytes.Index(name, []byte(".")); period >= 0 {
+		name = name[period+1:]
+	}
+	// And we should just replace the interpunct with a dot
+	name = bytes.ReplaceAll(name, []byte("·"), []byte("."))
+	return name
+}
+
+// source returns a space-trimmed slice of the n'th line.
+func source(lines [][]byte, n int) []byte {
+	n-- // in stack trace, lines are 1-indexed but our array is 0-indexed
+	if n < 0 || n >= len(lines) {
+		return unknown
+	}
+	return bytes.TrimSpace(lines[n])
+}