backtraces: add source line numbers too on linux

* Add source line numbers to backtraces on linux.

* Fix -g (broken after token caching).

* reset the #line directives after all the v code is compiled

* cleanup p.cgen.line setting inside p.next() .

* Support windows filepaths like "C:\Users\travis\build\vlang\v\v.exe.tmp.c" inside generated #line directives.

* Try to diagnose better windows-gcc failing.

* Revert "Try to diagnose better windows-gcc failing."

* implement and use cescaped_path/1 .

* Use cescaped_path/1 consistently throughout compiler/ .

compiler/cgen.v

@@ -63,8 +63,10 @@ fn (g mut CGen) genln(s string) {
 	g.cur_line = '$g.cur_line $s'
 	if g.cur_line != '' {
 		if g.line_directives && g.cur_line.trim_space() != '' {
+			if g.file.len > 0 && g.line > 0 {
 				g.lines << '\n#line $g.line "$g.file"'
 			}
+		}
 		g.lines << g.cur_line
 		g.prev_line = g.cur_line
 		g.cur_line = ''

compiler/fn.v

@@ -809,7 +809,7 @@ fn (p mut Parser) fn_call_args(f mut Fn) &Fn {
 	if p.v.pref.is_debug && f.name == 'panic' && !p.is_js {
 		mod_name := p.mod.replace('_dot_', '.')
 		fn_name := p.cur_fn.name.replace('${p.mod}__', '')
-		file_path := p.file_path.replace('\\', '\\\\') // escape \
+		file_path := cescaped_path(p.file_path)
 		p.cgen.resetln(p.cgen.cur_line.replace(
 			'v_panic (',
 			'panic_debug ($p.scanner.line_nr, tos3("$file_path"), tos3("$mod_name"), tos2((byte *)"$fn_name"), '

compiler/live.v

@@ -73,8 +73,8 @@ fn (v &V) generate_hot_reload_code() {
 		mut vexe := os.args[0]
 		
 		if os.user_os() == 'windows' {
-			vexe = vexe.replace('\\', '\\\\')
+			vexe = cescaped_path(vexe)
-			file = file.replace('\\', '\\\\')
+			file = cescaped_path(file)
 		}
 		
 		mut msvc := ''

compiler/main.v

@@ -338,6 +338,7 @@ fn (v mut V) compile() {
 	if v.pref.build_mode == .build_module {
 		v.generate_vh()
 	}
+
 	// parse generated V code (str() methods etc)
 	mut vgen_parser := v.new_parser_from_string(v.vgen_buf.str(), 'vgen')
 	// free the string builder which held the generated methods
@@ -383,6 +384,15 @@ fn (v mut V) generate_main() {
 	mut cgen := v.cgen
 	$if js { return }
 
+	///// After this point, the v files are compiled.
+	///// The rest is auto generated code, which will not have
+	///// different .v source file/line numbers.
+	lines_so_far := cgen.lines.join('\n').count('\n') + 5
+	cgen.genln('')
+	cgen.genln('////////////////// Reset the file/line numbers //////////')
+	cgen.lines << '#line $lines_so_far "${cescaped_path(os.realpath(cgen.out_path))}"'
+	cgen.genln('')
+	
 	if v.pref.build_mode == .default_mode {
 		mut consts_init_body := cgen.consts_init.join_lines()
 		// vlib can't have `init_consts()`
@@ -1042,3 +1052,7 @@ fn vhash() string {
 	C.snprintf(*char(buf), 50, '%s', C.V_COMMIT_HASH )
 	return tos_clone(buf)
 }
+
+fn cescaped_path(s string) string {
+  return s.replace('\\','\\\\')
+}

compiler/parser.v

@@ -100,7 +100,14 @@ fn (v mut V) new_parser_from_string(text string, id string) Parser {
 	return p
 }
 
+fn (v mut V) reset_cgen_file_line_parameters(){
+	v.cgen.line = 0
+	v.cgen.file = ''
+	v.cgen.line_directives = v.pref.is_debuggable
+}
+
 fn (v mut V) new_parser_from_file(path string) Parser {
+	v.reset_cgen_file_line_parameters()
 	//println('new_parser("$path")')
 	mut path_pcguard := ''
 	mut path_platform := '.v'
@@ -124,7 +131,6 @@ fn (v mut V) new_parser_from_file(path string) Parser {
 	if p.pref.building_v {
 		p.scanner.should_print_relative_paths_on_error = true
 	}
-	v.cgen.file = path
 	p.scan_tokens()
 	//p.scanner.debug_tokens()
 	return p
@@ -133,6 +139,7 @@ fn (v mut V) new_parser_from_file(path string) Parser {
 // creates a new parser. most likely you will want to use
 // `new_parser_file` or `new_parser_string` instead.
 fn (v mut V) new_parser(scanner &Scanner, id string) Parser {
+	v.reset_cgen_file_line_parameters()
 	mut p := Parser {
 		id: id
 		scanner: scanner
@@ -155,8 +162,6 @@ fn (v mut V) new_parser(scanner &Scanner, id string) Parser {
 		p.scanner.should_print_errors_in_color = false
 		p.scanner.should_print_relative_paths_on_error = true
 	}
-	v.cgen.line_directives = v.pref.is_debuggable
-	// v.cgen.file = path
 	return p
 }
 
@@ -195,6 +200,7 @@ fn (p mut Parser) next() {
 	 p.tok = res.tok
 	 p.lit = res.lit
 	 p.scanner.line_nr = res.line_nr
+	 p.cgen.line = res.line_nr
 }
 
 fn (p & Parser) peek() TokenKind {
@@ -230,6 +236,9 @@ fn (p &Parser) log(s string) {
 }
 
 fn (p mut Parser) parse(pass Pass) {	
+	p.cgen.line = 0
+	p.cgen.file = cescaped_path(os.realpath(p.file_path))
+	/////////////////////////////////////
 	p.pass = pass
 	p.token_idx = 0
 	p.next()
@@ -2807,7 +2816,7 @@ fn (p mut Parser) string_expr() {
 	// No ${}, just return a simple string
 	if p.peek() != .dollar || is_raw {
 		p.fgen("'$str'")
-		f := if is_raw { str.replace('\\', '\\\\') } else { format_str(str) }
+		f := if is_raw { cescaped_path(str) } else { format_str(str) }
 		// `C.puts('hi')` => `puts("hi");`
 		/*
 		Calling a C function sometimes requires a call to a string method
@@ -3849,7 +3858,7 @@ fn (p mut Parser) assert_statement() {
 	p.gen('bool $tmp = ')
 	p.check_types(p.bool_expression(), 'bool')
 	// TODO print "expected:  got" for failed tests
-	filename := p.file_path.replace('\\', '\\\\')
+	filename := cescaped_path(p.file_path)
 	p.genln(';
 \n
 

compiler/scanner.v

@@ -410,7 +410,7 @@ fn (s mut Scanner) scan() ScanRes {
 		// println( 'file: ' + @FILE + ' | line: ' + @LINE + ' | fn: ' + @FN)
 		// ... which is useful while debugging/tracing
 		if name == 'FN' { return scan_res(.str, s.fn_name) }
-		if name == 'FILE' { return scan_res(.str, os.realpath(s.file_path).replace('\\', '\\\\')) } // escape \
+		if name == 'FILE' { return scan_res(.str, cescaped_path(os.realpath(s.file_path))) }
 		if name == 'LINE' { return scan_res(.str, (s.line_nr+1).str()) }
 		if name == 'COLUMN' { return scan_res(.str, (s.current_column()).str()) }
 		if name == 'VHASH' { return scan_res(.str, vhash()) }

vlib/builtin/builtin.v

@@ -55,7 +55,32 @@ pub fn print_backtrace_skipping_top_frames(skipframes int) {
 			if C.backtrace_symbols_fd != 0 {
 				buffer := [100]byteptr
 				nr_ptrs := C.backtrace(*voidptr(buffer), 100)
-				C.backtrace_symbols_fd(*voidptr(&buffer[skipframes]), nr_ptrs-skipframes, 1)
+				nr_actual_frames := nr_ptrs-skipframes
+				mut sframes := []string
+				csymbols := *byteptr(C.backtrace_symbols(*voidptr(&buffer[skipframes]), nr_actual_frames))
+				for i in 0..nr_actual_frames {  sframes << tos2(csymbols[i]) }
+				for sframe in sframes {
+					executable := sframe.all_before('(')
+					addr := sframe.all_after('[').all_before(']')
+					cmd := 'addr2line -e $executable $addr'
+
+					// taken from os, to avoid depending on the os module inside builtin.v
+					f := byteptr(C.popen(cmd.str, 'r'))
+					if isnil(f) {
+						println(sframe) continue
+					}
+					buf := [1000]byte
+					mut output := ''
+					for C.fgets(buf, 1000, f) != 0 {
+						output += tos(buf, vstrlen(buf)) 
+					}
+					output = output.trim_space()+':'
+					if 0 != int(C.pclose(f)) {
+						println(sframe) continue
+					}
+					println( '${output:-45s} | $sframe')
+				}
+				//C.backtrace_symbols_fd(*voidptr(&buffer[skipframes]), nr_actual_frames, 1)
 				return
 			}else{
 				C.printf('backtrace_symbols_fd is missing, so printing backtraces is not available.\n')