cgen: panic with error message when `go` command fails (#10943)

vlib/builtin/builtin.c.v

@@ -3,6 +3,7 @@ module builtin
 type FnExitCb = fn ()
 
 fn C.atexit(f FnExitCb) int
+fn C.strerror(int) &char
 
 [noreturn]
 fn vhalt() {
@@ -100,6 +101,28 @@ pub fn panic(s string) {
 	vhalt()
 }
 
+// return a C-API error message matching to `errnum`
+pub fn c_error_number_str(errnum int) string {
+	mut err_msg := ''
+	$if freestanding {
+		err_msg = 'error $errnum'
+	} $else {
+		c_msg := C.strerror(errnum)
+		err_msg = string{
+			str: &byte(c_msg)
+			len: unsafe { C.strlen(c_msg) }
+			is_lit: 1
+		}
+	}
+	return err_msg
+}
+
+// panic with a C-API error message matching `errnum`
+[noreturn]
+pub fn panic_error_number(basestr string, errnum int) {
+	panic(basestr + c_error_number_str(errnum))
+}
+
 // eprintln prints a message with a line end, to stderr. Both stderr and stdout are flushed.
 pub fn eprintln(s string) {
 	if s.str == 0 {

vlib/builtin/builtin_nix.c.v

@@ -134,3 +134,11 @@ fn break_if_debugger_attached() {
 		_ = ptr
 	}
 }
+
+// These functions are Windows specific - provide dummys for *nix
+pub fn winapi_lasterr_str() string {
+	return ''
+}
+
+[noreturn]
+pub fn panic_lasterr() {}

vlib/builtin/builtin_windows.c.v

@@ -54,6 +54,8 @@ fn C.SymFromAddr(h_process voidptr, address u64, p_displacement voidptr, p_symbo
 
 fn C.SymGetLineFromAddr64(h_process voidptr, address u64, p_displacement voidptr, p_line &Line64) int
 
+fn C.FormatMessage(dwFlags u32, lpSource voidptr, dwMessageId u32, dwLanguageId u32, lpBuffer &voidptr, nSize u32, Arguments voidptr) u32
+
 // Ref - https://docs.microsoft.com/en-us/windows/win32/api/dbghelp/nf-dbghelp-symsetoptions
 const (
 	symopt_undname               = 0x00000002
@@ -277,3 +279,26 @@ fn break_if_debugger_attached() {
 		}
 	}
 }
+
+// return an error message generated from WinAPI's `LastError`
+pub fn winapi_lasterr_str() string {
+	mut msgbuf := &byte(0)
+	err_msg_id := C.GetLastError()
+	res := C.FormatMessage(C.FORMAT_MESSAGE_ALLOCATE_BUFFER | C.FORMAT_MESSAGE_FROM_SYSTEM,
+		C.NULL, err_msg_id, 0, &msgbuf, 0, C.NULL)
+	err_msg := if res == 0 {
+		'unknown error $err_msg_id'
+	} else {
+		string{
+			str: msgbuf
+			len: int(res)
+		}
+	}
+	return err_msg
+}
+
+// panic with an error message generated from WinAPI's `LastError`
+[noreturn]
+pub fn panic_lasterr(base string) {
+	panic(base + winapi_lasterr_str())
+}

vlib/v/checker/checker.v

@@ -6597,7 +6597,7 @@ pub fn (mut c Checker) if_expr(mut node ast.IfExpr) ast.Type {
 			}
 			c.skip_flags = cur_skip_flags
 			if c.fn_level == 0 && c.pref.output_cross_c && c.ct_cond_stack.len > 0 {
-				c.ct_cond_stack.pop()
+				c.ct_cond_stack.delete_last()
 			}
 		} else {
 			// smartcast sumtypes and interfaces when using `is`

vlib/v/gen/c/cgen.v

@@ -6087,6 +6087,7 @@ fn (mut g Gen) go_expr(node ast.GoExpr) {
 			'thread_$tmp'
 		}
 		g.writeln('HANDLE $simple_handle = CreateThread(0,0, (LPTHREAD_START_ROUTINE)$wrapper_fn_name, $arg_tmp_var, 0,0);')
+		g.writeln('if (!$simple_handle) panic_lasterr(tos3("`go ${name}()`: "));')
 		if node.is_expr && node.call_expr.return_type != ast.void_type {
 			g.writeln('$gohandle_name thread_$tmp = {')
 			g.writeln('\t.ret_ptr = $arg_tmp_var->ret_ptr,')
@@ -6098,7 +6099,8 @@ fn (mut g Gen) go_expr(node ast.GoExpr) {
 		}
 	} else {
 		g.writeln('pthread_t thread_$tmp;')
-		g.writeln('pthread_create(&thread_$tmp, NULL, (void*)$wrapper_fn_name, $arg_tmp_var);')
+		g.writeln('int ${tmp}_thr_res = pthread_create(&thread_$tmp, NULL, (void*)$wrapper_fn_name, $arg_tmp_var);')
+		g.writeln('if (${tmp}_thr_res) panic_error_number(tos3("`go ${name}()`: "), ${tmp}_thr_res);')
 		if !node.is_expr {
 			g.writeln('pthread_detach(thread_$tmp);')
 		}

vlib/v/markused/markused.v

@@ -280,6 +280,7 @@ pub fn mark_used(mut table ast.Table, pref &pref.Preferences, ast_files []&ast.F
 		files: ast_files
 		all_fns: all_fns
 		all_consts: all_consts
+		pref: pref
 	}
 	// println( all_fns.keys() )
 	walker.mark_exported_fns()

vlib/v/markused/walker.v

@@ -5,6 +5,7 @@ module markused
 // Walk the entire program starting at fn main and marks used (called) functions.
 // Unused functions can be safely skipped by the backends to save CPU time and space.
 import v.ast
+import v.pref
 
 pub struct Walker {
 pub mut:
@@ -12,6 +13,7 @@ pub mut:
 	used_fns    map[string]bool // used_fns['println'] == true
 	used_consts map[string]bool // used_consts['os.args'] == true
 	n_asserts   int
+	pref        &pref.Preferences
 mut:
 	files      []&ast.File
 	all_fns    map[string]ast.FnDecl
@@ -213,6 +215,13 @@ fn (mut w Walker) expr(node ast.Expr) {
 		}
 		ast.GoExpr {
 			w.expr(node.call_expr)
+			if w.pref.os == .windows {
+				w.fn_by_name('panic_lasterr')
+				w.fn_by_name('winapi_lasterr_str')
+			} else {
+				w.fn_by_name('c_error_number_str')
+				w.fn_by_name('panic_error_number')
+			}
 		}
 		ast.IndexExpr {
 			w.expr(node.left)