cgen: add fixed array bounds checking for non-literal index (#8832)

TESTS.md

@@ -18,6 +18,11 @@ Tip: use `v -cc tcc` when compiling tests for speed.
 
 General runnable tests for different features of the V compiler.
 
+* `vlib/v/tests/inout/compiler_test.v`
+
+Test output of running a V program matches an expected .out file.
+Check the source for how to test panics.
+
 ## Test building of actual V programs (examples, tools, V itself)
 
 * `v build-tools`
@@ -41,11 +46,12 @@ This verifies that `_keep.v` files would be unchanged by `vfmt -w`.
 This checks all source files are formatted and prints a summary.
 This is not required.
 
-## Other
 * `v test-fmt`
 
 Test all files in the current directory are formatted.
 
+## Markdown
+
 * `v check-md -hide-warnings .`
 
 Ensure that all .md files in the project are formatted properly,

vlib/builtin/builtin.c.v

@@ -274,3 +274,14 @@ pub fn is_atty(fd int) int {
 		return C.isatty(fd)
 	}
 }
+
+[inline]
+fn v_fixed_index(i int, len int) int {
+	$if !no_bounds_checking ? {
+		if i < 0 || i >= len {
+			s := 'fixed array index out of range (index: $i, len: $len)'
+			panic(s)
+		}
+	}
+	return i
+}

vlib/v/gen/c/cgen.v

@@ -4217,6 +4217,7 @@ fn (mut g Gen) index_expr(node ast.IndexExpr) {
 			g.write(')')
 		}
 		else {
+			// indexing
 			sym := g.table.get_final_type_symbol(node.left_type)
 			left_is_ptr := node.left_type.is_ptr()
 			if sym.kind == .array {
@@ -4397,7 +4398,15 @@ fn (mut g Gen) index_expr(node ast.IndexExpr) {
 					g.expr(node.left)
 				}
 				g.write('[')
-				g.expr(node.index)
+				direct := g.fn_decl != 0 && g.fn_decl.is_direct_arr
+				if direct || node.index is ast.IntegerLiteral {
+					g.expr(node.index)
+				} else {
+					// bounds check
+					g.write('v_fixed_index(')
+					g.expr(node.index)
+					g.write(', $info.size)')
+				}
 				g.write(']')
 				if is_fn_index_call {
 					g.write(')')

vlib/v/markused/markused.v

@@ -22,6 +22,7 @@ pub fn mark_used(mut the_table table.Table, pref &pref.Preferences, ast_files []
 		'__new_array_with_default',
 		'__new_array_with_array_default',
 		'new_array_from_c_array',
+		'v_fixed_index',
 		'memdup',
 		'vstrlen',
 		'__as_cast',

vlib/v/tests/inout/compiler_test.v

@@ -1,3 +1,7 @@
+// .out file:
+// To test a panic, remove everything after the long `===` line
+// You can also remove the line with 'line:' e.g. for a builtin fn
+
 import os
 import term
 import v.util
@@ -52,7 +56,7 @@ fn test_all() {
 			n_found := normalize_panic_message(found, vroot)
 			n_expected := normalize_panic_message(expected, vroot)
 			if found.contains('================ V panic ================') {
-				if n_found.contains(n_expected) {
+				if n_found.starts_with(n_expected) {
 					println(term.green('OK (panic)'))
 					continue
 				} else {
@@ -86,7 +90,10 @@ fn test_all() {
 
 fn normalize_panic_message(message string, vroot string) string {
 	mut msg := message.all_before('=========================================')
-	msg = msg.replace(vroot + os.path_separator, '')
+	// change windows to nix path
+	s := vroot.replace(os.path_separator, '/')
+	// remove vroot
+	msg = msg.replace(s + '/', '')
 	msg = msg.trim_space()
 	return msg
 }

vlib/v/tests/inout/fixed_array_index.out

@@ -0,0 +1,6 @@
+1
+================ V panic ================
+   module: builtin
+ function: v_fixed_index()
+  message: fixed array index out of range (index: 2, len: 2)
+     file: vlib/builtin/builtin.c.v

vlib/v/tests/inout/fixed_array_index.vv

@@ -0,0 +1,4 @@
+a := [1,2]!
+println(a[0])
+i := 2
+_ = a[i]

vlib/v/tests/inout/fixed_array_slice.out

@@ -0,0 +1,5 @@
+================ V panic ================
+   module: builtin
+ function: slice()
+  message: array.slice: slice bounds out of range (3 >= 2)
+     file: vlib/builtin/array.v

vlib/v/tests/inout/fixed_array_slice.vv

@@ -0,0 +1,3 @@
+a := [1,2]!
+i := 3
+_ = a[i..i]