1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
// SPDX-License-Identifier: Apache-2.0
// Copyright (c) 2024 Ryan Urchick
use super::super::{CertRule, RuleViolation};
use crate::manifest::{RuleCategory, Severity};
use lang_parsing_substrate::query;
use tree_sitter::Node;
pub struct Mem05C;
impl CertRule for Mem05C {
fn rule_id(&self) -> &'static str {
"MEM05-C"
}
fn description(&self) -> &'static str {
"Avoid large stack allocations"
}
fn severity(&self) -> Severity {
Severity::Medium
}
fn category(&self) -> RuleCategory {
RuleCategory::Rule
}
fn cert_id(&self) -> &'static str {
"MEM05-C"
}
fn scan(&self, node: &Node, source: &str, violations: &mut Vec<RuleViolation>) {
self.check_node(node, source, violations);
}
}
impl Mem05C {
fn check_node(&self, node: &Node, source: &str, violations: &mut Vec<RuleViolation>) {
for n in query::find_descendants(*node, |_| true) {
// Look for array declarations with variable size (VLA)
if n.kind() == "declaration" {
// Use AST-based detection: look for array_declarator in the declaration.
// This avoids false positives from array subscripts in initializers
// (e.g., `uint8_t x = arr[i]` is NOT a VLA, but `uint8_t arr[n]` IS).
if let Some(size_expr) = Self::find_array_declarator_size(&n, source) {
let size_expr = size_expr.trim();
// If size is not a numeric constant, it might be a VLA.
// ALL_CAPS identifiers are likely preprocessor constants.
if !size_expr.is_empty()
&& !size_expr.chars().all(|c| c.is_numeric())
&& !Self::is_likely_macro_constant(size_expr)
{
violations.push(RuleViolation {
rule_id: self.rule_id().to_string(),
severity: self.severity(),
line: n.start_position().row + 1,
column: n.start_position().column + 1,
file_path: String::new(),
message: "Variable-length array with runtime-sized allocation; \
use malloc instead"
.to_string(),
suggestion: Some(
"Use malloc/calloc for dynamic allocation".to_string(),
),
requires_manual_review: None,
});
}
}
}
// Check for recursive functions (potential stack overflow)
if n.kind() == "function_definition" {
if let Some(func_name) = self.extract_function_name(&n, source) {
if let Some(body) = n.child_by_field_name("body") {
if Self::body_calls_function(&body, source, &func_name) {
violations.push(RuleViolation {
rule_id: self.rule_id().to_string(),
severity: self.severity(),
line: n.start_position().row + 1,
column: n.start_position().column + 1,
file_path: String::new(),
message: "Recursive function can cause excessive stack allocation"
.to_string(),
suggestion: Some(
"Consider iterative approach or limit recursion depth"
.to_string(),
),
requires_manual_review: None,
});
}
}
}
}
}
}
/// Returns true if `body` (a compound_statement) contains a direct call to `func_name`.
/// Uses AST traversal of call_expression nodes to avoid matching occurrences in
/// string literals, comments, or the function's own declaration.
fn body_calls_function(node: &Node, source: &str, func_name: &str) -> bool {
query::find_first_descendant(*node, |n| {
if n.kind() != "call_expression" {
return false;
}
let Some(function) = n.child_by_field_name("function") else {
return false;
};
function.utf8_text(source.as_bytes()).unwrap_or("") == func_name
})
.is_some()
}
/// Check if a size expression is likely a preprocessor macro constant.
/// ALL_CAPS identifiers with optional underscores are conventionally macros.
/// Walk a declaration's AST to find an array_declarator and return its size expression.
/// Returns None if the declaration doesn't contain an array_declarator (e.g., it's a
/// scalar declaration like `uint8_t x = arr[i]` where `[i]` is a subscript, not a size).
fn find_array_declarator_size(decl_node: &Node, source: &str) -> Option<String> {
Self::find_array_size_recursive(decl_node, source)
}
fn find_array_size_recursive(node: &Node, source: &str) -> Option<String> {
if node.kind() == "array_declarator" {
// The array size is the child in brackets, typically the `size` field
// or the last child before `]`
if let Some(size_node) = node.child_by_field_name("size") {
let size_text = size_node
.utf8_text(source.as_bytes())
.unwrap_or("")
.to_string();
return Some(size_text);
}
// Fallback: extract text between [ and ]
let text = node.utf8_text(source.as_bytes()).unwrap_or("");
if let (Some(start), Some(end)) = (text.find('['), text.find(']')) {
let size = text[start + 1..end].trim().to_string();
if !size.is_empty() {
return Some(size);
}
}
return None;
}
// Recurse into children but skip init_declarator's value (the initializer)
// to avoid matching subscript expressions on the RHS of assignments
for i in 0..node.child_count() {
if let Some(child) = node.child(i) {
// Skip the value/initializer — subscripts there are NOT array declarations
if node.kind() == "init_declarator"
&& node.child_by_field_name("value").map(|v| v.id()) == Some(child.id())
{
continue;
}
if let Some(size) = Self::find_array_size_recursive(&child, source) {
return Some(size);
}
}
}
None
}
fn is_likely_macro_constant(expr: &str) -> bool {
!expr.is_empty()
&& expr
.chars()
.all(|c| c.is_ascii_uppercase() || c == '_' || c.is_ascii_digit())
&& expr
.chars()
.next()
.is_some_and(|c| c.is_ascii_uppercase() || c == '_')
}
fn extract_function_name(&self, node: &Node, source: &str) -> Option<String> {
let mut cursor = node.walk();
for child in node.children(&mut cursor) {
if child.kind() == "function_declarator" {
let mut inner_cursor = child.walk();
for inner_child in child.children(&mut inner_cursor) {
if inner_child.kind() == "identifier" {
return Some(
inner_child
.utf8_text(source.as_bytes())
.unwrap_or("")
.to_string(),
);
}
}
}
}
None
}
}