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// CERT C Rule: DCL08-C
// Properly encode relationships in constant definitions
//
// This rule checks that:
// 1. When constants have mathematical relationships, they should be encoded
// (e.g., OUT_STR_LEN = IN_STR_LEN + 2 instead of separate literals)
// 2. Constants should not encode false or impermanent relationships
use super::super::{CertRule, RuleViolation};
use crate::manifest::{RuleCategory, Severity};
use crate::utility::cert_c::ast_utils::get_node_text;
use lang_parsing_substrate::query;
use tree_sitter::Node;
pub struct Dcl08C;
impl CertRule for Dcl08C {
fn rule_id(&self) -> &'static str {
"DCL08-C"
}
fn description(&self) -> &'static str {
"Properly encode relationships in constant definitions"
}
fn severity(&self) -> Severity {
Severity::Low
}
fn category(&self) -> RuleCategory {
RuleCategory::Recommendation
}
fn cert_id(&self) -> &'static str {
"DCL08-C"
}
fn check(&self, root_node: &Node, source: &str) -> Vec<RuleViolation> {
let mut violations = Vec::new();
// First pass: collect all enum constants across the entire file
let mut all_enum_constants = std::collections::HashMap::new();
self.collect_all_enum_constants(root_node, source, &mut all_enum_constants);
// Second pass: check each enum for violations
for enum_node in query::find_descendants_of_kind(*root_node, "enum_specifier") {
self.check_enum_specifier(&enum_node, source, &mut violations, &all_enum_constants);
}
violations
}
}
impl Dcl08C {
/// Collect all enum constant names across the entire file
fn collect_all_enum_constants(
&self,
node: &Node,
source: &str,
constants: &mut std::collections::HashMap<String, usize>,
) {
for enum_node in query::find_descendants_of_kind(*node, "enum_specifier") {
let Some(body) = enum_node.child_by_field_name("body") else {
continue;
};
for enumerator in query::find_descendants_of_kind(body, "enumerator") {
if let Some(name_node) = enumerator.child_by_field_name("name") {
let name = get_node_text(&name_node, source);
let line = name_node.start_position().row + 1;
constants.insert(name.to_string(), line);
}
}
}
}
fn check_enum_specifier(
&self,
node: &Node,
source: &str,
violations: &mut Vec<RuleViolation>,
all_constants: &std::collections::HashMap<String, usize>,
) {
// Get the enum body
let body = match node.child_by_field_name("body") {
Some(b) => b,
None => return,
};
// Collect all enumerator definitions
let enumerators = query::find_descendants_of_kind(body, "enumerator");
// Need at least 1 enumerator to check
if enumerators.is_empty() {
return;
}
// Check for potential missing relationships (same enum, literal values only)
self.check_missing_relationships(&enumerators, source, violations, all_constants);
}
fn check_missing_relationships(
&self,
enumerators: &[Node],
source: &str,
violations: &mut Vec<RuleViolation>,
all_constants: &std::collections::HashMap<String, usize>,
) {
// Collect enumerator info for THIS enum: name and value (if literal)
let mut enum_values = Vec::new();
let mut this_enum_names = std::collections::HashSet::new();
for enumerator in enumerators {
if let Some(name_node) = enumerator.child_by_field_name("name") {
let name = get_node_text(&name_node, source);
this_enum_names.insert(name.to_string());
// Check if there's a value
if let Some(value_node) = enumerator.child_by_field_name("value") {
let value_text = get_node_text(&value_node, source);
// Check if it's a simple numeric literal
if let Ok(value) = value_text.parse::<i64>() {
enum_values.push((name, value, name_node.start_position()));
} else if value_text.contains('+') || value_text.contains('-') {
// This is a reference with arithmetic
// Check if it references a constant from THIS enum (that's OK)
// or a constant from a DIFFERENT scope (that's potentially misleading)
let references_other_enum = all_constants.iter().any(|(enum_name, _)| {
value_text.contains(enum_name.as_str())
&& !this_enum_names.contains(enum_name)
});
if references_other_enum {
// References a constant from a different enum - potentially misleading
let position = name_node.start_position();
violations.push(RuleViolation {
rule_id: self.rule_id().to_string(),
message: format!(
"Constant '{}' encodes a potentially misleading relationship: {}. \
If no permanent relationship exists, define constants independently.",
name, value_text
),
severity: self.severity(),
line: position.row + 1,
column: position.column + 1,
file_path: String::new(),
suggestion: Some(format!(
"Either define '{}' with its literal value or ensure the relationship with {} is permanent and accurate",
name, value_text
)),
requires_manual_review: Some(true),
});
}
}
}
}
}
// If all enumerators have explicit values AND there are 3 or more members, this is a
// protocol/register/command enum — the programmer deliberately assigned every value
// (e.g. wire-format spec, CAN command IDs). There is no implicit relationship to
// encode; skip the pair-offset check. 2-member enums like {IN_STR_LEN=18, OUT_STR_LEN=20}
// are the canonical DCL08-C example and are still checked.
if enum_values.len() == enumerators.len() && enumerators.len() >= 3 {
return;
}
// If all explicit values form a consecutive integer sequence (0,1,2,... or 1,2,3,...),
// this is just making enum numbering explicit — not an encoded relationship.
// Common patterns: {SUCCESS=0, FAIL=1}, {CHARGE=1, DISCHARGE=2}, {A=0, B=1, C=2}.
if enum_values.len() >= 2 {
let mut sorted_vals: Vec<i64> = enum_values.iter().map(|(_, v, _)| *v).collect();
sorted_vals.sort();
let is_consecutive = sorted_vals.windows(2).all(|w| w[1] == w[0] + 1);
if is_consecutive {
return;
}
}
// Check if any pair of values might have a relationship
// For noncompliant_1: IN_STR_LEN=18, OUT_STR_LEN=20 (20 = 18+2)
if enum_values.len() >= 2 {
// Check all pairs for simple arithmetic relationships
for i in 0..enum_values.len() {
for j in (i + 1)..enum_values.len() {
let (name1, val1, _) = &enum_values[i];
let (name2, val2, pos2) = &enum_values[j];
// Check if val2 could be expressed as val1 + offset
if val2 > val1 {
let offset = val2 - val1;
// Flag small offsets (like +2, +3) as potential relationships
if offset > 0 && offset <= 10 {
violations.push(RuleViolation {
rule_id: self.rule_id().to_string(),
message: format!(
"Constants '{}' and '{}' may have a relationship ({} = {} + {}). \
Consider encoding: {} = {} + {}",
name1, name2, val2, val1, offset, name2, name1, offset
),
severity: self.severity(),
line: pos2.row + 1,
column: pos2.column + 1,
file_path: String::new(),
suggestion: Some(format!(
"enum {{ {} = {}, {} = {} + {} }};",
name1, val1, name2, name1, offset
)),
requires_manual_review: Some(true),
});
}
}
}
}
}
}
#[allow(dead_code)]
fn contains_reference_with_arithmetic(
&self,
value_text: &str,
known_values: &[(&str, i64, tree_sitter::Point)],
) -> bool {
// Check if the value contains a reference to another enum constant plus arithmetic
for (name, _, _) in known_values {
if value_text.contains(name) && (value_text.contains('+') || value_text.contains('-')) {
return true;
}
}
false
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_rule_id() {
let rule = Dcl08C;
assert_eq!(rule.rule_id(), "DCL08-C");
}
#[test]
fn test_severity() {
let rule = Dcl08C;
assert_eq!(rule.severity(), Severity::Low);
}
}