fix: improve misra.py for missing prototype false positives (#8805)

The MISRA addon reported false positives for Rules 8.4 and 17.3 in cases
involving valid prototypes and function-pointer calls. We identified
these issues by comparing its results with reports previously generated
by our company’s internal tool on the same software.

The fix improves prototype and function-call detection in
addons/misra.py and adds a regression test covering both cases.

The bug report would have looked like below, but I don't have access to
"issues" panel.

# MISRA addon reports false positives for Rules 8.4 and 17.3

## Description

The MISRA addon reports false positives for Rules 8.4 and 17.3 when
valid function prototypes or function-pointer calls are present. The
issue was identified by comparing cppcheck results with reports
generated by our company's internal tool on the same software.

## Reproduction

```c
int regression_function(int value);

int regression_function(int value)
{
    return value;
}

int main(void)
{
    int local_prototype(int value);
    int (*callback)(int) = regression_function;

    return callback(0);
}
```

Run the MISRA addon on this file with Rules 8.4 and 17.3 enabled:

```bash
cppcheck --enable=all --addon=addons/misra.py \
  addons/test/misra/misra-regression-prototypes.c
```

## Expected result

No Rule 8.4 or Rule 17.3 violation is reported.

## Actual result

The addon reports violations for valid prototype and function-pointer
constructs.

Author: jfdeverge

addons/misra.py

@@ -538,6 +538,20 @@ def is_source_file(file):
     return file.endswith('.c')
 
 
+def has_prior_function_prototype(cfg, function):
+    """Return whether a global prototype precedes the function definition."""
+    for token in cfg.tokenlist:
+        if token == function.tokenDef:
+            break
+        if token.str != function.name or token.scope.type != 'Global':
+            continue
+        opening = token.next
+        if opening and opening.str == '(' and opening.link and \
+                opening.link.next and opening.link.next.str == ';':
+            return True
+    return False
+
+
 def is_header(file):
     return file.endswith('.h')
 
@@ -803,7 +817,8 @@ def get_function_pointer_type(tok):
     ret += '('
     tok = tok.next.next
     while tok and (tok.str not in '()'):
-        ret += ' ' + tok.str
+        if tok.varId is None:
+            ret += ' ' + tok.str
         tok = tok.next
     if (tok is None) or tok.str != ')':
         return None
@@ -2248,6 +2263,8 @@ def misra_8_4(self, cfg):
                 continue
             if func.token != func.tokenDef:
                 continue
+            if has_prior_function_prototype(cfg, func):
+                continue
             if func.tokenDef.str == 'main':
                 continue
             self.reportError(func.tokenDef, 8, 4)
@@ -3497,8 +3514,9 @@ def misra_17_3(self, cfg):
 
         # Additional check for implicit function calls in expressions
         for token in cfg.tokenlist:
-            if token.isName and token.function is None and token.valueType is None:
-                if token.next and token.next.str == "(" and token.next.valueType is None:
+            if token.isName and token.scope.type != 'Global' and token.function is None and token.valueType is None:
+                if token.next and token.next.str == "(" and token.next.valueType is None and \
+                        isFunctionCall(token.next, cfg.standards.c):
                     if token.next.next.str == "*" and \
                         token.next.next.next.isName and token.next.next.next.valueType is not None and \
                         token.next.next.next.valueType.pointer > 0 :

addons/test/misra/misra-regression-prototypes.c

@@ -0,0 +1,13 @@
+int regression_function(int value);
+
+int regression_function(int value)
+{
+    return value;
+}
+
+int main(void)
+{
+    int local_prototype(int value);
+    int (*callback)(int) = regression_function;
+    return callback(0);
+}

addons/test/misra_test.py

@@ -11,6 +11,7 @@
 from addons.misra import C11_STDLIB_IDENTIFIERS, C99_STDLIB_IDENTIFIERS,C90_STDLIB_IDENTIFIERS, isStdLibId, isKeyword
 
 TEST_SOURCE_FILES = [os.path.join('addons','test','misra','misra-test.c')]
+REGRESSION_SOURCE_FILE = os.path.join('addons', 'test', 'misra', 'misra-regression-prototypes.c')
 
 
 def remove_misra_config(s:str):
@@ -93,6 +94,20 @@ def test_json_out(checker, capsys, test_files):
     assert("Required" in json_output['c2012-21.3'][0]['extra'])
     assert("Advisory" in json_output['c2012-20.1'][0]['extra'])
 
+def test_function_prototype_and_pointer_call_regressions(checker, capsys):
+    dump_create(REGRESSION_SOURCE_FILE)
+    sys.argv.append("--cli")
+    try:
+        checker.loadRuleTexts("./addons/test/misra/misra_rules_dummy.txt")
+        checker.parseDump(REGRESSION_SOURCE_FILE + ".dump")
+        captured = capsys.readouterr().out
+        json_output = convert_json_output(captured.splitlines())
+        assert "c2012-8.4" not in json_output
+        assert "c2012-17.3" not in json_output
+    finally:
+        sys.argv.remove("--cli")
+        dump_remove(REGRESSION_SOURCE_FILE)
+
 
 def test_rules_cppcheck_severity(checker, capsys, test_files):
     checker.loadRuleTexts("./addons/test/misra/misra_rules_dummy.txt")