src, tools: add check for left leaning pointers

This commit adds a rule to cpplint to check that pointers in the code
base lean to the left and not right, and also fixes the violations
reported.

PR-URL: https://github.com/nodejs/node/pull/21010
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: James M Snell <jasnell@gmail.com>

tools/cpplint.py

@@ -527,6 +527,10 @@ _SEARCH_KERNEL_FILE = re.compile(r'\b(?:LINT_KERNEL_FILE)')
 
 _NULL_TOKEN_PATTERN = re.compile(r'\bNULL\b')
 
+_RIGHT_LEANING_POINTER_PATTERN = re.compile(r'[^=|(,\s><);&?:}]'
+                                            r'(?<!(sizeof|return))'
+                                            r'\s\*[a-zA-z_][0-9a-zA-z_]*')
+
 _regexp_compile_cache = {}
 
 # {str, set(int)}: a map from error categories to sets of linenumbers
@@ -4179,6 +4183,28 @@ def CheckNullTokens(filename, clean_lines, linenum, error):
     error(filename, linenum, 'readability/null_usage', 2,
           'Use nullptr instead of NULL')
 
+def CheckLeftLeaningPointer(filename, clean_lines, linenum, error):
+  """Check for left-leaning pointer placement.
+
+  Args:
+    filename: The name of the current file.
+    clean_lines: A CleansedLines instance containing the file.
+    linenum: The number of the line to check.
+    error: The function to call with any errors found.
+  """
+  line = clean_lines.elided[linenum]
+
+  # Avoid preprocessor lines
+  if Match(r'^\s*#', line):
+    return
+
+  if '/*' in line or '*/' in line:
+    return
+
+  for match in _RIGHT_LEANING_POINTER_PATTERN.finditer(line):
+    error(filename, linenum, 'readability/null_usage', 2,
+          'Use left leaning pointer instead of right leaning')
+
 def GetLineWidth(line):
   """Determines the width of the line in column positions.
 
@@ -4321,6 +4347,7 @@ def CheckStyle(filename, clean_lines, linenum, file_extension, nesting_state,
   CheckCheck(filename, clean_lines, linenum, error)
   CheckAltTokens(filename, clean_lines, linenum, error)
   CheckNullTokens(filename, clean_lines, linenum, error)
+  CheckLeftLeaningPointer(filename, clean_lines, linenum, error)
   classinfo = nesting_state.InnermostClass()
   if classinfo:
     CheckSectionSpacing(filename, clean_lines, classinfo, linenum, error)