tools: add cpplint rule for NULL usage

This commit is a suggestion for adding a rule for NULL usages in the
code base. This will currently report a number of errors which could be
ignored using // NOLINT (readability/null_usage)

PR-URL: https://github.com/nodejs/node/pull/17373
Reviewed-By: Jon Moss <me@jonathanmoss.me>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Timothy Gu <timothygu99@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>

2 files changed, 34 insertions, 10 deletions

diff --git a/tools/cpplint.py b/tools/cpplint.py
index ca42ddeb7b..460c1ecbfe 100644
--- a/tools/cpplint.py
+++ b/tools/cpplint.py
@@ -499,7 +499,6 @@ _ALT_TOKEN_REPLACEMENT = {
 _ALT_TOKEN_REPLACEMENT_PATTERN = re.compile(
     r'[ =()](' + ('|'.join(_ALT_TOKEN_REPLACEMENT.keys())) + r')(?=[ (]|$)')
 
-
 # These constants define types of headers for use with
 # _IncludeState.CheckNextIncludeOrder().
 _C_SYS_HEADER = 1
@@ -526,6 +525,8 @@ _SEARCH_C_FILE = re.compile(r'\b(?:LINT_C_FILE|'
 # Match string that indicates we're working on a Linux Kernel file.
 _SEARCH_KERNEL_FILE = re.compile(r'\b(?:LINT_KERNEL_FILE)')
 
+_NULL_TOKEN_PATTERN = re.compile(r'\bNULL\b')
+
 _regexp_compile_cache = {}
 
 # {str, set(int)}: a map from error categories to sets of linenumbers
@@ -4156,6 +4157,27 @@ def CheckAltTokens(filename, clean_lines, linenum, error):
           'Use operator %s instead of %s' % (
               _ALT_TOKEN_REPLACEMENT[match.group(1)], match.group(1)))
 
+def CheckNullTokens(filename, clean_lines, linenum, error):
+  """Check NULL usage.
+
+  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 line.find('/*') >= 0 or line.find('*/') >= 0:
+    return
+
+  for match in _NULL_TOKEN_PATTERN.finditer(line):
+    error(filename, linenum, 'readability/null_usage', 2,
+          'Use nullptr instead of NULL')
 
 def GetLineWidth(line):
   """Determines the width of the line in column positions.
@@ -4294,6 +4316,7 @@ def CheckStyle(filename, clean_lines, linenum, file_extension, nesting_state,
   CheckSpacingForFunctionCall(filename, clean_lines, linenum, error)
   CheckCheck(filename, clean_lines, linenum, error)
   CheckAltTokens(filename, clean_lines, linenum, error)
+  CheckNullTokens(filename, clean_lines, linenum, error)
   classinfo = nesting_state.InnermostClass()
   if classinfo:
     CheckSectionSpacing(filename, clean_lines, classinfo, linenum, error)
diff --git a/tools/icu/iculslocs.cc b/tools/icu/iculslocs.cc
index 485a179deb..ca312b7835 100644
--- a/tools/icu/iculslocs.cc
+++ b/tools/icu/iculslocs.cc
@@ -231,14 +231,14 @@ int dumpAllButInstalledLocales(int lev,
 int list(const char* toBundle) {
   UErrorCode status = U_ZERO_ERROR;
 
-  FILE* bf = NULL;
+  FILE* bf = NULL;  // NOLINT (readability/null_usage)
 
-  if (toBundle != NULL) {
+  if (toBundle != NULL) {  // NOLINT (readability/null_usage)
     if (VERBOSE) {
       printf("writing to bundle %s\n", toBundle);
     }
     bf = fopen(toBundle, "wb");
-    if (bf == NULL) {
+    if (bf == NULL) {  // NOLINT (readability/null_usage)
       printf("ERROR: Could not open '%s' for writing.\n", toBundle);
       return 1;
     }
@@ -258,6 +258,7 @@ int list(const char* toBundle) {
       ures_openDirect(packageName.data(), locale, &status));
   ASSERT_SUCCESS(&status, "while opening the bundle");
   LocalUResourceBundlePointer installedLocales(
+      // NOLINTNEXTLINE (readability/null_usage)
       ures_getByKey(bund.getAlias(), INSTALLEDLOCALES, NULL, &status));
   ASSERT_SUCCESS(&status, "while fetching installed locales");
 
@@ -266,7 +267,7 @@ int list(const char* toBundle) {
     printf("Locales: %d\n", count);
   }
 
-  if (bf != NULL) {
+  if (bf != NULL) {  // NOLINT (readability/null_usage)
     // write the HEADER
     fprintf(bf,
             "// Warning this file is automatically generated\n"
@@ -310,17 +311,17 @@ int list(const char* toBundle) {
 
     UBool exists;
     if (localeExists(key, &exists)) {
-      if (bf != NULL) fclose(bf);
+      if (bf != NULL) fclose(bf);  // NOLINT (readability/null_usage)
       return 1;  // get out.
     }
     if (exists) {
       validCount++;
       printf("%s\n", key);
-      if (bf != NULL) {
+      if (bf != NULL) {  // NOLINT (readability/null_usage)
         fprintf(bf, "        %s {\"\"}\n", key);
       }
     } else {
-      if (bf != NULL) {
+      if (bf != NULL) {  // NOLINT (readability/null_usage)
         fprintf(bf, "//      %s {\"\"}\n", key);
       }
       if (VERBOSE) {
@@ -329,7 +330,7 @@ int list(const char* toBundle) {
     }
   }
 
-  if (bf != NULL) {
+  if (bf != NULL) {  // NOLINT (readability/null_usage)
     fprintf(bf, "    } // %d/%d valid\n", validCount, count);
     // write the HEADER
     fprintf(bf, "}\n");
@@ -371,7 +372,7 @@ int main(int argc, const char* argv[]) {
       usage();
       return 0;
     } else if (!strcmp(arg, "-l")) {
-      if (list(NULL)) {
+      if (list(NULL)) {  // NOLINT (readability/null_usage)
         return 1;
       }
     } else if (!strcmp(arg, "-b") && (argsLeft >= 1)) {