Fix correct warning with c engine when skipping lines

Fixed bug where c engine would not print warnings for lines
it skipped in case the skipped line had an inline comment.
Also, its accounting of number of fields in such lines would
be off by one.

Author: Pankaj Pandey

pandas/_libs/src/parser/tokenizer.c

@@ -832,6 +832,9 @@ int tokenize_bytes(parser_t *self, size_t line_limit, int start_lines) {
                 } else if (IS_CARRIAGE(c)) {
                     self->state = EAT_CRNL;
                     break;
+                } else if (IS_COMMENT_CHAR(c)) {
+                    self->state = EAT_COMMENT;
+                    break;
                 } else if (!IS_WHITESPACE(c)) {
                     self->state = START_FIELD;
                     // fall through to subsequent state

pandas/tests/io/parser/comment.py

@@ -5,6 +5,8 @@
 for all of the parsers defined in parsers.py
 """
 
+import sys
+
 import numpy as np
 import pandas.util.testing as tm
 
@@ -116,3 +118,29 @@ def test_commment_first_line(self):
         expected = DataFrame({0: ['a', '1'], 1: ['b', '2'], 2: ['c', '3']})
         result = self.read_csv(StringIO(data), comment='#', header=None)
         tm.assert_frame_equal(result, expected)
+
+    def test_comment_whitespace_delimited(self):
+        test_input = """\
+1 2
+2 2 3
+3 2 3 # 3 fields
+4 2 3# 3 fields
+5 2 # 2 fields
+6 2# 2 fields
+7 # 1 field, NaN
+8# 1 field, NaN
+9 2 3 # skipped line
+# comment"""
+        captured_err = StringIO()
+        orig_stderr, sys.stderr = sys.stderr, captured_err
+        try:
+            df = self.read_csv(StringIO(test_input), comment='#', header=None,
+                               delimiter='\\s+', skiprows=0,
+                               error_bad_lines=False)
+        finally:
+            sys.stderr = orig_stderr
+        content = captured_err.getvalue()
+        # skipped lines 2, 3, 4, 9
+        assert content.count('Skipping line') == 4, content
+        expected = DataFrame([[1, 2], [5, 2], [6, 2], [7, np.nan], [8, np.nan]])
+        tm.assert_frame_equal(df, expected)