1 files changed, 108 insertions, 0 deletions
diff --git a/js/src/frontend/align_stack_comment.py b/js/src/frontend/align_stack_comment.py
new file mode 100755
index 0000000000..28d5d8cf7f
--- /dev/null
+++ b/js/src/frontend/align_stack_comment.py
@@ -0,0 +1,108 @@
+#!/usr/bin/python -B
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this file,
+# You can obtain one at http://mozilla.org/MPL/2.0/.
+
+
+""" Usage: align_stack_comment.py FILE
+
+    This script aligns the stack transition comment in BytecodeEmitter and
+    its helper classes.
+
+    The stack transition comment looks like the following:
+      //        [stack] VAL1 VAL2 VAL3
+"""
+
+import re
+import sys
+
+# The column index of '[' of '[stack]'
+ALIGNMENT_COLUMN = 20
+
+# The maximum column for comment
+MAX_CHARS_PER_LINE = 80
+
+stack_comment_pat = re.compile("^( *//) *(\[stack\].*)$")
+
+
+def align_stack_comment(path):
+    lines = []
+    changed = False
+
+    with open(path) as f:
+        max_head_len = 0
+        max_comment_len = 0
+
+        line_num = 0
+
+        for line in f:
+            line_num += 1
+            # Python includes \n in lines.
+            line = line.rstrip("\n")
+
+            m = stack_comment_pat.search(line)
+            if m:
+                head = m.group(1) + " "
+                head_len = len(head)
+                comment = m.group(2)
+                comment_len = len(comment)
+
+                if head_len > ALIGNMENT_COLUMN:
+                    print(
+                        "Warning: line {} overflows from alignment column {}: {}".format(
+                            line_num, ALIGNMENT_COLUMN, head_len
+                        ),
+                        file=sys.stderr,
+                    )
+
+                line_len = max(head_len, ALIGNMENT_COLUMN) + comment_len
+                if line_len > MAX_CHARS_PER_LINE:
+                    print(
+                        "Warning: line {} overflows from {} chars: {}".format(
+                            line_num, MAX_CHARS_PER_LINE, line_len
+                        ),
+                        file=sys.stderr,
+                    )
+
+                max_head_len = max(max_head_len, head_len)
+                max_comment_len = max(max_comment_len, comment_len)
+
+                spaces = max(ALIGNMENT_COLUMN - head_len, 0)
+                formatted = head + " " * spaces + comment
+
+                if formatted != line:
+                    changed = True
+
+                lines.append(formatted)
+            else:
+                lines.append(line)
+
+        print(
+            "Info: Minimum column number for [stack]: {}".format(max_head_len),
+            file=sys.stderr,
+        )
+        print(
+            "Info: Alignment column number for [stack]: {}".format(ALIGNMENT_COLUMN),
+            file=sys.stderr,
+        )
+        print(
+            "Info: Max length of stack transition comments: {}".format(max_comment_len),
+            file=sys.stderr,
+        )
+
+    if changed:
+        with open(path, "w") as f:
+            for line in lines:
+                print(line, file=f)
+    else:
+        print("No change.")
+
+
+if __name__ == "__main__":
+    if len(sys.argv) < 2:
+        print("Usage: align_stack_comment.py FILE", file=sys.stderr)
+        sys.exit(1)
+
+    for path in sys.argv[1:]:
+        print(path)
+        align_stack_comment(path)