From 7d6622e9f1fd274e7f6c2ff7526e4df269d36b26 Mon Sep 17 00:00:00 2001
From: Siarhei Siamashka <siarhei.siamashka@gmail.com>
Date: Thu, 14 Dec 2023 02:10:01 +0200
Subject: [PATCH] expander.py: trace line numbers back to the original source
 file
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Using the "#line" directives, it's possible to allow compilers to
report line numbers from the original source file. At least GCC
and Clang support this. It's useful for tracing the compilation
error locations back to the original file. Example:

  #include <iostream>
  #include <atcoder/lazysegtree>
  int main() {
    lazy_segtree<S, op, e, F, mapping, composition, id> seg(arr);
  }

== The current default behaviour: ==

$ ./expander.py example.cpp
$ g++ combined.cpp
combined.cpp: In function ‘int main()’:
combined.cpp:263:3: error: ‘lazy_segtree’ was not declared in this
                    scope; did you mean ‘atcoder::lazy_segtree’?

== With the new '--origname' option: ==

$ ./expander.py --origname=example.cpp example.cpp
$ g++ combined.cpp
example.cpp: In function ‘int main()’:
example.cpp:4:3: error: ‘lazy_segtree’ was not declared in this
                 scope; did you mean ‘atcoder::lazy_segtree’?
---
 expander.py | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/expander.py b/expander.py
index ff773da..e4b87f3 100755
--- a/expander.py
+++ b/expander.py
@@ -63,14 +63,18 @@ def expand_acl(self, acl_file_path: Path) -> List[str]:
             result.append(line)
         return result
 
-    def expand(self, source: str) -> str:
+    def expand(self, source: str, origname) -> str:
         self.included = set()
         result = []  # type: List[str]
+        linenum = 0
         for line in source.splitlines():
+            linenum += 1
             m = self.atcoder_include.match(line)
             if m:
                 acl_path = self.find_acl(m.group(1))
                 result.extend(self.expand_acl(acl_path))
+                if origname:
+                    result.append('#line ' + str(linenum + 1) + ' "' + origname + '"')
                 continue
 
             result.append(line)
@@ -88,6 +92,8 @@ def expand(self, source: str) -> str:
     parser.add_argument('-c', '--console',
                         action='store_true', help='Print to Console')
     parser.add_argument('--lib', help='Path to Atcoder Library')
+    parser.add_argument('--origname', help='report line numbers from the original ' +
+                                           'source file in GCC/Clang error messages')
     opts = parser.parse_args()
 
     lib_paths = []
@@ -99,7 +105,7 @@ def expand(self, source: str) -> str:
     lib_paths.append(Path.cwd())
     expander = Expander(lib_paths)
     source = open(opts.source).read()
-    output = expander.expand(source)
+    output = expander.expand(source, opts.origname)
 
     if opts.console:
         print(output)