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[v3] libcpp: Fix incorrect line numbers in large files [PR108900]

Message ID 20250311110044.1033574-1-Yash.Shinde@windriver.com
State New
Headers
Series [v3] libcpp: Fix incorrect line numbers in large files [PR108900] |

Commit Message

Yash Shinde March 11, 2025, 11 a.m. UTC 
  From: Yash Shinde <Yash.Shinde@windriver.com>

This patch addresses an issue in the C preprocessor where incorrect
line number information is generated when processing files with a
large number of lines. The problem arises from improper handling
of location intervals in the line map, particularly when locations
exceed LINE_MAP_MAX_LOCATION_WITH_PACKED_RANGES.

By ensuring that the highest location is not decremented if it
would move to a different ordinary map, this fix resolves
the line number discrepancies observed in certain test cases.
This change improves the accuracy of line number reporting, benefiting
users relying on precise code coverage and debugging information.

libcpp/ChangeLog:

	* files.cc (_cpp_stack_file): Do not decrement highest_location
	across distinct maps.

Signed-off-by: Jeremy Bettis <jbettis@google.com>
Signed-off-by: Yash Shinde <Yash.Shinde@windriver.com>
---
 libcpp/files.cc | 8 ++++++++
 1 file changed, 8 insertions(+)
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Patch

diff --git a/libcpp/files.cc b/libcpp/files.cc
index 1ed19c5555a..3e6ca119ad5 100644
--- a/libcpp/files.cc
+++ b/libcpp/files.cc
@@ -1046,6 +1046,14 @@  _cpp_stack_file (cpp_reader *pfile, _cpp_file *file, include_type type,
 		    && type < IT_DIRECTIVE_HWM
 		    && (pfile->line_table->highest_location
 			!= LINE_MAP_MAX_LOCATION - 1));
+
+  if (decrement && LINEMAPS_ORDINARY_USED (pfile->line_table))
+    {
+      const line_map_ordinary *map = LINEMAPS_LAST_ORDINARY_MAP (pfile->line_table);
+      if (map && map->start_location == pfile->line_table->highest_location)
+	decrement = false;
+    }
+
   if (decrement)
     pfile->line_table->highest_location--;