Major issue:

- Fix the uncrustify check (removed https reference to Microsoft).

New changes:
- Added missing string related to new check
- Added checker description for ftellTextModeFile
- Updated copyright.

Author: damorinCan

.gitignore

@@ -2,6 +2,7 @@
 *.gcno
 *.gch
 *.o
+*.a
 *.pyc
 /cppcheck
 /cppcheck.exe

lib/checkio.cpp

@@ -352,7 +352,6 @@ void CheckIO::checkFileUsage()
                 case Filepointer::Operation::UNIMPORTANT:
                     if (f.mode == OpenMode::CLOSED)
                         useClosedFileError(tok);
-                    // See https://learn.microsoft.com/en-us/cpp/c-runtime-library/reference/fopen-wfopen?view=msvc-170 
                     if (isftell && f.read_mode == Filepointer::ReadMode::READ_TEXT && printPortability)
                         ftellFileError(tok);
                     break;

lib/checkio.h

@@ -1,6 +1,6 @@
 /* -*- C++ -*-
  * Cppcheck - A tool for static C/C++ code analysis
- * Copyright (C) 2007-2025 Cppcheck team.
+ * Copyright (C) 2007-2026 Cppcheck team.
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -141,6 +141,7 @@ class CPPCHECKLIB CheckIO : public Check {
                "- Missing or wrong width specifiers in 'scanf' format string\n"
                "- Use a file that has been closed\n"
                "- File input/output without positioning results in undefined behaviour\n"
+               "- Using 'ftell' on a file opened in text mode\n"
                "- Read to a file that has only been opened for writing (or vice versa)\n"
                "- Repositioning operation on a file opened in append mode\n"
                "- The same file can't be open for read and write at the same time on different streams\n"

man/checkers/ftellTextModeFile.md

@@ -0,0 +1,52 @@
+# ftellModeTextFile 
+
+**Message**: According to Microsoft, the value returned by ftell may not reflect the physical byte offset for streams opened in text mode, because text mode causes carriage return-line feed translation. See also 7.21.9.4 in C11 standard.<br/>
+**Category**: Portability<br/>
+**Severity**: Style<br/>
+**Language**: C/C++
+
+## Description
+
+This checker detects the use of ftell() on a file open in text (or translate) mode. The text mode is not consistent
+ in between Linux and Windows system and may cause ftell() to return the wrong offset inside a text file.
+
+This warning helps improve code quality by:
+- Making the intent clear that the use of ftell() in "t" mode may cause portability problem.
+
+## Motivation
+
+This checker improves portability accross system.
+
+## How to fix
+
+According to C11, the file must be opened in binary mode 'b' to prevent this problem.
+
+Before:
+```cpp
+     FILE *f = fopen("Example.txt", "rt");
+     if (f)
+     {
+        fseek(f, 0, SEEK_END);
+        printf( "Offset %d\n", ftell(f);
+        fclose(f);
+     }
+
+```
+
+After:
+```cpp
+
+     FILE *f = fopen("Example.txt", "rb");
+     if (f)
+     {
+        fseek(f, 0, SEEK_END);
+        printf( "Offset %d\n", ftell(f);
+        fclose(f);
+     }
+
+```
+
+## Notes
+
+See https://learn.microsoft.com/en-us/cpp/c-runtime-library/reference/fopen-wfopen?view=msvc-170
+