ftell() have a different behavior in Windows 11 than before.

https://stackoverflow.com/questions/79762122/ftell-no-more-returning-the-correct-offset-on-a-text-file-with-windows-11-ente

Author: damorinCan

lib/checkio.cpp

@@ -53,6 +53,7 @@ namespace {
 // CVE ID used:
 static const CWE CWE119(119U);  // Improper Restriction of Operations within the Bounds of a Memory Buffer
 static const CWE CWE398(398U);  // Indicator of Poor Code Quality
+static const CWE CWE474(474U);  // Use of Function with Inconsistent Implementations
 static const CWE CWE664(664U);  // Improper Control of a Resource Through its Lifetime
 static const CWE CWE685(685U);  // Function Call With Incorrect Number of Arguments
 static const CWE CWE686(686U);  // Function Call With Incorrect Argument Type
@@ -116,6 +117,8 @@ namespace {
         nonneg int op_indent{};
         enum class AppendMode : std::uint8_t { UNKNOWN_AM, APPEND, APPEND_EX };
         AppendMode append_mode = AppendMode::UNKNOWN_AM;
+        enum class ReadMode : std::uint8_t { READ_TEXT, READ_BIN };
+        ReadMode read_mode = ReadMode::READ_BIN;
         std::string filename;
         explicit Filepointer(OpenMode mode_ = OpenMode::UNKNOWN_OM)
             : mode(mode_) {}
@@ -188,6 +191,7 @@ void CheckIO::checkFileUsage()
                 }
             } else if (Token::Match(tok, "%name% (") && tok->previous() && (!tok->previous()->isName() || Token::Match(tok->previous(), "return|throw"))) {
                 std::string mode;
+                bool isftell = false;
                 const Token* fileTok = nullptr;
                 const Token* fileNameTok = nullptr;
                 Filepointer::Operation operation = Filepointer::Operation::NONE;
@@ -249,6 +253,9 @@ void CheckIO::checkFileUsage()
                     fileTok = tok->tokAt(2);
                     if ((tok->str() == "ungetc" || tok->str() == "ungetwc") && fileTok)
                         fileTok = fileTok->nextArgument();
+                    else if (tok->str() == "ftell") {
+                        isftell = true;
+                    }
                     operation = Filepointer::Operation::UNIMPORTANT;
                 } else if (!Token::Match(tok, "if|for|while|catch|switch") && !mSettings->library.isFunctionConst(tok->str(), true)) {
                     const Token* const end2 = tok->linkAt(1);
@@ -304,10 +311,15 @@ void CheckIO::checkFileUsage()
                             f.append_mode = Filepointer::AppendMode::APPEND_EX;
                         else
                             f.append_mode = Filepointer::AppendMode::APPEND;
+                    }
+                    else if (mode.find('r') != std::string::npos &&
+                             mode.find('t') != std::string::npos) {
+                        f.read_mode = Filepointer::ReadMode::READ_TEXT;
                     } else
                         f.append_mode = Filepointer::AppendMode::UNKNOWN_AM;
                     f.mode_indent = indent;
                     break;
+
                 case Filepointer::Operation::POSITIONING:
                     if (f.mode == OpenMode::CLOSED)
                         useClosedFileError(tok);
@@ -340,6 +352,8 @@ void CheckIO::checkFileUsage()
                 case Filepointer::Operation::UNIMPORTANT:
                     if (f.mode == OpenMode::CLOSED)
                         useClosedFileError(tok);
+                    if (isftell && windows && f.read_mode == Filepointer::ReadMode::READ_TEXT && printPortability)
+                        ftellFileError(tok);
                     break;
                 case Filepointer::Operation::UNKNOWN_OP:
                     f.mode = OpenMode::UNKNOWN_OM;
@@ -398,6 +412,12 @@ void CheckIO::seekOnAppendedFileError(const Token *tok)
                 "seekOnAppendedFile", "Repositioning operation performed on a file opened in append mode has no effect.", CWE398, Certainty::normal);
 }
 
+void CheckIO::ftellFileError(const Token *tok)
+{
+    reportError(tok, Severity::portability,
+                "ftellTextModeFile", "For a text stream, its file position indicator contains unspecified information. See Section 7.21.9.4p2 of the C11 standard", CWE474, Certainty::normal);
+}
+
 void CheckIO::incompatibleFileOpenError(const Token *tok, const std::string &filename)
 {
     reportError(tok, Severity::warning,

lib/checkio.h

@@ -106,6 +106,7 @@ class CPPCHECKLIB CheckIO : public Check {
     void writeReadOnlyFileError(const Token *tok);
     void useClosedFileError(const Token *tok);
     void seekOnAppendedFileError(const Token *tok);
+    void ftellFileError(const Token *tok);
     void incompatibleFileOpenError(const Token *tok, const std::string &filename);
     void invalidScanfError(const Token *tok);
     void wrongPrintfScanfArgumentsError(const Token* tok,

test/testio.cpp

@@ -44,6 +44,7 @@ class TestIO : public TestFixture {
         TEST_CASE(fileIOwithoutPositioning);
         TEST_CASE(seekOnAppendedFile);
         TEST_CASE(fflushOnInputStream);
+        TEST_CASE(ftellCompatibility);
         TEST_CASE(incompatibleFileOpen);
 
         TEST_CASE(testScanf1); // Scanf without field limiters
@@ -704,6 +705,21 @@ class TestIO : public TestFixture {
         ASSERT_EQUALS("", errout_str()); // #6566
     }
 
+    void ftellCompatibility() {
+
+        check("void foo() {\n"
+              "     FILE *f = fopen(\"\", \"rt\");\n"
+              "     if (f)\n"
+              "     {\n"
+              "         fseek(f, 0, SEEK_END);\n"
+              "         (void)ftell(f);\n"
+              "         fclose(f);\n"
+              "     }\n"
+              "}\n", dinit(CheckOptions, $.platform = Platform::Type::Win32A, $.portability = true));
+        ASSERT_EQUALS("[test.cpp:6:16]: (portability) For a text stream, its file position indicator contains unspecified information. See Section 7.21.9.4p2 of the C11 standard [ftellTextModeFile]\n", errout_str());
+    }
+
+
     void fflushOnInputStream() {
         check("void foo()\n"
               "{\n"