fixup! Fix #958: warn when feof() is used as a while loop condition

Author: francois-berder

lib/checkio.cpp

@@ -2076,6 +2076,7 @@ void CheckIO::getErrorMessages(ErrorLogger *errorLogger, const Settings *setting
     c.useClosedFileError(nullptr);
     c.seekOnAppendedFileError(nullptr);
     c.incompatibleFileOpenError(nullptr, "tmp");
+    c.wrongfeofUsage(nullptr);
     c.invalidScanfError(nullptr);
     c.wrongPrintfScanfArgumentsError(nullptr, "printf",3,2);
     c.invalidScanfArgTypeError_s(nullptr,  1, "s", nullptr);

test/testio.cpp

@@ -755,6 +755,17 @@ class TestIO : public TestFixture {
               "  fclose(fp);\n"
               "}");
         ASSERT_EQUALS("[test.cpp:3:10]: (warning) Using feof() as a loop condition may cause the last line to be processed twice. [wrongfeofUsage]\n", errout_str());
+
+        check("int foo() {\n"
+              "  FILE * fp = fopen(\"test.txt\", \"r\");\n"
+              "  char line[100];\n"
+              "  while (fgets(line, sizeof(line), fp)) {}\n"
+              "  if (!feof(fp))\n"
+              "    return 1;\n"
+              "  fclose(fp);\n"
+              "  return 0;\n"
+              "}");
+        ASSERT_EQUALS("", errout_str());
     }