Fixed #4974 (CheckBufferOverrun::writeOutsideBufferSize() too strict)

lib/checkbufferoverrun.cpp

@@ -2239,6 +2239,7 @@ void CheckBufferOverrun::arrayIndexThenCheckError(const Token *tok, const std::s
 // the number of bytes provided at the 3. parameter.
 //
 // References:
+//  - http://pubs.opengroup.org/onlinepubs/9699919799/functions/write.html
 //  - http://gd.tuwien.ac.at/languages/c/programming-bbrown/c_075.htm
 //  - http://codewiki.wikidot.com/c:system-calls:write
 // -------------------------------------------------------------------------------------
@@ -2255,7 +2256,7 @@ void CheckBufferOverrun::writeOutsideBufferSize()
             if (Token::Match(tok, "pwrite|write (") && Token::Match(tok->tokAt(2)->nextArgument(), "%str% , %num%")) {
                 const std::string & functionName(tok->str());
                 tok = tok->tokAt(2)->nextArgument(); // set tokenptr to %str% parameter
-                const std::size_t stringLength = Token::getStrLength(tok);
+                const std::size_t stringLength = Token::getStrLength(tok)+1; // zero-terminated string!
                 tok = tok->tokAt(2); // set tokenptr to %num% parameter
                 const MathLib::bigint writeLength = MathLib::toLongNumber(tok->str());
                 if (static_cast<std::size_t>(writeLength) > stringLength)

test/testbufferoverrun.cpp

@@ -4012,7 +4012,7 @@ private:
         check("void f(void){\n"
               "write(1, \"Dump string \\n\", 100);\n"
               "}");                       // ^ number of bytes too big
-        ASSERT_EQUALS("[test.cpp:2]: (error) Writing 87 bytes outside buffer size.\n", errout.str());
+        ASSERT_EQUALS("[test.cpp:2]: (error) Writing 86 bytes outside buffer size.\n", errout.str());
 
         check("void f(void){\n"
               "write(1, \"Dump string \\n\", 10);\n"
@@ -4027,7 +4027,34 @@ private:
               "{\n"
               "    write(p.i[1], \"\", 1);\n"
               "}");
+        ASSERT_EQUALS("", errout.str());
+
+        check("static struct {\n"
+              "    int i[2];\n"
+              "} p;\n"
+              "void foo()\n"
+              "{\n"
+              "    write(p.i[1], \"\", 2);\n"
+              "}");
         ASSERT_EQUALS("[test.cpp:6]: (error) Writing 1 bytes outside buffer size.\n", errout.str());
+        // #4969
+        check("void foo()\n"
+              "{\n"
+              "    write(1, \"\\0\", 1);\n"
+              "}");
+        ASSERT_EQUALS("", errout.str());
+        // that is documented to be ok
+        check("void foo()\n"
+              "{\n"
+              "    write(1, 0, 0);\n"
+              "}");
+        ASSERT_EQUALS("", errout.str());
+        // ... that is not ok
+        check("void foo()\n"
+              "{\n"
+              "    write(1, 0, 1);\n"
+              "}");
+        TODO_ASSERT_EQUALS("[test.cpp:3]: (error) Writing 1 bytes outside buffer size.\n", "", errout.str());
     }
 };