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Borland C++: ANSWERS TO COMMON QUESTIONS G e t t i n g S t a r t e d ---------------------------------------------------------------------- Q. How do I install Borland C++? A. Run the INSTALL program from DISK 1. To start the installation, change your current drive to the one that has the install program on it and type INSTALL. You will be given instructions in a box at the bottom of the screen for each prompt. For example, if you will be installing from drive A:, type: A: INSTALL At this point, the INSTALL program will appear with menu selections and descriptions to guide you through the installation process. Q. How do I run Borland C++? A. After you have installed Borland C++, be sure to add the path to the 'BIN' subdirectory of your BC++ installation (e.g., C:\BORLANDC\BIN) to your DOS path. Now you can type "BC" at the DOS prompt and from any directory and you're ready to go. Q. What is a configuration file? A. A configuration file tells Borland C++ what options to default to and where to look for its library and header files. BC.EXE and BCW.EXE both look for a configuration file named TCCONFIG.TC, and BCC.EXE looks for a file named TURBOC.CFG. Q. How do I create a configuration file? A. When you run the INSTALL program it creates a configuration file named TURBOC.CFG for BCC.EXE. This file is just an ASCII file, which you can change with any text editor. It contains the path information for the library and header files for BCC.EXE to use. The INSTALL program does not create a TCCONFIG.TC file for BC.EXE and BCW.EXE because it installs the directory information directly into BC.EXE. You can create a configuration file for the IDEs by running BC.EXE, setting your options however you want to set them, and typing Alt-O/S. C o m m o n C + + Q u e s t i o n s ---------------------------------------------------------- Q. When linking C or Assembly language modules with C++ modules I get undefined symbol errors at link time. It appears that none of the C or Assembly public symbols can be found. A. C++ is a strongly typed language. In order to support the language to its fullest, Borland C++ must attach information to the symbols generated for function names and variables. When this is done, the symbol will no longer match the standard C style function name. In order to link correctly, the compiler must be notified that the symbol is declared in an external module without type information tacked on to the symbol. This is done by prototyping the function as type extern "C". Here is a quick example: extern "C" int normal_c_func( float, int, char ); // name not altered void cplusplus_function( int ); // name altered See related comments under Linker Errors and in the Paradox Engine question in this section. There is also more on extern "C" in the Borland C++ Programmer's Guide, Chapter 1. Q. Classes with static data members are getting linker errors ("undefined"). A. This code is built into Turbo C++ 1.0 but not in Borland C++ 2.0, 3.0, or 3.1. In the 1.0 compiler, static members without definitions were given a default value of 0. This default definition will no longer be made in the compiler. The programmer must now give an explicit definition for each static member. Here is a quick example: class A { static int i; }; A linker error saying that A::i is not defined will result unless the source also contains a line such as: int A::i = 1; //i needs to defined but not necessarily initialized In the case of a template class, you need to similarly define static data outside the class definition, and also include the actual type information for any type you plan to instantiate the template class with. For example: template <class T> class A { static int i; }; A<int>::i; //provide definition for an integer type A<Myclass>::i; //provide definition for a user-defined type Q. What potential problems can arise from typecasting a base class pointer into a derived class pointer so that the derived class's member functions can be called? A. Syntactically this is allowable. There is always the possibility of a base pointer actually pointing to a base class. If this is typecast to a derived type, the function being called may not exist in the base class. Therefore, you would be grabbing the address of a function that does not exist. Q: What's the difference between the keywords STRUCT and CLASS? A: The members of a STRUCT are PUBLIC by default, while in CLASS, they default to PRIVATE. They are otherwise functionally equivalent. Q: I have declared a derived class from a base class, but I can't access any of the base class members with the derived class function. A: Derived classes DO NOT get access to private members of a base class. In order to access members of a base class, the base class members must be declared as either public or protected. If they are public, then any portion of the program can access them. If they are protected, they are accessible by the class members, friends, and any derived classes. Q: How can I use the Paradox Engine 1.0 with C++?, A: Because the Paradox Engine functions are all compiled as C functions, you will have to assure that the names of the functions do not get "mangled" by the C++ compiler. To do this you need to prototype the Engine functions as extern "C". (Name mangling and the use of extern "C" are both described in detail in the Borland C++ Programmer's Guide.) In the pxengine.h header file insert the following code at the lines indicated. /* inserted at line # 268 */ #ifdef __cplusplus extern "C" { #endif /* inserted at line # 732, just before the final #endif */ #ifdef __cplusplus } #endif Paradox Engine version 2.0 is "aware" of C++ and thus does not require any modifications to its header file. Q: I have a class that is derived from three base classes. Can I insure that one base class constructor will be called before all other constructors? A: If you declare the base class as a virtual base class, its constructor will be called before any non-virtual base class constructors. Otherwise the constructors are called in left-to-right order on the declaration line for the class. Q: Are the standard library I/O functions still available for use with the C++ iostreams library? A: Yes, using #include <stdio.h> functions such as printf() and scanf() will continue to be available. However, using them in conjunction with stream oriented functions can lead to unpredictable behaviour. Q: When debugging my program in Turbo Debugger, I notice that none of my inline functions are expanded inline. Instead, they are all done as function calls. A: Whenever you compile your program with debugging information included, no functions are expanded inline. To verify that your inline functions are indeed expanding inline, compile a module with the -S flag of the command-line compiler, then examine the .ASM file that is generated. Q. In C++, given two variables of the same name, one local and one global, how do I access the global instance within the local scope? A. Use the scope (::) operator. For example: int x = 10; for(int x=0; x < ::x; x++) { cout << "Loop # " << x << "\n"; // This will loop 10 times } Q. Will the following two functions be overloaded by the compiler, or will the compiler flag it as an error? Why? void test( int x, double y); and int test( int a, double b); A. The compiler will flag this as a redeclaration error because neither return types nor argument names are considered when determining unique signatures for overloading functions. Only number and type of arguments are considered. Q. If I pass a character to a function which only accepts an int, what will the compiler do? Will it flag it as an error? A. No. The compiler will promote the char to an int and use the integer representation in the function instead of the character itself. The exception here is in the case of a template function, where no implicit conversions or promotions take place. Q. I was trying to allocate an array of function pointers using the new operator but I keep getting declaration syntax errors using the following syntax: new int(*[10])(); What's wrong? A. The new operator is a unary operator and binds first to the int keyword producing the following: (new int) (*[10])(); You need to put parentheses around the expression to produce the expected results: new (int (*[10]()); //array of function pointers Q. What are inline functions? What are their advantages? How are they declared? A. An inline function is a function which gets textually inserted by the compiler, much like macros. The advantage is that execution time is shortened because linker overhead is minimized. They are declared by using the inline keyword when the function is declared: inline void func(void) { cout << "printing inline function \n"; } or by including the function declaration and code body within a class: class test { public: void func(void) { cout << "inline function within a class.\n"} }; Q. If I don't specify either public or private sections in a class, what is the default? A. In a class, all members are private by default if neither public nor private sections are declared. Q. If I don't specifiy either the public or private keyword when inheriting from a base class, what is the default? A. In Borland C++ 2.0, the default is public inheritance, but in versions 3.0 and 3.1, the default is private inheritance. Q. What does the _seg modifier do? A. Using _seg causes a pointer to become a storage place for a segment value, rather than an offset ( or a segment/offset ). For instance, if "int _seg *x" contains the value 0x40, then when you use "*x", the value pointed to will be at segment 0x40, offset 0. If you add a value to the pointer, the value is multiplied by the size of the pointer type. That new value is used as an offset, and is combined with the segment value contained in the pointer. For instance, int _seg *x; int value; x = (int _seg *)0x40; value = *(x + 20); value is assigned the value of the integer at 0x40:0x28 (Remember, 20 * sizeof(int) = 40 = 0x28). You can find a more detailed description of _seg in the Borland C++ Programmer's Guide, Chapter 9. Q. Can I statically allocate more than 64K of data in a single module? A. Yes. Far data items are now supported: ... char far array1[60000L]; char far array2[60000L]; ... For arrays larger than 64k use: char huge array3[100000L]; Q. What is a friend member function? A. Declaring a friend gives non-members of a class access to the non-public members of a class. Q. Why do I get a "Type name expected" error on my definition of a friend class in my new class? A. You need to let the compiler know that the label you use for your friend class is another class. If you do not want to define your entire class, you can simply have "class xxx", where xxx is your label. For example: class Boo; //forward class declaration is required class Foo{ friend class Boo; ... }; Q: How can I output hex values in upper case using the iostream libraries? A: You need to set the state of the stream using setf(). For example, #include <iostream.h> int main(void) { cout << hex; cout << "\nNot upper-case : " << 255; cout.setf(ios::upper-case); cout << "\nUppercase : " << 255; return 0; } Q. What is the "this" pointer? A. "this" is a local variable in the body of a non-static member function. It is a pointer to the object for which the function was invoked. It cannot be used outside of a class member function body. Q. Why does a binary member function only accept a single argument? A. The first argument is defined implicitly. Q. Looking through the class libraries there are definitions in classes which look like: class test { int funct( void ) const; }; What is the const keyword doing here? A. There is a pointer to the object for which a function is called known as the 'this' pointer. By default the type of 'this' is X *const ( a constant pointer). The const keyword changes the type to const X *const ( a constant pointer to constant data ). Q: I want to use _new_handler and set_new_handler. A: Borland C++ supports _new_handler and set_new_handler. You can find a discussion of them in Chapter 3 of the Borland C++ Programmer's Guide. The type of _new_handler is as follows. typedef void (*vfp)(void); vfp _new_handler; vfp set_new_handler( vfp ); Q: I would like to use C++ fstreams on a file opened in binary mode, how is this done? A: Use ios::binary as the open mode for the file: #include <fstream.h> ifstream binfile; binfile.open("myfile.bin", ios::binary); Q: How can I get at the DOS file handle associated with my iostream? A: Using a combination of member functions fd() and rdbuf() you can get at the file handle. #include <fstream.h> #define fstrno(s) (((s).rdbuf())->fd()) ifstream test("test.txt"); cout << "handle is " << fstrno(test) << '\n'; Q: How can I increase the number of FILES available to my program under Borland C++ 3.1? A: Increasing the number of available files involves changing the following 3 files located in the Run-Time Library: _NFILE.H, FILES.C, and FILES2.C. For instructions on how to do this, download TI870 from the Borland fax line. Q: When using the BIDS library, if I try to create an Array or Bag of integers, I get the error "multiple declaration for detach()...". A: If you try to create a BI_ArrayAsVector<int>, BI_SArrayAsVector<int>, or BI_BagAsVector<unsigned>, the compiler will yield an error message. This is because each of these templates provides a version of detach() that takes an argument whose type is the type for which the template is being instantiated, plus a version that takes an argument of type int or unsigned int, which lets you specify the index for the item to be detached. Therefore, when instantiated with an integer, these two versions have the same signature, which is what causes the error. Integer types are not allowed here due to resulting ambiguity between the type and the index of the Bag or Array. Q: How do I get DPMI programs like BC++ 3.0 and 3.1 to run in a DOS session under OS/2 2.0? A: The DPMI programs within BC++ 3.0 and 3.1 can be run under OS/2 2.0 in a DOS (MVDM) session if the DPMI_DOS_API flag is enabled. To set this, pull up the menu for the DOS icon with the right mouse button, then mouse click on the arrow button appearing to the right of the OPEN menu choice. Choose SETTINGS from the resulting menu, then go to the SESSION tab of the notebook and click on the DOS SETTINGS button. Highlight DPMI_DOS_API in the listbox. Finally, make sure ENABLED is chosen in the upper right pulldown listbox, and save. Q: How come the bioscom() function does not work on my computer? A: bioscom() uses DOS interrupt 0x14 directly, and thus bioscom()'s functionality is tied directly to the BIOS of your computer. MS-DOS support for the serial communications port may be inadequate in several respects for high-performance serial I/O applications. First, MS-DOS provides no portable way to test for the existence or status of a particular serial port in a system. If a program "opens" COM2 and writes data to it, and the physical COM2 adapter is not present in the system, the program may simply hang. Similarly, if the serial port exists, but no character has been received and the program attempts to read a character, the program will hang until one is available. There is no traditional function call to check if a character is waiting. MS-DOS also provides no portable method to initialize the communication adapter to a particular baud rate, word length, and parity. An application must resort to ROM BIOS calls, manipulate the hardware directly, or rely on the user to configure the port properly with the MODE command before running the application that uses it. Because of all the problems mentioned above, we strongly recommend getting a third party communications package when attempting to do serial communications, or downloading the example program SERIAL.ZIP from our BBS at (408) 439-9096. C o m m o n W i n d o w s Q u e s t i o n s ---------------------------------------------------------------------- Q. Why isn't my DLL working correctly? A. One possibility is that you are not linking in the correct 'cw' library. If you are building a small model DLL, you should be using cwc, not cws. If you are building a medium model DLL, you should be using cwl, not cwm. Compact and large models should use cwc and cwl respectively. Q. I have a project that works fine using Borland C++ 2.0. When I use Borland C++ 3.1, the linker cannot find my cwinX.lib file, where X corresponds to the memory model I am using. What's wrong? A. Borland C++ 3.1 uses different library names than Borland C++ 2.0. Instead of cwinX.lib, use cwX.lib in your project files, when using Borland C++ 3.1. Q. Why isn't my program working correctly? I'm getting a message box from Windows saying "Unrecoverable Application Error". A. One possible answer is that the program was not built correctly. For example, the linker did not get the correct information to export functions. Diagnostic messages from the linker could indicate this. To check that you have built your program on DLL as expected, review the section in Chapter 8 of the Programmer's Guide that deals with exports. This section has a table with 8 columns describing the possible combinations you might have used to build your program. If the setup of your program corresponds to one of the last three columns, chances are that your program was not built correctly ( or, at least, as you intended ). Column 5 corresponds to the 'classical' method of building Windows programs (that is, all exports are declared in the module definition file (the .def file )). The columns that use -WE or -WDE will build 'better' code in sense that the compiler will not make 'exportable' any functions that it does not actually export. However, it is here that many people will run into problems. If you have any functions declared as exports in the .def file but the module is compiled with -WE or -WDE, then you probably have built the program incorrectly (the function will be exported only if it is preceded by _export in the source code). Q. How do I use the _export key word? A. Put the "_export" immediately before the function name in the function declaration to export that function. Here is a quick example: long FAR PASCAL _export func(void) {...} Q. I tried to run <filename>.EXE under Windows 3.0. A window popped up titled 'Application Compatibility Warning', and said, 'The application you are about to run... '. A. You did not run the resource compiler, i.e., C:> RC <filename>.RC at the command line at the time you created this program. If you plan to create a menu with menuitems in your window, you will need to create an RC file. If your program has menus and is a simple window that does not need an RC file, run the resource compiler with <filename>.EXE. Q. I ran the resource compiler and got the error message: RC: fatal error RW1010: Could not open <filename>.RC A. You do not have an RC file created for <filename>. If you do not need an RC file for this particular application, run the resource compiler with <filename>.EXE. This will create an application that will be able to run on Windows 3.0. Q. I run BCC.EXE and then RC.EXE and get the error message: RC: warning RW4002: Non-discardable segment # set to PRELOAD A. If # equals 1, then you forgot the CODE PRELOAD statement in your <filename>.DEF file. If # equals 2, then you forgot the DATA PRELOAD statement in your <filename>.DEF file. If two of these warnings occur, you have either forgotten both CODE and DATA statements or have not created a <filename>.DEF file. Q. I run RC.EXE and get the error message: RC: fatal error RW1030: <filename>.EXE: Unable to open A. You need to list more information after the CODE statement in your <filename>.DEF file (that is, CODE PRELOAD). Q. I run BCC.EXE and get the error message: Fatal: <filename>.def (<line #>): syntax error A. Check your DATA statement on line number # in <filename>.DEF for the correct code (that is, DATA PRELOAD). Q. I run the Borland C++ IDE directly from Windows, rather than from the DOS command line. It does not get a DOS path and cannot find the resource compiler RC, as that transfer item does not have an explicit path listed. A. Either run from a DOS shell (i.e., start DOS, then start Borland C++) or modify the path for the transfer item so it explicitly knows where RC.EXE lives. Q. What is new in Windows 3.1 programming? A. The file WIN31.DOC, found in the DOC directory, describes new techniques for writing Windows 3.1 applications as well as how to convert Windows 3.0 code to Windows 3.1 code. There is also a lot of very useful documentation in the online Help files. New functions and messages, OLE, DDEML, Common Dialogs, TOOLHELP and many more topics are covered in the new online Help files. Q. If I use the new compiler, will my application remain compatible with Windows 3.0? A. The file WIN31.DOC, found in the DOC directory discusses how to maintain compatibility with Windows 3.0. Q. What are WIN30, WIN31, and STRICT? Why do I get error messages about them when I compile? A. The symbols WIN30, WIN31, and STRICT are new to Windows 3.1. They are used to control what is defined in the WINDOWS.H header file. The file WIN31.DOC, found in the DOC directory, has additional information on these symbols. The WIN30 and WIN31 symbols help define the version of Windows that your application expects to run under. The STRICT symbol is used to enforce stricter data types, which is especially helpful when writing C++ code. When STRICT is defined, WIN31 must also be defined. To make your OWL code strict compliant you will need to change some data types, such as the hInstance arguments to WinMain() and the TApplication constructor. For example, int WinMain( HANDLE, HANDLE, LPSTR, int ); // Non STRICT style int WinMain( HINSTANCE, HINSTANCE, LPSTR, int ); // STRICT style To define WIN30, WIN31, or STRICT you can declare them either in your code: #define WIN31 #define STRICT at the command line: -DWIN31 -DSTRICT or in the IDE (via OPTIONS|COMPILER|CODE GENERATION|DEFINES): WIN31;STRICT Note that WIN30 and WIN31 are only meaningful for OWL applications. STRICT can be used with and without OWL. Q. Why do I get a 'suspicious pointer conversion' warning or 'cannot convert' error (in C++ code) when I try to use the address of my window procedure or call back function? A. Windows 3.1 has introduced a new type, WNDPROC, which takes the place of the FARPROC type in some cases, such as the data type of the lpfnWndProc member of the WNDCLASS structure. If you are getting a warning or error when setting up a WNDCLASS structure that will be passed to RegisterClass(), use a WNDPROC cast to resolve the type mismatch. If you were previously using a FARPROC cast, simply change it to a WNDCLASS cast. For example, void FAR PASCAL f( void ); WNDCLASS wcTemp; wcTemp.lpfnWndProc = f; // Warning in C or error in C++ wcTemp.lpfnWndProc = (FARPROC)f; // Windows 3.0 style type cast wcTemp.lpfnWndProc = (WNDPROC)f; // Windows 3.1 style type cast Q. How can I use the new features of Windows 3.1 in my applications? A. There are a number of examples that shipped with the new compiler that use the new features of Windows 3.1, such as OLE, DDEML and Common Dialogs. There are also lengthy descriptions of programming techniques for the new features of Windows 3.1 in the online Help files. Q. Why don't some of the new Windows 3.1 API functions, such as ChooseColor(), do anything when I call them? A. The new Windows 3.1 functions that are passed structures as parameters require that the size field of the structure be initialized to the size of the structure. This technique allows for backward compatability in future versions of these functions. If the size field is not set correctly the function will not do anything. For example, CHOOSECOLOR ccTemp; // Data structure ccTemp.lStructSize = sizeof( ccTemp ); // Set the size first! if( ChooseColor( &ccTemp ) != 0 ) etc . . . // Then call the function Q. Why is my DDEML application crashing? A. DDEML can crash in seemingly random ways if the conversation handle or application instance identifier is incorrect or corrupted. Use TDW to watch the value of the conversation handle and the application instance identifier. If it changes, is corrupted, or you inadvertently pass the DDE Management Library an invalid value, that particular call may not fail but DDEML may become unstable and crash at some time in the future. Also note that before DdeInitialize() is called for the first time, the application instance identifier argument MUST be set to 0. I n t e g r a t e d E n v i r o n m e n t ---------------------------------------------------------------------- Q: Why doesn't my mouse work well with Borland C++? A: The most likely cause is that you are using an older mouse driver. You'll need to get a newer version. Driver versions required for full compatibility include: Logitech driver 5.01+, Microsoft 7.04+, Genius 9.06+. Q. Why is Borland C++ not able to find any of my #include files? A. The compiler searches for include files in the Borland C++ Include Directories path. You can specify this path through the Options|Directories menu. The INSTALL program initially sets this path to the directory where it copied all the Borland C++ *.h files. Q. Why do I get the message: Linker Error: Unable to open input file 'C0x.OBJ' A. The linker searches for Borland C++ start-up and library files in the Borland C++ Library Directories path. You can specify this path through the Options|Directories menu. The INSTALL program initially sets this path to the directory where it copied the start-up and library files. Also be sure that you installed the memory model that the linker is looking for. The 'x' in the error message corresponds to the memory model, e.g. 's' for small, 'l' for large, etc. Q. How do I get Borland C++ to link in my own libraries or use multiple source files? A. Borland C++'s Project Manager is designed to allow you to work with multiple files. Q. Why does the linker tell me that all the graphics library routines are undefined? A. The Options|Linker|Libraries|Graphics Library item must be set ON if you are using any Borland C++ graphics functions and have not specified GRAPHICS.LIB in a project file. Q. Why does Borland C++ report "Unable to open include file 'stdarg.h'" when I try to #include <stdio.h>? A. The most probable reason is that you have exceeded the number of files that DOS can have open simultaneously. Add the line FILES=20 to your DOS CONFIG.SYS file. This allows DOS to open up to 20 files at the same time. CONFIG.SYS will only be effective after you have rebooted your computer. See the IBM DOS Reference Manual for details on the CONFIG.SYS file. Q. I run BC.EXE directly from Windows, rather than from the DOS command line. It does not get a DOS path and cannot find the resource compiler RC, as that transfer item does not have an explicit path listed. A. Either run from a DOS shell (i.e., start DOS, then start Borland C++) or modify the path for the transfer item so it explicitly knows where RC.EXE lives. Q. Where is the BCINST.EXE utility I have used in previous versions of the compiler? A. The capabilities of BCINST have been incorporated into other areas of the product and thus BCINST is no longer necessary. To remap key bindings, use the Turbo Editor Macro Compiler (TEMC). Colors can be changed from within the IDE under Options | Environment | Colors. Q. When I Make, Run, or Trace a program, Borland C++ sometimes goes through the compile and link process even when the object files are up-to-date. A. Borland C++'s MAKE logic works solely on a file's date and time stamp. If one of your source files is marked with a date that's sometime in the future, the object files that are created from it will always be older than the source file, and Borland C++ will always try to rebuild the file. You can fix this by using TOUCH.COM to set the file to the current date and time. You should also make sure that your system's date and time are always properly set. TOUCH.COM is documented in the file UTIL.DOC. Q. How come my old Turbo C project files don't work anymore? A. Project files now contain much more information about a project now, and hence are no longer stored in ASCII format. To create a project file, select PROJECT from the main menu, and follow the menus. To convert your old project files to the new format, use the supplied utility file PRJCNVT.EXE (documented in UTIL.DOC). Q. How can I convert my Turbo C 2.0 project files to the new format? A. There is a conversion utility in your Borland C++ BIN directory called PRJCNVT.EXE. This program will perform the conversion. Q. How come my project file is automatically loaded when I start Borland C++? I want to work on a different program. A. If there is only one project file in the current directory, Borland C++ will load and use that one file. If there are no project files, or if there are multiple project files, Borland C++ does not automatically load one. Go ahead and create a new project. To use a specific project file, you can specify the name of that project file on the command line used to start Borland C++. For example, 'bc farley.prj' would start up BC++ and load the 'farley' project. Q. My right mouse button appears to do nothing. Can I change this so it will set breakpoints? A. Yes, under the menu for Options|Environment|Mouse there is a dialog box for the right mouse button. You can change it to set breakpoints, or to do many other things. Q. How can I find out where my "null pointer assignment" is occurring? A. Set a watch on the following expressions: *(char *)0,4m (char *)4 Step through the program. When the values change, the just-executed line is the one that is causing the problem. Q. When I compile my program, I get the following error: Error: C:\BORLANDC\INCLUDE\STDIO.H: Overlays only supported in medium, large, and huge memory models What is happening? A. The Overlay Support option has been selected and does not work in the tiny, small, or compact memory models. You can turn this option off with: Options | Compiler | Code Generation | Overlay Support Also note that overlays are not supported under Windows. Q. When I try to load a new file after editing a file, the first file remains on the screen. How do I close the first file? A. Use Alt-F3 (or Ctrl-F4) to close the current file. Also, use F6 to move from one file to the next, if there is more than one file open at a time. Q. I'm doing a search and replace operation, and the editor prompts me for each replacement. I've selected "Change All", but it still does it. A. To disable the prompting, you must unselect the "Prompt on replace" option on the left side of the dialog box. Q. When I try to use the any of the pseudo registers, like _AX, I get the error message "Undefined symbol '_AX' in function..." when I compile. Why? A. You are only allowed to use the pseudo registers in the Borland C++ and ANSI modes of the compiler. You can change this setting in the Options | Compiler | Source menu. Q. Since I don't have a mouse, can I still copy blocks of code from one file to another? A. Yes. You can mark the beginning and end of a block by moving to the appropriate area and pressing Ctrl-K-B (mark beginning) and Ctrl-K-K (mark end). You can then use the copy and paste commands in the Edit menu. Q: How do I stop all of the files I have ever edited from constantly being open when I bring up Borland C++? A: By default, Borland C++ saves what is called the desktop configuration. This configuration is saved in a file with a .DSK extension. By deleting any files of this type (usually located in the current directory and/or the BORLANDC\BIN directory), then entering Options/Environment/Preferences and removing the check from 'auto save desktop', you will begin with a clean desktop each time you invoke Borland C++. Q: How do I view 32-bit registers when I compile my code with Options| Compiler|Advanced Code Generation|Instruction Set|80386 set? A: Add the appropriate 32-bit register psuedovariable to the Watch window. For example, if you were interested in the value of EAX, you'd add _EAX to the Watch window. C o m m a n d - L i n e C o m p i l e r ---------------------------------------------------------------------- Q. Why is Borland C++ not able to find any of my #include files? A. The compiler searches for include files in the Borland C++ Include Directories path. You specify this path with the -I option. The INSTALL program initially writes a configuration file (TURBOC.CFG) that sets this path to the directory where it copied all the Borland C++ *.h files. You may edit this file to change the default path, or create this file in your current working directory and place any relevant paths and other command line compiler options in it. A sample turboc.cfg file may contain the following: -ml -IC:\BC31\INCLUDE;C:\BC31\CLASSLIB\INCLUDE -LC:\BC31\LIB;C:\BC31\CLASSLIB\LIB Q. Why do I get the message: Linker Error: Unable to open input file 'C0x.OBJ' A. The linker searches for Borland C++ start-up and library files in the Borland C++ Library Directories path. You can specify this path with the -L option. If you allow BCC to invoke the linker, it will search the directories in the configuration file (TURBOC.CFG) written by the INSTALL program (see above). If you run TLINK, the configuration file is not read. TLINK does use the configuration file TLINK.CFG, so you can specify library paths in this file. Q. Why does the linker tell me that all the graphics library routines are undefined? A. BCC will not search the graphics library unless you tell it to. You should specify the graphics library on the command line. For example, to compile BGIDEMO, type BCC BGIDEMO.C GRAPHICS.LIB<Enter> Q. I run BCC.EXE and get the error message: Fatal: <filename>.def (<line #>): syntax error A. Check your DATA statement on line number # in <filename>.def for the correct code (that is, DATA PRELOAD). G e n e r a l I / O ---------------------------------------------------------------------- Q. The '\n' in cprintf() does not return the cursor to the beginning of the line. It only moves the cursor down one line. A. cprintf() interprets '\n' as a Line Feed. To force the cursor to the beginning of the line, manually insert a Carriage Return: cprintf("\n\r"); Q. How do I print to the printer from a Borland C++ program? A. Borland C++ uses a FILE pointer (stdprn) defined in the STDIO.H file. You do not need to open stdprn before using it: #include <stdio.h> int main(void) { fprintf(stdprn, "Hello, printer!\n"); } Note that if your printer is line-buffered, the output is flushed only after a '\n' is sent. Q. I am reading and writing binary files. My program is translating the Carriage Return (0x0D) and Line Feed (0x0A) characters. How do I prevent this from happening? A. Files opened in text mode will translate these characters for DOS. To read a file in binary mode, open it in binary mode. For example, #include <stdio.h> int main(void) { FILE *binary_fp; char buffer[100]; binary_fp = fopen("MYFILE.BIN", "rb"); fread(buffer, sizeof(char), 100, binary_fp); : } The default file mode is text. Q. Why don't printf() and puts() print text in color? A. Use the console I/O functions cprintf() and cputs() for color output. #include <conio.h> int main(void) { textcolor(BLUE); cprintf("I'm blue."); } Q. How do I print a long integer? A. Use the "%ld" format: long int l = 70000L; printf("%ld", l); Q. How do I print a long double? A. Use the "%Lf" format. long double ldbl = 1E500; printf("%Lf", ldbl); E x a m p l e P r o g r a m s ---------------------------------------------------------------------- Q. How do I compile and run the BGIDEMO program? A. 1. Make sure that the following Borland C++ files are in your current directory: BGIDEMO.C *.BGI *.CHR OR change the third parameter of the initgraph() function call to the full directory path to the location of the above files (using double backslashes). For example: initgraph(&gdriver, &gmode, "c:\\borlandc\\bgi"); 2. Run Borland C++. 3. Load BGIDEMO.C into the Editor by pressing F3, then typing BGIDEMO<Enter> 3. Go to the Run menu and choose the Run item. Q. How do I create a COM file? A. DOS versions 3.2 and earlier include an EXE2BIN utility that converts EXE files to COM files. Users who do not have EXE2BIN can use TLINK, the Borland C++ command-line linker, to create a COM file instead of an EXE file. Use the /t option. For example: BCC -mt -lt tiny will create TINY.COM instead of TINY.EXE. The -l switch passes the /t argument to the linker in this case. There are certain limitations in converting an EXE file to a COM file. These limitations are documented in the IBM Disk Operating System manual under EXE2BIN. Borland C++'s TINY model is compatible with the COM format, but programs that use Borland C++'s floating-point routines cannot be used in a TINY model application. Q: The following program compiles/links successfully in C but not in C++. Why? #include <stdlib.h> int compare(const int *one, const int *two) { if (*one > *two) return -1; else return 1; } int a[3] = { 50, 10, 20 }; void main() { qsort(a, 3, sizeof(a[0]), compare); } A: The fourth parameter to compare is the function pointer, and here's how it's declared in stdlib.h: void qsort (void *__base, size_t __nelem, size_t __width, int _Cdecl (*__fcmp)(const void *, const void *)); However, the above program WILL NOT compile in C++, because of the strong typing features of the C++ language. The compiler refuses to convert the void parameters in the declaration to __fcmp function to int parameters. However, because C++ permits casting of function pointers, you can fix the call to QSORT in C++ like this: qsort(a, 3, sizeof(a[0]), (int (*)(const void *,const void *))compare); By casting the COMPARE function to be of the same type as the declaration in stdlib.h, C++ will accept and compile it. Q: How can I allocate a doubly dimensioned array? A: You may use either malloc() with C or C++, or the new operator with C++: malloc(): to create a 2 by 3 character array int i; char** p; p = (char **) malloc(2); for (i=0; i<2; i++) p[i] = (char *) malloc(3); new: int j; char** q; q = new char* [2]; for (j=0; j<2; j++) q[j] = new char [3]; G r a p h i c s ---------------------------------------------------------------------- Q. Why do I get the error message: BGI Error: graphics not initialized (use 'initgraph') when I use a graphics function? My program has already called initgraph(). A. For some reason initgraph() failed. To find out why, check the return value of graphresult(). For example: #include <graphics.h> int main(void) { int gerr; /* graphics error */ int gdriver = DETECT, gmode; /* Initialize graphics using auto-detection and look for the .BGI and .CHR files in the C:\BORLANDC\BGI directory. */ initgraph(&gdriver, &gmode, "C:\\BORLANDC\\BGI"); if ((gerr = graphresult()) != grOk) { printf("Error : %s\n", grapherrormsg(gerr)); exit(1); } : } M a t h / F l o a t i n g P o i n t ---------------------------------------------------------------------- Q. Why do I get incorrect results from all the math library functions like cos(), tan() and atof()? A. You must #include <math.h> before you call any of the standard Borland C++ math functions. In general, Borland C++ assumes that a function that is not declared returns an int. In the case of math functions, they usually return a double. For example /* WRONG */ /* RIGHT */ #include <math.h> int main(void) int main(void) { { printf("%f", cos(0)); printf("%f", cos(0)); } } Q. How do I "trap" a floating-point error? A. See the signal() and matherr() functions in the Borland C++ Library Reference. The signal() function may be used to trap errors in the 80x87 or the 80x87 emulator. The matherr() function traps errors in the Math Library functions. L i n k e r E r r o r s ---------------------------------------------------------------------- Q. I am linking C functions with C++ functions. The linker reports that all of my C functions are undefined. Why? A. Linking C++ modules with C modules requires the use of a linkage specification. Prototypes for C functions within C++ modules must be in one of the following forms: extern "C" declaration extern "C" { declarations } For example, if a C module contains functions "char *SCopy(char*, char*);" and "void ClearScreen(void)", they must be declared in a C++ module in one of the following ways: extern "C" char *SCopy(char*, char*); extern "C" void ClearScreen(void); or extern "C" { char *SCopy(char*, char*) void ClearScreen(void); } For further examples, see the standard header files. For additional comment, see Common C++ Questions. Q. Why do I get the message: Linker Error: Unable to open input file 'C0x.OBJ' A. See the "Integrated Environment" section above. Q. Why do I get the message: Linker Error: Undefined symbol '_main' in module C0 A. Every C program must contain a function called main(). This is the first function executed in your program. The function name must be all in lower case. If your program does not have one, create one. If you are using multiple source files, the file that contains the function main() must be one of the files listed in the Project. Note that an underscore character '_' is prepended to all external Borland C++ symbols. Q. Why does the linker tell me that all the graphics library routines are undefined? A. See the "Integrated Environment" and "Command-line Compiler" sections above. Q. What is a 'Fixup overflow'? A. This usually means you are attempting to link object files that were not all compiled under the same memory model. See the listing of TLINK error messages in the Borland C++ Tools and Utilities Guide. Q. I am linking my own assembly language functions with Borland C++. The linker reports that all of my functions are undefined. A. Make sure that you have put an underbar character '_' in front of all assembly language function names to be called by Borland C++. Your assembly language program should be assembled with Case Sensitivity. If compiling as C++ (rather than C), see the "Common C++ Questions" section above which discusses the use of extern "C". Q: I am getting an error out of the linker "segment group exceeds 64K : _text". A: If you are using the BGIOBJ utility, the default segment into which the objects will be place is _text. You should try using BGIOBJ with the /f option to place the resultant objects into a separate segment. You will then need to use the functions registerfarbgidriver and registerfarbgifont to register the objects for the graphics system. See UTIL.DOC for instructions on using these functions. Q: I am attempting to link Turbo C 2.0 objects into my Borland C++ programs, but continually get unresolved external symbols at link time. A: The names of many of the "helper" functions have changed from what they were in Turbo C 2.0. If you are getting undefined symbols like _LXLSH and _FMUL, this is the problem you are running into. Your best solution is to get the source code to the old object modules and recompile with Borland C++. The only other possibility would be to extract the helper function objects from the Turbo C 2.0 libraries and link them into the Borland C++ program. Q: Why am I getting the error "printf: floating point formats not linked"? A: You probably have your libraries out of order on the tlink command line. Here's how to directly use tlink: tlink <options> <objs>,exe_name,map_name,<libs> <options>: The options are listed by simply typing TLINK at the command line. <objs>: The ordering of the obj's is critical. The first one must be c0x (where 'x' corresponds to: s,m,c,l,h depending on which memory model is being used). Then the list of the remaining object files go next. exe_name: This entry is optional. If a name is not specified, the comma MUST be supplied anyway. map_name: This entry is optional. If a name is not specified, the comma MUST be supplied anyway. <libs>: The ordering of the lib's is critical. Any user-supplied and/or third party libraries must be listed first. If the program is using any BGI routines, the graphics library must be next. Next comes the emu.lib (for emulation) or the fp87.lib (if you are exclusively planning to use the coprocessor). The mathx library comes next, where 'x' corresponds to the first letter of the memory model in use. Finally the cx.lib must be last in the list, where 'x' corresponds to the first letter of the memory model in use. For example, if you are using the large memory model and BGI routines, the tlink line might look like the following: tlink /v c0l myobj,,,mylib graphics emu mathl cl If the object file or library is not in the current directory, the complete pathname must be supplied. Frequently this causes the command line to exceed 128 characters, which will force the use of a linker response file (this is decribed in the User's Manual). Q. I'm porting an application that uses communal variables to C++. I've set up the compiler to recognize them, but I still get linker errors: Error: <name> defined in module <a> is duplicated in module <b> A. C++ doesn't support explicit COMDEFs; you must use static variables or switch to C. O t h e r Q u e s t i o n s ---------------------------------------------------------------------- Q. I get a "floating point formats not linked" message when I run my program. What can I do about it? A. Floating point formats (for scanf() and related functions) are not always linked, for savings in executable size. To force their inclusion, put the following somewhere in your source files: extern unsigned _floatconvert; #pragma extref _floatconvert Q. How do I change the stack size? A. The size of the stack of a Borland C++ program is determined at run time by the global variable _stklen. To change the size to, for example, 10,000 bytes, include the following line in your program: extern unsigned _stklen = 10000; This statement must not be inside any function definition. The default stack size is 4,096 bytes (4K), and you may increase the stack to 65519 (0xFFEF) or just under 64K in the compact, large, or huge memory models. Q. I'm getting a 'Stack Overflow!' message when I run my program. How can I work around this? A. If you are using the compact, large, of huge memory models, you may increase the stack size by following the procedure above. In the smaller memory models, your only option is to decrease the amount of stack space or near heap space used in your program. Stack overflows are usually caused by a large amount of local data or recursive functions. You can decrease the amount of stack space used in several ways: 1) By declaring your local variables static (see the BC++ Programmer's Guide for the effects of using the "static" keyword): int main(void) int main(void) { { char x[5000]; --> static char x[5000]; : : } } 2) By making your variables global rather than local: char x[5000]; //global allocation above main() int main(void) { : } 3) Or by allocating your variables dynamically off the far heap: #include <alloc.h> int main(void) { char far* x; x = (char far*)farmalloc(5000); //dynamic allocation // or in the case of C++ you can use the new operator // x = new char[5000]; : } Q. My program comes up with the message 'Null pointer assignment' after it terminates. What does this mean? A. Before a small-data model Borland C++ program returns to DOS, it will check to see if the beginning of its data segment has been corrupted. This message is to warn you that you have used uninitialized pointers or that your program has corrupted memory in some other way. Q. Why are .EXE files generated by BC.EXE larger than those generated by BCC.EXE? A. In the default configuration, BC.EXE includes debugging information in the .EXE files that it creates, and BCC.EXE does not. If you don't want to produce this debugging information, you can shut it off in the Integrated Development Environment by selecting Alt-O|B|N. Q. Why do I get "declaration syntax error" messages on dos.h? A. You have set the "ANSI keywords only" option ON. Keep this option OFF when using any keywords specific to Borland C++. See the Borland C++ Programmer's Guide for a list of keywords. Q. I get errors when compiling the windows.h header file. Why? A. Be sure that you have "Borland C++" selected as your keywords option. This option can be toggled under Options | Compiler | Source. Q. I have a working program that dynamically allocates memory using malloc() or calloc() in small data models (tiny, small, and medium). When I compile this program in large data models (compact, large, and huge), my program hangs. A. Make sure that you have #include <alloc.h> in your program. Q. I am linking my own assembly language functions with Borland C++. But the linker reports that all of my functions are undefined. A. See answer above in the "Linker" section. Q. My far pointers "wrap around" when they are incremented over 64K. How do I reference a data object that is greater than 64K? A. Use huge pointers. Q. How do I interface Borland C++ routines to a Turbo Pascal program? A. See the example programs CPASDEMO.PAS and CPASDEMO.C. Q. How do I get Clipper to link with Borland C++? A. If you are having trouble, contact Nantucket Technical Support. Q. I'm trying to build an app based on one of Borland's libraries (ObjectWindows, Turbo Vision, the container classes in the CLASSLIB directory, or the Runtime Library), and I get linker errors, or it won't run right. What's going wrong? A. You may be using a switch that affects linkage in your files, that was not used when the library itself was compiled, or you need to change the library in question. Here are some examples: - If you use far vtables (-Vf or Options|Compiler|C++|Far virtual tables) to compile a file you developed which includes iostream.h, it won't build correctly until you rebuild the iostream library with the same option. - If you use word alignment (-a or Options|Compiler|Code Generation|Word alignment) in building a Turbo Vision application, you must build the Turbo Vision library from source with the same option. - If you opt to use the templates implementation of the container class library to build ObjectWindows applications, you must rebuild the necessary ObjectWindows libraries from source using the templates implementation of the class library (the BIDxxxx.LIB files.) Q. I got a "bad call to intrinsic function" message when attempting to compile one of my source files. What does this mean? A. This message appeared because you tried to use an intrinsic function in a small model DLL. Either avoid using intrinsic functions in your DLL (see Appendix A of the User's Guide), or turn off the -Oi and -O2 switches (Options|Compiler|Optimizations| inline intrinsic or |Fastest Code). Q: I open up a file in append mode, and append some data to the end of the file. When I look at the data in an ascii editor, I can't see the appended data. Why? A: The data is being appended after the End-of-File mark, and the ascii editor is not displaying the data after the EOF mark. To eliminate the EOF mark: 1) Get the file length with the filelength() function: FILE *file_pointer = fopen( "file.nam","a" ); long length = filelength( fileno( file_pointer )); 2) Use the chsize() function to change the file length to the current length-1: chsize( fileno( file_pointer ), (length -1)); 3) Then write your appended data to the file. Q: I run my program, allocate some memory, and check the amount of memory available with coreleft(). Then I free some memory and call coreleft() again. It reports the same number. Why? A: Coreleft does NOT return the amount of memory available. It returns the total memory available above the highest block allocated. It does NOT return any amount of memory available in "holes" below the highest allocated block.