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/***********************************************************************/ TURBO DEBUGGER 2.0 COMMON QUESTIONS AND ANSWERS ----------------------------------------------- Below is a list of the most commonly asked questions about Turbo Debugger. Following this list is an explanation of some of the new mouse features in Turbo Debugger 2.0. 1. How does TD handle screen output for graphics- and text-based programs? Turbo Debugger has a number of strategies that it can use to control how and when the screen gets refreshed. If you are debugging a program that uses a graphics display mode, if you want to use Borland pop-up utilities such as SideKick and SideKick Plus while inside Turbo Debugger, or if you want to run programs from Turbo Debugger's DOS Shell that write directly to video memory, you should review the following tips. The default screen-updating mode is "Flip"; this means that Turbo Debugger uses an alternate video display page on adapters that support multiple display pages. This results in fast screen-swapping between Turbo Debugger and your program, but it also can interfere with the operation of pop-up utilities and graphics programs. Pop-up utilities may not appear on the screen, even though they are active and processing your keystrokes. You must select "Swap" mode for display updating in order for these programs to work properly. Use Turbo Debugger's -ds command-line option to do this, or use the TDINST utility to permanently set this mode. "Swap" mode makes screen updating slower, but it makes sure that Turbo Debugger's screen does not interfere with either your program's or any other program's display. You may also need to use "Swap" when you use the DOS Shell command or run an editor from within TD. Most programs expect to run on video page 0, and do not check to see what the current video page is. TD's DOS Shell and any editors that TD runs in "Flip" mode do not run from video page 0, and the programs may appear to hang, even though you will be able to type in keystrokes normally. If this happens, use the -ds command-line option when you run TD or reinstall TD to use "Swap" instead of "Flip." If you are debugging a graphics mode application, you must specify the -ds command-line option ("Swap" contents) and you may want to use Turbo Debugger's -vg command-line option (Graphics Save). This causes additional memory to be set aside for saving the entire graphics image your program produces. If you don't use this option, a "red cloud" may appear on your program's screen. These options can also be set permanently by using the TDINST program. The Graphics Save option takes an additional 8K of memory and slows screen-swapping. If you are running a graphics program that changes the EGA palette, make sure you use the -vp command-line option to save the palette. 2. Can Turbo Debugger execute other programs while you are still using the debugger? The DOS Shell and Edit commands in the Module and File windows can swap the program you are debugging to disk in order to make room to run DOS or your editor. The default amount of memory to swap is 128K. You can use TDINST to set a different amount if that's not enough memory to run your editor or other programs. Setting the swap size to 0K tells Turbo Debugger to swap the entire user program to disk before running the DOS command processor. Only your program gets swapped to disk; Turbo Debugger remains in memory. 3. How can I break out of a program even though interrupts are disabled? If you have an 80386-chip-based computer and are using TD386, option -B allows break even when interrupts are disabled. For example, this option enables a break from CLI JMP $ 4. Why can't I press Ctrl-Break to get out of a program running on a remote machine? The program running in the remote machine has taken control of Interrupt 1B (Ctrl-Break). TDREMOTE does not take back control of Interrupt 1B until you stop execution of the running program on the debugger side by completing the program or pressing Ctrl-F2 (Program Reset). 5. What are some of the syntactic and parsing differences between Turbo Debugger's built-in assembler and the standalone Turbo Assembler? A discussion follows this short example program: .model small .data abc struc mem1 dd ? mem2 db ? mem3 db " " abc ends align 16 a abc <1,2,"xyz"> msg1 db "testing 1 2 3", 0 msg2 db "hello world", 0 nmptr dw msg1 fmptr dd msg1,msg2 nfmptr dw fmptr xx dw seg a .code push cs pop ds mov bx,offset a mov bx,nmptr les si,fmptr mov ah,4ch int 21h end The assembler expression parser does not accept all legal TASM instruction operands. This allows TD's assembler expressions to be more general and allows multiple levels of memory-referencing, more like that used in C and Pascal. However, there are a few constructs that you may be used to that you'll have to specify differently for the TD assembler expression parser to accept them: a. Size overrides should always appear inside the brackets; PTR is optional after the size. Also, when referring to a structure, you must use the name of the struc, not the name of the variable: OK: [byte ptr bx] [dword si] [abc bx] BAD: byte ptr[bx] [struc abc bx] [a bx] b. You must specify a structure name when accessing the members of a structure via a register pointer: OK: [abc ptr bx].mem1 [abc bx].mem3 + 1 BAD: [bx].mem1 c. You can't use multiple instances of [] unless they are adjacent, and you can only follow an [] expression with a dot and a structure member name or another [] expression: OK: 4[bx][si] [abc bx].mem2 BAD: [bx]4[si] [bx]+4 d. If you use a register as part of a memory expression and you don't specify a size, WORD is assumed: [bx] is the same as [word bx] e. You can use any register you want between [], not just the combinations of BX, BP, SI, and DI allowed in instruction operands: OK: [ax+bx] [bx+sp] f. You can use multiple levels of [] to follow chains of pointers: OK: [byte [[nfmptr]+4]] g. Be careful using registers to access memory locations. You may get unexpected results if your segment registers are not set up properly. If you don't explicitly specify a segment register, Turbo Debugger uses the DS register to reference memory. h. When you do specify a segment register, make sure you follow the same rule for size overrides: put it INSIDE the brackets: OK: [byte es:di] [es:fmptr] BAD: es:[byte di] i. Use the OFFSET operator to get the address of a variable or structure. Turbo Debugger automatically supplies the [] around a variable name if you just type the variable name alone: a contents of structure a [a] contents of structure a offset a address of structure a j. You can use the type overrides and the format control count to examine any area of memory displayed as you wish: [byte es:bx],10 10 bytes pointed to by es:bx [dword ds:si],4 4 dwords pointed to by ds:si This is very useful when specifying watch expressions. k. Sometimes you use a word memory location or register to point to a paragraph in memory that contains a data structure. Access the structure with expressions like [abc [xx]:0].mem1 [abc es:0].mem3 6. Are there any syntactic or parsing differences between Turbo Debugger's C expression evaluation and Turbo C++'s? You can't pass constant-string arguments when evaluating functions. OK: myfunc(123) myfunc(string_variable) BAD: myfunc("constant") 7. Are there any syntactic or parsing differences between Turbo Debugger's Pascal expression evaluation and Turbo Pascal's? a. Turbo Debugger does not support expressions for set constructors: OK: [4..7] BAD: [myvar1..myvar2] [3+4..7+8] b. You can't pass constant-string arguments when evaluating functions or procedures. OK: MyFunc(123) MyFunc(StringVariable) BAD: MyFunc('Constant') MyFunc(StringConstant), where StringConstant is defined with a "const" declaration and is not a typed constant. c. You can't evaluate procedures or functions that have structure VALUE parameters. You can evaluate procedures or functions that have structure VARIABLE parameters, though. 8. What should I be aware of when I am debugging multilanguage programs with Turbo Debugger? Turbo Debugger's default source language is "Source," which means it chooses the expression language based on the current source module. This can cause some confusion if your program has source modules written in different languages (like C and assembler). Since you are actually entering a language expression any time Turbo Debugger prompts you for a value or an address, this can cause some unexpected results: a. Even if you are in a CPU window or a Dump window, you must still enter addresses in the source language, despite the fact that the window is displaying in hex. For example, to display the contents of memory address 1234:5678, you must type one of the following expressions, depending on your current source language: C 0x1234:0x5678 Pascal $1234:$5678 Assembler 1234:5678 b. When your current language is assembler, you must be careful when entering hex numbers, since they are interpreted EXACTLY as they would be in an assembler source file. This means that if you want to enter a number that starts with one of the hex digits A - F, you must first precede the letter with a 0 so Turbo Debugger knows you are entering a number. Likewise, if your number ends in B or D (indicating a binary or decimal number), you must add an H to indicate that you really want a hex number: OK: 0aaaa 123dh 89abh BAD: aaaa 123d 89ab 9. Why does the text "Cannot be changed" come up when I do an assignment in the Data/Evaluate/Modify "New value" pane? If you use the Data/Evaluate/Modify command (Ctrl-F4) to change a variable by direct assignment, the "New value" pane will say "Cannot be changed." This doesn't mean the assignment didn't take effect. What it does mean is that the assignment expression as a whole is not a memory-referencing expression whose value you can change by moving to the bottom pane. Here are some examples of direct assignment expressions: C x = 4 Pascal ratio := 1.234 Assembler wval = 4 shl 2 If you had typed just "x," "ratio," or "wval" into the top pane, then you would be able to move to the bottom pane and enter a new value. The direct assignment method using the "=" or ":=" assignment operator is quicker and more convenient if you don't care about examining the value of the variable before modifying it. 10. Why does an inspector occasionally display question marks when inspecting a Turbo C++ register variable? If you inspect a register variable that is not in the current scope, you'll see ???? for the value. A register variable only displays a value if the register is in your current scope (valid at the current location in your program). 11. What is the most likely reason for Turbo Debugger to hang when starting up on a PC-compatible computer? If your computer is a Tandy 1000A, IBM PC Convertible, or NEC MultiSpeed, or if TD hangs when loading on your system, run TDINST and change the item in the Options\Miscellaneous menu so that NMI Intercept is not set. Some computers use the NMI (Non-Maskable Interrupt) in ways that conflict with TD, so you must disable TD's use of this interrupt in order to run the program. Also, if you are using a 80386-based machine and have the SuperKey utility loaded, be careful not to press a key when TD386 is loading, since SuperKey may capture the keystroke and cause unexpected results. 12. What could happen when global breakpoints are set on local variables? When you set global breakpoints using local variables, make sure the breakpoints are cleared before you exit the procedure or function that the variables are defined in. The best way to do this is to put a breakpoint on the last line of the procedure or function. If you do not clear the breakpoints, your program will break unexpectedly and may even hang on some machines because the breakpoints are being set in memory that is not currently being used by the procedure or function. 13. How can I save options set in TDINST to TD286.EXE? If you have a configuration file (tdconfig.td) already made for TD.EXE, TD286.EXE will automatically use this configuration file. You can save a configuration made in TDINST to TD286.EXE directly if you state this on the command line. For instance, TDINST TD286.EXE When you want to save this configuration in TDINST, just select Save\Modify td.exe. 14. Why is execution is slower when tracing (F7) than when stepping (F8) through my programs? Turbo Debugger now has the capability for reverse execution. This means that when you are tracing through your program TD is saving all the information about the source line you just traced over. If you want faster execution you can (F8) step over the instruction or toggle the Full History option to 'No' in the Execution History window. * Common questions about using mouse support in Turbo Debugger 2.0. Turbo Debugger 2.0 now provides mouse support that allows you to manipulate elements within the user interface. The following lists mouse-related terms to help you become accustomed to using Turbo Debugger's mouse support. If you have a mouse driver installed by default, Turbo Debugger and TDINST will try to use your mouse. If you do not wish to use your mouse during a debugging session, you can use the command-line switch '-p-' to turn the mouse off. This can also be set in TDINST in the Options\Input & prompting dialog box. Clicking and Dragging Most mice provide two or three buttons that allow for various functions inside an application. In Turbo Debugger you can, among other things, use the left mouse button to select options, move items around on the screen, and set breakpoints. The right mouse button has some of the same functionality as the left mouse button, but you can also open local menus within windows using this button. Double clicking the mouse on options in a list will select that item. For instance, in the File|Open dialog box you can highlight a file by clicking the mouse once on the file name. You can load the file by double clicking on the name. The commands shown at the bottom of the screen, like F1-Help, can also be selected using the mouse. Dragging the mouse consists of depressing the mouse button and moving the mouse cursor to a new location. Mouse drivers Your mouse driver is the application that you install to make your mouse active inside Turbo Debugger and other programs. Most mouse drivers will work with Turbo Debugger but may have to be updated to a newer version if you are having problems using an older version. If you have problems with the mouse once you have loaded TD or TDINST, you might try using the Display Swap option that can be specified either in TDINST or on the command-line with the -ds switch. Consult your mouse manual to ensure proper use of the mouse and its driver. Early versions of mouse drivers don't support screen display modes larger than 80 columns by 24 lines. As a result, your mouse driver might not work correctly when you use Turbo Debugger's enhanced display modes EGA 80x43, VGA 80x50, or EGA/VGA graphics modes. Scroll bars Scroll bars, located at the right and bottom of all windows, allow you to specify a new position within a window by clicking the mouse on an indicator on the scroll bar and dragging it to a new location. Arrows located at either end of a scroll bar also allow you to scroll through the window when you click and hold the mouse on the arrow heads. Icons An icon is a window that has been shrunk down to a smaller representation of the window. These icons can be moved with the mouse by clicking on the border of the icon and dragging it to a new location. Arrows located at the top right of each viewer allow you to zoom and unzoom the viewer when you click the mouse on the arrows. When you iconize a window, it is stored at the bottom right side of the screen. If any other windows are currently showing at this position the icon will be put behind that window. The global Window menu allows you to pick from a list of currently open windows. This will also take you to an iconized window. Resize box The resize box is located at the bottom right of each window. You can click the mouse on the box and drag the mouse to resize the viewer. Using the mouse you can also resize the viewer by clicking the mouse on the right border of any window and dragging it. Windows and inspectors can be moved using the mouse by clicking on the top and left borders and dragging the window to a new location. Double clicking the mouse on the top border is a short cut to zoom/unzoom the current window. Dialog boxes Dialog boxes allow you to select options, specify files to save or restore, and choose different settings. You can click the mouse to make prompts or panes within the dialog box active. Help for the current dialog box is available in by clicking on the Help button in the box. Close buttons A Close button is located at the top left of all windows and dialog boxes. It lets you close the current window or dialog box when you click the mouse on it. If you have entered any information into a dialog box and you use the Close button to close it, the settings you specified in the dialog box will not be saved. This is the same as clicking the mouse on the Cancel button inside a dialog box. You must select the OK button in dialog boxes in order to save these settings.