HISTORY.TXT

 History

    0.95e [11 January 2003]  Fixed a bug in the assember.
    0.95f [10 September 2003]  Converted to NASM; fixed some syntax
       incompatibilities.
    0.98 [27 October 2003]  Added EMS commands and copyright conditions.

    ------- changes below done by japheth

    0.99 [27 Septemb 2006]
       - bugfix: IF was not displayed correctly.
       - FS and GS registers displayed if cpu is 80386+.
       - RX displays the standard 32bit registers.
       - R register [value] understands the standard 32bit registers.
    0.99a [28 Septemb 2006] 
       - bugfix: JECXZ had wrong prefix (66h, should be 67h).
       - A and D understand the 32bit opcodes LOOP(Z|NZ|E|NE)D.
    0.99b [29 Septemb 2006]
       - L and W now work with FAT32 drives.
    0.99c [29 Septemb 2006]
       - RX changed. Now it toggles 16/32 bit register dump.
       - RN displays floating point register status.
    0.99d [2 October 2006]
       - bugfix: RN displayed error-pointer registers wrong.
    0.99e [12 October 2006]
       - XR command added to reallocate EMS handle.
       - XA command allows to allocate zero pages on EMS 4.0.
       - TM [0|1] added to be able to switch T to the ms-dos debug
         compatible behaviour (that is, T jumps into 'INT xx').
    0.99f [17 October 2006]
       - debug's EMS functions may work even with a "hidden" EMM.
       - bugfix: display of mappable pages didn't account for amount of
         these pages == 0.
    0.99g [25 October 2006]
       - bugfix: U was unable to recognise [ESP] related memory operands
         (i.e. mov eax,[esp]).
    0.99h [7 November 2006]
       - bugfix: R trying to display content of effective address has
         caused a GPF in v86-mode if this address was FFFFh of FFFDh.
       - IW, ID, OW and OD implemented.
    0.99i [14 November 2006]
       - bugfix: a child PSP was created but not terminated, causing files
         not to be closed. It became obvious if stdin and/or stdout were
         redirected to files ("C:\>DEBUG >yyy")
    0.99j [16 November 2006]
       - bugfix: using T if current instruction is an INT xx (and trace
         mode == 0) stopped debuggee one instruction *after* the INT (due
         to a x86 design weakness).
       - bugfix: the 0.99i bugfix had some problems on FreeDOS.
    1.00 [25 November 2006]
       - bugfix: debuggee's psp was saved after program load only, but
          this has to be done every time the debugger regains control.
       - There is now a DPMI aware version of debug, DebugX, createable
         from the source.
       - bugfix in disassembler: RETF did not have a corresponding RETFD
         entry (to switch with prefix 66h)
    1.01 [26 November 2006]
       - bugfix: MC2 didn't work.
       - Register names can be used anywhere where a number is expected
         as input.
    1.02 [29 November 2006]
       - bugfix: 'I d' and 'O d' didn't work because the parser assumed
         ID and OD commands.
       - DebugX bugfix: T= and G= didn't work in protected-mode.
       - bugfix: loading a file at another location than cs:100h was not
         supported in versions 0.99 - 1.01.
       - Debugger can be loaded high.
    1.03 [1 February 2007]
       - Debug bugfix: previous version of DEBUG.COM did not reliably reset
         "auto-reset" breakpoints (used for processing INTs).
       - DebugX: DI now works in real-mode as well.
       - DM command added.
    1.04 [2 March 2007]
       - making single-step through the DOS kernel possible.
    1.05 [1 April 2007] 
       - program exit code displayed.
       - DM displays the PSP "name".
       - autorepeat for D, DX, T and U added.
       - DebugX: DX added.
    1.06 [21 May 2007] 
       - bugfix: SMSW/LMSW in assembler didn't accept a 32bit operand.
       - bugfix: OW/OD didn't accept the value parameter.
       - key '-' supported in E command to step backward.
    1.07 [3 November 2007]
       - bugfix: entering ranges with upper bound was refused.
       - DebugX bugfix: if help cmd waited for a keypress, it displayed
         garbage if cpu was in protected-mode and CWSDPMI was used.
       - Tracing into an INT (TM 1) now works if interrupt vector points
         to ROM code.
    1.08 [23 November 2007]
       - bugfix: segment prefix was lost for mnemonics without arguments
         (patch by Oleg O. Chukaev).
    1.09 [30 December 2007]
       - DebugX: several bugfixes for A and U handling 32bit code segments.
       - bugfix: U split lines if instruction size exceeded 6.
       - bugfix: M didn't work with "upper bound" ranges.
       - DebugX change: the 32-bit variant of the LOOPx instruction was
         indicated by displaying ECX as first operand. Now a suffix (W/D)
         is attached to the opcode instead.
       - bugfix: A didn't choose the short (=signed) form of arith
         instructions (adc, add, ...) if E/AX was first operand.
    1.10 [25 January 2008]
       - DebugX: to intercept DPMI initial switches to protected-mode,
         int 2Fh is now hooked later. This allows to debug applications
         which install their own DPMI host during initialization.
       - DebugX: DL understands an optional "count" argument.
    1.11 [6 February 2008]
       - bugfix: debugger lost debuggee's HiWord(EFL) in real-mode.
       - bugfix: if debuggee set CR0 AM bit and EFL AC flag, an
         exception 11h occured in the debugger.
       - DebugX bugfix: G command was unable to set/restore breakpoints if
         HiWord(EIP) wasn't clear.
       - DebugX bugfix: U ignored HiWord of argument's offset part.
       - DebugX bugfix: E ignored HiWord of argument's offset part.
       - DebugX bugfix: M didn't accept first argument's offset > FFFF.
       - DebugX bugfix: running in NTVDM and pressing Ctrl-C while debuggee
         is in protected-mode no longer drops to real-mode.
       - DebugX: RN now renders floating point register content properly
         (Debug.com still just displays raw hex format for size reasons).
       - DebugX: DI got an optional 'count' parameter.
       - DebugX: D default segment part is checked if it is valid in pmode
         and changed to value of client's DS if no.
    1.12 [14 February 2008]
       - bugfix: length 0 in range wasn't interpreted as 64 kB.
       - DebugX bugfix: E in prompt mode didn't work with 32bit offsets.
       - DebugX bugfix: L and W didn't work with buffer offset >= 10000h.
       - DebugX bugfix: Q while debuggee was in pmode caused a GPF if
         HiWord(EIP) or HiWord(ESP) wasn't zero.
       - DebugX: DI additionally displays DPMI exception vectors.
       - DebugX: when running in NTVDM, DEBXXVDD.DLL will be loaded, which
         will make L and W work with sectors on this platform.
       - DebugX: DM now works in protected-mode as well.
       - now all commands are described in DEBUG.TXT.
    1.13 [27 February 2008]
       - Debug bugfix: L and W with sectors worked for DebugX only in v1.12.
    1.14 [12 January 2009]
       - DebugX bugfix: 'D ip' caused a syntax error.
       - DebugX bugfix: if debugger stepped into an INT in protected-mode,
         the carry flag was cleared.
       - H improved.
       - source converted to Masm syntax.
       - samples in Masm syntax added.
    1.15 [12 April 2009]
       - bugfix: in v1.04 - v1.14, restoring debuggee's interrupt vectors
         23+24 caused a memory corruption (8 bytes) due to a wrong segment
         register value.
    1.16 [20 April 2009]
       - bugfix: 'mnc' command was rejected. Syntax changed to 'mc n'.
       - bugfix: in v1.14-1.15, 'g' didn't reliably detect whether a bp was
         external.
       - bugfix: 'g' command could get confused by opcode CD 03.
       - DebugX bugfix: 'a' command ignored hiword of current offset in
         32bit segments.
       - DebugX bugfix: when debuggee was in protected-mode and then
         terminated during execution of 'p' or 't' command, the try to
         restore an internal bp may have caused memory corruption.
    1.17 [28 April 2009]
       - bugfix: R <32bit register> <new value> didn't work in v1.16.
       - bugfix: DPMICL16.ASM wasn't a sample for a 16bit DPMI client.
       - bugfix: under some conditions 'm' was silently rejected.
    1.18 [18 May 2009]
       - DebugX bugfix: RN required a 80386 cpu.
       - DebugX bugfix: RN always assumed that current mode is real-mode.
         However, the layout of FSAVE/FRSTOR differs for protected-mode.
       - bugfix: 'A' command didn't accept a semi-colon right after the
         mnemonic (example: clc;)
       - if cpu is 80386+, the 32bit version of FSAVE/FRSTOR is used now,
         which improves display of the FPU status.
       - 'r' command: EFL added to 386 register display.
       - for FLDENV, FSTENV, FSAVE and FRSTOR, 16/32 bits variants with
         suffixes W/D were added: FLDENVW/FLDENVD, FSTENVW/FSTENVD, ...
       - DebugX: 'rm' command added to display MMX registers.
       - DebugX: instructions MOVD, MOVQ, EMMS added to assembler and 
         disassembler.
       - layout of tables in debugtbl.inc modified to make them use
         symbolic constants and addresses. This allows to modify this
         file directly.
    1.19 [18 October 2010]
       - DebugX bugfix: breakpoints set with G couldn't be reset if the
         debuggee's current mode (real-mode / protected-mode) did change
         inside G.
    1.20 [20 October 2010]
       - DebugX: bugfix of v1.19 modified to navigate around a couple of
         CWSDPMI bugs.
    1.21 [29 October 2010]
       - DebugX bugfix: internal breakpoints set by T or P still had
         problems if a mode switch occured.
    1.22 [11 November 2010]
       - DebugX bugfix: wrong value of PSP displayed with DM if debuggee
         was halted in real-mode after initial switch to protected-mode.
       - DebugX bugfix: line assembler didn't handle PC-relative addresses 
         correctly if source or destination was > 0xFFFF.
    1.23 [15 April 2011]
       - bugfix 'a' command: entering a segment register name may have
         "terminated" debug unexpectedly.
       - bugfix: XS always assumed 255 EMS handles. Now it tries to get
         the number of EMS handles by using EMS4 function 5402h.
       - 'a' command: the segment prefix syntax as it is implemented by
         MS debug is accepted now ( which is a segment register followed
         by a colon ).
       - file makex.bat added.
    1.24 [4 July 2011]
       - bugfix: line assembler didn't encode 32-bit addressing with SIB
         byte correctly in v1.23.
       - debug script DPMICL16.SCR added.
    1.25 [8 August 2011]
       - 2 variants (F & G) added to makex.bat
    1.26 [16.1.2020]
       - bugfix 'a' cmd: 'MOV sreg, mem' and 'MOV mem, sreg' needed a size.
       - bugfix 'xm' cmd: logical page displayed was 2 digits only.
       - DebugX: interrupt and exception 07 intercepted.
       - DebugX: int 2Fh was "rehooked" if protected-mode debuggee caused a
         break in real-mode.
       - bugfix 'xs' cmd: no of pages of just the first handle was displayed,
         and the handle total was not correct.
    1.27 [8.11.2020]
       - added new variant DebugXU.COM. This version does not use int 15h, 
         ah=87h inside the DX command, thus avoiding to disable a possibly
         active unreal mode. The catch is that this version's DX command won't
         work in V86 mode.
       - disassembler handles operand size prefix for one-byte "push <imm>" 
         opcodes correctly. OTOH, for 2/4 byte "push <imm>" opcodes, the 
         disassembler no longer displays the operand size, since the size
         is obvious.
       - if InDOS flag is set, a '!' is preceding the debugger prompt.
       - BIOS used when waiting for a key in help msg display.
       - 'e' cmd uses BIOS if InDOS flag set.
    1.28 [10.3.2022]
       - DebugX bugfix e-cmd: used wrong offset when reading from 32-bit 
         segments.
       - DebugX bugfix d-cmd: hiword(ecx) wasn't cleared, resulting in a
         "default" length for 32-bit segment dump > 128.
       - DebugX bugfix g/t/p-cmd: if debuggee is stopped in protected-mode,
         saved stack at debugger's PSP:[2Eh] must not be "adjusted".
       - added debug displays (created if _DEBUG is defined)
       - DebugX: int 2Fh, ax=1686h to detect mode no longer used - this makes 
         interrupt 2Fh traceable.
       - bugfix 'e' cmd: don't stop input after byte '0d' has been entered.
    1.29 [6.5.2022]
       - DebugX bugfix c/d/e/m/s-cmd: an offset beyond 0ffffh was rejected if
         the segment descriptor's 'default-size' flag wasn't set.
       - DebugX bugfix e-cmd interactive mode: offset increment and decrement
         was always 16-bit only.
       - DebugX bugfix e-cmd non-interactive mode: skip test for 16-bit wrap 
         if segment is larger than 64 kB.
       - regression in debugxg. v1.28: the driver version crashed when it 
         became active because the new mode detection code always returned 
         status "in protected-mode".
       - regression in DebugX, v1.28: on rare conditions, the debugger used
         a wrong pointer (debuggee's SS:ESP instead of SS:SP) to clear TF on 
         the debuggee's stack.
       - clear TF if child process is to be canceled ( else a "memory corrupt"
         error may appear in DOS ).
       - DebugX, e-cmd: don't use int 21h, ah=8 directly in interactive mode.
       - volume unlock: removed setting registers dx/bh, since useless.
       - DebugX: behavior of q-cmd changed if debuggee is in protected-mode.
         Entering 'q' at the '#' prompt will (hopefully) make the debuggee
         exit protected-mode and debugx's real-mode prompt '-' should appear.
       - DebugX: new command variant 'qq' to terminate a DPMI client that has
         intercepted protected-mode int 21h and refuses to quit.
       - another variant - DebugXV - may be created. It allows to flip video
         screen between debugger and debuggee.
    2.00 [5.12.2022]
       - fixed: routine int21ah9 did use DOS, even if InDos flag was set.
       - fixed: reading stdin from file wasn't fully MS Debug compatible.
       - fixed: correctly handle tabs if output is via BIOS.
       - fixed L/W cmds: error msg for read/write drive was crumbled since
         v1.18.
       - ensured the correct video page is used when debugger has to display
         something if the InDOS flag is set AND page swapping is active.
       - mktables.c fix: didn't generate a valid debugtbl.inc.
       - added a "boot" variant of the debugger - DebugB.bin.
       - added a ring0 (PL0) variant of the debugger - DebugR.bin.
       - DI cmd may be activated for standard Debug.com.
       - DebugX fix: restore hooked protected-mode interrupts when client
         terminates.
       - DebugX fix: c & s cmds finally work with 32-bit offsets.
       - DebugX fix, e cmd: generate a GPF if no data alias can be found for
         a code segment ( instead of silently skip the write ).
       - DebugX fix: disassembly of [CS:IP] in register dump may have caused
         a GPF in debugger if the memory address was beyond seg limit - 3.
       - DebugX fix, g cmd: if multiple breakpoints with different segment
         parts were set in protected-mode, hazardous writes may have happened.
       - DebugX fix, m cmd: '$' qualifier for the source address segment was
         rejected.
       - DebugX fix, c & m cmds: if both source and destination segment parts
         were readonly, the scratch selector was used twice.
       - DebugX: added cmdline option /2.
       - DebugX: hook into protected-mode debug interface Int 41h and make
         debugger visible there.
       - DebugX, a & e cmd: usage of scratch descriptor for readonly segments
         now hidden, so the displayed address' segment part isn't changed.
       - DebugX, a & d cmd: default segments are no longer automatically
         converted to selectors during initial switch to protected-mode.
       - DebugX: exceptions 0dh/0eh are set/reset on debugger entry/exit.
       - DebugXV: stop in debugger if SYSREQ is pressed.
    2.01 [7.1.2024]
       - fixed: addr/opsize prefixes "toggle", but just once.
       - fixed: debug exceptions occuring inside debug are now ignored.
       - fixed dm cmd: invalid last mcb no longer displayed.
       - added a ring0 (PL0) variant for long mode - DebugRL.bin.
       - DebugR(L): added bp & bc cmds.
    2.02 [11.2.2024]
       - fixed S cmd: position display was corrupted in v2.00-v2.01.
    2.50 [1.6.2024]
       - DebugR fix: debugger assumed a 32-bit ring0 SS register on init;
         if this wasn't true, a crash may have occured.
       - fix r cmd: the disassembler tried to show memory contents for the LEA
         instruction - this may have caused a GPF.
       - DebugX fix e cmd, prompt mode: segment part changed to scratch sel
         after first line in protected-mode if it was a r/o selector.
       - fix e cmd, prompt mode: '-' after byte input did skip that input.
       - fix u cmd: address size prefix 67h for string instructions.
       - fix n cmd: names > 128 chars may have modified debug's code seg.
       - fix l & q cmd: failure of debuggee termination was ignored and the
         command continued, leaving an orphaned debuggee in memory.
       - fix a cmd: regression since v1.18: "call/jmp [mem_ref]" without a size
         given did default to a far call/jmp.
       - fix u cmd: operand size prefix 66h for 8/16/32-bit relative jmps.
       - fix a cmd: NEar qualifier was accepted/ignored for immediate far
         jmp/call.
       - u cmd, call far [mem]: qualifiers "FAR"/"DWORD FAR" changed to
         "FAR16"/"FAR32".
       - DebugR(L): Q cmd may be activated for this variant.
       - cmds bp/bc accept up to 4 permanent breakpoints.
       - cmds bp/bc implemented, but inactive for Debug & DebugX; activated in
         DebugXg & DebugXv variants.
       - G/T/P cmds: if possible, 386 debug registers will be used to set
         temporary breakpoints. Active for DebugX, DebugR(L).
       - new cmdline options /s and /v for debugger variants that may use
         hardware breakpoints ( option /v not for DebugR(L) variant ).
       - g cmd: if a breakpoint cannot be written, the cmd is aborted.
       - Debug & DebugX may now be created in .exe file format.
       - mktables.c: creates ASMTBL.INC/DISTBL.INC instead of DEBUGTBL.INC.
       - cmds a, u: instruction RDTSC added.
       - another variant of DebugR - DebugRV, with support for V86 mode.
       - DebugR(V) dt cmd: optionally displays trapped ports.
       - DebugRV di cmd: displays IDT & IVT vectors.
       - DebugR rn cmd: won't run cmd if CR0.EM is set.