docs/source/debugger/general.rst
.. _debugger-general-list:
:ref:debugger-command-help
displays built-in help in the console
:ref:debugger-command-do
evaluates the given expression
:ref:debugger-command-symlist
lists registered symbols
:ref:debugger-command-softreset
executes a soft reset
:ref:debugger-command-hardreset
executes a hard reset
:ref:debugger-command-print
prints one or more <item>s to the console
:ref:debugger-command-printf
prints one or more <item>s to the console using <format>
:ref:debugger-command-logerror
outputs one or more <item>s to the error.log
:ref:debugger-command-tracelog
outputs one or more <item>s to the trace file using <format>
:ref:debugger-command-tracesym
outputs one or more <item>s to the trace file
:ref:debugger-command-history
displays recently visited PC addresses and opcodes
:ref:debugger-command-trackpc
visually track visited opcodes
:ref:debugger-command-trackmem
record which PC writes to each memory address
:ref:debugger-command-pcatmem
query which PC wrote to a given memory address
:ref:debugger-command-rewind
go back in time by loading the most recent rewind state
:ref:debugger-command-statesave
save a state file for the emulated system
:ref:debugger-command-stateload
load a state file for the emulated system
:ref:debugger-command-snap
save a screen snapshot
:ref:debugger-command-source
read commands from file and executes them one by one
:ref:debugger-command-time
prints the current machine time to the console
:ref:debugger-command-quit
exit the debugger and end the emulation session
.. _debugger-command-help:
help [<topic>]
Displays built-in debugger help in the debugger console. If no <topic> is specified, top-level topics are listed. Most debugger commands have correspondingly named help topics.
Examples:
help
Lists top-level help topics.
help expressions
Displays built-in help for debugger expression syntax.
help wpiset
Displays built-in help for the
:ref:wpiset <debugger-command-wpset> command.
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.. _debugger-command-do:
do <expression>
The do command simply evaluates the supplied expression. This is
often used to set or modify device state variable (e.g. CPU registers),
or to write to memory. See :ref:debugger-express for details about
expression syntax.
Examples:
do pc = 0
Sets the register pc to 0.
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.. _debugger-command-symlist:
symlist [<cpu>]
Lists registered symbols and their values. If <cpu> is not
specified, symbols in the global symbol table are displayed; otherwise,
symbols specific to the device <cpu> are displayed. Symbols are
listed alphabetically. Read-only symbols are noted. See
:ref:debugger-devicespec for details on how to specify a CPU.
Examples:
symlist
Displays the global symbol table.
symlist 2
Displays the symbols for the third CPU in the system (zero-based
index).
symlist audiocpu
Displays symbols for the CPU with the absolute tag :audiocpu.
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.. _debugger-command-softreset:
softreset
Executes a soft reset. This calls the reset member functions of all the devices in the system (by default, pressing F3 during emulation has the same effect).
Examples:
softreset
Executes a soft reset.
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.. _debugger-command-hardreset:
hardreset
Executes a hard reset. This tears down the emulation session and starts another session with the same system and options (by default, pressing Shift+F3 during emulation has the same effect). Note that this will lose history in the debugger console and error log.
Examples:
hardreset
Executes a hard reset.
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.. _debugger-command-print:
print <item>[,…]
The print command prints the results of one or more expressions to the debugger console as hexadecimal numbers.
Examples:
print pc
Prints the value of the pc register the console as a hex number.
print a,b,a+b
Prints a, b, and the value of a+b to the console as hex
numbers.
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.. _debugger-command-printf:
printf <format>[,<argument>[,…]]
Prints a C-style formatted message to the debugger console. Only a very limited subset of format specifiers and escape sequences are available:
%c Prints the corresponding argument as an 8-bit character. %[-][0][<n>]d Prints the corresponding argument as a decimal number with optional left justification, zero fill and minimum field width. %[-][0][<n>]o Prints the corresponding argument as an octal number with optional left justification, zero fill and minimum field width. %[-][0][<n>]x Prints the corresponding argument as a lowercase hexadecimal number with optional left justification, zero fill and minimum field width. %[-][0][<n>]X Prints the corresponding argument as an uppercase hexadecimal number with optional left justification, zero fill and minimum field width. %[-][<n>][.[<n>]]s Prints a null-terminated string of 8-bit characters from the address and address space given by the corresponding argument, with optional left justification, minimum and maximum field widths. %% Prints a literal percent symbol. \n Prints a line break. \\ Prints a literal backslash.
All other format specifiers are ignored.
Examples:
printf "PC=%04X",pc
Prints PC=<pcval> where <pcval> is the hexadecimal value of
the pc register with a minimum of four digits and zero fill.
printf "A=%d, B=%d\\nC=%d",a,b,a+b
Prints A=<aval>, B=<bval> on one line, and C=<a+bval> on a
second line.
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.. _debugger-command-logerror:
logerror <format>[,<argument>[,…]]
Prints a C-style formatted message to the error log. See
:ref:debugger-command-printf for details about the limited set of
supported format specifiers and escape sequences.
Examples:
logerror "PC=%04X",pc
Logs PC=<pcval> where <pcval> is the hexadecimal value of
the pc register with a minimum of four digits and zero fill.
logerror "A=%d, B=%d\\nC=%d",a,b,a+b
Logs A=<aval>, B=<bval> on one line, and C=<a+bval> on a
second line.
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.. _debugger-command-tracelog:
tracelog <format>[,<argument>[,…]]
Prints a C-style formatted message to the currently open trace file (see
:ref:debugger-command-trace for more information). If no trace file
is open, this command has no effect. See :ref:debugger-command-printf
for details about the limited set of supported format specifiers and
escape sequences.
Examples:
tracelog "PC=%04X",pc
Outputs PC=<pcval> where <pcval> is the hexadecimal value of
the pc register with a minimum of four digits and zero fill if a
trace log file is open.
tracelog "A=%d, B=%d\\nC=%d",a,b,a+b
Outputs A=<aval>, B=<bval> on one line, and C=<a+bval> on a
second line if a trace log file is open.
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.. _debugger-command-tracesym:
tracesym <item>[,…]
Prints the specified symbols to the currently open trace file (see
:ref:debugger-command-trace for more information). If no trace file
is open, this command has no effect.
Examples:
tracesym pc
Outputs PC=<pcval> where <pcval> is the value of the pc
register in its default format if a trace log file is open.
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.. _debugger-command-history:
history [<CPU>[,<length>]]
Displays recently visited PC addresses, and disassembly of the
instructions at those addresses. If present, the first argument selects
the CPU (see :ref:debugger-devicespec for details); if no CPU is
specified, the visible CPU is assumed. The second argument, if present,
limits the maximum number of addresses shown. Addresses are shown in
order from least to most recently visited.
Examples:
history ,5
Displays up to five most recently visited PC addresses and
instructions for the visible CPU.
history 3
Displays recently visited PC addresses and instructions for the
fourth CPU in the system (zero-based index).
history audiocpu,1
Displays the most recently visited PC address and instruction for
the CPU with the absolute tag :audiocpu.
.. _debugger-command-trackpc:
trackpc [<enable>[,<CPU>[,<clear>]]]
Turns visited PC address tracking for disassembly views on or off.
Instructions at addresses visited while tracking is on are highlighted
in debugger disassembly views. The first argument is a Boolean
specifying whether tracking should be turned on or off (defaults to on).
The second argument specifies the CPU to enable or disable tracking for
(see :ref:debugger-devicespec for details); if no CPU is specified,
the visible CPU is assumed. The third argument is a Boolean specifying
whether existing data should be cleared (defaults to false).
Examples:
trackpc 1
Begin or tracking the current CPU’s PC.
trackpc 1,0,1
Begin or continue tracking PC on the first CPU in the system
(zero-based index), but clear the history tracked so far.
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.. _debugger-command-trackmem:
trackmem [<enable>,[<CPU>,[<clear>]]]
Enables or disables logging the PC address each time a memory address is
written to. The first argument is a Boolean specifying whether tracking
should be enabled or disabled (defaults to enabled). The second
argument specifies the CPU to enable or disable tracking for (see
:ref:debugger-devicespec for details); if no CPU is specified, the
visible CPU is assumed. The third argument is a Boolean specifying
whether existing data should be cleared (defaults to false).
Use :ref:debugger-command-pcatmem to retrieve this data.
Right-clicking a debugger memory view will also display the logged PC
value for the given address in some configurations.
Examples:
trackmem
Begin or continue tracking memory writes for the visible CPU.
trackmem 1,0,1
Begin or continue tracking memory writes for the first CPU in the
system (zero-based index), but clear existing tracking data.
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.. _debugger-command-pcatmem:
pcatmem[{d|i|o}] <address>[:<space>]
Returns the PC value at the time the specified address was most recently
written to. The argument is the requested address, optionally followed
by a colon and a CPU and/or address space (see
:ref:debugger-devicespec for details). The optional d, i or
o suffix controls the default address space for the command.
Tracking must be enabled for the data this command uses to be recorded
(see :ref:debugger-command-trackmem). Right-clicking a debugger
memory view will also display the logged PC value for the given address
in some configurations.
Examples:
pcatmem 400000
Print the PC value when location 400000 in the visible CPU’s program
space was most recently written.
pcatmem 3bc:io
Print the PC value when location 3bc in the visible CPU’s io
space was most recently written.
pcatmem 1400:audiocpu
Print the PC value when location 1400 in the CPU :audiocpu’s
program space was most recently written.
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.. _debugger-command-rewind:
rewind
Loads the most recent RAM-based saved state. When enabled, rewind
states are saved when :ref:debugger-command-step,
:ref:debugger-command-over and :ref:debugger-command-out commands
are used, storing the machine state as of the moment before stepping.
May be abbreviated to rw.
Consecutively loading rewind states can work like reverse execution. Depending on which steps forward were taken previously, the behavior can be similar to GDB's reverse-stepi and reverse-next commands. All output for this command is currently echoed into the running machine window.
Previous memory and PC tracking statistics are cleared. Actual reverse execution does not occur.
Examples:
rewind
Load the previous RAM-based save state.
rw
Abbreviated form of the command.
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.. _debugger-command-statesave:
statesave <filename>
Creates a save state at the current moment in emulated time. The state
file is written to the configured save state directory (see the
:ref:state_directory <mame-commandline-statedirectory> option), and
the .sta extension is automatically appended to the specified file
name. May be abbreviates to ss.
All output from this command is currently echoed into the running machine window.
Examples:
statesave foo
Saves the emulated machine state to the file foo.sta in the
configured save state directory.
ss bar
Abbreviated form of the command – saves the emulated machine state
to bar.sta.
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.. _debugger-command-stateload:
stateload <filename>
Restores a saved state file from disk. The specified state file is read
from the configured save state directory (see the
:ref:state_directory <mame-commandline-statedirectory> option), and the
.sta extension is automatically appended to the specified file name.
May be abbreviated to sl.
All output for this command is currently echoed into the running machine window. Previous memory and PC tracking statistics are cleared.
Examples:
stateload foo
Loads state from file foo.sta to the configured save state
directory.
sl bar
Abbreviated form of the command – loads the file bar.sta.
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.. _debugger-command-snap:
snap [<filename>[,<scrnum>]]
Takes a snapshot of the emulated video display and saves it to the
configured snapshot directory (see the
:ref:snapshot_directory <mame-commandline-snapshotdirectory> option).
If a file name is specified, a single screenshot for the specified
screen is saved using the specified filename (or the first emulated
screen in the system if a screen is not specified). If a file name is
not specified, the configured snapshot view and file name pattern are
used (see the :ref:snapview <mame-commandline-snapview> and
:ref:snapname <mame-commandline-snapname> options).
If a file name is specified, the .png extension is automatically appended. The screen number is specified as a zero-based index, as seen in the names of automatically-generated single-screen views in MAME’s video options menus.
Examples:
snap
Takes a snapshot using the configured snapshot view and file name
options.
snap shinobi
Takes a snapshot of the first emulated video screen and saves it as
shinobi.png in the configured snapshot directory.
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.. _debugger-command-source:
source <filename>
Reads the specified file in text mode and executes each line as a debugger command. This is similar to running a shell script or batch file.
Examples:
source break_and_trace.cmd
Reads and executes debugger commands from break_and_trace.cmd.
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.. _debugger-command-time:
Prints the total elapsed emulated time to the debugger console.
Examples:
time
Prints the elapsed emulated time.
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.. _debugger-command-quit:
quit
Closes the debugger and ends the emulation session immediately. Either exits MAME or returns to the system selection menu, depending on whether the system was specified on the command line when starting MAME.
Examples:
quit
Exits the emulation session immediately.
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