|Debugging with GDB: Cygwin Native|
GDB supports native debugging of MS Windows programs, including DLLs with and without symbolic debugging information.
MS-Windows programs that call
SetConsoleMode to switch off the
special meaning of the ‘Ctrl-C’ keystroke cannot be interrupted
by typing C-c. For this reason, GDB on MS-Windows
supports C-BREAK as an alternative interrupt key
sequence, which can be used to interrupt the debuggee even if it
There are various additional Cygwin-specific commands, described in this section. Working with DLLs that have no debugging symbols is described in Non-debug DLL Symbols.
This is a prefix of MS Windows-specific commands which print information about the target system and important OS structures.
info w32 selector
This command displays information returned by
the Win32 API
It takes an optional argument that is evaluated to
a long value to give the information about this given selector.
Without argument, this command displays information
about the six segment registers.
info w32 thread-information-block
This command displays thread specific information stored in the
Thread Information Block (readable on the X86 CPU family using
selector for 32-bit programs and
$gs for 64-bit programs).
This command signals an event with user-provided id. Used to resume crashing process when attached to it using MS-Windows JIT debugging (AeDebug).
To use it, create or edit the following keys in
HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug and/or
(for x86_64 versions):
Debugger(REG_SZ) — a command to launch the debugger. Suggested command is:
fully-qualified-path-to-gdb.exe -ex "attach %ld" -ex "signal-event %ld" -ex "continue".
%ld will be replaced by the process ID of the
crashing process, the second
%ld will be replaced by the ID of
the event that blocks the crashing process, waiting for GDB
Auto(REG_SZ) — either
1will make the system run debugger specified by the Debugger key automatically,
0will cause a dialog box with “OK” and “Cancel” buttons to appear, which allows the user to either terminate the crashing process (OK) or debug it (Cancel).
set cygwin-exceptions mode
If mode is
on, GDB will break on exceptions that
happen inside the Cygwin DLL. If mode is
GDB will delay recognition of exceptions, and may ignore some
exceptions which seem to be caused by internal Cygwin DLL
“bookkeeping”. This option is meant primarily for debugging the
Cygwin DLL itself; the default value is
off to avoid annoying
GDB users with false
Displays whether GDB will break on exceptions that happen inside the Cygwin DLL itself.
set new-console mode
If mode is
on the debuggee will
be started in a new console on next start.
If mode is
off, the debuggee will
be started in the same console as the debugger.
Displays whether a new console is used when the debuggee is started.
set new-group mode
This boolean value controls whether the debuggee should start a new group or stay in the same group as the debugger. This affects the way the Windows OS handles ‘Ctrl-C’.
Displays current value of new-group boolean.
This boolean value adds debug output concerning kernel events related
to the debuggee seen by the debugger. This includes events that
signal thread and process creation and exit, DLL loading and
unloading, console interrupts, and debugging messages produced by the
OutputDebugString API call.
This boolean value adds debug output concerning execute events (such as resume thread) seen by the debugger.
This boolean value adds debug output concerning exceptions in the debuggee seen by the debugger.
This boolean value adds debug output concerning debuggee memory reads and writes by the debugger.
This boolean values specifies whether the debuggee is called via a shell or directly (default value is on).
Displays if the debuggee will be started with a shell.
|• Non-debug DLL Symbols:||Support for DLLs without debugging symbols|