Debugging with GDB: Objfiles In Python

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#### 23.2.2.23 Objfiles In Python

GDB loads symbols for an inferior from various symbol-containing files (see Files). These include the primary executable file, any shared libraries used by the inferior, and any separate debug info files (see Separate Debug Files). GDB calls these symbol-containing files objfiles.

The following objfile-related functions are available in the `gdb` module:

Function: gdb.current_objfile ()

  When auto-loading a Python script (see Python Auto-loading), GDB sets the “current objfile” to the corresponding objfile. This function returns the current objfile. If there is no current objfile, this function returns `None`.

Function: gdb.objfiles ()

  Return a sequence of all the objfiles current known to GDB. See Objfiles In Python.

Function: gdb.lookup_objfile (name [, by_build_id])

  Look up name, a file name or build ID, in the list of objfiles for the current program space (see Progspaces In Python). If the objfile is not found throw the Python `ValueError` exception.

  If name is a relative file name, then it will match any source file name with the same trailing components. For example, if name is ‘`gcc/expr.c`’, then it will match source file name of `/build/trunk/gcc/expr.c`, but not `/build/trunk/libcpp/expr.c` or `/build/trunk/gcc/x-expr.c`.

  If by_build_id is provided and is `True` then name is the build ID of the objfile. Otherwise, name is a file name. This is supported only on some operating systems, notably those which use the ELF format for binary files and the GNU Binutils. For more details about this feature, see the description of the `--build-id` command-line option in Command Line Options in The GNU Linker.

Each objfile is represented by an instance of the `gdb.Objfile` class.

Variable: Objfile.filename

  The file name of the objfile as a string, with symbolic links resolved.

  The value is `None` if the objfile is no longer valid. See the `gdb.Objfile.is_valid` method, described below.

Variable: Objfile.username

  The file name of the objfile as specified by the user as a string.

  The value is `None` if the objfile is no longer valid. See the `gdb.Objfile.is_valid` method, described below.

Variable: Objfile.owner

  For separate debug info objfiles this is the corresponding `gdb.Objfile` object that debug info is being provided for. Otherwise this is `None`. Separate debug info objfiles are added with the `gdb.Objfile.add_separate_debug_file` method, described below.

Variable: Objfile.build_id

  The build ID of the objfile as a string. If the objfile does not have a build ID then the value is `None`.

  This is supported only on some operating systems, notably those which use the ELF format for binary files and the GNU Binutils. For more details about this feature, see the description of the `--build-id` command-line option in Command Line Options in The GNU Linker.

Variable: Objfile.progspace

  The containing program space of the objfile as a `gdb.Progspace` object. See Progspaces In Python.

Variable: Objfile.pretty_printers

  The `pretty_printers` attribute is a list of functions. It is used to look up pretty-printers. A `Value` is passed to each function in order; if the function returns `None`, then the search continues. Otherwise, the return value should be an object which is used to format the value. See Pretty Printing API, for more information.

Variable: Objfile.type_printers

  The `type_printers` attribute is a list of type printer objects. See Type Printing API, for more information.

Variable: Objfile.frame_filters

  The `frame_filters` attribute is a dictionary of frame filter objects. See Frame Filter API, for more information.

One may add arbitrary attributes to `gdb.Objfile` objects in the usual Python way. This is useful if, for example, one needs to do some extra record keeping associated with the objfile.

In this contrived example we record the time when GDB loaded the objfile.

    (gdb) python
    import datetime
    def new_objfile_handler(event):
        # Set the time_loaded attribute of the new objfile.
        event.new_objfile.time_loaded = datetime.datetime.today()
    gdb.events.new_objfile.connect(new_objfile_handler)
    end
    (gdb) file ./hello
    Reading symbols from ./hello...done.
    (gdb) python print gdb.objfiles()[0].time_loaded
    2014-10-09 11:41:36.770345

A `gdb.Objfile` object has the following methods:

Function: Objfile.is_valid ()

  Returns `True` if the `gdb.Objfile` object is valid, `False` if not. A `gdb.Objfile` object can become invalid if the object file it refers to is not loaded in GDB any longer. All other `gdb.Objfile` methods will throw an exception if it is invalid at the time the method is called.

Function: Objfile.add_separate_debug_file (file)

  Add file to the list of files that GDB will search for debug information for the objfile. This is useful when the debug info has been removed from the program and stored in a separate file. GDB has built-in support for finding separate debug info files (see Separate Debug Files), but if the file doesn’t live in one of the standard places that GDB searches then this function can be used to add a debug info file from a different place.

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