bfd/doc/opncls.texi

@section Opening and closing BFDs


@subsection Functions for opening and closing


@findex _bfd_new_bfd
@subsubsection @code{_bfd_new_bfd}
@deftypefn {Function} bfd *_bfd_new_bfd (void);
Return a new BFD.  All BFD's are allocated through this routine.

@end deftypefn
@findex _bfd_new_bfd_contained_in
@subsubsection @code{_bfd_new_bfd_contained_in}
@deftypefn {Function} bfd *_bfd_new_bfd_contained_in (bfd *);
Allocate a new BFD as a member of archive OBFD.

@end deftypefn
@findex _bfd_free_cached_info
@subsubsection @code{_bfd_free_cached_info}
@deftypefn {Function} bool _bfd_free_cached_info (bfd *);
Free objalloc memory.

@end deftypefn
@findex bfd_fopen
@subsubsection @code{bfd_fopen}
@deftypefn {Function} bfd *bfd_fopen (const char *filename, const char *target, const char *mode, int fd);
Open the file @var{filename} with the target @var{target}.
Return a pointer to the created BFD.  If @var{fd} is not -1,
then @code{fdopen} is used to open the file; otherwise, @code{fopen}
is used.  @var{mode} is passed directly to @code{fopen} or
@code{fdopen}.

Calls @code{bfd_find_target}, so @var{target} is interpreted as by
that function.

The new BFD is marked as cacheable iff @var{fd} is -1.

If @code{NULL} is returned then an error has occured.   Possible errors
are @code{bfd_error_no_memory}, @code{bfd_error_invalid_target} or
@code{system_call} error.

On error, @var{fd} is always closed.

A copy of the @var{filename} argument is stored in the newly created
BFD.  It can be accessed via the bfd_get_filename() macro.

@end deftypefn
@findex bfd_openr
@subsubsection @code{bfd_openr}
@deftypefn {Function} bfd *bfd_openr (const char *filename, const char *target);
Open the file @var{filename} (using @code{fopen}) with the target
@var{target}.  Return a pointer to the created BFD.

Calls @code{bfd_find_target}, so @var{target} is interpreted as by
that function.

If @code{NULL} is returned then an error has occured.   Possible errors
are @code{bfd_error_no_memory}, @code{bfd_error_invalid_target} or
@code{system_call} error.

A copy of the @var{filename} argument is stored in the newly created
BFD.  It can be accessed via the bfd_get_filename() macro.

@end deftypefn
@findex bfd_fdopenr
@subsubsection @code{bfd_fdopenr}
@deftypefn {Function} bfd *bfd_fdopenr (const char *filename, const char *target, int fd);
@code{bfd_fdopenr} is to @code{bfd_fopenr} much like @code{fdopen} is to
@code{fopen}.  It opens a BFD on a file already described by the
@var{fd} supplied.

When the file is later @code{bfd_close}d, the file descriptor will
be closed.  If the caller desires that this file descriptor be
cached by BFD (opened as needed, closed as needed to free
descriptors for other opens), with the supplied @var{fd} used as
an initial file descriptor (but subject to closure at any time),
call bfd_set_cacheable(bfd, 1) on the returned BFD.  The default
is to assume no caching; the file descriptor will remain open
until @code{bfd_close}, and will not be affected by BFD operations
on other files.

Possible errors are @code{bfd_error_no_memory},
@code{bfd_error_invalid_target} and @code{bfd_error_system_call}.

On error, @var{fd} is closed.

A copy of the @var{filename} argument is stored in the newly created
BFD.  It can be accessed via the bfd_get_filename() macro.

@end deftypefn
@findex bfd_fdopenw
@subsubsection @code{bfd_fdopenw}
@deftypefn {Function} bfd *bfd_fdopenw (const char *filename, const char *target, int fd);
@code{bfd_fdopenw} is exactly like @code{bfd_fdopenr} with the exception that
the resulting BFD is suitable for output.

@end deftypefn
@findex bfd_openstreamr
@subsubsection @code{bfd_openstreamr}
@deftypefn {Function} bfd *bfd_openstreamr (const char * filename, const char * target, void * stream);
Open a BFD for read access on an existing stdio stream.  When
the BFD is passed to @code{bfd_close}, the stream will be closed.

A copy of the @var{filename} argument is stored in the newly created
BFD.  It can be accessed via the bfd_get_filename() macro.

@end deftypefn
@findex bfd_openr_iovec
@subsubsection @code{bfd_openr_iovec}
@deftypefn {Function} bfd *bfd_openr_iovec (const char *filename, const char *target, void *(*open_func) (struct bfd *nbfd, void *open_closure), void *open_closure, file_ptr (*pread_func) (struct bfd *nbfd, void *stream, void *buf, file_ptr nbytes, file_ptr offset), int (*close_func) (struct bfd *nbfd, void *stream), int (*stat_func) (struct bfd *abfd, void *stream, struct stat *sb));
Create and return a BFD backed by a read-only @var{stream}.
The @var{stream} is created using @var{open_func}, accessed using
@var{pread_func} and destroyed using @var{close_func}.

Calls @code{bfd_find_target}, so @var{target} is interpreted as by
that function.

Calls @var{open_func} (which can call @code{bfd_zalloc} and
@code{bfd_get_filename}) to obtain the read-only stream backing
the BFD.  @var{open_func} either succeeds returning the
non-@code{NULL} @var{stream}, or fails returning @code{NULL}
(setting @code{bfd_error}).

Calls @var{pread_func} to request @var{nbytes} of data from
@var{stream} starting at @var{offset} (e.g., via a call to
@code{bfd_read}).  @var{pread_func} either succeeds returning the
number of bytes read (which can be less than @var{nbytes} when
end-of-file), or fails returning -1 (setting @code{bfd_error}).

Calls @var{close_func} when the BFD is later closed using
@code{bfd_close}.  @var{close_func} either succeeds returning 0, or
fails returning -1 (setting @code{bfd_error}).

Calls @var{stat_func} to fill in a stat structure for bfd_stat,
bfd_get_size, and bfd_get_mtime calls.  @var{stat_func} returns 0
on success, or returns -1 on failure (setting @code{bfd_error}).

If @code{bfd_openr_iovec} returns @code{NULL} then an error has
occurred.  Possible errors are @code{bfd_error_no_memory},
@code{bfd_error_invalid_target} and @code{bfd_error_system_call}.

A copy of the @var{filename} argument is stored in the newly created
BFD.  It can be accessed via the bfd_get_filename() macro.

@end deftypefn
@findex bfd_openw
@subsubsection @code{bfd_openw}
@deftypefn {Function} bfd *bfd_openw (const char *filename, const char *target);
Create a BFD, associated with file @var{filename}, using the
file format @var{target}, and return a pointer to it.

Possible errors are @code{bfd_error_system_call}, @code{bfd_error_no_memory},
@code{bfd_error_invalid_target}.

A copy of the @var{filename} argument is stored in the newly created
BFD.  It can be accessed via the bfd_get_filename() macro.

@end deftypefn
@findex bfd_elf_bfd_from_remote_memory
@subsubsection @code{bfd_elf_bfd_from_remote_memory}
@deftypefn {Function} bfd *bfd_elf_bfd_from_remote_memory (bfd *templ, bfd_vma ehdr_vma, bfd_size_type size, bfd_vma *loadbasep, int (*target_read_memory) (bfd_vma vma, bfd_byte *myaddr, bfd_size_type len));
Create a new BFD as if by bfd_openr.  Rather than opening a
file, reconstruct an ELF file by reading the segments out of
remote memory based on the ELF file header at EHDR_VMA and the
ELF program headers it points to.  If non-zero, SIZE is the
known extent of the object.  If not null, *LOADBASEP is filled
in with the difference between the VMAs from which the
segments were read, and the VMAs the file headers (and hence
BFD's idea of each section's VMA) put them at.

The function TARGET_READ_MEMORY is called to copy LEN bytes
from the remote memory at target address VMA into the local
buffer at MYADDR; it should return zero on success or an
errno code on failure.  TEMPL must be a BFD for an ELF
target with the word size and byte order found in the remote
memory.

@end deftypefn
@findex bfd_close
@subsubsection @code{bfd_close}
@deftypefn {Function} bool bfd_close (bfd *abfd);
Close a BFD. If the BFD was open for writing, then pending
operations are completed and the file written out and closed.
If the created file is executable, then @code{chmod} is called
to mark it as such.

All memory attached to the BFD is released.

The file descriptor associated with the BFD is closed (even
if it was passed in to BFD by @code{bfd_fdopenr}).

@code{TRUE} is returned if all is ok, otherwise @code{FALSE}.

@end deftypefn
@findex bfd_close_all_done
@subsubsection @code{bfd_close_all_done}
@deftypefn {Function} bool bfd_close_all_done (bfd *);
Close a BFD.  Differs from @code{bfd_close} since it does not
complete any pending operations.  This routine would be used
if the application had just used BFD for swapping and didn't
want to use any of the writing code.

If the created file is executable, then @code{chmod} is called
to mark it as such.

All memory attached to the BFD is released.

@code{TRUE} is returned if all is ok, otherwise @code{FALSE}.

@end deftypefn
@findex bfd_create
@subsubsection @code{bfd_create}
@deftypefn {Function} bfd *bfd_create (const char *filename, bfd *templ);
Create a new BFD in the manner of @code{bfd_openw}, but without
opening a file. The new BFD takes the target from the target
used by @var{templ}. The format is always set to @code{bfd_object}.

A copy of the @var{filename} argument is stored in the newly created
BFD.  It can be accessed via the bfd_get_filename() macro.

@end deftypefn
@findex bfd_make_writable
@subsubsection @code{bfd_make_writable}
@deftypefn {Function} bool bfd_make_writable (bfd *abfd);
Takes a BFD as created by @code{bfd_create} and converts it
into one like as returned by @code{bfd_openw}.  It does this
by converting the BFD to BFD_IN_MEMORY.  It's assumed that
you will call @code{bfd_make_readable} on this bfd later.

@code{TRUE} is returned if all is ok, otherwise @code{FALSE}.

@end deftypefn
@findex bfd_make_readable
@subsubsection @code{bfd_make_readable}
@deftypefn {Function} bool bfd_make_readable (bfd *abfd);
Takes a BFD as created by @code{bfd_create} and
@code{bfd_make_writable} and converts it into one like as
returned by @code{bfd_openr}.  It does this by writing the
contents out to the memory buffer, then reversing the
direction.

@code{TRUE} is returned if all is ok, otherwise @code{FALSE}.

@end deftypefn
@findex bfd_calc_gnu_debuglink_crc32
@subsubsection @code{bfd_calc_gnu_debuglink_crc32}
@deftypefn {Function} uint32_t bfd_calc_gnu_debuglink_crc32 (uint32_t crc, const bfd_byte *buf, bfd_size_type len);
Computes a CRC value as used in the .gnu_debuglink section.
Advances the previously computed @var{crc} value by computing
and adding in the crc32 for @var{len} bytes of @var{buf}.

Return the updated CRC32 value.

@end deftypefn
@findex bfd_get_debug_link_info
@subsubsection @code{bfd_get_debug_link_info}
@deftypefn {Function} char *bfd_get_debug_link_info (bfd *abfd, uint32_t *crc32_out);
Extracts the filename and CRC32 value for any separate debug
information file associated with @var{abfd}.

Returns the filename of the associated debug information file,
or NULL if there is no such file.  If the filename was found
then the contents of @var{crc32_out} are updated to hold the
corresponding CRC32 value for the file.

The returned filename is allocated with @code{malloc}; freeing
it is the responsibility of the caller.

@end deftypefn
@findex bfd_get_alt_debug_link_info
@subsubsection @code{bfd_get_alt_debug_link_info}
@deftypefn {Function} char *bfd_get_alt_debug_link_info (bfd * abfd, bfd_size_type *buildid_len, bfd_byte **buildid_out);
Fetch the filename and BuildID value for any alternate debuginfo
associated with @var{abfd}.  Return NULL if no such info found,
otherwise return filename and update @var{buildid_len} and
@var{buildid_out}.  The returned filename and build_id are
allocated with @code{malloc}; freeing them is the responsibility
of the caller.

@end deftypefn
@findex bfd_follow_gnu_debuglink
@subsubsection @code{bfd_follow_gnu_debuglink}
@deftypefn {Function} char *bfd_follow_gnu_debuglink (bfd *abfd, const char *dir);
Takes a BFD and searches it for a .gnu_debuglink section.  If this
section is found, it examines the section for the name and checksum
of a '.debug' file containing auxiliary debugging information.  It
then searches the filesystem for this .debug file in some standard
locations, including the directory tree rooted at @var{dir}, and if
found returns the full filename.

If @var{dir} is NULL, the search will take place starting at
the current directory.

Returns @code{NULL} on any errors or failure to locate the .debug
file, otherwise a pointer to a heap-allocated string
containing the filename.  The caller is responsible for
freeing this string.

@end deftypefn
@findex bfd_follow_gnu_debugaltlink
@subsubsection @code{bfd_follow_gnu_debugaltlink}
@deftypefn {Function} char *bfd_follow_gnu_debugaltlink (bfd *abfd, const char *dir);
Takes a BFD and searches it for a .gnu_debugaltlink section.  If this
section is found, it examines the section for the name of a file
containing auxiliary debugging information.  It then searches the
filesystem for this file in a set of standard locations, including
the directory tree rooted at @var{dir}, and if found returns the
full filename.

If @var{dir} is NULL, the search will take place starting at
the current directory.

Returns @code{NULL} on any errors or failure to locate the debug
file, otherwise a pointer to a heap-allocated string
containing the filename.  The caller is responsible for
freeing this string.

@end deftypefn
@findex bfd_create_gnu_debuglink_section
@subsubsection @code{bfd_create_gnu_debuglink_section}
@deftypefn {Function} struct bfd_section *bfd_create_gnu_debuglink_section (bfd *abfd, const char *filename);
Takes a @var{BFD} and adds a .gnu_debuglink section to it.  The
section is sized to be big enough to contain a link to the specified
@var{filename}.

A pointer to the new section is returned if all is ok.  Otherwise
@code{NULL} is returned and bfd_error is set.

@end deftypefn
@findex bfd_fill_in_gnu_debuglink_section
@subsubsection @code{bfd_fill_in_gnu_debuglink_section}
@deftypefn {Function} bool bfd_fill_in_gnu_debuglink_section (bfd *abfd, struct bfd_section *sect, const char *filename);
Takes a @var{BFD} and containing a .gnu_debuglink section @var{SECT}
and fills in the contents of the section to contain a link to the
specified @var{filename}.  The filename should be absolute or
relative to the current directory.

@code{TRUE} is returned if all is ok.  Otherwise @code{FALSE} is returned
and bfd_error is set.

@end deftypefn
@findex bfd_follow_build_id_debuglink
@subsubsection @code{bfd_follow_build_id_debuglink}
@deftypefn {Function} char *bfd_follow_build_id_debuglink (bfd *abfd, const char *dir);
Takes @var{abfd} and searches it for a .note.gnu.build-id section.
If this section is found, it extracts the value of the NT_GNU_BUILD_ID
note, which should be a hexadecimal value @var{NNNN+NN} (for
32+ hex digits).  It then searches the filesystem for a file named
@var{.build-id/NN/NN+NN.debug} in a set of standard locations,
including the directory tree rooted at @var{dir}.  The filename
of the first matching file to be found is returned.  A matching
file should contain a .note.gnu.build-id section with the same
@var{NNNN+NN} note as @var{abfd}, although this check is currently
not implemented.

If @var{dir} is NULL, the search will take place starting at
the current directory.

Returns @code{NULL} on any errors or failure to locate the debug
file, otherwise a pointer to a heap-allocated string
containing the filename.  The caller is responsible for
freeing this string.

@end deftypefn
@findex bfd_set_filename
@subsubsection @code{bfd_set_filename}
@deftypefn {Function} const char *bfd_set_filename (bfd *abfd, const char *filename);
Set the filename of @var{abfd}, copying the FILENAME parameter to
bfd_alloc'd memory owned by @var{abfd}.  Returns a pointer the
newly allocated name, or NULL if the allocation failed.

@end deftypefn