xref: /netbsd-src/external/gpl3/binutils.old/dist/bfd/doc/section.texi (revision e992f068c547fd6e84b3f104dc2340adcc955732)

@section Sections
The raw data contained within a BFD is maintained through the
section abstraction.  A single BFD may have any number of
sections.  It keeps hold of them by pointing to the first;
each one points to the next in the list.

Sections are supported in BFD in @code{section.c}.

@menu
* Section Input::
* Section Output::
* typedef asection::
* section prototypes::
@end menu

@node Section Input, Section Output, Sections, Sections
@subsection Section input
When a BFD is opened for reading, the section structures are
created and attached to the BFD.

Each section has a name which describes the section in the
outside world---for example, @code{a.out} would contain at least
three sections, called @code{.text}, @code{.data} and @code{.bss}.

Names need not be unique; for example a COFF file may have several
sections named @code{.data}.

Sometimes a BFD will contain more than the ``natural'' number of
sections. A back end may attach other sections containing
constructor data, or an application may add a section (using
@code{bfd_make_section}) to the sections attached to an already open
BFD. For example, the linker creates an extra section
@code{COMMON} for each input file's BFD to hold information about
common storage.

The raw data is not necessarily read in when
the section descriptor is created. Some targets may leave the
data in place until a @code{bfd_get_section_contents} call is
made. Other back ends may read in all the data at once.  For
example, an S-record file has to be read once to determine the
size of the data.

@node Section Output, typedef asection, Section Input, Sections
@subsection Section output
To write a new object style BFD, the various sections to be
written have to be created. They are attached to the BFD in
the same way as input sections; data is written to the
sections using @code{bfd_set_section_contents}.

Any program that creates or combines sections (e.g., the assembler
and linker) must use the @code{asection} fields @code{output_section} and
@code{output_offset} to indicate the file sections to which each
section must be written.  (If the section is being created from
scratch, @code{output_section} should probably point to the section
itself and @code{output_offset} should probably be zero.)

The data to be written comes from input sections attached
(via @code{output_section} pointers) to
the output sections.  The output section structure can be
considered a filter for the input section: the output section
determines the vma of the output data and the name, but the
input section determines the offset into the output section of
the data to be written.

E.g., to create a section "O", starting at 0x100, 0x123 long,
containing two subsections, "A" at offset 0x0 (i.e., at vma
0x100) and "B" at offset 0x20 (i.e., at vma 0x120) the @code{asection}
structures would look like:

@example
   section name          "A"
     output_offset   0x00
     size            0x20
     output_section ----------->  section name    "O"
                             |    vma             0x100
   section name          "B" |    size            0x123
     output_offset   0x20    |
     size            0x103   |
     output_section  --------|
@end example

@subsection Link orders
The data within a section is stored in a @dfn{link_order}.
These are much like the fixups in @code{gas}.  The link_order
abstraction allows a section to grow and shrink within itself.

A link_order knows how big it is, and which is the next
link_order and where the raw data for it is; it also points to
a list of relocations which apply to it.

The link_order is used by the linker to perform relaxing on
final code.  The compiler creates code which is as big as
necessary to make it work without relaxing, and the user can
select whether to relax.  Sometimes relaxing takes a lot of
time.  The linker runs around the relocations to see if any
are attached to data which can be shrunk, if so it does it on
a link_order by link_order basis.


@node typedef asection, section prototypes, Section Output, Sections
@subsection typedef asection
Here is the section structure:


@example

typedef struct bfd_section
@{
  /* The name of the section; the name isn't a copy, the pointer is
     the same as that passed to bfd_make_section.  */
  const char *name;

  /* The next section in the list belonging to the BFD, or NULL.  */
  struct bfd_section *next;

  /* The previous section in the list belonging to the BFD, or NULL.  */
  struct bfd_section *prev;

  /* A unique sequence number.  */
  unsigned int id;

  /* A unique section number which can be used by assembler to
     distinguish different sections with the same section name.  */
  unsigned int section_id;

  /* Which section in the bfd; 0..n-1 as sections are created in a bfd.  */
  unsigned int index;

  /* The field flags contains attributes of the section. Some
     flags are read in from the object file, and some are
     synthesized from other information.  */
  flagword flags;

#define SEC_NO_FLAGS                      0x0

  /* Tells the OS to allocate space for this section when loading.
     This is clear for a section containing debug information only.  */
#define SEC_ALLOC                         0x1

  /* Tells the OS to load the section from the file when loading.
     This is clear for a .bss section.  */
#define SEC_LOAD                          0x2

  /* The section contains data still to be relocated, so there is
     some relocation information too.  */
#define SEC_RELOC                         0x4

  /* A signal to the OS that the section contains read only data.  */
#define SEC_READONLY                      0x8

  /* The section contains code only.  */
#define SEC_CODE                         0x10

  /* The section contains data only.  */
#define SEC_DATA                         0x20

  /* The section will reside in ROM.  */
#define SEC_ROM                          0x40

  /* The section contains constructor information. This section
     type is used by the linker to create lists of constructors and
     destructors used by @code{g++}. When a back end sees a symbol
     which should be used in a constructor list, it creates a new
     section for the type of name (e.g., @code{__CTOR_LIST__}), attaches
     the symbol to it, and builds a relocation. To build the lists
     of constructors, all the linker has to do is catenate all the
     sections called @code{__CTOR_LIST__} and relocate the data
     contained within - exactly the operations it would peform on
     standard data.  */
#define SEC_CONSTRUCTOR                  0x80

  /* The section has contents - a data section could be
     @code{SEC_ALLOC} | @code{SEC_HAS_CONTENTS}; a debug section could be
     @code{SEC_HAS_CONTENTS}  */
#define SEC_HAS_CONTENTS                0x100

  /* An instruction to the linker to not output the section
     even if it has information which would normally be written.  */
#define SEC_NEVER_LOAD                  0x200

  /* The section contains thread local data.  */
#define SEC_THREAD_LOCAL                0x400

  /* The section's size is fixed.  Generic linker code will not
     recalculate it and it is up to whoever has set this flag to
     get the size right.  */
#define SEC_FIXED_SIZE                  0x800

  /* The section contains common symbols (symbols may be defined
     multiple times, the value of a symbol is the amount of
     space it requires, and the largest symbol value is the one
     used).  Most targets have exactly one of these (which we
     translate to bfd_com_section_ptr), but ECOFF has two.  */
#define SEC_IS_COMMON                  0x1000

  /* The section contains only debugging information.  For
     example, this is set for ELF .debug and .stab sections.
     strip tests this flag to see if a section can be
     discarded.  */
#define SEC_DEBUGGING                  0x2000

  /* The contents of this section are held in memory pointed to
     by the contents field.  This is checked by bfd_get_section_contents,
     and the data is retrieved from memory if appropriate.  */
#define SEC_IN_MEMORY                  0x4000

  /* The contents of this section are to be excluded by the
     linker for executable and shared objects unless those
     objects are to be further relocated.  */
#define SEC_EXCLUDE                    0x8000

  /* The contents of this section are to be sorted based on the sum of
     the symbol and addend values specified by the associated relocation
     entries.  Entries without associated relocation entries will be
     appended to the end of the section in an unspecified order.  */
#define SEC_SORT_ENTRIES              0x10000

  /* When linking, duplicate sections of the same name should be
     discarded, rather than being combined into a single section as
     is usually done.  This is similar to how common symbols are
     handled.  See SEC_LINK_DUPLICATES below.  */
#define SEC_LINK_ONCE                 0x20000

  /* If SEC_LINK_ONCE is set, this bitfield describes how the linker
     should handle duplicate sections.  */
#define SEC_LINK_DUPLICATES           0xc0000

  /* This value for SEC_LINK_DUPLICATES means that duplicate
     sections with the same name should simply be discarded.  */
#define SEC_LINK_DUPLICATES_DISCARD       0x0

  /* This value for SEC_LINK_DUPLICATES means that the linker
     should warn if there are any duplicate sections, although
     it should still only link one copy.  */
#define SEC_LINK_DUPLICATES_ONE_ONLY  0x40000

  /* This value for SEC_LINK_DUPLICATES means that the linker
     should warn if any duplicate sections are a different size.  */
#define SEC_LINK_DUPLICATES_SAME_SIZE 0x80000

  /* This value for SEC_LINK_DUPLICATES means that the linker
     should warn if any duplicate sections contain different
     contents.  */
#define SEC_LINK_DUPLICATES_SAME_CONTENTS \
  (SEC_LINK_DUPLICATES_ONE_ONLY | SEC_LINK_DUPLICATES_SAME_SIZE)

  /* This section was created by the linker as part of dynamic
     relocation or other arcane processing.  It is skipped when
     going through the first-pass output, trusting that someone
     else up the line will take care of it later.  */
#define SEC_LINKER_CREATED           0x100000

  /* This section contains a section ID to distinguish different
     sections with the same section name.  */
#define SEC_ASSEMBLER_SECTION_ID     0x100000

  /* This section should not be subject to garbage collection.
     Also set to inform the linker that this section should not be
     listed in the link map as discarded.  */
#define SEC_KEEP                     0x200000

  /* This section contains "short" data, and should be placed
     "near" the GP.  */
#define SEC_SMALL_DATA               0x400000

  /* Attempt to merge identical entities in the section.
     Entity size is given in the entsize field.  */
#define SEC_MERGE                    0x800000

  /* If given with SEC_MERGE, entities to merge are zero terminated
     strings where entsize specifies character size instead of fixed
     size entries.  */
#define SEC_STRINGS                 0x1000000

  /* This section contains data about section groups.  */
#define SEC_GROUP                   0x2000000

  /* The section is a COFF shared library section.  This flag is
     only for the linker.  If this type of section appears in
     the input file, the linker must copy it to the output file
     without changing the vma or size.  FIXME: Although this
     was originally intended to be general, it really is COFF
     specific (and the flag was renamed to indicate this).  It
     might be cleaner to have some more general mechanism to
     allow the back end to control what the linker does with
     sections.  */
#define SEC_COFF_SHARED_LIBRARY     0x4000000

  /* This input section should be copied to output in reverse order
     as an array of pointers.  This is for ELF linker internal use
     only.  */
#define SEC_ELF_REVERSE_COPY        0x4000000

  /* This section contains data which may be shared with other
     executables or shared objects. This is for COFF only.  */
#define SEC_COFF_SHARED             0x8000000

  /* This section should be compressed.  This is for ELF linker
     internal use only.  */
#define SEC_ELF_COMPRESS            0x8000000

  /* When a section with this flag is being linked, then if the size of
     the input section is less than a page, it should not cross a page
     boundary.  If the size of the input section is one page or more,
     it should be aligned on a page boundary.  This is for TI
     TMS320C54X only.  */
#define SEC_TIC54X_BLOCK           0x10000000

  /* This section should be renamed.  This is for ELF linker
     internal use only.  */
#define SEC_ELF_RENAME             0x10000000

  /* Conditionally link this section; do not link if there are no
     references found to any symbol in the section.  This is for TI
     TMS320C54X only.  */
#define SEC_TIC54X_CLINK           0x20000000

  /* This section contains vliw code.  This is for Toshiba MeP only.  */
#define SEC_MEP_VLIW               0x20000000

  /* All symbols, sizes and relocations in this section are octets
     instead of bytes.  Required for DWARF debug sections as DWARF
     information is organized in octets, not bytes.  */
#define SEC_ELF_OCTETS             0x40000000

  /* Indicate that section has the no read flag set. This happens
     when memory read flag isn't set. */
#define SEC_COFF_NOREAD            0x40000000

  /* Indicate that section has the purecode flag set.  */
#define SEC_ELF_PURECODE           0x80000000

  /*  End of section flags.  */

  /* Some internal packed boolean fields.  */

  /* See the vma field.  */
  unsigned int user_set_vma : 1;

  /* A mark flag used by some of the linker backends.  */
  unsigned int linker_mark : 1;

  /* Another mark flag used by some of the linker backends.  Set for
     output sections that have an input section.  */
  unsigned int linker_has_input : 1;

  /* Mark flag used by some linker backends for garbage collection.  */
  unsigned int gc_mark : 1;

  /* Section compression status.  */
  unsigned int compress_status : 2;
#define COMPRESS_SECTION_NONE    0
#define COMPRESS_SECTION_DONE    1
#define DECOMPRESS_SECTION_SIZED 2

  /* The following flags are used by the ELF linker. */

  /* Mark sections which have been allocated to segments.  */
  unsigned int segment_mark : 1;

  /* Type of sec_info information.  */
  unsigned int sec_info_type:3;
#define SEC_INFO_TYPE_NONE      0
#define SEC_INFO_TYPE_STABS     1
#define SEC_INFO_TYPE_MERGE     2
#define SEC_INFO_TYPE_EH_FRAME  3
#define SEC_INFO_TYPE_JUST_SYMS 4
#define SEC_INFO_TYPE_TARGET    5
#define SEC_INFO_TYPE_EH_FRAME_ENTRY 6

  /* Nonzero if this section uses RELA relocations, rather than REL.  */
  unsigned int use_rela_p:1;

  /* Bits used by various backends.  The generic code doesn't touch
     these fields.  */

  unsigned int sec_flg0:1;
  unsigned int sec_flg1:1;
  unsigned int sec_flg2:1;
  unsigned int sec_flg3:1;
  unsigned int sec_flg4:1;
  unsigned int sec_flg5:1;

  /* End of internal packed boolean fields.  */

  /*  The virtual memory address of the section - where it will be
      at run time.  The symbols are relocated against this.  The
      user_set_vma flag is maintained by bfd; if it's not set, the
      backend can assign addresses (for example, in @code{a.out}, where
      the default address for @code{.data} is dependent on the specific
      target and various flags).  */
  bfd_vma vma;

  /*  The load address of the section - where it would be in a
      rom image; really only used for writing section header
      information.  */
  bfd_vma lma;

  /* The size of the section in *octets*, as it will be output.
     Contains a value even if the section has no contents (e.g., the
     size of @code{.bss}).  */
  bfd_size_type size;

  /* For input sections, the original size on disk of the section, in
     octets.  This field should be set for any section whose size is
     changed by linker relaxation.  It is required for sections where
     the linker relaxation scheme doesn't cache altered section and
     reloc contents (stabs, eh_frame, SEC_MERGE, some coff relaxing
     targets), and thus the original size needs to be kept to read the
     section multiple times.  For output sections, rawsize holds the
     section size calculated on a previous linker relaxation pass.  */
  bfd_size_type rawsize;

  /* The compressed size of the section in octets.  */
  bfd_size_type compressed_size;

  /* If this section is going to be output, then this value is the
     offset in *bytes* into the output section of the first byte in the
     input section (byte ==> smallest addressable unit on the
     target).  In most cases, if this was going to start at the
     100th octet (8-bit quantity) in the output section, this value
     would be 100.  However, if the target byte size is 16 bits
     (bfd_octets_per_byte is "2"), this value would be 50.  */
  bfd_vma output_offset;

  /* The output section through which to map on output.  */
  struct bfd_section *output_section;

  /* If an input section, a pointer to a vector of relocation
     records for the data in this section.  */
  struct reloc_cache_entry *relocation;

  /* If an output section, a pointer to a vector of pointers to
     relocation records for the data in this section.  */
  struct reloc_cache_entry **orelocation;

  /* The number of relocation records in one of the above.  */
  unsigned reloc_count;

  /* The alignment requirement of the section, as an exponent of 2 -
     e.g., 3 aligns to 2^3 (or 8).  */
  unsigned int alignment_power;

  /* Information below is back end specific - and not always used
     or updated.  */

  /* File position of section data.  */
  file_ptr filepos;

  /* File position of relocation info.  */
  file_ptr rel_filepos;

  /* File position of line data.  */
  file_ptr line_filepos;

  /* Pointer to data for applications.  */
  void *userdata;

  /* If the SEC_IN_MEMORY flag is set, this points to the actual
     contents.  */
  unsigned char *contents;

  /* Attached line number information.  */
  alent *lineno;

  /* Number of line number records.  */
  unsigned int lineno_count;

  /* Entity size for merging purposes.  */
  unsigned int entsize;

  /* Points to the kept section if this section is a link-once section,
     and is discarded.  */
  struct bfd_section *kept_section;

  /* When a section is being output, this value changes as more
     linenumbers are written out.  */
  file_ptr moving_line_filepos;

  /* What the section number is in the target world.  */
  int target_index;

  void *used_by_bfd;

  /* If this is a constructor section then here is a list of the
     relocations created to relocate items within it.  */
  struct relent_chain *constructor_chain;

  /* The BFD which owns the section.  */
  bfd *owner;

  /* A symbol which points at this section only.  */
  struct bfd_symbol *symbol;
  struct bfd_symbol **symbol_ptr_ptr;

  /* Early in the link process, map_head and map_tail are used to build
     a list of input sections attached to an output section.  Later,
     output sections use these fields for a list of bfd_link_order
     structs.  The linked_to_symbol_name field is for ELF assembler
     internal use.  */
  union @{
    struct bfd_link_order *link_order;
    struct bfd_section *s;
    const char *linked_to_symbol_name;
  @} map_head, map_tail;

  /* Points to the output section this section is already assigned to,
     if any.  This is used when support for non-contiguous memory
     regions is enabled.  */
  struct bfd_section *already_assigned;

  /* Explicitly specified section type, if non-zero.  */
  unsigned int type;

@} asection;

static inline const char *
bfd_section_name (const asection *sec)
@{
  return sec->name;
@}

static inline bfd_size_type
bfd_section_size (const asection *sec)
@{
  return sec->size;
@}

static inline bfd_vma
bfd_section_vma (const asection *sec)
@{
  return sec->vma;
@}

static inline bfd_vma
bfd_section_lma (const asection *sec)
@{
  return sec->lma;
@}

static inline unsigned int
bfd_section_alignment (const asection *sec)
@{
  return sec->alignment_power;
@}

static inline flagword
bfd_section_flags (const asection *sec)
@{
  return sec->flags;
@}

static inline void *
bfd_section_userdata (const asection *sec)
@{
  return sec->userdata;
@}
static inline bool
bfd_is_com_section (const asection *sec)
@{
  return (sec->flags & SEC_IS_COMMON) != 0;
@}

/* Note: the following are provided as inline functions rather than macros
   because not all callers use the return value.  A macro implementation
   would use a comma expression, eg: "((ptr)->foo = val, TRUE)" and some
   compilers will complain about comma expressions that have no effect.  */
static inline bool
bfd_set_section_userdata (asection *sec, void *val)
@{
  sec->userdata = val;
  return true;
@}

static inline bool
bfd_set_section_vma (asection *sec, bfd_vma val)
@{
  sec->vma = sec->lma = val;
  sec->user_set_vma = true;
  return true;
@}

static inline bool
bfd_set_section_lma (asection *sec, bfd_vma val)
@{
  sec->lma = val;
  return true;
@}

static inline bool
bfd_set_section_alignment (asection *sec, unsigned int val)
@{
  sec->alignment_power = val;
  return true;
@}

/* These sections are global, and are managed by BFD.  The application
   and target back end are not permitted to change the values in
   these sections.  */
extern asection _bfd_std_section[4];

#define BFD_ABS_SECTION_NAME "*ABS*"
#define BFD_UND_SECTION_NAME "*UND*"
#define BFD_COM_SECTION_NAME "*COM*"
#define BFD_IND_SECTION_NAME "*IND*"

/* Pointer to the common section.  */
#define bfd_com_section_ptr (&_bfd_std_section[0])
/* Pointer to the undefined section.  */
#define bfd_und_section_ptr (&_bfd_std_section[1])
/* Pointer to the absolute section.  */
#define bfd_abs_section_ptr (&_bfd_std_section[2])
/* Pointer to the indirect section.  */
#define bfd_ind_section_ptr (&_bfd_std_section[3])

static inline bool
bfd_is_und_section (const asection *sec)
@{
  return sec == bfd_und_section_ptr;
@}

static inline bool
bfd_is_abs_section (const asection *sec)
@{
  return sec == bfd_abs_section_ptr;
@}

static inline bool
bfd_is_ind_section (const asection *sec)
@{
  return sec == bfd_ind_section_ptr;
@}

static inline bool
bfd_is_const_section (const asection *sec)
@{
  return (sec >= _bfd_std_section
          && sec < _bfd_std_section + (sizeof (_bfd_std_section)
                                       / sizeof (_bfd_std_section[0])));
@}

/* Return TRUE if input section SEC has been discarded.  */
static inline bool
discarded_section (const asection *sec)
@{
  return (!bfd_is_abs_section (sec)
          && bfd_is_abs_section (sec->output_section)
          && sec->sec_info_type != SEC_INFO_TYPE_MERGE
          && sec->sec_info_type != SEC_INFO_TYPE_JUST_SYMS);
@}

#define BFD_FAKE_SECTION(SEC, SYM, NAME, IDX, FLAGS)                   \
  /* name, next, prev, id,  section_id, index, flags, user_set_vma, */ \
  @{  NAME, NULL, NULL, IDX, 0,          0,     FLAGS, 0,               \
                                                                       \
  /* linker_mark, linker_has_input, gc_mark, decompress_status,     */ \
     0,           0,                1,       0,                        \
                                                                       \
  /* segment_mark, sec_info_type, use_rela_p,                       */ \
     0,            0,             0,                                   \
                                                                       \
  /* sec_flg0, sec_flg1, sec_flg2, sec_flg3, sec_flg4, sec_flg5,    */ \
     0,        0,        0,        0,        0,        0,              \
                                                                       \
  /* vma, lma, size, rawsize, compressed_size,                      */ \
     0,   0,   0,    0,       0,                                       \
                                                                       \
  /* output_offset, output_section, relocation, orelocation,        */ \
     0,             &SEC,           NULL,       NULL,                  \
                                                                       \
  /* reloc_count, alignment_power, filepos, rel_filepos,            */ \
     0,           0,               0,       0,                         \
                                                                       \
  /* line_filepos, userdata, contents, lineno, lineno_count,        */ \
     0,            NULL,     NULL,     NULL,   0,                      \
                                                                       \
  /* entsize, kept_section, moving_line_filepos,                    */ \
     0,       NULL,         0,                                         \
                                                                       \
  /* target_index, used_by_bfd, constructor_chain, owner,           */ \
     0,            NULL,        NULL,              NULL,               \
                                                                       \
  /* symbol,                    symbol_ptr_ptr,                     */ \
     (struct bfd_symbol *) SYM, &SEC.symbol,                           \
                                                                       \
  /* map_head, map_tail, already_assigned, type                     */ \
     @{ NULL @}, @{ NULL @}, NULL,             0                           \
                                                                       \
    @}

/* We use a macro to initialize the static asymbol structures because
   traditional C does not permit us to initialize a union member while
   gcc warns if we don't initialize it.
   the_bfd, name, value, attr, section [, udata]  */
#ifdef __STDC__
#define GLOBAL_SYM_INIT(NAME, SECTION) \
  @{ 0, NAME, 0, BSF_SECTION_SYM, SECTION, @{ 0 @}@}
#else
#define GLOBAL_SYM_INIT(NAME, SECTION) \
  @{ 0, NAME, 0, BSF_SECTION_SYM, SECTION @}
#endif

@end example

@node section prototypes,  , typedef asection, Sections
@subsection Section prototypes
These are the functions exported by the section handling part of BFD.

@findex bfd_section_list_clear
@subsubsection @code{bfd_section_list_clear}
@strong{Synopsis}
@example
void bfd_section_list_clear (bfd *);
@end example
@strong{Description}@*
Clears the section list, and also resets the section count and
hash table entries.

@findex bfd_get_section_by_name
@subsubsection @code{bfd_get_section_by_name}
@strong{Synopsis}
@example
asection *bfd_get_section_by_name (bfd *abfd, const char *name);
@end example
@strong{Description}@*
Return the most recently created section attached to @var{abfd}
named @var{name}.  Return NULL if no such section exists.

@findex bfd_get_next_section_by_name
@subsubsection @code{bfd_get_next_section_by_name}
@strong{Synopsis}
@example
asection *bfd_get_next_section_by_name (bfd *ibfd, asection *sec);
@end example
@strong{Description}@*
Given @var{sec} is a section returned by @code{bfd_get_section_by_name},
return the next most recently created section attached to the same
BFD with the same name, or if no such section exists in the same BFD and
IBFD is non-NULL, the next section with the same name in any input
BFD following IBFD.  Return NULL on finding no section.

@findex bfd_get_linker_section
@subsubsection @code{bfd_get_linker_section}
@strong{Synopsis}
@example
asection *bfd_get_linker_section (bfd *abfd, const char *name);
@end example
@strong{Description}@*
Return the linker created section attached to @var{abfd}
named @var{name}.  Return NULL if no such section exists.

@findex bfd_get_section_by_name_if
@subsubsection @code{bfd_get_section_by_name_if}
@strong{Synopsis}
@example
asection *bfd_get_section_by_name_if
   (bfd *abfd,
    const char *name,
    bool (*func) (bfd *abfd, asection *sect, void *obj),
    void *obj);
@end example
@strong{Description}@*
Call the provided function @var{func} for each section
attached to the BFD @var{abfd} whose name matches @var{name},
passing @var{obj} as an argument. The function will be called
as if by

@example
       func (abfd, the_section, obj);
@end example

It returns the first section for which @var{func} returns true,
otherwise @code{NULL}.

@findex bfd_get_unique_section_name
@subsubsection @code{bfd_get_unique_section_name}
@strong{Synopsis}
@example
char *bfd_get_unique_section_name
   (bfd *abfd, const char *templat, int *count);
@end example
@strong{Description}@*
Invent a section name that is unique in @var{abfd} by tacking
a dot and a digit suffix onto the original @var{templat}.  If
@var{count} is non-NULL, then it specifies the first number
tried as a suffix to generate a unique name.  The value
pointed to by @var{count} will be incremented in this case.

@findex bfd_make_section_old_way
@subsubsection @code{bfd_make_section_old_way}
@strong{Synopsis}
@example
asection *bfd_make_section_old_way (bfd *abfd, const char *name);
@end example
@strong{Description}@*
Create a new empty section called @var{name}
and attach it to the end of the chain of sections for the
BFD @var{abfd}. An attempt to create a section with a name which
is already in use returns its pointer without changing the
section chain.

It has the funny name since this is the way it used to be
before it was rewritten....

Possible errors are:
@itemize @bullet

@item
@code{bfd_error_invalid_operation} -
If output has already started for this BFD.
@item
@code{bfd_error_no_memory} -
If memory allocation fails.
@end itemize

@findex bfd_make_section_anyway_with_flags
@subsubsection @code{bfd_make_section_anyway_with_flags}
@strong{Synopsis}
@example
asection *bfd_make_section_anyway_with_flags
   (bfd *abfd, const char *name, flagword flags);
@end example
@strong{Description}@*
Create a new empty section called @var{name} and attach it to the end of
the chain of sections for @var{abfd}.  Create a new section even if there
is already a section with that name.  Also set the attributes of the
new section to the value @var{flags}.

Return @code{NULL} and set @code{bfd_error} on error; possible errors are:
@itemize @bullet

@item
@code{bfd_error_invalid_operation} - If output has already started for @var{abfd}.
@item
@code{bfd_error_no_memory} - If memory allocation fails.
@end itemize

@findex bfd_make_section_anyway
@subsubsection @code{bfd_make_section_anyway}
@strong{Synopsis}
@example
asection *bfd_make_section_anyway (bfd *abfd, const char *name);
@end example
@strong{Description}@*
Create a new empty section called @var{name} and attach it to the end of
the chain of sections for @var{abfd}.  Create a new section even if there
is already a section with that name.

Return @code{NULL} and set @code{bfd_error} on error; possible errors are:
@itemize @bullet

@item
@code{bfd_error_invalid_operation} - If output has already started for @var{abfd}.
@item
@code{bfd_error_no_memory} - If memory allocation fails.
@end itemize

@findex bfd_make_section_with_flags
@subsubsection @code{bfd_make_section_with_flags}
@strong{Synopsis}
@example
asection *bfd_make_section_with_flags
   (bfd *, const char *name, flagword flags);
@end example
@strong{Description}@*
Like @code{bfd_make_section_anyway}, but return @code{NULL} (without calling
bfd_set_error ()) without changing the section chain if there is already a
section named @var{name}.  Also set the attributes of the new section to
the value @var{flags}.  If there is an error, return @code{NULL} and set
@code{bfd_error}.

@findex bfd_make_section
@subsubsection @code{bfd_make_section}
@strong{Synopsis}
@example
asection *bfd_make_section (bfd *, const char *name);
@end example
@strong{Description}@*
Like @code{bfd_make_section_anyway}, but return @code{NULL} (without calling
bfd_set_error ()) without changing the section chain if there is already a
section named @var{name}.  If there is an error, return @code{NULL} and set
@code{bfd_error}.

@findex bfd_set_section_flags
@subsubsection @code{bfd_set_section_flags}
@strong{Synopsis}
@example
bool bfd_set_section_flags (asection *sec, flagword flags);
@end example
@strong{Description}@*
Set the attributes of the section @var{sec} to the value @var{flags}.
Return @code{TRUE} on success, @code{FALSE} on error.  Possible error
returns are:

@itemize @bullet

@item
@code{bfd_error_invalid_operation} -
The section cannot have one or more of the attributes
requested. For example, a .bss section in @code{a.out} may not
have the @code{SEC_HAS_CONTENTS} field set.
@end itemize

@findex bfd_rename_section
@subsubsection @code{bfd_rename_section}
@strong{Synopsis}
@example
void bfd_rename_section
   (asection *sec, const char *newname);
@end example
@strong{Description}@*
Rename section @var{sec} to @var{newname}.

@findex bfd_map_over_sections
@subsubsection @code{bfd_map_over_sections}
@strong{Synopsis}
@example
void bfd_map_over_sections
   (bfd *abfd,
    void (*func) (bfd *abfd, asection *sect, void *obj),
    void *obj);
@end example
@strong{Description}@*
Call the provided function @var{func} for each section
attached to the BFD @var{abfd}, passing @var{obj} as an
argument. The function will be called as if by

@example
       func (abfd, the_section, obj);
@end example

This is the preferred method for iterating over sections; an
alternative would be to use a loop:

@example
          asection *p;
          for (p = abfd->sections; p != NULL; p = p->next)
             func (abfd, p, ...)
@end example

@findex bfd_sections_find_if
@subsubsection @code{bfd_sections_find_if}
@strong{Synopsis}
@example
asection *bfd_sections_find_if
   (bfd *abfd,
    bool (*operation) (bfd *abfd, asection *sect, void *obj),
    void *obj);
@end example
@strong{Description}@*
Call the provided function @var{operation} for each section
attached to the BFD @var{abfd}, passing @var{obj} as an
argument. The function will be called as if by

@example
       operation (abfd, the_section, obj);
@end example

It returns the first section for which @var{operation} returns true.

@findex bfd_set_section_size
@subsubsection @code{bfd_set_section_size}
@strong{Synopsis}
@example
bool bfd_set_section_size (asection *sec, bfd_size_type val);
@end example
@strong{Description}@*
Set @var{sec} to the size @var{val}. If the operation is
ok, then @code{TRUE} is returned, else @code{FALSE}.

Possible error returns:
@itemize @bullet

@item
@code{bfd_error_invalid_operation} -
Writing has started to the BFD, so setting the size is invalid.
@end itemize

@findex bfd_set_section_contents
@subsubsection @code{bfd_set_section_contents}
@strong{Synopsis}
@example
bool bfd_set_section_contents
   (bfd *abfd, asection *section, const void *data,
    file_ptr offset, bfd_size_type count);
@end example
@strong{Description}@*
Sets the contents of the section @var{section} in BFD
@var{abfd} to the data starting in memory at @var{location}.
The data is written to the output section starting at offset
@var{offset} for @var{count} octets.

Normally @code{TRUE} is returned, but @code{FALSE} is returned if
there was an error.  Possible error returns are:
@itemize @bullet

@item
@code{bfd_error_no_contents} -
The output section does not have the @code{SEC_HAS_CONTENTS}
attribute, so nothing can be written to it.
@item
@code{bfd_error_bad_value} -
The section is unable to contain all of the data.
@item
@code{bfd_error_invalid_operation} -
The BFD is not writeable.
@item
and some more too.
@end itemize
This routine is front end to the back end function
@code{_bfd_set_section_contents}.

@findex bfd_get_section_contents
@subsubsection @code{bfd_get_section_contents}
@strong{Synopsis}
@example
bool bfd_get_section_contents
   (bfd *abfd, asection *section, void *location, file_ptr offset,
    bfd_size_type count);
@end example
@strong{Description}@*
Read data from @var{section} in BFD @var{abfd}
into memory starting at @var{location}. The data is read at an
offset of @var{offset} from the start of the input section,
and is read for @var{count} bytes.

If the contents of a constructor with the @code{SEC_CONSTRUCTOR}
flag set are requested or if the section does not have the
@code{SEC_HAS_CONTENTS} flag set, then the @var{location} is filled
with zeroes. If no errors occur, @code{TRUE} is returned, else
@code{FALSE}.

@findex bfd_malloc_and_get_section
@subsubsection @code{bfd_malloc_and_get_section}
@strong{Synopsis}
@example
bool bfd_malloc_and_get_section
   (bfd *abfd, asection *section, bfd_byte **buf);
@end example
@strong{Description}@*
Read all data from @var{section} in BFD @var{abfd}
into a buffer, *@var{buf}, malloc'd by this function.

@findex bfd_copy_private_section_data
@subsubsection @code{bfd_copy_private_section_data}
@strong{Synopsis}
@example
bool bfd_copy_private_section_data
   (bfd *ibfd, asection *isec, bfd *obfd, asection *osec);
@end example
@strong{Description}@*
Copy private section information from @var{isec} in the BFD
@var{ibfd} to the section @var{osec} in the BFD @var{obfd}.
Return @code{TRUE} on success, @code{FALSE} on error.  Possible error
returns are:

@itemize @bullet

@item
@code{bfd_error_no_memory} -
Not enough memory exists to create private data for @var{osec}.
@end itemize
@example
#define bfd_copy_private_section_data(ibfd, isection, obfd, osection) \
       BFD_SEND (obfd, _bfd_copy_private_section_data, \
                 (ibfd, isection, obfd, osection))
@end example

@findex bfd_generic_is_group_section
@subsubsection @code{bfd_generic_is_group_section}
@strong{Synopsis}
@example
bool bfd_generic_is_group_section (bfd *, const asection *sec);
@end example
@strong{Description}@*
Returns TRUE if @var{sec} is a member of a group.

@findex bfd_generic_group_name
@subsubsection @code{bfd_generic_group_name}
@strong{Synopsis}
@example
const char *bfd_generic_group_name (bfd *, const asection *sec);
@end example
@strong{Description}@*
Returns group name if @var{sec} is a member of a group.

@findex bfd_generic_discard_group
@subsubsection @code{bfd_generic_discard_group}
@strong{Synopsis}
@example
bool bfd_generic_discard_group (bfd *abfd, asection *group);
@end example
@strong{Description}@*
Remove all members of @var{group} from the output.