Ubuntu Manpage: llvm-ar - LLVM archiver

NAME

       llvm-ar - LLVM archiver

SYNOPSIS

       llvm-ar [-]{dmpqrtx}[Rabfikou] [relpos] [count] <archive> [files…]

DESCRIPTION

       The  llvm-ar  command is similar to the common Unix utility, ar. It archives several files
       together into a single file. The intent for this is to produce archive libraries  by  LLVM
       bitcode that can be linked into an LLVM program. However, the archive can contain any kind
       of file. By default, llvm-ar generates a symbol table that makes  linking  faster  because
       only  the  symbol  table  needs  to  be  consulted, not each individual file member of the
       archive.

       The llvm-ar command can be used to read SVR4, GNU and BSD style  archive  files.  However,
       right  now  it  can  only write in the GNU format. If an SVR4 or BSD style archive is used
       with the r (replace) or q (quick update) operations, the archive will be reconstructed  in
       GNU format.

       Here’s where llvm-ar departs from previous ar implementations:

       Symbol Table
          Since  llvm-ar supports bitcode files. The symbol table it creates is in GNU format and
          includes both native and bitcode files.

       Long Paths
          Currently llvm-ar can read GNU and BSD long file names, but only writes  archives  with
          the GNU format.

OPTIONS

       The options to llvm-ar are compatible with other ar implementations.  However, there are a
       few modifiers (R) that are not found in other ar implementations. The options  to  llvm-ar
       specify  a  single  basic  operation to perform on the archive, a variety of modifiers for
       that operation, the name of the archive file, and an optional list of  file  names.  These
       options are used to determine how llvm-ar should process the archive file.

       The  Operations  and  Modifiers  are  explained  in the sections below. The minimal set of
       options is at least one operator and the name of the archive. Typically archive files  end
       with  a  .a  suffix,  but this is not required. Following the archive-name comes a list of
       files that indicate the specific members of the archive to operate on. If the files option
       is  not  specified,  it  generally  means either “none” or “all” members, depending on the
       operation.

   Operations
       d
          Delete files from the archive. No modifiers are  applicable  to  this  operation.   The
          files  options  specify  which members should be removed from the archive. It is not an
          error if a specified file does not appear in the archive.  If no files  are  specified,
          the archive is not modified.

       m[abi]
          Move files from one location in the archive to another. The a, b, and i modifiers apply
          to this operation. The files will all be moved to the location given by the  modifiers.
          If  no  modifiers  are  used,  the files will be moved to the end of the archive. If no
          files are specified, the archive is not modified.

       p
          Print files to the standard output. This operation simply prints the files indicated to
          the  standard  output.  If  no  files  are  specified,  the entire  archive is printed.
          Printing bitcode files is ill-advised as they might confuse your terminal settings. The
          p operation never modifies the archive.

       q
          Quickly  append files to the end of the archive.  This operation quickly adds the files
          to the archive without checking for duplicates that should  be  removed  first.  If  no
          files  are  specified,  the  archive  is not modified.  Because of the way that llvm-ar
          constructs the archive file, its dubious whether the q operation is any faster than the
          r operation.

       r[abu]
          Replace  or  insert  file  members. The a, b,  and u modifiers apply to this operation.
          This operation will replace existing files or insert them at the end of the archive  if
          they do not exist. If no files are specified, the archive is not modified.

       t[v]
          Print  the  table  of  contents.  Without any modifiers, this operation just prints the
          names of the members to the standard output. With the v modifier, llvm-ar  also  prints
          out the file type (B=bitcode, S=symbol table, blank=regular file), the permission mode,
          the owner and group, the size, and the date. If any files are specified, the listing is
          only  for  those  files. If no files are specified, the table of contents for the whole
          archive is printed.

       x[oP]
          Extract archive members back to files. The o modifier applies to this  operation.  This
          operation  retrieves  the  indicated files from the archive and writes them back to the
          operating system’s file system. If no  files  are  specified,  the  entire  archive  is
          extract.

   Modifiers (operation specific)
       The modifiers below are specific to certain operations. See the Operations section (above)
       to determine which modifiers are applicable to which operations.

       [a]
          When inserting or moving member files, this option specifies the destination of the new
          files as being after the relpos member. If relpos is not found, the files are placed at
          the end of the archive.

       [b]
          When inserting or moving member files, this option specifies the destination of the new
          files  as  being before the relpos member. If relpos is not found, the files are placed
          at the end of the archive. This modifier is identical to the i modifier.

       [i]
          A synonym for the b option.

       [o]
          When extracting files,  this  option  will  cause  llvm-ar  to  preserve  the  original
          modification times of the files it writes.

       [u]
          When replacing existing files in the archive, only replace those files that have a time
          stamp than the time stamp of the member in the archive.

   Modifiers (generic)
       The modifiers below may be applied to any operation.

       [c]
          For all operations, llvm-ar will  always  create  the  archive  if  it  doesn’t  exist.
          Normally,  llvm-ar  will  print  a warning message indicating that the archive is being
          created. Using this modifier turns off that warning.

       [s]
          This modifier requests that an archive index (or symbol table) be added to the archive.
          This is the default mode of operation. The symbol table will contain all the externally
          visible functions and global variables defined by all the bitcode files in the archive.

       [S]
          This modifier is the opposite of the s modifier. It instructs llvm-ar to not build  the
          symbol  table. If both s and S are used, the last modifier to occur in the options will
          prevail.

       [v]
          This modifier instructs llvm-ar to be verbose about what  it  is  doing.  Each  editing
          operation  taken against the archive will produce a line of output saying what is being
          done.

STANDARDS

       The llvm-ar utility is intended to provide a superset of the  IEEE  Std  1003.2  (POSIX.2)
       functionality  for ar. llvm-ar can read both SVR4 and BSD4.4 (or macOS) archives. If the f
       modifier is given to the x or  r  operations  then  llvm-ar  will  write  SVR4  compatible
       archives.  Without  this modifier, llvm-ar will write BSD4.4 compatible archives that have
       long names immediately after the header and indicated using the “#1/ddd” notation for  the
       name in the header.

FILE FORMAT

The file format for LLVM Archive files is similar to that of BSD 4.4 or macOS archive
files. In fact, except for the symbol table, the ar commands on those operating systems
should be able to read LLVM archive files. The details of the file format follow.

Each archive begins with the archive magic number which is the eight printable characters
“!<arch>n” where n represents the newline character (0x0A). Following the magic number,
the file is composed of even length members that begin with an archive header and end with
a n padding character if necessary (to make the length even). Each file member is composed
of a header (defined below), an optional newline-terminated “long file name” and the
contents of the file.

The fields of the header are described in the items below. All fields of the header
contain only ASCII characters, are left justified and are right padded with space
characters.

name - char[16]
This field of the header provides the name of the archive member. If the name is longer
than 15 characters or contains a slash (/) character, then this field contains #1/nnn
where nnn provides the length of the name and the #1/ is literal. In this case, the
actual name of the file is provided in the nnn bytes immediately following the header.
If the name is 15 characters or less, it is contained directly in this field and
terminated with a slash (/) character.

date - char[12]
This field provides the date of modification of the file in the form of a decimal
encoded number that provides the number of seconds since the epoch (since 00:00:00 Jan
1, 1970) per Posix specifications.

uid - char[6]
This field provides the user id of the file encoded as a decimal ASCII string. This
field might not make much sense on non-Unix systems. On Unix, it is the same value as
the st_uid field of the stat structure returned by the stat(2) operating system call.

gid - char[6]
This field provides the group id of the file encoded as a decimal ASCII string. This
field might not make much sense on non-Unix systems. On Unix, it is the same value as
the st_gid field of the stat structure returned by the stat(2) operating system call.

mode - char[8]
This field provides the access mode of the file encoded as an octal ASCII string. This
field might not make much sense on non-Unix systems. On Unix, it is the same value as
the st_mode field of the stat structure returned by the stat(2) operating system call.

size - char[10]
This field provides the size of the file, in bytes, encoded as a decimal ASCII string.

fmag - char[2]
This field is the archive file member magic number. Its content is always the two
characters back tick (0x60) and newline (0x0A). This provides some measure utility in
identifying archive files that have been corrupted.

offset - vbr encoded 32-bit integer
The offset item provides the offset into the archive file where the bitcode member is
stored that is associated with the symbol. The offset value is 0 based at the start of
the first “normal” file member. To derive the actual file offset of the member, you
must add the number of bytes occupied by the file signature (8 bytes) and the symbol
tables. The value of this item is encoded using variable bit rate encoding to reduce
the size of the symbol table. Variable bit rate encoding uses the high bit (0x80) of
each byte to indicate if there are more bytes to follow. The remaining 7 bits in each
byte carry bits from the value. The final byte does not have the high bit set.

length - vbr encoded 32-bit integer
The length item provides the length of the symbol that follows. Like this offset item,
the length is variable bit rate encoded.

symbol - character array
The symbol item provides the text of the symbol that is associated with the offset. The
symbol is not terminated by any character. Its length is provided by the length field.
Note that is allowed (but unwise) to use non-printing characters (even 0x00) in the
symbol. This allows for multiple encodings of symbol names.

EXIT STATUS

       If llvm-ar succeeds, it will exit with 0.  A usage error, results in an exit code of 1.  A
       hard  (file system typically) error results in an exit code of 2. Miscellaneous or unknown
       errors result in an exit code of 3.

AUTHOR

       Maintained by the LLVM Team (https://llvm.org/).

COPYRIGHT

       2003-2019, LLVM Project