Provided by: llvm-3.3_3.3-16ubuntu1_amd64 
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 both SVR4 and BSD style archive files. However, it
cannot be used to write them. While the llvm-ar command produces files that are almost
identical to the format used by other ar implementations, it has two significant
departures in order to make the archive appropriate for LLVM. The first departure is that
llvm-ar only uses BSD4.4 style long path names (stored immediately after the header) and
never contains a string table for long names. The second departure is that the symbol
table is formated for efficient construction of an in-memory data structure that permits
rapid (red-black tree) lookups. Consequently, archives produced with llvm-ar usually won't
be readable or editable with any ar implementation or useful for linking. Using the f
modifier to flatten file names will make the archive readable by other ar implementations
but not for linking because the symbol table format for LLVM is unique. If an SVR4 or BSD
style archive is used with the r (replace) or q (quick update) operations, the archive
will be reconstructed in LLVM format. This means that the string table will be dropped (in
deference to BSD 4.4 long names) and an LLVM symbol table will be added (by default). The
system symbol table will be retained.
Here's where llvm-ar departs from previous ar implementations:
Symbol Table
Since llvm-ar is intended to archive bitcode files, the symbol table won't make much
sense to anything but LLVM. Consequently, the symbol table's format has been
simplified. It consists simply of a sequence of pairs of a file member index number as
an LSB 4byte integer and a null-terminated string.
Long Paths
Some ar implementations (SVR4) use a separate file member to record long path names (>
15 characters). llvm-ar takes the BSD 4.4 and Mac OS X approach which is to simply
store the full path name immediately preceding the data for the file. The path name is
null terminated and may contain the slash (/) character.
Directory Recursion
Most ar implementations do not recurse through directories but simply ignore
directories if they are presented to the program in the files option. llvm-ar, however,
can recurse through directory structures and add all the files under a directory, if
requested.
TOC Verbose Output
When llvm-ar prints out the verbose table of contents (tv option), it precedes the
usual output with a character indicating the basic kind of content in the file. A blank
means the file is a regular file. A 'B' means the file is an LLVM bitcode file. An 'S'
means the file is the symbol table.
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[k]
Print files to the standard output. The k modifier applies to this operation. 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[Rf]
Quickly append files to the end of the archive. The R, and f modifiers apply to this
operation. 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[Rabfu]
Replace or insert file members. The R, a, b, f, 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.
[f]
Normally, llvm-ar stores the full path name to a file as presented to it on the command
line. With this option, truncated (15 characters max) names are used. This ensures name
compatibility with older versions of ar but may also thwart correct extraction of the
files (duplicates may overwrite). If used with the R option, the directory recursion
will be performed but the file names will all be flattened to simple file names.
[i]
A synonym for the b option.
[k]
Normally, llvm-ar will not print the contents of bitcode files when the p operation is
used. This modifier defeats the default and allows the bitcode members to be printed.
[N]
This option is ignored by llvm-ar but provided for compatibility.
[o]
When extracting files, this option will cause llvm-ar to preserve the original
modification times of the files it writes.
[P]
use full path names when matching
[R]
This modifier instructions the r option to recursively process directories. Without R,
directories are ignored and only those files that refer to files will be added to the
archive. When R is used, any directories specified with files will be scanned
(recursively) to find files to be added to the archive. Any file whose name begins with
a dot will not be added.
[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.
Using this modifier is more efficient that using llvm-ranlib|llvm-ranlib which also
creates the symbol table.
[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 Mac OS X) 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 Mac OSX 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.
The LLVM symbol table has the special name "#_LLVM_SYM_TAB_#". It is presumed that no
regular archive member file will want this name. The LLVM symbol table is simply composed
of a sequence of triplets: byte offset, length of symbol, and the symbol itself. Symbols
are not null or newline terminated. Here are the details on each of these items:
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.
SEE ALSO
llvm-ranlib|llvm-ranlib, ar(1)
AUTHOR
Maintained by The LLVM Team (http://llvm.org/).
COPYRIGHT
2003-2013, LLVM Project