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.
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.
COPYRIGHT¶
2003-2019, LLVM Project
