1 llvm-ar - LLVM archiver
2 =======================
9 **llvm-ar** [-]{dmpqrtx}[Rabfikouz] [relpos] [count] <archive> [files...]
16 The **llvm-ar** command is similar to the common Unix utility, ``ar``. It
17 archives several files together into a single file. The intent for this is
18 to produce archive libraries by LLVM bitcode that can be linked into an
19 LLVM program. However, the archive can contain any kind of file. By default,
20 **llvm-ar** generates a symbol table that makes linking faster because
21 only the symbol table needs to be consulted, not each individual file member
24 The **llvm-ar** command can be used to *read* both SVR4 and BSD style archive
25 files. However, it cannot be used to write them. While the **llvm-ar** command
26 produces files that are *almost* identical to the format used by other ``ar``
27 implementations, it has two significant departures in order to make the
28 archive appropriate for LLVM. The first departure is that **llvm-ar** only
29 uses BSD4.4 style long path names (stored immediately after the header) and
30 never contains a string table for long names. The second departure is that the
31 symbol table is formated for efficient construction of an in-memory data
32 structure that permits rapid (red-black tree) lookups. Consequently, archives
33 produced with **llvm-ar** usually won't be readable or editable with any
34 ``ar`` implementation or useful for linking. Using the ``f`` modifier to flatten
35 file names will make the archive readable by other ``ar`` implementations
36 but not for linking because the symbol table format for LLVM is unique. If an
37 SVR4 or BSD style archive is used with the ``r`` (replace) or ``q`` (quick
38 update) operations, the archive will be reconstructed in LLVM format. This
39 means that the string table will be dropped (in deference to BSD 4.4 long names)
40 and an LLVM symbol table will be added (by default). The system symbol table
43 Here's where **llvm-ar** departs from previous ``ar`` implementations:
48 Since **llvm-ar** is intended to archive bitcode files, the symbol table
49 won't make much sense to anything but LLVM. Consequently, the symbol table's
50 format has been simplified. It consists simply of a sequence of pairs
51 of a file member index number as an LSB 4byte integer and a null-terminated
58 Some ``ar`` implementations (SVR4) use a separate file member to record long
59 path names (> 15 characters). **llvm-ar** takes the BSD 4.4 and Mac OS X
60 approach which is to simply store the full path name immediately preceding
61 the data for the file. The path name is null terminated and may contain the
68 **llvm-ar** can compress the members of an archive to save space. The
69 compression used depends on what's available on the platform and what choices
70 the LLVM Compressor utility makes. It generally favors bzip2 but will select
71 between "no compression" or bzip2 depending on what makes sense for the
78 Most ``ar`` implementations do not recurse through directories but simply
79 ignore directories if they are presented to the program in the *files*
80 option. **llvm-ar**, however, can recurse through directory structures and
81 add all the files under a directory, if requested.
87 When **llvm-ar** prints out the verbose table of contents (``tv`` option), it
88 precedes the usual output with a character indicating the basic kind of
89 content in the file. A blank means the file is a regular file. A 'Z' means
90 the file is compressed. A 'B' means the file is an LLVM bitcode file. An
91 'S' means the file is the symbol table.
100 The options to **llvm-ar** are compatible with other ``ar`` implementations.
101 However, there are a few modifiers (*zR*) that are not found in other ``ar``
102 implementations. The options to **llvm-ar** specify a single basic operation to
103 perform on the archive, a variety of modifiers for that operation, the name of
104 the archive file, and an optional list of file names. These options are used to
105 determine how **llvm-ar** should process the archive file.
107 The Operations and Modifiers are explained in the sections below. The minimal
108 set of options is at least one operator and the name of the archive. Typically
109 archive files end with a ``.a`` suffix, but this is not required. Following
110 the *archive-name* comes a list of *files* that indicate the specific members
111 of the archive to operate on. If the *files* option is not specified, it
112 generally means either "none" or "all" members, depending on the operation.
121 Delete files from the archive. No modifiers are applicable to this operation.
122 The *files* options specify which members should be removed from the
123 archive. It is not an error if a specified file does not appear in the archive.
124 If no *files* are specified, the archive is not modified.
130 Move files from one location in the archive to another. The *a*, *b*, and
131 *i* modifiers apply to this operation. The *files* will all be moved
132 to the location given by the modifiers. If no modifiers are used, the files
133 will be moved to the end of the archive. If no *files* are specified, the
134 archive is not modified.
140 Print files to the standard output. The *k* modifier applies to this
141 operation. This operation simply prints the *files* indicated to the
142 standard output. If no *files* are specified, the entire archive is printed.
143 Printing bitcode files is ill-advised as they might confuse your terminal
144 settings. The *p* operation never modifies the archive.
150 Quickly append files to the end of the archive. The *R*, *f*, and *z*
151 modifiers apply to this operation. This operation quickly adds the
152 *files* to the archive without checking for duplicates that should be
153 removed first. If no *files* are specified, the archive is not modified.
154 Because of the way that **llvm-ar** constructs the archive file, its dubious
155 whether the *q* operation is any faster than the *r* operation.
161 Replace or insert file members. The *R*, *a*, *b*, *f*, *u*, and *z*
162 modifiers apply to this operation. This operation will replace existing
163 *files* or insert them at the end of the archive if they do not exist. If no
164 *files* are specified, the archive is not modified.
170 Print the table of contents. Without any modifiers, this operation just prints
171 the names of the members to the standard output. With the *v* modifier,
172 **llvm-ar** also prints out the file type (B=bitcode, Z=compressed, S=symbol
173 table, blank=regular file), the permission mode, the owner and group, the
174 size, and the date. If any *files* are specified, the listing is only for
175 those files. If no *files* are specified, the table of contents for the
176 whole archive is printed.
182 Extract archive members back to files. The *o* modifier applies to this
183 operation. This operation retrieves the indicated *files* from the archive
184 and writes them back to the operating system's file system. If no
185 *files* are specified, the entire archive is extract.
190 Modifiers (operation specific)
191 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
194 The modifiers below are specific to certain operations. See the Operations
195 section (above) to determine which modifiers are applicable to which operations.
200 When inserting or moving member files, this option specifies the destination of
201 the new files as being after the *relpos* member. If *relpos* is not found,
202 the files are placed at the end of the archive.
208 When inserting or moving member files, this option specifies the destination of
209 the new files as being before the *relpos* member. If *relpos* is not
210 found, the files are placed at the end of the archive. This modifier is
211 identical to the the *i* modifier.
217 Normally, **llvm-ar** stores the full path name to a file as presented to it on
218 the command line. With this option, truncated (15 characters max) names are
219 used. This ensures name compatibility with older versions of ``ar`` but may also
220 thwart correct extraction of the files (duplicates may overwrite). If used with
221 the *R* option, the directory recursion will be performed but the file names
222 will all be flattened to simple file names.
228 A synonym for the *b* option.
234 Normally, **llvm-ar** will not print the contents of bitcode files when the
235 *p* operation is used. This modifier defeats the default and allows the
236 bitcode members to be printed.
242 This option is ignored by **llvm-ar** but provided for compatibility.
248 When extracting files, this option will cause **llvm-ar** to preserve the
249 original modification times of the files it writes.
255 use full path names when matching
261 This modifier instructions the *r* option to recursively process directories.
262 Without *R*, directories are ignored and only those *files* that refer to
263 files will be added to the archive. When *R* is used, any directories specified
264 with *files* will be scanned (recursively) to find files to be added to the
265 archive. Any file whose name begins with a dot will not be added.
271 When replacing existing files in the archive, only replace those files that have
272 a time stamp than the time stamp of the member in the archive.
278 When inserting or replacing any file in the archive, compress the file first.
280 modifier is safe to use when (previously) compressed bitcode files are added to
281 the archive; the compressed bitcode files will not be doubly compressed.
290 The modifiers below may be applied to any operation.
295 For all operations, **llvm-ar** will always create the archive if it doesn't
296 exist. Normally, **llvm-ar** will print a warning message indicating that the
297 archive is being created. Using this modifier turns off that warning.
303 This modifier requests that an archive index (or symbol table) be added to the
304 archive. This is the default mode of operation. The symbol table will contain
305 all the externally visible functions and global variables defined by all the
306 bitcode files in the archive. Using this modifier is more efficient that using
307 llvm-ranlib|llvm-ranlib which also creates the symbol table.
313 This modifier is the opposite of the *s* modifier. It instructs **llvm-ar** to
314 not build the symbol table. If both *s* and *S* are used, the last modifier to
315 occur in the options will prevail.
321 This modifier instructs **llvm-ar** to be verbose about what it is doing. Each
322 editing operation taken against the archive will produce a line of output saying
333 The **llvm-ar** utility is intended to provide a superset of the IEEE Std 1003.2
334 (POSIX.2) functionality for ``ar``. **llvm-ar** can read both SVR4 and BSD4.4 (or
335 Mac OS X) archives. If the ``f`` modifier is given to the ``x`` or ``r`` operations
336 then **llvm-ar** will write SVR4 compatible archives. Without this modifier,
337 **llvm-ar** will write BSD4.4 compatible archives that have long names
338 immediately after the header and indicated using the "#1/ddd" notation for the
346 The file format for LLVM Archive files is similar to that of BSD 4.4 or Mac OSX
347 archive files. In fact, except for the symbol table, the ``ar`` commands on those
348 operating systems should be able to read LLVM archive files. The details of the
351 Each archive begins with the archive magic number which is the eight printable
352 characters "!<arch>\n" where \n represents the newline character (0x0A).
353 Following the magic number, the file is composed of even length members that
354 begin with an archive header and end with a \n padding character if necessary
355 (to make the length even). Each file member is composed of a header (defined
356 below), an optional newline-terminated "long file name" and the contents of
359 The fields of the header are described in the items below. All fields of the
360 header contain only ASCII characters, are left justified and are right padded
361 with space characters.
366 This field of the header provides the name of the archive member. If the name is
367 longer than 15 characters or contains a slash (/) character, then this field
368 contains ``#1/nnn`` where ``nnn`` provides the length of the name and the ``#1/``
369 is literal. In this case, the actual name of the file is provided in the ``nnn``
370 bytes immediately following the header. If the name is 15 characters or less, it
371 is contained directly in this field and terminated with a slash (/) character.
377 This field provides the date of modification of the file in the form of a
378 decimal encoded number that provides the number of seconds since the epoch
379 (since 00:00:00 Jan 1, 1970) per Posix specifications.
385 This field provides the user id of the file encoded as a decimal ASCII string.
386 This field might not make much sense on non-Unix systems. On Unix, it is the
387 same value as the st_uid field of the stat structure returned by the stat(2)
388 operating system call.
394 This field provides the group id of the file encoded as a decimal ASCII string.
395 This field might not make much sense on non-Unix systems. On Unix, it is the
396 same value as the st_gid field of the stat structure returned by the stat(2)
397 operating system call.
403 This field provides the access mode of the file encoded as an octal ASCII
404 string. This field might not make much sense on non-Unix systems. On Unix, it
405 is the same value as the st_mode field of the stat structure returned by the
406 stat(2) operating system call.
412 This field provides the size of the file, in bytes, encoded as a decimal ASCII
413 string. If the size field is negative (starts with a minus sign, 0x02D), then
414 the archive member is stored in compressed form. The first byte of the archive
415 member's data indicates the compression type used. A value of 0 (0x30) indicates
416 that no compression was used. A value of 2 (0x32) indicates that bzip2
417 compression was used.
423 This field is the archive file member magic number. Its content is always the
424 two characters back tick (0x60) and newline (0x0A). This provides some measure
425 utility in identifying archive files that have been corrupted.
429 The LLVM symbol table has the special name "#_LLVM_SYM_TAB_#". It is presumed
430 that no regular archive member file will want this name. The LLVM symbol table
431 is simply composed of a sequence of triplets: byte offset, length of symbol,
432 and the symbol itself. Symbols are not null or newline terminated. Here are
433 the details on each of these items:
436 offset - vbr encoded 32-bit integer
438 The offset item provides the offset into the archive file where the bitcode
439 member is stored that is associated with the symbol. The offset value is 0
440 based at the start of the first "normal" file member. To derive the actual
441 file offset of the member, you must add the number of bytes occupied by the file
442 signature (8 bytes) and the symbol tables. The value of this item is encoded
443 using variable bit rate encoding to reduce the size of the symbol table.
444 Variable bit rate encoding uses the high bit (0x80) of each byte to indicate
445 if there are more bytes to follow. The remaining 7 bits in each byte carry bits
446 from the value. The final byte does not have the high bit set.
450 length - vbr encoded 32-bit integer
452 The length item provides the length of the symbol that follows. Like this
453 *offset* item, the length is variable bit rate encoded.
457 symbol - character array
459 The symbol item provides the text of the symbol that is associated with the
460 *offset*. The symbol is not terminated by any character. Its length is provided
461 by the *length* field. Note that is allowed (but unwise) to use non-printing
462 characters (even 0x00) in the symbol. This allows for multiple encodings of
472 If **llvm-ar** succeeds, it will exit with 0. A usage error, results
473 in an exit code of 1. A hard (file system typically) error results in an
474 exit code of 2. Miscellaneous or unknown errors result in an
482 llvm-ranlib|llvm-ranlib, ar(1)