1C99(1P) POSIX Programmer's Manual C99(1P)
2
6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
10
13 c99 — compile standard C programs
14
16 c99 [options...] pathname [[pathname] [−I directory]
17 [−L directory] [−l library]]...
18
20 The c99 utility is an interface to the standard C compilation system;
21 it shall accept source code conforming to the ISO C standard. The sys‐
22 tem conceptually consists of a compiler and link editor. The input
23 files referenced by pathname operands and −l option-arguments shall be
24 compiled and linked to produce an executable file. (It is unspecified
25 whether the linking occurs entirely within the operation of c99; some
26 implementations may produce objects that are not fully resolved until
27 the file is executed.)
28 If the −c option is specified, for all pathname operands of the form
30 file.c, the files:
31 $(basename pathname .c).o
33 shall be created as the result of successful compilation. If the −c
35 option is not specified, it is unspecified whether such .o files are
36 created or deleted for the file.c operands.
37 If there are no options that prevent link editing (such as −c or −E),
39 and all input files compile and link without error, the resulting exe‐
40 cutable file shall be written according to the −o outfile option (if
41 present) or to the file a.out.
42 The executable file shall be created as specified in Section 1.1.1.4,
44 File Read, Write, and Creation, except that the file permission bits
45 shall be set to: S_IRWXO | S_IRWXG | S_IRWXU
46 and the bits specified by the umask of the process shall be cleared.
48
50 The c99 utility shall conform to the Base Definitions volume of
51 POSIX.1‐2008, Section 12.2, Utility Syntax Guidelines, except that:
52 * Options can be interspersed with operands.
54 * The order of specifying the −L and −l options, and the order of
56 specifying −l options with respect to pathname operands is signifi‐
57 cant.
58 * Conforming applications shall specify each option separately; that
60 is, grouping option letters (for example, −cO) need not be recog‐
61 nized by all implementations.
62 The following options shall be supported:
64 −c Suppress the link-edit phase of the compilation, and do not
66 remove any object files that are produced.
67 −D name[=value]
69 Define name as if by a C-language #define directive. If no
70 =value is given, a value of 1 shall be used. The −D option
71 has lower precedence than the −U option. That is, if name is
72 used in both a −U and a −D option, name shall be undefined
73 regardless of the order of the options. Additional implemen‐
74 tation-defined names may be provided by the compiler. Imple‐
75 mentations shall support at least 2048 bytes of −D defini‐
76 tions and 256 names.
77 −E Copy C-language source files to standard output, expanding
79 all preprocessor directives; no compilation shall be per‐
80 formed. If any operand is not a text file, the effects are
81 unspecified.
82 −g Produce symbolic information in the object or executable
84 files; the nature of this information is unspecified, and may
85 be modified by implementation-defined interactions with other
86 options.
87 −I directory
89 Change the algorithm for searching for headers whose names
90 are not absolute pathnames to look in the directory named by
91 the directory pathname before looking in the usual places.
92 Thus, headers whose names are enclosed in double-quotes ("")
93 shall be searched for first in the directory of the file with
94 the #include line, then in directories named in −I options,
95 and last in the usual places. For headers whose names are
96 enclosed in angle brackets ("<>"), the header shall be
97 searched for only in directories named in −I options and then
98 in the usual places. Directories named in −I options shall be
99 searched in the order specified. If the −I option is used to
100 specify a directory that is one of the usual places searched
101 by default, the results are unspecified. Implementations
102 shall support at least ten instances of this option in a sin‐
103 gle c99 command invocation.
104 −L directory
106 Change the algorithm of searching for the libraries named in
107 the −l objects to look in the directory named by the direc‐
108 tory pathname before looking in the usual places. Directories
109 named in −L options shall be searched in the order specified.
110 If the −L option is used to specify a directory that is one
111 of the usual places searched by default, the results are
112 unspecified. Implementations shall support at least ten
113 instances of this option in a single c99 command invocation.
114 If a directory specified by a −L option contains files with
115 names starting with any of the strings "libc.", "libl.",
116 "libpthread.", "libm.", "librt.", "libtrace.", "libxnet.", or
117 "liby.", the results are unspecified.
118 −l library
120 Search the library named liblibrary.a. A library shall be
121 searched when its name is encountered, so the placement of a
122 −l option is significant. Several standard libraries can be
123 specified in this manner, as described in the EXTENDED
124 DESCRIPTION section. Implementations may recognize implemen‐
125 tation-defined suffixes other than .a as denoting libraries.
126 −O optlevel
128 Specify the level of code optimization. If the optlevel
129 option-argument is the digit '0', all special code optimiza‐
130 tions shall be disabled. If it is the digit '1', the nature
131 of the optimization is unspecified. If the −O option is omit‐
132 ted, the nature of the system's default optimization is
133 unspecified. It is unspecified whether code generated in the
134 presence of the −O 0 option is the same as that generated
135 when −O is omitted. Other optlevel values may be supported.
136 −o outfile
138 Use the pathname outfile, instead of the default a.out, for
139 the executable file produced. If the −o option is present
140 with −c or −E, the result is unspecified.
141 −s Produce object or executable files, or both, from which sym‐
143 bolic and other information not required for proper execution
144 using the exec family defined in the System Interfaces volume
145 of POSIX.1‐2008 has been removed (stripped). If both −g and
146 −s options are present, the action taken is unspecified.
147 −U name Remove any initial definition of name.
149 Multiple instances of the −D, −I, −L, −l, and −U options can be speci‐
151 fied.
152
154 The application shall ensure that at least one pathname operand is
155 specified. The following forms for pathname operands shall be sup‐
156 ported:
157 file.c A C-language source file to be compiled and optionally
159 linked. The application shall ensure that the operand is of
160 this form if the −c option is used.
161 file.a A library of object files typically produced by the ar util‐
163 ity, and passed directly to the link editor. Implementations
164 may recognize implementation-defined suffixes other than .a
165 as denoting object file libraries.
166 file.o An object file produced by c99 −c and passed directly to the
168 link editor. Implementations may recognize implementation-
169 defined suffixes other than .o as denoting object files.
170 The processing of other files is implementation-defined.
172
174 Not used.
175
177 Each input file shall be one of the following: a text file containing a
178 C-language source program, an object file in the format produced by c99
179 −c, or a library of object files, in the format produced by archiving
180 zero or more object files, using ar. Implementations may supply addi‐
181 tional utilities that produce files in these formats. Additional input
182 file formats are implementation-defined.
183
185 The following environment variables shall affect the execution of c99:
186 LANG Provide a default value for the internationalization vari‐
188 ables that are unset or null. (See the Base Definitions vol‐
189 ume of POSIX.1‐2008, Section 8.2, Internationalization Vari‐
190 ables for the precedence of internationalization variables
191 used to determine the values of locale categories.)
192 LC_ALL If set to a non-empty string value, override the values of
194 all the other internationalization variables.
195 LC_CTYPE Determine the locale for the interpretation of sequences of
197 bytes of text data as characters (for example, single-byte as
198 opposed to multi-byte characters in arguments and input
199 files).
200 LC_MESSAGES
202 Determine the locale that should be used to affect the format
203 and contents of diagnostic messages written to standard
204 error.
205 NLSPATH Determine the location of message catalogs for the processing
207 of LC_MESSAGES.
208 TMPDIR Provide a pathname that should override the default directory
210 for temporary files, if any. On XSI-conforming systems, pro‐
211 vide a pathname that shall override the default directory for
212 temporary files, if any.
213
215 Default.
216
218 If more than one pathname operand ending in .c (or possibly other
219 unspecified suffixes) is given, for each such file:
220 "%s:\n", <pathname>
222 may be written. These messages, if written, shall precede the process‐
224 ing of each input file; they shall not be written to the standard out‐
225 put if they are written to the standard error, as described in the
226 STDERR section.
227 If the −E option is specified, the standard output shall be a text file
229 that represents the results of the preprocessing stage of the language;
230 it may contain extra information appropriate for subsequent compilation
231 passes.
232
234 The standard error shall be used only for diagnostic messages. If more
235 than one pathname operand ending in .c (or possibly other unspecified
236 suffixes) is given, for each such file:
237 "%s:\n", <pathname>
239 may be written to allow identification of the diagnostic and warning
241 messages with the appropriate input file. These messages, if written,
242 shall precede the processing of each input file; they shall not be
243 written to the standard error if they are written to the standard out‐
244 put, as described in the STDOUT section.
245 This utility may produce warning messages about certain conditions that
247 do not warrant returning an error (non-zero) exit value.
248
250 Object files or executable files or both are produced in unspecified
251 formats. If the pathname of an object file or executable file to be
252 created by c99 resolves to an existing directory entry for a file that
253 is not a regular file, it is unspecified whether c99 shall attempt to
254 create the file or shall issue a diagnostic and exit with a non-zero
255 exit status.
256
258 Standard Libraries
259 The c99 utility shall recognize the following −l options for standard
260 libraries:
261 −l c This option shall make available all interfaces referenced in
263 the System Interfaces volume of POSIX.1‐2008, with the possi‐
264 ble exception of those interfaces listed as residing in
265 <aio.h>, <arpa/inet.h>, <complex.h>, <fenv.h>, <math.h>,
266 <mqueue.h>, <netdb.h>, <net/if.h>, <netinet/in.h>,
267 <pthread.h>, <sched.h>, <semaphore.h>, <spawn.h>,
268 <sys/socket.h>, pthread_kill(), and pthread_sigmask() in
269 <signal.h>, <trace.h>, interfaces marked as optional in
270 <sys/mman.h>, interfaces marked as ADV (Advisory Information)
271 in <fcntl.h>, and interfaces beginning with the prefix clock_
272 or time_ in <time.h>. This option shall not be required to
273 be present to cause a search of this library.
274 −l l This option shall make available all interfaces required by
276 the C-language output of lex that are not made available
277 through the −l c option.
278 −l pthread
280 This option shall make available all interfaces referenced in
281 <pthread.h> and pthread_kill() and pthread_sigmask() refer‐
282 enced in <signal.h>. An implementation may search this
283 library in the absence of this option.
284 −l m This option shall make available all interfaces referenced in
286 <math.h>, <complex.h>, and <fenv.h>. An implementation may
287 search this library in the absence of this option.
288 −l rt This option shall make available all interfaces referenced in
290 <aio.h>, <mqueue.h>, <sched.h>, <semaphore.h>, and <spawn.h>,
291 interfaces marked as optional in <sys/mman.h>, interfaces
292 marked as ADV (Advisory Information) in <fcntl.h>, and inter‐
293 faces beginning with the prefix clock_ and time_ in <time.h>.
294 An implementation may search this library in the absence of
295 this option.
296 −l trace This option shall make available all interfaces referenced in
298 <trace.h>. An implementation may search this library in the
299 absence of this option.
300 −l xnet This option shall make available all interfaces referenced in
302 <arpa/inet.h>, <netdb.h>, <net/if.h>, <netinet/in.h>, and
303 <sys/socket.h>. An implementation may search this library in
304 the absence of this option.
305 −l y This option shall make available all interfaces required by
307 the C-language output of yacc that are not made available
308 through the −l c option.
309 In the absence of options that inhibit invocation of the link editor,
311 such as −c or −E, the c99 utility shall cause the equivalent of a −l c
312 option to be passed to the link editor after the last pathname operand
313 or −l option, causing it to be searched after all other object files
314 and libraries are loaded.
315 It is unspecified whether the libraries libc.a, libl.a, libm.a,
317 libpthread.a, librt.a, libtrace.a, libxnet.a, or liby.a exist as regu‐
318 lar files. The implementation may accept as −l option-arguments names
319 of objects that do not exist as regular files.
320 External Symbols
322 The C compiler and link editor shall support the significance of exter‐
323 nal symbols up to a length of at least 31 bytes; the action taken upon
324 encountering symbols exceeding the implementation-defined maximum sym‐
325 bol length is unspecified.
326 The compiler and link editor shall support a minimum of 511 external
328 symbols per source or object file, and a minimum of 4095 external sym‐
329 bols in total. A diagnostic message shall be written to the standard
330 output if the implementation-defined limit is exceeded; other actions
331 are unspecified.
332 Header Search
334 If a file with the same name as one of the standard headers defined in
335 the Base Definitions volume of POSIX.1‐2008, Chapter 13, Headers, not
336 provided as part of the implementation, is placed in any of the usual
337 places that are searched by default for headers, the results are
338 unspecified.
339 Programming Environments
341 All implementations shall support one of the following programming
342 environments as a default. Implementations may support more than one of
343 the following programming environments. Applications can use sysconf()
344 or getconf to determine which programming environments are supported.
345 Table 4-4: Programming Environments: Type Sizes
347 ┌────────────────────────┬─────────┬─────────┬─────────┬─────────┐
349 │Programming Environment │ Bits in │ Bits in │ Bits in │ Bits in │
350 │ getconf Name │ int │ long │ pointer │ off_t │
351 ├────────────────────────┼─────────┼─────────┼─────────┼─────────┤
352 │_POSIX_V7_ILP32_OFF32 │ 32 │ 32 │ 32 │ 32 │
353 │_POSIX_V7_ILP32_OFFBIG │ 32 │ 32 │ 32 │ ≥64 │
354 │_POSIX_V7_LP64_OFF64 │ 32 │ 64 │ 64 │ 64 │
355 │_POSIX_V7_LPBIG_OFFBIG │ ≥32 │ ≥64 │ ≥64 │ ≥64 │
356 └────────────────────────┴─────────┴─────────┴─────────┴─────────┘
357 All implementations shall support one or more environments where the
358 widths of the following types are no greater than the width of type
359 long:
360 blksize_t ptrdiff_t tcflag_t
362 cc_t size_t wchar_t
363 mode_t speed_t wint_t
364 nfds_t ssize_t
365 pid_t suseconds_t
366 The executable files created when these environments are selected shall
368 be in a proper format for execution by the exec family of functions.
369 Each environment may be one of the ones in Table 4-4, Programming Envi‐
370 ronments: Type Sizes, or it may be another environment. The names for
371 the environments that meet this requirement shall be output by a get‐
372 conf command using the POSIX_V7_WIDTH_RESTRICTED_ENVS argument, as a
373 <newline>-separated list of names suitable for use with the getconf −v
374 option. If more than one environment meets the requirement, the names
375 of all such environments shall be output on separate lines. Any of
376 these names can then be used in a subsequent getconf command to obtain
377 the flags specific to that environment with the following suffixes
378 added as appropriate:
379 _CFLAGS To get the C compiler flags.
381 _LDFLAGS To get the linker/loader flags.
383 _LIBS To get the libraries.
385 This requirement may be removed in a future version.
387 When this utility processes a file containing a function called main(),
389 it shall be defined with a return type equivalent to int. Using return
390 from the initial call to main() shall be equivalent (other than with
391 respect to language scope issues) to calling exit() with the returned
392 value. Reaching the end of the initial call to main() shall be equiva‐
393 lent to calling exit(0). The implementation shall not declare a proto‐
394 type for this function.
395 Implementations provide configuration strings for C compiler flags,
397 linker/loader flags, and libraries for each supported environment.
398 When an application needs to use a specific programming environment
399 rather than the implementation default programming environment while
400 compiling, the application shall first verify that the implementation
401 supports the desired environment. If the desired programming environ‐
402 ment is supported, the application shall then invoke c99 with the
403 appropriate C compiler flags as the first options for the compile, the
404 appropriate linker/loader flags after any other options except −l but
405 before any operands or −l options, and the appropriate libraries at the
406 end of the operands and −l options.
407 Conforming applications shall not attempt to link together object files
409 compiled for different programming models. Applications shall also be
410 aware that binary data placed in shared memory or in files might not be
411 recognized by applications built for other programming models.
412 Table 4-5: Programming Environments: c99 Arguments
414 ┌────────────────────────┬─────────────────────┬───────────────────────────────┐
416 │Programming Environment │ │ c99 Arguments │
417 │ getconf Name │ Use │ getconf Name │
418 ├────────────────────────┼─────────────────────┼───────────────────────────────┤
419 │_POSIX_V7_ILP32_OFF32 │ C Compiler Flags │ POSIX_V7_ILP32_OFF32_CFLAGS │
420 │ │ Linker/Loader Flags │ POSIX_V7_ILP32_OFF32_LDFLAGS │
421 │ │ Libraries │ POSIX_V7_ILP32_OFF32_LIBS │
422 ├────────────────────────┼─────────────────────┼───────────────────────────────┤
423 │_POSIX_V7_ILP32_OFFBIG │ C Compiler Flags │ POSIX_V7_ILP32_OFFBIG_CFLAGS │
424 │ │ Linker/Loader Flags │ POSIX_V7_ILP32_OFFBIG_LDFLAGS │
425 │ │ Libraries │ POSIX_V7_ILP32_OFFBIG_LIBS │
426 ├────────────────────────┼─────────────────────┼───────────────────────────────┤
427 │_POSIX_V7_LP64_OFF64 │ C Compiler Flags │ POSIX_V7_LP64_OFF64_CFLAGS │
428 │ │ Linker/Loader Flags │ POSIX_V7_LP64_OFF64_LDFLAGS │
429 │ │ Libraries │ POSIX_V7_LP64_OFF64_LIBS │
430 ├────────────────────────┼─────────────────────┼───────────────────────────────┤
431 │_POSIX_V7_LPBIG_OFFBIG │ C Compiler Flags │ POSIX_V7_LPBIG_OFFBIG_CFLAGS │
432 │ │ Linker/Loader Flags │ POSIX_V7_LPBIG_OFFBIG_LDFLAGS │
433 │ │ Libraries │ POSIX_V7_LPBIG_OFFBIG_LIBS │
434 └────────────────────────┴─────────────────────┴───────────────────────────────┘
435 In addition to the type size programming environments above, all imple‐
436 mentations also support a multi-threaded programming environment that
437 is orthogonal to all of the programming environments listed above. The
438 getconf utility can be used to get flags for the threaded programming
439 environment, as indicated in Table 4-6, Threaded Programming Environ‐
440 ment: c99 Arguments.
441 Table 4-6: Threaded Programming Environment: c99 Arguments
443 ┌────────────────────────┬─────────────────────┬──────────────────────────┐
445 │Programming Environment │ │ c99 Arguments │
446 │ getconf Name │ Use │ getconf Name │
447 ├────────────────────────┼─────────────────────┼──────────────────────────┤
448 │_POSIX_THREADS │ C Compiler Flags │ POSIX_V7_THREADS_CFLAGS │
449 │ │ Linker/Loader Flags │ POSIX_V7_THREADS_LDFLAGS │
450 └────────────────────────┴─────────────────────┴──────────────────────────┘
451 These programming environment flags may be used in conjunction with any
452 of the type size programming environments supported by the implementa‐
453 tion.
454
456 The following exit values shall be returned:
457 0 Successful compilation or link edit.
459 >0 An error occurred.
461
463 When c99 encounters a compilation error that causes an object file not
464 to be created, it shall write a diagnostic to standard error and con‐
465 tinue to compile other source code operands, but it shall not perform
466 the link phase and return a non-zero exit status. If the link edit is
467 unsuccessful, a diagnostic message shall be written to standard error
468 and c99 exits with a non-zero status. A conforming application shall
469 rely on the exit status of c99, rather than on the existence or mode of
470 the executable file.
471 The following sections are informative.
473
475 Since the c99 utility usually creates files in the current directory
476 during the compilation process, it is typically necessary to run the
477 c99 utility in a directory in which a file can be created.
478 On systems providing POSIX Conformance (see the Base Definitions volume
480 of POSIX.1‐2008, Chapter 2, Conformance), c99 is required only with the
481 C-Language Development option; XSI-conformant systems always provide
482 c99.
483 Some historical implementations have created .o files when −c is not
485 specified and more than one source file is given. Since this area is
486 left unspecified, the application cannot rely on .o files being cre‐
487 ated, but it also must be prepared for any related .o files that
488 already exist being deleted at the completion of the link edit.
489 There is the possible implication that if a user supplies versions of
491 the standard functions (before they would be encountered by an implicit
492 −l c or explicit −l m), that those versions would be used in place of
493 the standard versions. There are various reasons this might not be
494 true (functions defined as macros, manipulations for clean name space,
495 and so on), so the existence of files named in the same manner as the
496 standard libraries within the −L directories is explicitly stated to
497 produce unspecified behavior.
498 All of the functions specified in the System Interfaces volume of
500 POSIX.1‐2008 may be made visible by implementations when the Standard C
501 Library is searched. Conforming applications must explicitly request
502 searching the other standard libraries when functions made visible by
503 those libraries are used.
504 In the ISO C standard the mapping from physical source characters to
506 the C source character set is implementation-defined. Implementations
507 may strip white-space characters before the terminating <newline> of a
508 (physical) line as part of this mapping and, as a consequence of this,
509 one or more white-space characters (and no other characters) between a
510 <backslash> character and the <newline> character that terminates the
511 line produces implementation-defined results. Portable applications
512 should not use such constructs.
513 Some c99 compilers not conforming to POSIX.1‐2008 do not support tri‐
515 graphs by default.
516
518 1. The following usage example compiles foo.c and creates the exe‐
519 cutable file foo:
520 c99 −o foo foo.c
522 The following usage example compiles foo.c and creates the object
524 file foo.o:
525 c99 −c foo.c
527 The following usage example compiles foo.c and creates the exe‐
529 cutable file a.out:
530 c99 foo.c
532 The following usage example compiles foo.c, links it with bar.o,
534 and creates the executable file a.out. It may also create and
535 leave foo.o:
536 c99 foo.c bar.o
538 2. The following example shows how an application using threads inter‐
540 faces can test for support of and use a programming environment
541 supporting 32-bit int, long, and pointer types and an off_t type
542 using at least 64 bits:
543 offbig_env=$(getconf _POSIX_V7_ILP32_OFFBIG)
545 if [ $offbig_env != "-1" ] && [ $offbig_env != "undefined" ]
546 then
547 c99 $(getconf POSIX_V7_ILP32_OFFBIG_CFLAGS) \
548 $(getconf POSIX_V7_THREADS_CFLAGS) -D_XOPEN_SOURCE=700 \
549 $(getconf POSIX_V7_ILP32_OFFBIG_LDFLAGS) \
550 $(getconf POSIX_V7_THREADS_LDFLAGS) foo.c -o foo \
551 $(getconf POSIX_V7_ILP32_OFFBIG_LIBS) \
552 -l pthread
553 else
554 echo ILP32_OFFBIG programming environment not supported
555 exit 1
556 fi
557 3. The following examples clarify the use and interactions of −L and
559 −l options.
560 Consider the case in which module a.c calls function f() in library
562 libQ.a, and module b.c calls function g() in library libp.a.
563 Assume that both libraries reside in /a/b/c. The command line to
564 compile and link in the desired way is:
565 c99 −L /a/b/c main.o a.c −l Q b.c −l p
567 In this case the −L option need only precede the first −l option,
569 since both libQ.a and libp.a reside in the same directory.
570 Multiple −L options can be used when library name collisions occur.
572 Building on the previous example, suppose that the user wants to
573 use a new libp.a, in /a/a/a, but still wants f() from
574 /a/b/c/libQ.a:
575 c99 −L /a/a/a −L /a/b/c main.o a.c −l Q b.c −l p
577 In this example, the linker searches the −L options in the order
579 specified, and finds /a/a/a/libp.a before /a/b/c/libp.a when
580 resolving references for b.c. The order of the −l options is still
581 important, however.
582 4. The following example shows how an application can use a program‐
584 ming environment where the widths of the following types: blk‐
585 size_t, cc_t, mode_t, nfds_t, pid_t, ptrdiff_t, size_t, speed_t,
586 ssize_t, suseconds_t, tcflag_t, wchar_t, wint_t
587 are no greater than the width of type long:
589 # First choose one of the listed environments ...
591 # ... if there are no additional constraints, the first one will do:
593 CENV=$(getconf POSIX_V7_WIDTH_RESTRICTED_ENVS | head -n l)
594 # ... or, if an environment that supports large files is preferred,
596 # look for names that contain "OFF64" or "OFFBIG". (This chooses
597 # the last one in the list if none match.)
598 for CENV in $(getconf POSIX_V7_WIDTH_RESTRICTED_ENVS)
599 do
600 case $CENV in
601 *OFF64*|*OFFBIG*) break ;;
602 esac
603 done
604 # The chosen environment name can now be used like this:
606 c99 $(getconf ${CENV}_CFLAGS) -D _POSIX_C_SOURCE=200809L \
608 $(getconf ${CENV}_LDFLAGS) foo.c -o foo \
609 $(getconf ${CENV}_LIBS)
610
612 The c99 utility is based on the c89 utility originally introduced in
613 the ISO POSIX‐2:1993 standard.
614 Some of the changes from c89 include the ability to intersperse options
616 and operands (which many c89 implementations allowed despite it not
617 being specified), the description of −l as an option instead of an op‐
618 erand, and the modification to the contents of the Standard Libraries
619 section to account for new headers and options; for example, <spawn.h>
620 added to the description of −l rt, and −l trace added for the Tracing
621 option.
622 POSIX.1‐2008 specifies that the c99 utility must be able to use regular
624 files for *.o files and for a.out files. Implementations are free to
625 overwrite existing files of other types when attempting to create
626 object files and executable files, but are not required to do so. If
627 something other than a regular file is specified and using it fails for
628 any reason, c99 is required to issue a diagnostic message and exit with
629 a non-zero exit status. But for some file types, the problem may not be
630 noticed for a long time. For example, if a FIFO named a.out exists in
631 the current directory, c99 may attempt to open a.out and will hang in
632 the open() call until another process opens the FIFO for reading. Then
633 c99 may write most of the a.out to the FIFO and fail when it tries to
634 seek back close to the start of the file to insert a timestamp (FIFOs
635 are not seekable files). The c99 utility is also allowed to issue a
636 diagnostic immediately if it encounters an a.out or *.o file that is
637 not a regular file. For portable use, applications should ensure that
638 any a.out, −o option-argument, or *.o files corresponding to any *.c
639 files do not conflict with names already in use that are not regular
640 files or symbolic links that point to regular files.
641 On many systems, multi-threaded applications run in a programming envi‐
643 ronment that is distinct from that used by single-threaded applica‐
644 tions. This multi-threaded programming environment (in addition to
645 needing to specify −l pthread at link time) may require additional
646 flags to be set when headers are processed at compile time (−D_REEN‐
647 TRANT being common). This programming environment is orthogonal to the
648 type size programming environments discussed above and listed in Table
649 4-4, Programming Environments: Type Sizes. This version of the stan‐
650 dard adds getconf utility calls to provide the C compiler flags and
651 linker/loader flags needed to support multi-threaded applications. Note
652 that on a system where single-threaded applications are a special case
653 of a multi-threaded application, both of these getconf calls may return
654 NULL strings; on other implementations both of these strings may be
655 non-NULL strings.
656 The C standardization committee invented trigraphs (e.g., "??!" to rep‐
658 resent '|') to address character portability problems in development
659 environments based on national variants of the 7-bit ISO/IEC 646:1991
660 standard character set. However, these environments were already obso‐
661 lete by the time the first ISO C standard was published, and in prac‐
662 tice trigraphs have not been used for their intended purpose, and usu‐
663 ally are intended to have their original meaning in K&R C. For exam‐
664 ple, in practice a C-language source string like "What??!" is usually
665 intended to end in two <question-mark> characters and an <exclamation-
666 mark>, not in '|'.
667
669 None.
670
672 Section 1.1.1.4, File Read, Write, and Creation, ar, getconf, make, nm,
673 strip, umask
674 The Base Definitions volume of POSIX.1‐2008, Chapter 8, Environment
676 Variables, Section 12.2, Utility Syntax Guidelines, Chapter 13, Headers
677 The System Interfaces volume of POSIX.1‐2008, exec, sysconf()
679
681 Portions of this text are reprinted and reproduced in electronic form
682 from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
683 -- Portable Operating System Interface (POSIX), The Open Group Base
684 Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
685 cal and Electronics Engineers, Inc and The Open Group. (This is
686 POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
687 event of any discrepancy between this version and the original IEEE and
688 The Open Group Standard, the original IEEE and The Open Group Standard
689 is the referee document. The original Standard can be obtained online
690 at http://www.unix.org/online.html .
691 Any typographical or formatting errors that appear in this page are
693 most likely to have been introduced during the conversion of the source
694 files to man page format. To report such errors, see https://www.ker‐
695 nel.org/doc/man-pages/reporting_bugs.html .
696IEEE/The Open Group 2013 C99(1P)