C99(1P) POSIX Programmer's Manual C99(1P)
PROLOG
This manual page is part of the POSIX Programmer's Manual. The Linux implementation of
this interface may differ (consult the corresponding Linux manual page for details of
Linux behavior), or the interface may not be implemented on Linux.
NAME
c99 - compile standard C programs
SYNOPSIS
c99 [-c][-D name[=value]]...[-E][-g][-I directory] ... [-L directory]
... [-o outfile][-Ooptlevel][-s][-U name]... operand ...
DESCRIPTION
The c99 utility is an interface to the standard C compilation system; it shall accept
source code conforming to the ISO C standard. The system conceptually consists of a com-
piler and link editor. The files referenced by operands shall be compiled and linked to
produce an executable file. (It is unspecified whether the linking occurs entirely within
the operation of c99; some implementations may produce objects that are not fully resolved
until the file is executed.)
If the -c option is specified, for all pathname operands of the form file .c, the files:
$(basename pathname .c).o
shall be created as the result of successful compilation. If the -c option is not speci-
fied, it is unspecified whether such .o files are created or deleted for the file .c oper-
ands.
If there are no options that prevent link editing (such as -c or -E), and all operands
compile and link without error, the resulting executable file shall be written according
to the -o outfile option (if present) or to the file a.out.
The executable file shall be created as specified in File Read, Write, and Creation,
except that the file permission bits shall be set to:
S_IRWXO | S_IRWXG | S_IRWXU
and the bits specified by the umask of the process shall be cleared.
OPTIONS
The c99 utility shall conform to the Base Definitions volume of IEEE Std 1003.1-2001, Sec-
tion 12.2, Utility Syntax Guidelines, except that:
* The -l library operands have the format of options, but their position within a list of
operands affects the order in which libraries are searched.
* The order of specifying the -I and -L options is significant.
* Conforming applications shall specify each option separately; that is, grouping option
letters (for example, -cO) need not be recognized by all implementations.
The following options shall be supported:
-c Suppress the link-edit phase of the compilation, and do not remove any object files
that are produced.
-g Produce symbolic information in the object or executable files; the nature of this
information is unspecified, and may be modified by implementation-defined interac-
tions with other options.
-s Produce object or executable files, or both, from which symbolic and other informa-
tion not required for proper execution using the exec family defined in the System
Interfaces volume of IEEE Std 1003.1-2001 has been removed (stripped). If both -g
and -s options are present, the action taken is unspecified.
-o outfile
Use the pathname outfile, instead of the default a.out, for the executable file
produced. If the -o option is present with -c or -E, the result is unspecified.
-D name[=value]
Define name as if by a C-language #define directive. If no = value is given, a
value of 1 shall be used. The -D option has lower precedence than the -U option.
That is, if name is used in both a -U and a -D option, name shall be undefined
regardless of the order of the options. Additional implementation-defined names may
be provided by the compiler. Implementations shall support at least 2048 bytes of
-D definitions and 256 names.
-E Copy C-language source files to standard output, expanding all preprocessor direc-
tives; no compilation shall be performed. If any operand is not a text file, the
effects are unspecified.
-I directory
Change the algorithm for searching for headers whose names are not absolute path-
names to look in the directory named by the directory pathname before looking in
the usual places. Thus, headers whose names are enclosed in double-quotes ( "" )
shall be searched for first in the directory of the file with the #include line,
then in directories named in -I options, and last in the usual places. For headers
whose names are enclosed in angle brackets ( "<>" ), the header shall be searched
for only in directories named in -I options and then in the usual places. Directo-
ries named in -I options shall be searched in the order specified. Implementations
shall support at least ten instances of this option in a single c99 command invoca-
tion.
-L directory
Change the algorithm of searching for the libraries named in the -l objects to look
in the directory named by the directory pathname before looking in the usual
places. Directories named in -L options shall be searched in the order specified.
Implementations shall support at least ten instances of this option in a single c99
command invocation. If a directory specified by a -L option contains files named
libc.a, libm.a, libl.a, or liby.a, the results are unspecified.
-O optlevel
Specify the level of code optimization. If the optlevel option-argument is the
digit '0', all special code optimizations shall be disabled. If it is the digit
'1', the nature of the optimization is unspecified. If the -O option is omitted,
the nature of the system's default optimization is unspecified. It is unspecified
whether code generated in the presence of the -O 0 option is the same as that gen-
erated when -O is omitted. Other optlevel values may be supported.
-U name
Remove any initial definition of name.
Multiple instances of the -D, -I, -U, and -L options can be specified.
OPERANDS
An operand is either in the form of a pathname or the form -l library. The application
shall ensure that at least one operand of the pathname form is specified. The following
operands shall be supported:
file.c A C-language source file to be compiled and optionally linked. The application
shall ensure that the operand is of this form if the -c option is used.
file.a A library of object files typically produced by the ar utility, and passed directly
to the link editor. Implementations may recognize implementation-defined suffixes
other than .a as denoting object file libraries.
file.o An object file produced by c99 -c and passed directly to the link editor. Implemen-
tations may recognize implementation-defined suffixes other than .o as denoting
object files.
The processing of other files is implementation-defined.
-l library
(The letter ell.) Search the library named:
liblibrary.a
A library shall be searched when its name is encountered, so the placement of a -l operand
is significant. Several standard libraries can be specified in this manner, as described
in the EXTENDED DESCRIPTION section. Implementations may recognize implementation-defined
suffixes other than .a as denoting libraries.
STDIN
Not used.
INPUT FILES
The input file shall be one of the following: a text file containing a C-language source
program, an object file in the format produced by c99 -c, or a library of object files, in
the format produced by archiving zero or more object files, using ar. Implementations may
supply additional utilities that produce files in these formats. Additional input file
formats are implementation-defined.
ENVIRONMENT VARIABLES
The following environment variables shall affect the execution of c99:
LANG Provide a default value for the internationalization variables that are unset or
null. (See the Base Definitions volume of IEEE Std 1003.1-2001, Section 8.2, Inter-
nationalization Variables for the precedence of internationalization variables used
to determine the values of locale categories.)
LC_ALL If set to a non-empty string value, override the values of all the other interna-
tionalization variables.
LC_CTYPE
Determine the locale for the interpretation of sequences of bytes of text data as
characters (for example, single-byte as opposed to multi-byte characters in argu-
ments and input files).
LC_MESSAGES
Determine the locale that should be used to affect the format and contents of diag-
nostic messages written to standard error.
NLSPATH
Determine the location of message catalogs for the processing of LC_MESSAGES .
TMPDIR Provide a pathname that should override the default directory for temporary files,
if any. On XSI-conforming systems, provide a pathname that shall override the
default directory for temporary files, if any.
ASYNCHRONOUS EVENTS
Default.
STDOUT
If more than one file operand ending in .c (or possibly other unspecified suffixes) is
given, for each such file:
"%s:\n", <file>
may be written. These messages, if written, shall precede the processing of each input
file; they shall not be written to the standard output if they are written to the standard
error, as described in the STDERR section.
If the -E option is specified, the standard output shall be a text file that represents
the results of the preprocessing stage of the language; it may contain extra information
appropriate for subsequent compilation passes.
STDERR
The standard error shall be used only for diagnostic messages. If more than one file oper-
and ending in .c (or possibly other unspecified suffixes) is given, for each such file:
"%s:\n", <file>
may be written to allow identification of the diagnostic and warning messages with the
appropriate input file. These messages, if written, shall precede the processing of each
input file; they shall not be written to the standard error if they are written to the
standard output, as described in the STDOUT section.
This utility may produce warning messages about certain conditions that do not warrant
returning an error (non-zero) exit value.
OUTPUT FILES
Object files or executable files or both are produced in unspecified formats.
EXTENDED DESCRIPTION
Standard Libraries
The c99 utility shall recognize the following -l operands for standard libraries:
-l c This operand shall make visible all functions referenced in the System Interfaces
volume of IEEE Std 1003.1-2001, with the possible exception of those functions
listed as residing in <aio.h>, <arpa/inet.h>, <complex.h>, <fenv.h>, <math.h>,
<mqueue.h>, <netdb.h>, <netinet/in.h>, <pthread.h>, <sched.h>, <semaphore.h>,
<spawn.h>, <sys/socket.h>, pthread_kill(), and pthread_sigmask() in <signal.h>,
<trace.h>, functions marked as extensions other than as part of the MF or MPR
extensions in <sys/mman.h>, functions marked as ADV in <fcntl.h>, and functions
marked as CS, CPT, and TMR in <time.h>. This operand shall not be required to be
present to cause a search of this library.
-l l This operand shall make visible all functions required by the C-language output of
lex that are not made available through the -l c operand.
-l pthread
This operand shall make visible all functions referenced in <pthread.h> and
pthread_kill() and pthread_sigmask() referenced in <signal.h>. An implementation
may search this library in the absence of this operand.
-l m This operand shall make visible all functions referenced in <math.h>, <complex.h>,
and <fenv.h>. An implementation may search this library in the absence of this op-
erand.
-l rt This operand shall make visible all functions referenced in <aio.h>, <mqueue.h>,
<sched.h>, <semaphore.h>, and <spawn.h>, functions marked as extensions other than
as part of the MF or MPR extensions in <sys/mman.h>, functions marked as ADV in
<fcntl.h>, and functions marked as CS, CPT, and TMR in <time.h>. An implementation
may search this library in the absence of this operand.
-l trace
This operand shall make visible all functions referenced in <trace.h>. An imple-
mentation may search this library in the absence of this operand.
-l xnet
This operand makes visible all functions referenced in <arpa/inet.h>, <netdb.h>,
<netinet/in.h>, and <sys/socket.h>. An implementation may search this library in
the absence of this operand.
-l y This operand shall make visible all functions required by the C-language output of
yacc that are not made available through the -l c operand.
In the absence of options that inhibit invocation of the link editor, such as -c or -E,
the c99 utility shall cause the equivalent of a -l c operand to be passed to the link edi-
tor as the last -l operand, causing it to be searched after all other object files and
libraries are loaded.
It is unspecified whether the libraries libc.a, libm.a, librt.a, libpthread.a, libl.a,
liby.a, or libxnet.a exist as regular files. The implementation may accept as -l operands
names of objects that do not exist as regular files.
External Symbols
The C compiler and link editor shall support the significance of external symbols up to a
length of at least 31 bytes; the action taken upon encountering symbols exceeding the
implementation-defined maximum symbol length is unspecified.
The compiler and link editor shall support a minimum of 511 external symbols per source or
object file, and a minimum of 4095 external symbols in total. A diagnostic message shall
be written to the standard output if the implementation-defined limit is exceeded; other
actions are unspecified.
Programming Environments
All implementations shall support one of the following programming environments as a
default. Implementations may support more than one of the following programming environ-
ments. Applications can use sysconf() or getconf to determine which programming environ-
ments are supported.
Table: Programming Environments: Type Sizes
Programming Environment Bits in Bits in Bits in Bits in
getconf Name int long pointer off_t
_POSIX_V6_ILP32_OFF32 32 32 32 32
_POSIX_V6_ILP32_OFFBIG 32 32 32 >=64
_POSIX_V6_LP64_OFF64 32 64 64 64
_POSIX_V6_LPBIG_OFFBIG >=32 >=64 >=64 >=64
All implementations shall support one or more environments where the widths of the follow-
ing types are no greater than the width of type long: blksize_t, cc_t, mode_t, nfds_t,
pid_t, ptrdiff_t, size_t, speed_t, ssize_t, suseconds_t, tcflag_t, useconds_t, wchar_t,
wint_t
The executable files created when these environments are selected shall be in a proper
format for execution by the exec family of functions. Each environment may be one of the
ones in Programming Environments: Type Sizes, or it may be another environment. The names
for the environments that meet this requirement shall be output by a getconf command using
the _POSIX_V6_WIDTH_RESTRICTED_ENVS argument. If more than one environment meets the
requirement, the names of all such environments shall be output on separate lines. Any of
these names can then be used in a subsequent getconf command to obtain the flags specific
to that environment with the following suffixes added as appropriate:
_CFLAGS
To get the C compiler flags.
_LDFLAGS
To get the linker/loader flags.
_LIBS To get the libraries.
This requirement may be removed in a future version of IEEE Std 1003.1.
When this utility processes a file containing a function called main(), it shall be
defined with a return type equivalent to int. Using return from the initial call to main()
shall be equivalent (other than with respect to language scope issues) to calling exit()
with the returned value. Reaching the end of the initial call to main() shall be equiva-
lent to calling exit(0). The implementation shall not declare a prototype for this func-
tion.
Implementations provide configuration strings for C compiler flags, linker/loader flags,
and libraries for each supported environment. When an application needs to use a specific
programming environment rather than the implementation default programming environment
while compiling, the application shall first verify that the implementation supports the
desired environment. If the desired programming environment is supported, the application
shall then invoke c99 with the appropriate C compiler flags as the first options for the
compile, the appropriate linker/loader flags after any other options but before any oper-
ands, and the appropriate libraries at the end of the operands.
Conforming applications shall not attempt to link together object files compiled for dif-
ferent programming models. Applications shall also be aware that binary data placed in
shared memory or in files might not be recognized by applications built for other program-
ming models.
Table: Programming Environments: c99 and cc Arguments
Programming Environment c99 and cc Arguments
getconf Name Use getconf Name
_POSIX_V6_ILP32_OFF32 C Compiler Flags POSIX_V6_ILP32_OFF32_CFLAGS
Linker/Loader Flags POSIX_V6_ILP32_OFF32_LDFLAGS
Libraries POSIX_V6_ILP32_OFF32_LIBS
_POSIX_V6_ILP32_OFFBIG C Compiler Flags POSIX_V6_ILP32_OFFBIG_CFLAGS
Linker/Loader Flags POSIX_V6_ILP32_OFFBIG_LDFLAGS
Libraries POSIX_V6_ILP32_OFFBIG_LIBS
_POSIX_V6_LP64_OFF64 C Compiler Flags POSIX_V6_LP64_OFF64_CFLAGS
Linker/Loader Flags POSIX_V6_LP64_OFF64_LDFLAGS
Libraries POSIX_V6_LP64_OFF64_LIBS
_POSIX_V6_LPBIG_OFFBIG C Compiler Flags POSIX_V6_LPBIG_OFFBIG_CFLAGS
Linker/Loader Flags POSIX_V6_LPBIG_OFFBIG_LDFLAGS
Libraries POSIX_V6_LPBIG_OFFBIG_LIBS
EXIT STATUS
The following exit values shall be returned:
0 Successful compilation or link edit.
>0 An error occurred.
CONSEQUENCES OF ERRORS
When c99 encounters a compilation error that causes an object file not to be created, it
shall write a diagnostic to standard error and continue to compile other source code oper-
ands, but it shall not perform the link phase and return a non-zero exit status. If the
link edit is unsuccessful, a diagnostic message shall be written to standard error and c99
exits with a non-zero status. A conforming application shall rely on the exit status of
c99, rather than on the existence or mode of the executable file.
The following sections are informative.
APPLICATION USAGE
Since the c99 utility usually creates files in the current directory during the compila-
tion process, it is typically necessary to run the c99 utility in a directory in which a
file can be created.
On systems providing POSIX Conformance (see the Base Definitions volume of
IEEE Std 1003.1-2001, Chapter 2, Conformance), c99 is required only with the C-Language
Development option; XSI-conformant systems always provide c99.
Some historical implementations have created .o files when -c is not specified and more
than one source file is given. Since this area is left unspecified, the application cannot
rely on .o files being created, but it also must be prepared for any related .o files that
already exist being deleted at the completion of the link edit.
Some historical implementations have permitted -L options to be interspersed with -l oper-
ands on the command line. For an application to compile consistently on systems that do
not behave like this, it is necessary for a conforming application to supply all -L
options before any of the -l options.
There is the possible implication that if a user supplies versions of the standard func-
tions (before they would be encountered by an implicit -l c or explicit -l m), that those
versions would be used in place of the standard versions. There are various reasons this
might not be true (functions defined as macros, manipulations for clean name space, and so
on), so the existence of files named in the same manner as the standard libraries within
the -L directories is explicitly stated to produce unspecified behavior.
All of the functions specified in the System Interfaces volume of IEEE Std 1003.1-2001 may
be made visible by implementations when the Standard C Library is searched. Conforming
applications must explicitly request searching the other standard libraries when functions
made visible by those libraries are used.
EXAMPLES
1. The following usage example compiles foo.c and creates the executable file foo:
c99 -o foo foo.c
The following usage example compiles foo.c and creates the object file foo.o:
c99 -c foo.c
The following usage example compiles foo.c and creates the executable file a.out:
c99 foo.c
The following usage example compiles foo.c, links it with bar.o, and creates the exe-
cutable file a.out. It may also create and leave foo.o:
c99 foo.c bar.o
2. The following example shows how an application using threads interfaces can test for
support of and use a programming environment supporting 32-bit int, long, and pointer
types and an off_t type using at least 64 bits:
if [ $(getconf _POSIX_V6_ILP32_OFFBIG) != "-1" ]
then
c99 $(getconf POSIX_V6_ILP32_OFFBIG_CFLAGS) -D_XOPEN_SOURCE=600 \
$(getconf POSIX_V6_ILP32_OFFBIG_LDFLAGS) foo.c -o foo \
$(getconf POSIX_V6_ILP32_OFFBIG_LIBS) -l pthread
else
echo ILP32_OFFBIG programming environment not supported
exit 1
fi
3. The following examples clarify the use and interactions of -L options and -l operands.
Consider the case in which module a.c calls function f() in library libQ.a, and module b.c
calls function g() in library libp.a. Assume that both libraries reside in /a/b/c. The
command line to compile and link in the desired way is:
c99 -L /a/b/c main.o a.c -l Q b.c -l p
In this case the -l Q operand need only precede the first -l p operand, since both libQ.a
and libp.a reside in the same directory.
Multiple -L operands can be used when library name collisions occur. Building on the pre-
vious example, suppose that the user wants to use a new libp.a, in /a/a/a, but still wants
f() from /a/b/c/libQ.a:
c99 -L /a/a/a -L /a/b/c main.o a.c -l Q b.c -l p
In this example, the linker searches the -L options in the order specified, and finds
/a/a/a/libp.a before /a/b/c/libp.a when resolving references for b.c. The order of the -l
operands is still important, however.
4. The following example shows how an application can use a programming environment where
the widths of the following types: blksize_t, cc_t, mode_t, nfds_t, pid_t, ptrdiff_t,
size_t, speed_t, ssize_t, suseconds_t, tcflag_t, useconds_t, wchar_t, wint_t
are no greater than the width of type long:
# First choose one of the listed environments ...
# ... if there are no additional constraints, the first one will do:
CENV=$(getconf _POSIX_V6_WIDTH_RESTRICTED_ENVS | head -n l)
# ... or, if an environment that supports large files is preferred,
# look for names that contain "OFF64" or "OFFBIG". (This chooses
# the last one in the list if none match.)
for CENV in $(getconf _POSIX_V6_WIDTH_RESTRICTED_ENVS)
do
case $CENV in
*OFF64*|*OFFBIG*) break ;;
esac
done
# The chosen environment name can now be used like this:
c99 $(getconf ${CENV}_CFLAGS) -D _POSIX_C_SOURCE=200112L \
$(getconf ${CENV}_LDFLAGS) foo.c -o foo \
$(getconf ${CENV}_LIBS)
RATIONALE
The c99 utility is based on the c89 utility originally introduced in the ISO POSIX-2:1993
standard.
Some of the changes from c89 include the modification to the contents of the Standard
Libraries section to account for new headers and options; for example, <spawn.h> added to
the -l rt operand, and the -l trace operand added for the Tracing functions.
FUTURE DIRECTIONS
None.
SEE ALSO
File Read, Write, and Creation, ar, getconf, make, nm, strip, umask(), the System Inter-
faces volume of IEEE Std 1003.1-2001, exec, sysconf(), the Base Definitions volume of
IEEE Std 1003.1-2001, Chapter 13, Headers
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form from IEEE Std
1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System
Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by
the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and The Open Group
Standard, the original IEEE and The Open Group Standard is the referee document. The orig-
inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .
IEEE/The Open Group 2003 C99(1P)
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