CC

NAME

SYNOPSIS

WARNING

DESCRIPTION

OPTIONS

-o  file

Place linker output in file file. This applies regardless to whatever sort of output is being produced, whether it be an executable file, an object file, an assembler file or preprocessed C code. If `-o' is not specified, the default is to put an executable file in `a.out', the object file `source.c' in `source.o', an assembler file in `source.s', and preprocessed C on standard output.

-mtm

Compile code for the target machine given by tm. If this switch is not given, then the default is to compile for the machine given by the MACHINE environment variable. The following machine types are currently defined: 68000, 68010, and sun2 (all of which compile for the 68000 instruction set); 68020 and sun3 (both of which compile for the 68020 instruction set); and spur. See below for additional -m switches to control other machine-dependent features.

-c

Compile or assemble the source files, but do not link. Produce object files with names made by replacing `.c' or `.s' with `.o' at the end of the input file names. Do nothing at all for object files specified as input.

-S

Compile into assembler code but do not assemble. The assembler output file name is made by replacing `.c' with `.s' at the end of the input file name. Do nothing at all for assembler source files or object files specified as input.

-E

Run only the C preprocessor. Preprocess all the C source files specified and output the results to standard output.

-v

Compiler driver program prints the commands it executes as it runs the preprocessor, compiler proper, assembler and linker. Some of these are directed to print their own version numbers.

-Bprefix

Compiler driver program tries prefix as a prefix for each program it tries to run. These programs are `cpp', `cc1.Itm' (where tm is the target machine for which code is being generated, such as given in the -m switch), `as' and `ld'. For each subprogram to be run, the compiler driver first tries the `-B' prefix, if any. If that name is not found, or if `-B' was not Specified, the driver tries standard prefixes corresponding to system directories. If neither of those results in a file name that is found, the unmodified program name is searched for using the directories specified in your `PATH' environment variable. The run-time support file `gnulib' is also searched for using the `-B' prefix, if needed. If it is not found there, the two standard prefixes above are tried, and that is all. The file is left out of the link if it is not found by those means. Most of the time, on most machines, you can do without it.

These options control the C preprocessor, which is run on each C source file before actual compilation. If you use the `-E' option, nothing is done except C preprocessing. Some of these options make sense only together with `-E' because they request preprocessor output that is not suitable for actual compilation.

-C

Tell the preprocessor not to discard comments. Used with the `-E' option.

-Idir

Search directory dir for include files.

-I-

Any directories specified with `-I' options before the `-I-' option are searched only for the case of `#include "file"'; they are not searched for `#include <file>'. If additional directories are specified with `-I' options after the `-I-', these directories are searched for all `#include' directives. (Ordinally all `-I' directories are used this way.) In addition, the `-I-' option inhibits the use of the current directory as the first search directory for `#include "file"'. Therefore, the current directory is searched only if it is requested explicitly with `-I.'. Specifying both `-I-' and `-I.' allows you to control precisely which directories are searched before the current one and which are searched after.

-nostdinc

Do not search the standard system directories for header files. Only the directories you have specified with `-I' options (and the current directory, if appropriate) are searched. Between `-nostdinc' and `-I-', you can eliminate all directories from the search path except those you specify.

-M

Tell the preprocessor to output a rule suitable for make describing the dependencies of each source file. For each source file, the preprocessor outputs one make-rule whose target is the object file name for that source file and whose dependencies are all the files `#include'd in it. This rule may be a single line or may be continued `\'-newline if it is long.`-M' implies `-E'.

-MM

Like `-M' but the output mentions only the user-header files included with `#include "file"'. System header files included with `#include <file>' are omitted.`-MM' implies `-E'.

-Dmacro

Define macro macro with the empty string as its definition.

-Dmacro=defn

Define macro macro as defn.

-Umacro

Undefine macro macro.

-T

Support ANSI C trigraphs. You don't want to know about this brain-damage. The `-ansi' option also has this effect.

These options control the details of C compilation itself.

-ansi

Support all ANSI standard C programs. This turns off certain features of GNU C that are incompatible with ANSI C, such as the asm, inline and typeof keywords, and predefined macros such as unix and vax that identify the type of system you are using. It also enables the undesirable and rarely used ANSI trigraph feature. The `-ansi' option does not cause non-ANSI programs to be rejected gratuitously. For that, `-pedantic' is required in addition to `-ansi'. The macro __STRICT_ANSI__ is predefined when the `-ansi' option is used. Some header files may notice this macro and refrain from declaring certain functions or defining certain macros that the ANSI standard doesn't call for; this is to avoid interfering with any programs that might use these names for other things.

-traditional

Attempt to support some aspects of traditional C compilers. Specifically:
* All extern declarations take effect globally even if they are written inside of a function definition. This includes implicit declarations of functions.
* The keywords typeof, inline, signed, const and volatile are not recognized.
* Comparisons between pointers and integers are always allowed.
* Integer types unsigned short and unsigned char promote to unsigned int.
* Out-of-range floating point literals are not an error.
* All automatic variables not declared register are preserved by longjmp. Ordinarily, GNU C follows ANSI C: automatic variables not declared volatile may be clobbered.
* In the preprocessor, comments convert to nothing at all, rather than to a space. This allows traditional token concatenation.
* In the preprocessor, macro arguments are recognized within string constants in a macro definition (and their values are stringified, though without additional quote marks, when they appear in such a context). The preprocessor also considers a string constant to end at a newline.
* The predefined macro __STDC__ is not defined when you use `-traditional', but __GNUC__ is (since the GNU extensions which __GNUC__ indicates are not affected by `-traditional'). If you need to write header files that work differently depending on whether `-traditional' is in use, by testing both of these predefined macros you can distinguish four situations: GNU C, traditional GNU C, other ANSI C compilers, and other old C compilers.

-O

Optimize. Optimizing compilation takes somewhat more time, and a lot more memory for a large function.
Without `-O', the compiler's goal is to reduce the cost of compilation and to make debugging produce the expected results. Statements are independent: if you stop the program with a breakpoint between statements, you can then assign a new value to any variable or change the program counter to any other statement in the function and get exactly the results you would expect from the source code. Without `-O', only variables declared register are allocated in registers. The resulting compiled code is a little worse than produced by PCC without `-O'.
With `-O', the compiler tries to reduce code size and execution time. Some of the `-f' options described below turn specific kinds of optimization on or off.

-g

Produce debugging information in the operating system's native format (for DBX or SDB). GDB also can work with this debugging information. Unlike most other C compilers, GNU CC allows you to use `-g' with`-O'.
The short cuts taken by optimized code may occasionally produce surprising results: some variables you declared may not exist at all; flow of control may briefly move where you did not expect it; some statements may not be executed because they compute constant results or their values were already at hand; some statements may execute in different places because they were moved out of loops. Nevertheless it proves possible to debug optimized output. This makes it reasonable to use the optimizer for programs that might have bugs.

-gg

Produce debugging information in GDB's (the GNU Debugger's) own format. This requires the GNU assembler and linker in order to work. This feature will probably be eliminated. It was intended to enable GDB to read the symbol table faster, but it doesn't result in enough of a speedup to be worth the larger object files and executables. We are working on other ways of making GDB start even faster, which work with DBX format debugging information and could be made to work with SDB format.

-w

Inhibit all warning messages.

-W

Print extra warning messages for these events:
* An automatic variable is used without first being initialized. These warnings are possible only in optimizing compilation, because they require data flow information that is computed only when optimizing. They occur only for variables that are candidates for register allocation. Therefore, they do not occur for a variable that is declared volatile, or whose address is taken, or whose size is other than 1,2,4 or 8 bytes. Also, they do not occur for structures, unions or arrays, even when they are in registers. Note that there may be no warning about a variable that is used only to compute a value that itself is never used, because such computations may be deleted by the flow analysis pass before the warnings are printed. These warnings are made optional because GNU CC is not smart enough to see all the reasons why the code might be correct despite appearing to have an error.
* A nonvolatile automatic variable might be changed by a call to longjmp. These warnings as well are possible only in optimizing compilation. The compiler sees only the calls to setjmp. It cannot know where longjmp will be called; in fact, a signal handler could call it at any point in the code. As a result, you may get a warning even when there is in fact no problem because longjmp cannot in fact be called at the place which would cause a problem.
* A function can return either with or without a value. (Falling off the end of the function body is considered returning without a value.) Spurious warning can occur because GNU CC does not realize that certain functions (including abort and longjmp) will never return.
* An expression-statement contains no side effects.

-Wimplicit

Warn whenever a function is implicitly declared.

-Wreturn-type

Warn whenever a function is defined with a return-type that defaults to int. Also warn about any return statement with no return-value in a function whose return-type is not void.

-Wunused

Warn whenever a local variable is unused aside from its declaration.

-Wcomment

Warn whenever a comment-start sequence `/*' appears in a comment.

-Wall

All of the above -W options combined.

-Wwrite-strings

Give string constants the type const char[length] so that copying the address of one into a non-const char * pointer will get a warning. These warnings will help you find at compile time code that can try to write into a string constant, but only if you have been very careful about using const in declarations and prototypes. Otherwise, it will just be a nuisance; this is why we did not make -Wall request these warnings.

-p

Generate extra code to write profile information suitable for the analysis program prof.

-pg

Generate extra code to write profile information suitable for the analysis program gprof.

-llibrary

Search a standard list of directories for a library named library, which is actually a file named `liblibrary.a'. The linker uses this file as if it had been specified precisely by name. The directories searched include several standard system directories plus any that you specify with `-L'. Normally the files found this way are library files - archive files whose members are object files. The linker handles an archive file by scanning through it for members which define symbols that have so far been referenced but not defined. But if the file that is found is an ordinary object file, it is linked in the usual fashion. The only difference between an `-l' option and specifying a file name is that `-l' searches several directories.

-Ldir

Add directory dir to the list of directories to be searched for `-l'.

-nostdlib

Don't use the standard system libraries and startup files when linking. Only the files you specify (plus `gnulib') will be passed to the linker.

-mmachinespec

Machine-dependent option specifying something about the type of target machine.

These are the `-m' options defined for 68000-class machines:

        -m68881

Generate output containing 68881 instructions for floating point. This is the default if you use the unmodified sources.

        -mfpa

Generate output containing Sun FPA instructions for floating point.

        -msoft-float

Generate output containing library calls for floating point.

        -mshort

Consider type int to be 16 bits wide, like short int.

        -mnobitfield

Do not use the bit-field instructions. `-m68000' implies `-mnobitfield'.

        -mbitfield

Do use the bit-field instructions. `-m68020' implies `-mbitfield'. This is the default if you use the unmodified sources.

        -mrtd

Use a different function-calling convention, in which functions that take a fixed number of arguments return with the rtd instruction, which pops their arguments while returning. This saves one instruction in the caller since there is no need to pop the arguments there. This calling convention is incompatible with the one normally used on Unix, so you cannot use it if you need to call libraries compiled with the Unix compiler. Also, you must provide function prototypes for all functions that take variable numbers of arguments (including printf); otherwise incorrect code will be generated for calls to those functions. In addition, seriously incorrect code will result if you call a function with too many arguments. (Normally, extra arguments are harmlessly ignored.) The rtd instruction is supported by the 68010 and 68020 processors, but not by the 68000.

These are the `-m' options defined in the VAX machine description:

        -munix

Do not output certain jump instructions (aobleq and so on) that the Unix assembler for the VAX cannot handle across long ranges.

        -mgnu

Do output those jump instructions, on the assumption that you will assemble with the GNU assembler.

        -mg

Output code for g-format floating point numbers instead of d-format.

-fflag

Specify machine-independent flags. Most flags have both positive and negative forms; the negative form of `-ffoo' would be `-fno-foo'. In the table below, only one of the forms is listed---the one which is not the default. You can figure out the other form by either removing `no-' or adding it.

        -ffloat-store

Do not store floating-point variables in registers. This prevents undesirable excess precision on machines such as the 68000 where the floating registers (of the 68881) keep more precision than a double is supposed to have. For most programs, the excess precision does only good, but a few programs rely on the precise definition of IEEE floating point. Use `-ffloat-store' for such programs.

        -fno-asm

Do not recognize asm, inline or typeof as a keyword. These words may then be used as identifiers.

        -fno-defer-pop

Always pop the arguments to each function call as soon as that function returns. Normally the compiler (when optimizing) lets arguments accumulate on the stack for several function calls and pops them all at once.

        -fstrength-reduce

Perform the optimizations of loop strength reduction and elimination of iteration variables.

        -fcombine-regs

Allow the combine pass to combine an instruction that copies one register into another. This might or might not produce better code when used in addition to `-O'.

        -fforce-mem

Force memory operands to be copied into registers before doing arithmetic on them. This may produce better code by making all memory references potential common subexpressions. When they are not common subexpressions, instruction combination should eliminate the separate register-load.

        -fforce-addr

Force memory address constants to be copied into registers before doing arithmetic on them. This may produce better code just as `-fforce-mem' may.

        -fomit-frame-pointer

Don't keep the frame pointer in a register for functions that don't need one. This avoids the instructions to save, set up and restore frame pointers; it also makes an extra register available in many functions. It also makes debugging impossible. On some machines, such as the VAX, this flag has no effect, because the standard calling sequence automatically handles the frame pointer and nothing is saved by pretending it doesn't exist. The machine-description macro FRAME_POINTER_REQUIRED controls whether a target machine supports this flag.

        -finline-functions

Integrate all simple functions into their callers. The compiler heuristically decides which functions are simple enough to be worth integrating in this way. If all calls to a given function are integrated, and the function is declared static, then the function is normally not output as assembler code in its own right.

        -fkeep-inline-functions

Even if all calls to a given function are integrated, and the function is declared static, nevertheless output a separate run-time callable version of the function.

        -fwritable-strings

Store string constants in the writable data segment and don't uniquize them. This is for compatibility with old programs which assume they can write into string constants. Writing into string constants is a very bad idea; ``constants'' should be constant.

        -fcond-mismatch

Allow conditional expressions with mismatched types in the second and third arguments. The value of such an expression is void.

        -fno-function-cse

Do not put function addresses in registers; make each instruction that calls a constant function contain the function's address explicitly. This option results in less efficient code, but some strange hacks that alter the assembler output may be confused by the optimizations performed when this option is not used.

        -fvolatile

Consider all memory references through pointers to be volatile.

        -fshared-data

Requests that the data and non-const variables of this compilation be shared data rather than private data. The distinction makes sense only on certain operating systems, where shared data is shared between processes running the same program, while private data exists in one copy per process.

        -funsigned-char

Let the type charbe the unsigned, like unsigned char. Each kind of machine has a default for what char should be. It is either like unsigned char by default of like signed char by default. (Actually, at present, the default is always signed.) The type char is always a distinct type from either signed char or unsigned char, even though its behavior is always just like one of those two. Note that this is equivalent to `-fno-signed-char', which is the negative form of `-fsigned-char'.

        -fsigned-char

Let the type char be the same as signed char. Note that this is equivalent to `-fno-unsigned-char', which is the negative form of `-funsigned-char'.

        -ffixed-reg

Treat the register named reg as a fixed register; generated code should never refer to it (except perhaps as a stack pointer, frame pointer or in some other fixed role). reg must be the name of a register. The register names accepted are machine-specific and are defined in the REGISTER_NAMES macro in the machine description macro file. This flag does not have a negative form, because it specifies a three-way choice.

        -fcall-used-reg

Treat the register named reg as an allocatable register that is clobbered by function calls. It may be allocated for temporaries or variables that do not live across a call. Functions compiled this way will not save and restore the register reg. Use of this flag for a register that has a fixed pervasive role in the machine's execution model, such as the stack pointer or frame pointer, will produce disastrous results. This flag does not have a negative form, because it specifies a three-way choice.

        -fcall-saved-reg

Treat the register named reg as an allocatable register saved by functions. It may be allocated even for temporaries or variables that live across a call. Functions compiled this way will save and restore the register reg if they use it. Use of this flag for a register that has a fixed pervasive role in the machine's execution model, such as the stack pointer or frame pointer, will produce disastrous results. A different sort of disaster will result from the use of this flag for a register in which function values may be returned. This flag does not have a negative form, because it specifies a three-way choice.

-dletters

Says to make debugging dumps at times specified by letters. Here are the possible letters:

        r

Dump after RTL generation.

        j

Dump after first jump optimization.

        J

Dump after last jump optimization.

        s

Dump after CSE (including the jump optimization that sometimes follows CSE).

        L

Dump after loop optimization.

        f

Dump after flow analysis.

        c

Dump after instruction combination.

        l

Dump after local register allocation.

        g

Dump after global register allocation.

        m

Print statistics on memory usage, at the end of the run.

-pedantic

Issue all the warnings demanded by strict ANSI standard C; reject all programs that use forbidden extensions. Valid ANSI standard C programs should compile properly with or without this option (though a rare few will require `-ansi'. However, without this option, certain GNU extensions and traditional C features are supported as well. With this option, they are rejected. There is no reason to use this option; it exists only to satisfy pedants.

FILES

SEE ALSO

BUGS

COPYING

AUTHORS

Index

NAME

SYNOPSIS

WARNING

DESCRIPTION

OPTIONS

FILES

SEE ALSO

BUGS

COPYING

AUTHORS