Cannot Find “getopt.h” File When Compiling Under Windows

Often times, issues arise when compiling C/C++ code developed for Linux under Windows. One annoying problem is when the code requires some header which is only available in the POSIX API. A header commonly used for parsing the command line arguments is getopt.h. Unfortunately, this header is only available under Linux. After some digging around, I found a port of this header file for Windows here.

In case the repository went down in the future, I’ve pasted the code here. All credits go to the original author. Click on the link below for the full code.

#ifndef __GETOPT_H__
/**
 * DISCLAIMER
 * This file has no copyright assigned and is placed in the Public Domain.
 * This file is part of the mingw-w64 runtime package.
 *
 * The mingw-w64 runtime package and its code is distributed in the hope that it 
 * will be useful but WITHOUT ANY WARRANTY.  ALL WARRANTIES, EXPRESSED OR 
 * IMPLIED ARE HEREBY DISCLAIMED.  This includes but is not limited to 
 * warranties of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 */

#pragma warning(disable:4996);

#define __GETOPT_H__

/* All the headers include this file. */
#include <crtdefs.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <stdarg.h>
#include <stdio.h>
#include <windows.h>

#ifdef __cplusplus
extern "C" {
#endif

#define	REPLACE_GETOPT		/* use this getopt as the system getopt(3) */

#ifdef REPLACE_GETOPT
int	opterr = 1;		/* if error message should be printed */
int	optind = 1;		/* index into parent argv vector */
int	optopt = '?';		/* character checked for validity */
#undef	optreset		/* see getopt.h */
#define	optreset		__mingw_optreset
int	optreset;		/* reset getopt */
char    *optarg;		/* argument associated with option */
#endif

//extern int optind;		/* index of first non-option in argv      */
//extern int optopt;		/* single option character, as parsed     */
//extern int opterr;		/* flag to enable built-in diagnostics... */
//				/* (user may set to zero, to suppress)    */
//
//extern char *optarg;		/* pointer to argument of current option  */

#define PRINT_ERROR	((opterr) && (*options != ':'))

#define FLAG_PERMUTE	0x01	/* permute non-options to the end of argv */
#define FLAG_ALLARGS	0x02	/* treat non-options as args to option "-1" */
#define FLAG_LONGONLY	0x04	/* operate as getopt_long_only */

/* return values */
#define	BADCH		(int)'?'
#define	BADARG		((*options == ':') ? (int)':' : (int)'?')
#define	INORDER 	(int)1

#ifndef __CYGWIN__
#define __progname __argv[0]
#else
extern char __declspec(dllimport) *__progname;
#endif

#ifdef __CYGWIN__
static char EMSG[] = "";
#else
#define	EMSG		""
#endif

static int getopt_internal(int, char * const *, const char *,
			   const struct option *, int *, int);
static int parse_long_options(char * const *, const char *,
			      const struct option *, int *, int);
static int gcd(int, int);
static void permute_args(int, int, int, char * const *);

static char *place = EMSG; /* option letter processing */

/* XXX: set optreset to 1 rather than these two */
static int nonopt_start = -1; /* first non option argument (for permute) */
static int nonopt_end = -1;   /* first option after non options (for permute) */

/* Error messages */
static const char recargchar[] = "option requires an argument -- %c";
static const char recargstring[] = "option requires an argument -- %s";
static const char ambig[] = "ambiguous option -- %.*s";
static const char noarg[] = "option doesn't take an argument -- %.*s";
static const char illoptchar[] = "unknown option -- %c";
static const char illoptstring[] = "unknown option -- %s";

static void
_vwarnx(const char *fmt,va_list ap)
{
  (void)fprintf(stderr,"%s: ",__progname);
  if (fmt != NULL)
    (void)vfprintf(stderr,fmt,ap);
  (void)fprintf(stderr,"\n");
}

static void
warnx(const char *fmt,...)
{
  va_list ap;
  va_start(ap,fmt);
  _vwarnx(fmt,ap);
  va_end(ap);
}

/*
 * Compute the greatest common divisor of a and b.
 */
static int
gcd(int a, int b)
{
	int c;

	c = a % b;
	while (c != 0) {
		a = b;
		b = c;
		c = a % b;
	}

	return (b);
}

/*
 * Exchange the block from nonopt_start to nonopt_end with the block
 * from nonopt_end to opt_end (keeping the same order of arguments
 * in each block).
 */
static void
permute_args(int panonopt_start, int panonopt_end, int opt_end,
	char * const *nargv)
{
	int cstart, cyclelen, i, j, ncycle, nnonopts, nopts, pos;
	char *swap;

	/*
	 * compute lengths of blocks and number and size of cycles
	 */
	nnonopts = panonopt_end - panonopt_start;
	nopts = opt_end - panonopt_end;
	ncycle = gcd(nnonopts, nopts);
	cyclelen = (opt_end - panonopt_start) / ncycle;

	for (i = 0; i < ncycle; i++) {
		cstart = panonopt_end+i;
		pos = cstart;
		for (j = 0; j < cyclelen; j++) {
			if (pos >= panonopt_end)
				pos -= nnonopts;
			else
				pos += nopts;
			swap = nargv[pos];
			/* LINTED const cast */
			((char **) nargv)[pos] = nargv[cstart];
			/* LINTED const cast */
			((char **)nargv)[cstart] = swap;
		}
	}
}

#ifdef REPLACE_GETOPT
/*
 * getopt --
 *	Parse argc/argv argument vector.
 *
 * [eventually this will replace the BSD getopt]
 */
int
getopt(int nargc, char * const *nargv, const char *options)
{

	/*
	 * We don't pass FLAG_PERMUTE to getopt_internal() since
	 * the BSD getopt(3) (unlike GNU) has never done this.
	 *
	 * Furthermore, since many privileged programs call getopt()
	 * before dropping privileges it makes sense to keep things
	 * as simple (and bug-free) as possible.
	 */
	return (getopt_internal(nargc, nargv, options, NULL, NULL, 0));
}
#endif /* REPLACE_GETOPT */

//extern int getopt(int nargc, char * const *nargv, const char *options);

#ifdef _BSD_SOURCE
/*
 * BSD adds the non-standard `optreset' feature, for reinitialisation
 * of `getopt' parsing.  We support this feature, for applications which
 * proclaim their BSD heritage, before including this header; however,
 * to maintain portability, developers are advised to avoid it.
 */
# define optreset  __mingw_optreset
extern int optreset;
#endif
#ifdef __cplusplus
}
#endif
/*
 * POSIX requires the `getopt' API to be specified in `unistd.h';
 * thus, `unistd.h' includes this header.  However, we do not want
 * to expose the `getopt_long' or `getopt_long_only' APIs, when
 * included in this manner.  Thus, close the standard __GETOPT_H__
 * declarations block, and open an additional __GETOPT_LONG_H__
 * specific block, only when *not* __UNISTD_H_SOURCED__, in which
 * to declare the extended API.
 */
#endif /* !defined(__GETOPT_H__) */

#if !defined(__UNISTD_H_SOURCED__) && !defined(__GETOPT_LONG_H__)
#define __GETOPT_LONG_H__

#ifdef __cplusplus
extern "C" {
#endif

struct option		/* specification for a long form option...	*/
{
  const char *name;		/* option name, without leading hyphens */
  int         has_arg;		/* does it take an argument?		*/
  int        *flag;		/* where to save its status, or NULL	*/
  int         val;		/* its associated status value		*/
};

enum    		/* permitted values for its `has_arg' field...	*/
{
  no_argument = 0,      	/* option never takes an argument	*/
  required_argument,		/* option always requires an argument	*/
  optional_argument		/* option may take an argument		*/
};

/*
 * parse_long_options --
 *	Parse long options in argc/argv argument vector.
 * Returns -1 if short_too is set and the option does not match long_options.
 */
static int
parse_long_options(char * const *nargv, const char *options,
	const struct option *long_options, int *idx, int short_too)
{
	char *current_argv, *has_equal;
	size_t current_argv_len;
	int i, ambiguous, match;

#define IDENTICAL_INTERPRETATION(_x, _y)                                \
	(long_options[(_x)].has_arg == long_options[(_y)].has_arg &&    \
	 long_options[(_x)].flag == long_options[(_y)].flag &&          \
	 long_options[(_x)].val == long_options[(_y)].val)

	current_argv = place;
	match = -1;
	ambiguous = 0;

	optind++;

	if ((has_equal = strchr(current_argv, '=')) != NULL) {
		/* argument found (--option=arg) */
		current_argv_len = has_equal - current_argv;
		has_equal++;
	} else
		current_argv_len = strlen(current_argv);

	for (i = 0; long_options[i].name; i++) {
		/* find matching long option */
		if (strncmp(current_argv, long_options[i].name,
		    current_argv_len))
			continue;

		if (strlen(long_options[i].name) == current_argv_len) {
			/* exact match */
			match = i;
			ambiguous = 0;
			break;
		}
		/*
		 * If this is a known short option, don't allow
		 * a partial match of a single character.
		 */
		if (short_too && current_argv_len == 1)
			continue;

		if (match == -1)	/* partial match */
			match = i;
		else if (!IDENTICAL_INTERPRETATION(i, match))
			ambiguous = 1;
	}
	if (ambiguous) {
		/* ambiguous abbreviation */
		if (PRINT_ERROR)
			warnx(ambig, (int)current_argv_len,
			     current_argv);
		optopt = 0;
		return (BADCH);
	}
	if (match != -1) {		/* option found */
		if (long_options[match].has_arg == no_argument
		    && has_equal) {
			if (PRINT_ERROR)
				warnx(noarg, (int)current_argv_len,
				     current_argv);
			/*
			 * XXX: GNU sets optopt to val regardless of flag
			 */
			if (long_options[match].flag == NULL)
				optopt = long_options[match].val;
			else
				optopt = 0;
			return (BADARG);
		}
		if (long_options[match].has_arg == required_argument ||
		    long_options[match].has_arg == optional_argument) {
			if (has_equal)
				optarg = has_equal;
			else if (long_options[match].has_arg ==
			    required_argument) {
				/*
				 * optional argument doesn't use next nargv
				 */
				optarg = nargv[optind++];
			}
		}
		if ((long_options[match].has_arg == required_argument)
		    && (optarg == NULL)) {
			/*
			 * Missing argument; leading ':' indicates no error
			 * should be generated.
			 */
			if (PRINT_ERROR)
				warnx(recargstring,
				    current_argv);
			/*
			 * XXX: GNU sets optopt to val regardless of flag
			 */
			if (long_options[match].flag == NULL)
				optopt = long_options[match].val;
			else
				optopt = 0;
			--optind;
			return (BADARG);
		}
	} else {			/* unknown option */
		if (short_too) {
			--optind;
			return (-1);
		}
		if (PRINT_ERROR)
			warnx(illoptstring, current_argv);
		optopt = 0;
		return (BADCH);
	}
	if (idx)
		*idx = match;
	if (long_options[match].flag) {
		*long_options[match].flag = long_options[match].val;
		return (0);
	} else
		return (long_options[match].val);
#undef IDENTICAL_INTERPRETATION
}

/*
 * getopt_internal --
 *	Parse argc/argv argument vector.  Called by user level routines.
 */
static int
getopt_internal(int nargc, char * const *nargv, const char *options,
	const struct option *long_options, int *idx, int flags)
{
	char *oli;				/* option letter list index */
	int optchar, short_too;
	static int posixly_correct = -1;

	if (options == NULL)
		return (-1);

	/*
	 * XXX Some GNU programs (like cvs) set optind to 0 instead of
	 * XXX using optreset.  Work around this braindamage.
	 */
	if (optind == 0)
		optind = optreset = 1;

	/*
	 * Disable GNU extensions if POSIXLY_CORRECT is set or options
	 * string begins with a '+'.
	 *
	 * CV, 2009-12-14: Check POSIXLY_CORRECT anew if optind == 0 or
	 *                 optreset != 0 for GNU compatibility.
	 */
	if (posixly_correct == -1 || optreset != 0)
		posixly_correct = (getenv("POSIXLY_CORRECT") != NULL);
	if (*options == '-')
		flags |= FLAG_ALLARGS;
	else if (posixly_correct || *options == '+')
		flags &= ~FLAG_PERMUTE;
	if (*options == '+' || *options == '-')
		options++;

	optarg = NULL;
	if (optreset)
		nonopt_start = nonopt_end = -1;
start:
	if (optreset || !*place) {		/* update scanning pointer */
		optreset = 0;
		if (optind >= nargc) {          /* end of argument vector */
			place = EMSG;
			if (nonopt_end != -1) {
				/* do permutation, if we have to */
				permute_args(nonopt_start, nonopt_end,
				    optind, nargv);
				optind -= nonopt_end - nonopt_start;
			}
			else if (nonopt_start != -1) {
				/*
				 * If we skipped non-options, set optind
				 * to the first of them.
				 */
				optind = nonopt_start;
			}
			nonopt_start = nonopt_end = -1;
			return (-1);
		}
		if (*(place = nargv[optind]) != '-' ||
		    (place[1] == '\0' && strchr(options, '-') == NULL)) {
			place = EMSG;		/* found non-option */
			if (flags & FLAG_ALLARGS) {
				/*
				 * GNU extension:
				 * return non-option as argument to option 1
				 */
				optarg = nargv[optind++];
				return (INORDER);
			}
			if (!(flags & FLAG_PERMUTE)) {
				/*
				 * If no permutation wanted, stop parsing
				 * at first non-option.
				 */
				return (-1);
			}
			/* do permutation */
			if (nonopt_start == -1)
				nonopt_start = optind;
			else if (nonopt_end != -1) {
				permute_args(nonopt_start, nonopt_end,
				    optind, nargv);
				nonopt_start = optind -
				    (nonopt_end - nonopt_start);
				nonopt_end = -1;
			}
			optind++;
			/* process next argument */
			goto start;
		}
		if (nonopt_start != -1 && nonopt_end == -1)
			nonopt_end = optind;

		/*
		 * If we have "-" do nothing, if "--" we are done.
		 */
		if (place[1] != '\0' && *++place == '-' && place[1] == '\0') {
			optind++;
			place = EMSG;
			/*
			 * We found an option (--), so if we skipped
			 * non-options, we have to permute.
			 */
			if (nonopt_end != -1) {
				permute_args(nonopt_start, nonopt_end,
				    optind, nargv);
				optind -= nonopt_end - nonopt_start;
			}
			nonopt_start = nonopt_end = -1;
			return (-1);
		}
	}

	/*
	 * Check long options if:
	 *  1) we were passed some
	 *  2) the arg is not just "-"
	 *  3) either the arg starts with -- we are getopt_long_only()
	 */
	if (long_options != NULL && place != nargv[optind] &&
	    (*place == '-' || (flags & FLAG_LONGONLY))) {
		short_too = 0;
		if (*place == '-')
			place++;		/* --foo long option */
		else if (*place != ':' && strchr(options, *place) != NULL)
			short_too = 1;		/* could be short option too */

		optchar = parse_long_options(nargv, options, long_options,
		    idx, short_too);
		if (optchar != -1) {
			place = EMSG;
			return (optchar);
		}
	}

	if ((optchar = (int)*place++) == (int)':' ||
	    (optchar == (int)'-' && *place != '\0') ||
	    (oli = (char*)strchr(options, optchar)) == NULL) {
		/*
		 * If the user specified "-" and  '-' isn't listed in
		 * options, return -1 (non-option) as per POSIX.
		 * Otherwise, it is an unknown option character (or ':').
		 */
		if (optchar == (int)'-' && *place == '\0')
			return (-1);
		if (!*place)
			++optind;
		if (PRINT_ERROR)
			warnx(illoptchar, optchar);
		optopt = optchar;
		return (BADCH);
	}
	if (long_options != NULL && optchar == 'W' && oli[1] == ';') {
		/* -W long-option */
		if (*place)			/* no space */
			/* NOTHING */;
		else if (++optind >= nargc) {	/* no arg */
			place = EMSG;
			if (PRINT_ERROR)
				warnx(recargchar, optchar);
			optopt = optchar;
			return (BADARG);
		} else				/* white space */
			place = nargv[optind];
		optchar = parse_long_options(nargv, options, long_options,
		    idx, 0);
		place = EMSG;
		return (optchar);
	}
	if (*++oli != ':') {			/* doesn't take argument */
		if (!*place)
			++optind;
	} else {				/* takes (optional) argument */
		optarg = NULL;
		if (*place)			/* no white space */
			optarg = place;
		else if (oli[1] != ':') {	/* arg not optional */
			if (++optind >= nargc) {	/* no arg */
				place = EMSG;
				if (PRINT_ERROR)
					warnx(recargchar, optchar);
				optopt = optchar;
				return (BADARG);
			} else
				optarg = nargv[optind];
		}
		place = EMSG;
		++optind;
	}
	/* dump back option letter */
	return (optchar);
}

/*
 * getopt_long --
 *	Parse argc/argv argument vector.
 */
int
getopt_long(int nargc, char * const *nargv, const char *options,
    const struct option *long_options, int *idx)
{

	return (getopt_internal(nargc, nargv, options, long_options, idx,
	    FLAG_PERMUTE));
}

/*
 * getopt_long_only --
 *	Parse argc/argv argument vector.
 */
int
getopt_long_only(int nargc, char * const *nargv, const char *options,
    const struct option *long_options, int *idx)
{

	return (getopt_internal(nargc, nargv, options, long_options, idx,
	    FLAG_PERMUTE|FLAG_LONGONLY));
}

//extern int getopt_long(int nargc, char * const *nargv, const char *options,
//    const struct option *long_options, int *idx);
//extern int getopt_long_only(int nargc, char * const *nargv, const char *options,
//    const struct option *long_options, int *idx);
/*
 * Previous MinGW implementation had...
 */
#ifndef HAVE_DECL_GETOPT
/*
 * ...for the long form API only; keep this for compatibility.
 */
# define HAVE_DECL_GETOPT	1
#endif

#ifdef __cplusplus
}
#endif

#endif /* !defined(__UNISTD_H_SOURCED__) && !defined(__GETOPT_LONG_H__) */