aboutsummaryrefslogtreecommitdiffstats
path: root/erts/etc/common/erlc.c
blob: f63ba3ee648d86c254595a41ffd67837275ec024 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
/*
 * %CopyrightBegin%
 *
 * Copyright Ericsson AB 1997-2012. All Rights Reserved.
 *
 * The contents of this file are subject to the Erlang Public License,
 * Version 1.1, (the "License"); you may not use this file except in
 * compliance with the License. You should have received a copy of the
 * Erlang Public License along with this software. If not, it can be
 * retrieved online at http://www.erlang.org/.
 *
 * Software distributed under the License is distributed on an "AS IS"
 * basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
 * the License for the specific language governing rights and limitations
 * under the License.
 *
 * %CopyrightEnd%
 */
/*
 * Purpose: Common compiler front-end.
 */
#ifdef HAVE_CONFIG_H
#  include "config.h"
#endif

#include "sys.h"
#ifdef __WIN32__
#include <winbase.h>
/* FIXE ME config_win32.h? */
#define HAVE_STRERROR 1
#define snprintf _snprintf
#endif

#include <ctype.h>

#define NO 0
#define YES 1

#define ASIZE(a) (sizeof(a)/sizeof(a[0]))

static int debug = 0;		/* Bit flags for debug printouts. */

static char** eargv_base;	/* Base of vector. */
static char** eargv;		/* First argument for erl. */

static int eargc;		/* Number of arguments in eargv. */

#ifdef __WIN32__
#  define QUOTE(s) possibly_quote(s)
#  define IS_DIRSEP(c) ((c) == '/' || (c) == '\\')
#  define ERL_NAME "erl.exe"
#else
#  define QUOTE(s) s
#  define IS_DIRSEP(c) ((c) == '/')
#  define ERL_NAME "erl"
#endif

#define UNSHIFT(s) eargc++, eargv--; eargv[0] = QUOTE(s)
#define PUSH(s) eargv[eargc++] = QUOTE(s)
#define PUSH2(s, t) PUSH(s); PUSH(t)
#define PUSH3(s, t, u) PUSH2(s, t); PUSH(u)

static char* output_type = NULL; /* Type of output file. */
#ifdef __WIN32__
static int pause_after_execution = 0;
#endif

/*
 * Local functions.
 */

static char* process_opt(int* pArgc, char*** pArgv, int offset);
static void error(char* format, ...);
static void usage(void);
static char* emalloc(size_t size);
static char* strsave(char* string);
static void push_words(char* src);
static int run_erlang(char* name, char** argv);
static char* get_default_emulator(char* progname);
#ifdef __WIN32__
static char* possibly_quote(char* arg);
#endif

/*
 * Supply a strerror() function if libc doesn't.
 */
#ifndef HAVE_STRERROR

extern int sys_nerr;

#ifndef SYS_ERRLIST_DECLARED
extern const char * const sys_errlist[];
#endif /* !SYS_ERRLIST_DECLARED */

char *strerror(int errnum)
{
  static char *emsg[1024];

  if (errnum != 0) {
    if (errnum > 0 && errnum < sys_nerr) 
      sprintf((char *) &emsg[0], "(%s)", sys_errlist[errnum]);
    else 
      sprintf((char *) &emsg[0], "errnum = %d ", errnum);
  }
  else {
    emsg[0] = '\0';
  }
  return (char *) &emsg[0];
}
#endif /* !HAVE_STRERROR */

static char *
get_env(char *key)
{
#ifdef __WIN32__
    DWORD size = 32;
    char *value = NULL;
    while (1) {
	DWORD nsz;
	if (value)
	    free(value);
	value = emalloc(size);
	SetLastError(0);
	nsz = GetEnvironmentVariable((LPCTSTR) key, (LPTSTR) value, size);
	if (nsz == 0 && GetLastError() == ERROR_ENVVAR_NOT_FOUND) {
	    free(value);
	    return NULL;
	}
	if (nsz <= size)
	    return value;
	size = nsz;
    }
#else
    return getenv(key);
#endif
}

static void
free_env_val(char *value)
{
#ifdef __WIN32__
    if (value)
	free(value);
#endif
}


int
main(int argc, char** argv)
{
    char cwd[MAXPATHLEN];	/* Current working directory. */
    int eargv_size;
    int eargc_base;		/* How many arguments in the base of eargv. */
    char* emulator;
    char *env;

    env = get_env("ERLC_EMULATOR");
    emulator = env ? env : get_default_emulator(argv[0]);

    if (strlen(emulator) >= MAXPATHLEN)
        error("Value of environment variable ERLC_EMULATOR is too large");

    /*
     * Allocate the argv vector to be used for arguments to Erlang.
     * Arrange for starting to pushing information in the middle of
     * the array, to allow easy adding of emulator options (like -pa)
     * before '-s erlcompile compile_cmdline...'.
     *
     * Oh, by the way, we will push the compiler command in the
     * base of the eargv vector, and move it up later.
     */

    eargv_size = argc*6+100;
    eargv_base = (char **) emalloc(eargv_size*sizeof(char*));
    eargv = eargv_base;
    eargc = 0;
    push_words(emulator);
    eargc_base = eargc;
    eargv = eargv + eargv_size/2;
    eargc = 0;

    free_env_val(env);

    /*
     * Push initial arguments.
     */

    PUSH("+sbtu");
    PUSH("-noinput");
    PUSH2("-mode", "minimal");
    PUSH2("-boot", "start_clean");
    PUSH3("-s", "erl_compile", "compile_cmdline");

    /*
     * Push standard arguments to Erlang.
     *
     * The @cwd argument was once needed, but from on R13B02 is optional.
     * For maximum compatibility between erlc and erl of different versions,
     * still provide the @cwd argument, unless it is too long to be
     * represented as an atom.
     */
    if (getcwd(cwd, sizeof(cwd)) == NULL)
	error("Failed to get current working directory: %s", strerror(errno));
#ifdef __WIN32__
    (void) GetShortPathName(cwd, cwd, sizeof(cwd));
#endif    
    if (strlen(cwd) < 256) {
	PUSH2("@cwd", cwd);
    }

    /*
     * Parse all command line switches.
     */

    while (argc > 1 && (argv[1][0] == '-' || argv[1][0] == '+')) {

	/*
	 * Options starting with '+' are passed on to Erlang.
	 */

	if (argv[1][0] == '+') {
	    PUSH2("@option", argv[1]+1);
	} else {
	    /*
	     * Interpret options starting with '-'.
	     */
	    
	    switch (argv[1][1]) {
	    case 'b':
		output_type = process_opt(&argc, &argv, 0);
		PUSH2("@output_type", output_type);
		break;
	    case 'c':		/* Allowed for compatibility with 'erl'. */
		if (strcmp(argv[1], "-compile") != 0)
		    goto error;
		break;
	    case 'd':
		debug = 1;
		break;
	    case 'D':
		{
		    char* def = process_opt(&argc, &argv, 0);
		    char* equals;
		    
		    def = strsave(def);	/* Do not clobber original. */
		    if ((equals = strchr(def, '=')) == NULL) {
			PUSH2("@d", def);
		    } else {
			*equals = '\0';
			equals++;
			PUSH3("@dv", def, equals);
		    }
		}
		break;
	    case 'I':
		PUSH2("@i", process_opt(&argc, &argv, 0));
		break;
	    case 'M':
		{
		    char *buf, *key, *val;
		    size_t buf_len;

		    if (argv[1][2] == '\0') { /* -M */
			/* Push the following options:
			 *   o  'makedep'
			 *   o  {makedep_output, standard_io}
			 */
			buf = strsave("makedep");
			PUSH2("@option", buf);

			key = "makedep_output";
			val = "standard_io";
			buf_len = 1 + strlen(key) + 1 + strlen(val) + 1 + 1;
			buf = emalloc(buf_len);
			snprintf(buf, buf_len, "{%s,%s}", key, val);
			PUSH2("@option", buf);
		    } else if (argv[1][3] == '\0') {
			switch(argv[1][2]) {
			case 'D': /* -MD */
			    /* Push the following options:
			     *   o  'makedep'
			     */
			    buf = strsave("makedep");
			    PUSH2("@option", buf);
			    break;
			case 'F': /* -MF <file> */
			    /* Push the following options:
			     *   o  'makedep'
			     *   o  {makedep_output, <file>}
			     */
			    buf = strsave("makedep");
			    PUSH2("@option", buf);

			    key = "makedep_output";
			    val = process_opt(&argc, &argv, 1);
			    buf_len = 1 + strlen(key) + 2 + strlen(val) + 2 + 1;
			    buf = emalloc(buf_len);
			    snprintf(buf, buf_len, "{%s,\"%s\"}", key, val);
			    PUSH2("@option", buf);
			    break;
			case 'T': /* -MT <target> */
			    /* Push the following options:
			     *   o  {makedep_target, <target>}
			     */
			    key = "makedep_target";
			    val = process_opt(&argc, &argv, 1);
			    buf_len = 1 + strlen(key) + 2 + strlen(val) + 2 + 1;
			    buf = emalloc(buf_len);
			    snprintf(buf, buf_len, "{%s,\"%s\"}", key, val);
			    PUSH2("@option", buf);
			    break;
			case 'Q': /* -MQ <target> */
			    /* Push the following options:
			     *   o  {makedep_target, <target>}
			     *   o  makedep_quote_target
			     */
			    key = "makedep_target";
			    val = process_opt(&argc, &argv, 1);
			    buf_len = 1 + strlen(key) + 2 + strlen(val) + 2 + 1;
			    buf = emalloc(buf_len);
			    snprintf(buf, buf_len, "{%s,\"%s\"}", key, val);
			    PUSH2("@option", buf);

			    buf = strsave("makedep_quote_target");
			    PUSH2("@option", buf);
			    break;
			case 'G': /* -MG */
			    /* Push the following options:
			     *   o  makedep_add_missing
			     */
			    buf = strsave("makedep_add_missing");
			    PUSH2("@option", buf);
			    break;
			case 'P': /* -MP */
			    /* Push the following options:
			     *   o  makedep_phony
			     */
			    buf = strsave("makedep_phony");
			    PUSH2("@option", buf);
			    break;
			default:
			    goto error;
			}
		    }
		}
		break;
	    case 'o':
		PUSH2("@outdir", process_opt(&argc, &argv, 0));
		break;
	    case 'O':
		PUSH("@optimize");
		if (argv[1][2] == '\0')
		    PUSH("1");
		else
		    PUSH(argv[1]+2);
		break;
	    case 'p':
		{
		    int c = argv[1][2];
		    
		    if (c != 'a' && c != 'z') {
			goto error;
#ifdef __WIN32__
		    } else if (strcmp(argv[1], "-pause") == 0) {
			pause_after_execution = 1;
#endif
		    } else {
			char option[4];

			UNSHIFT(process_opt(&argc, &argv, 1));
			option[0] = '-';
			option[1] = 'p';
			option[2] = c;
			option[3] = '\0';
			UNSHIFT(strsave(option));
		    }
		}
		break;
	    case 's':
		if (strcmp(argv[1], "-smp") == 0) {
		    UNSHIFT(argv[1]);
		} else {
		    goto error;
		}
		break;
	    case 'v':		/* Verbose. */
		PUSH2("@verbose", "true");
		break;
	    case 'V':
		/** XXX Version perhaps, but of what? **/
		break;
	    case 'W':		/* Enable warnings. */
		if (strcmp(argv[1]+2, "all") == 0) {
		    PUSH2("@warn", "999");
		} else if (strcmp(argv[1]+2, "error") == 0) {
		    PUSH2("@option", "warnings_as_errors");
		} else if (isdigit((int)argv[1][2])) {
		    PUSH2("@warn", argv[1]+2);
		} else {
		    PUSH2("@warn", "1");
		}
		break;
	    case 'E':
	    case 'S':
	    case 'P':
		{
		    char* buf;

		    /* 
		     * From the given upper-case letter, construct
		     * a quoted atom.  This is a convenience for the
		     * Erlang compiler, to avoid fighting with the shell's
		     * quoting.
		     */

		    buf = emalloc(4);
		    buf[0] = '\'';
		    buf[1] = argv[1][1];
		    buf[2] = '\'';
		    buf[3] = '\0';

		    PUSH2("@option", buf);
		}
		break;

	    case '-':
		goto no_more_options;

	    default:
	    error:
		usage();
		break;
	    }
	}
	argc--, argv++;
    }

 no_more_options:

    if (argc <= 1) {
	/*
	 * To avoid starting an Erlang system unless absolutely needed
	 * exit if no files were specified on the command line.
	 */
	exit(0);
    }

    /*
     * The rest of the command line must be filenames.  Simply push them.
     */

    PUSH("@files");
    while (argc > 1) {
	PUSH(argv[1]);
	argc--, argv++;
    }

    /*
     * Move up the commands for invoking the emulator and adjust eargv
     * accordingly.
     */

    while (--eargc_base >= 0) {
	UNSHIFT(eargv_base[eargc_base]);
    }
    
    /*
     * Invoke Erlang with the collected options.
     */

    PUSH(NULL);
    return run_erlang(eargv[0], eargv);
}

static char*
process_opt(int* pArgc, char*** pArgv, int offset)
{
    int argc = *pArgc;
    char** argv = *pArgv;
    int c = argv[1][1];
    
    if (argv[1][2+offset] != '\0') {
	/*
	 * The option was given as -x<value>.
	 */
	return argv[1]+2+offset;
    }

    /*
     * Look at the next argument.
     */

    argc--, argv++;
    if (argc < 2 || argv[1][0] == '-')
	error("No value given to -%c option", c);
    *pArgc = argc;
    *pArgv = argv;
    return argv[1];
}

static void
push_words(char* src)
{
    char sbuf[MAXPATHLEN];
    char* dst;

    dst = sbuf;
    while ((*dst++ = *src++) != '\0') {
	if (isspace((int)*src)) {
	    *dst = '\0';
	    PUSH(strsave(sbuf));
	    dst = sbuf;
	    do {
		src++;
	    } while (isspace((int)*src));
	}
    }
    if (sbuf[0])
	PUSH(strsave(sbuf));
}
#ifdef __WIN32__
char *make_commandline(char **argv)
{
    static char *buff = NULL;
    static int siz = 0;
    int num = 0;
    char **arg, *p;

    if (*argv == NULL) { 
	return "";
    }
    for (arg = argv; *arg != NULL; ++arg) {
	num += strlen(*arg)+1;
    }
    if (!siz) {
	siz = num;
	buff = malloc(siz*sizeof(char));
    } else if (siz < num) {
	siz = num;
	buff = realloc(buff,siz*sizeof(char));
    }
    p = buff;
    for (arg = argv; *arg != NULL; ++arg) {
	strcpy(p,*arg);
	p+=strlen(*arg);
	*p++=' ';
    }
    *(--p) = '\0';

    if (debug) {
	printf("Processed commandline:%s\n",buff);
    }
    return buff;
}

int my_spawnvp(char **argv)
{
    STARTUPINFO siStartInfo;
    PROCESS_INFORMATION piProcInfo;
    DWORD ec;

    memset(&siStartInfo,0,sizeof(STARTUPINFO));
    siStartInfo.cb = sizeof(STARTUPINFO); 
    siStartInfo.dwFlags = STARTF_USESTDHANDLES;
    siStartInfo.hStdInput = GetStdHandle(STD_INPUT_HANDLE);
    siStartInfo.hStdOutput = GetStdHandle(STD_OUTPUT_HANDLE);
    siStartInfo.hStdError = GetStdHandle(STD_ERROR_HANDLE);
    siStartInfo.wShowWindow = SW_HIDE;
    siStartInfo.dwFlags |= STARTF_USESHOWWINDOW;


    if (!CreateProcess(NULL, 
		       make_commandline(argv),
		       NULL, 
		       NULL, 
		       TRUE, 
		       0,
		       NULL, 
		       NULL, 
		       &siStartInfo, 
		       &piProcInfo)) {
	return -1;
    }
    CloseHandle(piProcInfo.hThread);

    WaitForSingleObject(piProcInfo.hProcess,INFINITE);
    if (!GetExitCodeProcess(piProcInfo.hProcess,&ec)) {
	return 0;
    }
    return (int) ec;
}    
#endif /* __WIN32__ */


static int
run_erlang(char* progname, char** argv)
{
#ifdef __WIN32__
    int status;
#endif

    if (debug) {
	int i = 0;
	while (argv[i] != NULL)
	    printf(" %s", argv[i++]);
	printf("\n");
    }

#ifdef __WIN32__
    /*
     * Alas, we must wait here for the program to finish.
     * Otherwise, the shell from which we was executed will think
     * we are finished and print a prompt and read keyboard input.
     */

    status = my_spawnvp(argv)/*_spawnvp(_P_WAIT,progname,argv)*/;
    if (status == -1) {
	fprintf(stderr, "erlc: Error executing '%s': %d", progname, 
		GetLastError());
    }
    if (pause_after_execution) {
	fprintf(stderr, "Press ENTER to continue . . .\n");
	while (getchar() != '\n')
	    ;
    }
    return status;
#else
    execvp(progname, argv);
    error("Error %d executing \'%s\'.", errno, progname);
    return 2;
#endif
}

static void
usage(void)
{
    static struct {
	char* name;
	char* desc;
    } options[] = {
	{"-b type", "type of output file (e.g. jam or beam)"},
	{"-d", "turn on debugging of erlc itself"},
	{"-Dname", "define name"},
	{"-Dname=value", "define name to have value"},
	{"-help", "shows this help text"},
	{"-I path", "where to search for include files"},
	{"-M", "generate a rule for make(1) describing the dependencies"},
	{"-MF file", "write the dependencies to 'file'"},
	{"-MT target", "change the target of the rule emitted by dependency "
		"generation"},
	{"-MQ target", "same as -MT but quote characters special to make(1)"},
	{"-MG", "consider missing headers as generated files and add them to "
		"the dependencies"},
	{"-MP", "add a phony target for each dependency"},
	{"-MD", "same as -M -MT file (with default 'file')"},
	{"-o name", "name output directory or file"},
	{"-pa path", "add path to the front of Erlang's code path"},
	{"-pz path", "add path to the end of Erlang's code path"},
	{"-smp", "compile using SMP emulator"},
	{"-v", "verbose compiler output"},
	{"-Werror", "make all warnings into errors"},
	{"-W0", "disable warnings"},
	{"-Wnumber", "set warning level to number"},
	{"-Wall", "enable all warnings"},
	{"-W", "enable warnings (default; same as -W1)"},
	{"-E", "generate listing of expanded code (Erlang compiler)"},
	{"-S", "generate assembly listing (Erlang compiler)"},
	{"-P", "generate listing of preprocessed code (Erlang compiler)"},
	{"+term", "pass the Erlang term unchanged to the compiler"},
    };
    int i;

    fprintf(stderr, "Usage:\terlc [options] file.ext ...\n");
    fprintf(stderr, "Options:\n");
    for (i = 0; i < sizeof(options)/sizeof(options[0]); i++) {
	fprintf(stderr, "%-14s %s\n", options[i].name, options[i].desc);
    }
    exit(1);
}

static void
error(char* format, ...)
{
    char sbuf[1024];
    va_list ap;
    
    va_start(ap, format);
    erts_vsnprintf(sbuf, sizeof(sbuf), format, ap);
    va_end(ap);
    fprintf(stderr, "erlc: %s\n", sbuf);
    exit(1);
}

static char*
emalloc(size_t size)
{
  char *p = malloc(size);
  if (p == NULL)
    error("Insufficient memory");
  return p;
}

static char*
strsave(char* string)
{
  char* p = emalloc(strlen(string)+1);
  strcpy(p, string);
  return p;
}

static char*
get_default_emulator(char* progname)
{
    char sbuf[MAXPATHLEN];
    char* s;

    if (strlen(progname) >= sizeof(sbuf))
        return ERL_NAME;

    strcpy(sbuf, progname);
    for (s = sbuf+strlen(sbuf); s >= sbuf; s--) {
	if (IS_DIRSEP(*s)) {
	    strcpy(s+1, ERL_NAME);
#ifdef __WIN32__
	    if (_access(sbuf, 0) != -1) {
		return strsave(sbuf);
	    }
#else
	    if (access(sbuf, 1) != -1) {
		return strsave(sbuf);
	    }
#endif
	    break;
	}
    }
    return ERL_NAME;
}

#ifdef __WIN32__
static char*
possibly_quote(char* arg)
{
    int mustQuote = NO;
    int n = 0;
    char* s;
    char* narg;

    if (arg == NULL) {
	return arg;
    }

    /*
     * Scan the string to find out if it needs quoting and return
     * the original argument if not.
     */

    for (s = arg; *s; s++, n++) {
	switch(*s) {
	case ' ':
	    mustQuote = YES;
	    continue;
	case '"':
	    mustQuote = YES;
	    n++;
	    continue;
	case '\\':
	    if(s[1] == '"')
		n++;
	    continue;
	default:
	    continue;
	}
    }
    if (!mustQuote) {
	return arg;
    }

    /*
     * Insert the quotes and put a backslash in front of every quote
     * inside the string.
     */

    s = narg = emalloc(n+2+1);
    for (*s++ = '"'; *arg; arg++, s++) {
	if (*arg == '"' || (*arg == '\\' && arg[1] == '"')) {
	    *s++ = '\\';
	}
	*s = *arg;
    }
    if (s[-1] == '\\') {
	*s++ ='\\';
    }
    *s++ = '"';
    *s = '\0';
    return narg;
}
#endif /* __WIN32__ */