make.h

   1 /* Miscellaneous global declarations and portability cruft for GNU Make.
   2 Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
   3 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011,
   4 2012 Free Software Foundation, Inc.
   5 This file is part of GNU Make.
   6
   7 GNU Make is free software; you can redistribute it and/or modify it under the
   8 terms of the GNU General Public License as published by the Free Software
   9 Foundation; either version 3 of the License, or (at your option) any later
  10 version.
  11
  12 GNU Make is distributed in the hope that it will be useful, but WITHOUT ANY
  13 WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
  14 A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License along with
  17 this program.  If not, see <http://www.gnu.org/licenses/>.  */
  18
  19 /* We use <config.h> instead of "config.h" so that a compilation
  20    using -I. -I$srcdir will use ./config.h rather than $srcdir/config.h
  21    (which it would do because make.h was found in $srcdir).  */
  22 #include <config.h>
  23 #undef  HAVE_CONFIG_H
  24 #define HAVE_CONFIG_H 1
  25
  26 /* Specify we want GNU source code.  This must be defined before any
  27    system headers are included.  */
  28
  29 #define _GNU_SOURCE 1
  30
  31 /* AIX requires this to be the first thing in the file.  */
  32 #if HAVE_ALLOCA_H
  33 # include <alloca.h>
  34 #else
  35 # ifdef _AIX
  36  #pragma alloca
  37 # else
  38 #  if !defined(__GNUC__) && !defined(WINDOWS32)
  39 #   ifndef alloca /* predefined by HP cc +Olibcalls */
  40 char *alloca ();
  41 #   endif
  42 #  endif
  43 # endif
  44 #endif
  45
  46 /* Disable assert() unless we're a maintainer.
  47    Some asserts are compute-intensive.  */
  48 #ifndef MAKE_MAINTAINER_MODE
  49 # define NDEBUG 1
  50 #endif
  51
  52
  53 #ifdef  CRAY
  54 /* This must happen before #include <signal.h> so
  55    that the declaration therein is changed.  */
  56 # define signal bsdsignal
  57 #endif
  58
  59 /* If we're compiling for the dmalloc debugger, turn off string inlining.  */
  60 #if defined(HAVE_DMALLOC_H) && defined(__GNUC__)
  61 # define __NO_STRING_INLINES
  62 #endif
  63
  64 #include <sys/types.h>
  65 #include <sys/stat.h>
  66 #include <signal.h>
  67 #include <stdio.h>
  68 #include <ctype.h>
  69
  70 #ifdef HAVE_SYS_TIMEB_H
  71 /* SCO 3.2 "devsys 4.2" has a prototype for `ftime' in <time.h> that bombs
  72    unless <sys/timeb.h> has been included first.  */
  73 # include <sys/timeb.h>
  74 #endif
  75 #if TIME_WITH_SYS_TIME
  76 # include <sys/time.h>
  77 # include <time.h>
  78 #else
  79 # if HAVE_SYS_TIME_H
  80 #  include <sys/time.h>
  81 # else
  82 #  include <time.h>
  83 # endif
  84 #endif
  85
  86 #include <errno.h>
  87
  88 #ifndef errno
  89 extern int errno;
  90 #endif
  91
  92 #ifndef isblank
  93 # define isblank(c)     ((c) == ' ' || (c) == '\t')
  94 #endif
  95
  96 #ifdef  HAVE_UNISTD_H
  97 # include <unistd.h>
  98 /* Ultrix's unistd.h always defines _POSIX_VERSION, but you only get
  99    POSIX.1 behavior with `cc -YPOSIX', which predefines POSIX itself!  */
 100 # if defined (_POSIX_VERSION) && !defined (ultrix) && !defined (VMS)
 101 #  define POSIX 1
 102 # endif
 103 #endif
 104
 105 /* Some systems define _POSIX_VERSION but are not really POSIX.1.  */
 106 #if (defined (butterfly) || defined (__arm) || (defined (__mips) && defined (_SYSTYPE_SVR3)) || (defined (sequent) && defined (i386)))
 107 # undef POSIX
 108 #endif
 109
 110 #if !defined (POSIX) && defined (_AIX) && defined (_POSIX_SOURCE)
 111 # define POSIX 1
 112 #endif
 113
 114 #ifndef RETSIGTYPE
 115 # define RETSIGTYPE     void
 116 #endif
 117
 118 #ifndef sigmask
 119 # define sigmask(sig)   (1 << ((sig) - 1))
 120 #endif
 121
 122 #ifndef HAVE_SA_RESTART
 123 # define SA_RESTART 0
 124 #endif
 125
 126 #ifdef  HAVE_LIMITS_H
 127 # include <limits.h>
 128 #endif
 129 #ifdef  HAVE_SYS_PARAM_H
 130 # include <sys/param.h>
 131 #endif
 132
 133 #ifndef PATH_MAX
 134 # ifndef POSIX
 135 #  define PATH_MAX      MAXPATHLEN
 136 # endif
 137 #endif
 138 #ifndef MAXPATHLEN
 139 # define MAXPATHLEN 1024
 140 #endif
 141
 142 #ifdef  PATH_MAX
 143 # define GET_PATH_MAX   PATH_MAX
 144 # define PATH_VAR(var)  char var[PATH_MAX]
 145 #else
 146 # define NEED_GET_PATH_MAX 1
 147 # define GET_PATH_MAX   (get_path_max ())
 148 # define PATH_VAR(var)  char *var = alloca (GET_PATH_MAX)
 149 unsigned int get_path_max (void);
 150 #endif
 151
 152 #ifndef CHAR_BIT
 153 # define CHAR_BIT 8
 154 #endif
 155
 156 #ifndef USHRT_MAX
 157 # define USHRT_MAX 65535
 158 #endif
 159
 160 /* Nonzero if the integer type T is signed.
 161    Use <= to avoid GCC warnings about always-false expressions.  */
 162 #define INTEGER_TYPE_SIGNED(t) ((t) -1 <= 0)
 163
 164 /* The minimum and maximum values for the integer type T.
 165    Use ~ (t) 0, not -1, for portability to 1's complement hosts.  */
 166 #define INTEGER_TYPE_MINIMUM(t) \
 167   (! INTEGER_TYPE_SIGNED (t) ? (t) 0 : ~ (t) 0 << (sizeof (t) * CHAR_BIT - 1))
 168 #define INTEGER_TYPE_MAXIMUM(t) (~ (t) 0 - INTEGER_TYPE_MINIMUM (t))
 169
 170 #ifndef CHAR_MAX
 171 # define CHAR_MAX INTEGER_TYPE_MAXIMUM (char)
 172 #endif
 173
 174 #ifdef STAT_MACROS_BROKEN
 175 # ifdef S_ISREG
 176 #  undef S_ISREG
 177 # endif
 178 # ifdef S_ISDIR
 179 #  undef S_ISDIR
 180 # endif
 181 #endif  /* STAT_MACROS_BROKEN.  */
 182
 183 #ifndef S_ISREG
 184 # define S_ISREG(mode)  (((mode) & S_IFMT) == S_IFREG)
 185 #endif
 186 #ifndef S_ISDIR
 187 # define S_ISDIR(mode)  (((mode) & S_IFMT) == S_IFDIR)
 188 #endif
 189
 190 #ifdef VMS
 191 # include <types.h>
 192 # include <unixlib.h>
 193 # include <unixio.h>
 194 # include <perror.h>
 195 /* Needed to use alloca on VMS.  */
 196 # include <builtins.h>
 197 #endif
 198
 199 #ifndef __attribute__
 200 /* This feature is available in gcc versions 2.5 and later.  */
 201 # if __GNUC__ < 2 || (__GNUC__ == 2 && __GNUC_MINOR__ < 5) || __STRICT_ANSI__
 202 #  define __attribute__(x)
 203 # endif
 204 /* The __-protected variants of `format' and `printf' attributes
 205    are accepted by gcc versions 2.6.4 (effectively 2.7) and later.  */
 206 # if __GNUC__ < 2 || (__GNUC__ == 2 && __GNUC_MINOR__ < 7)
 207 #  define __format__ format
 208 #  define __printf__ printf
 209 # endif
 210 #endif
 211 #define UNUSED  __attribute__ ((unused))
 212
 213 #if defined (STDC_HEADERS) || defined (__GNU_LIBRARY__)
 214 # include <stdlib.h>
 215 # include <string.h>
 216 # define ANSI_STRING 1
 217 #else   /* No standard headers.  */
 218 # ifdef HAVE_STRING_H
 219 #  include <string.h>
 220 #  define ANSI_STRING 1
 221 # else
 222 #  include <strings.h>
 223 # endif
 224 # ifdef HAVE_MEMORY_H
 225 #  include <memory.h>
 226 # endif
 227 # ifdef HAVE_STDLIB_H
 228 #  include <stdlib.h>
 229 # else
 230 void *malloc (int);
 231 void *realloc (void *, int);
 232 void free (void *);
 233
 234 void abort (void) __attribute__ ((noreturn));
 235 void exit (int) __attribute__ ((noreturn));
 236 # endif /* HAVE_STDLIB_H.  */
 237
 238 #endif /* Standard headers.  */
 239
 240 /* These should be in stdlib.h.  Make sure we have them.  */
 241 #ifndef EXIT_SUCCESS
 242 # define EXIT_SUCCESS 0
 243 #endif
 244 #ifndef EXIT_FAILURE
 245 # define EXIT_FAILURE 1
 246 #endif
 247
 248 #ifndef  ANSI_STRING
 249
 250 /* SCO Xenix has a buggy macro definition in <string.h>.  */
 251 #undef  strerror
 252 #if !defined(__DECC)
 253 char *strerror (int errnum);
 254 #endif
 255
 256 #endif  /* !ANSI_STRING.  */
 257 #undef  ANSI_STRING
 258
 259 #if HAVE_INTTYPES_H
 260 # include <inttypes.h>
 261 #endif
 262 #if HAVE_STDINT_H
 263 # include <stdint.h>
 264 #endif
 265 #define FILE_TIMESTAMP uintmax_t
 266
 267 #if !defined(HAVE_STRSIGNAL)
 268 char *strsignal (int signum);
 269 #endif
 270
 271 /* ISDIGIT offers the following features:
 272    - Its arg may be any int or unsigned int; it need not be an unsigned char.
 273    - It's guaranteed to evaluate its argument exactly once.
 274       NOTE!  Make relies on this behavior, don't change it!
 275    - It's typically faster.
 276    POSIX 1003.2-1992 section 2.5.2.1 page 50 lines 1556-1558 says that
 277    only '0' through '9' are digits.  Prefer ISDIGIT to isdigit() unless
 278    it's important to use the locale's definition of `digit' even when the
 279    host does not conform to POSIX.  */
 280 #define ISDIGIT(c) ((unsigned) (c) - '0' <= 9)
 281
 282 /* Test if two strings are equal. Is this worthwhile?  Should be profiled.  */
 283 #define streq(a, b) \
 284    ((a) == (b) || \
 285     (*(a) == *(b) && (*(a) == '\0' || !strcmp ((a) + 1, (b) + 1))))
 286
 287 /* Test if two strings are equal, but match case-insensitively on systems
 288    which have case-insensitive filesystems.  Should only be used for
 289    filenames!  */
 290 #ifdef HAVE_CASE_INSENSITIVE_FS
 291 # define patheq(a, b) \
 292     ((a) == (b) \
 293      || (tolower((unsigned char)*(a)) == tolower((unsigned char)*(b)) \
 294          && (*(a) == '\0' || !strcasecmp ((a) + 1, (b) + 1))))
 295 #else
 296 # define patheq(a, b) streq(a, b)
 297 #endif
 298
 299 #define strneq(a, b, l) (strncmp ((a), (b), (l)) == 0)
 300
 301 #if defined(__GNUC__) || defined(ENUM_BITFIELDS)
 302 # define ENUM_BITFIELD(bits)    :bits
 303 #else
 304 # define ENUM_BITFIELD(bits)
 305 #endif
 306
 307 /* Handle gettext and locales.  */
 308
 309 #if HAVE_LOCALE_H
 310 # include <locale.h>
 311 #else
 312 # define setlocale(category, locale)
 313 #endif
 314
 315 #include <gettext.h>
 316
 317 #define _(msgid)            gettext (msgid)
 318 #define N_(msgid)           gettext_noop (msgid)
 319 #define S_(msg1,msg2,num)   ngettext (msg1,msg2,num)
 320
 321 /* Handle other OSs.
 322    To overcome an issue parsing paths in a DOS/Windows environment when
 323    built in a unix based environment, override the PATH_SEPARATOR_CHAR
 324    definition unless being built for Cygwin. */
 325 #if defined(HAVE_DOS_PATHS) && !defined(__CYGWIN__)
 326 # undef PATH_SEPARATOR_CHAR
 327 # define PATH_SEPARATOR_CHAR ';'
 328 #elif !defined(PATH_SEPARATOR_CHAR)
 329 # if defined (VMS)
 330 #  define PATH_SEPARATOR_CHAR ','
 331 # else
 332 #  define PATH_SEPARATOR_CHAR ':'
 333 # endif
 334 #endif
 335
 336 /* This is needed for getcwd() and chdir(), on some W32 systems.  */
 337 #if defined(HAVE_DIRECT_H)
 338 # include <direct.h>
 339 #endif
 340
 341 #ifdef WINDOWS32
 342 # include <fcntl.h>
 343 # include <malloc.h>
 344 # define pipe(_p)        _pipe((_p), 512, O_BINARY)
 345 # define kill(_pid,_sig) w32_kill((_pid),(_sig))
 346
 347 void sync_Path_environment (void);
 348 int w32_kill (pid_t pid, int sig);
 349 char *end_of_token_w32 (const char *s, char stopchar);
 350 int find_and_set_default_shell (const char *token);
 351
 352 /* indicates whether or not we have Bourne shell */
 353 extern int no_default_sh_exe;
 354
 355 /* is default_shell unixy? */
 356 extern int unixy_shell;
 357 #endif  /* WINDOWS32 */
 358
 359 #if defined(HAVE_SYS_RESOURCE_H) && defined(HAVE_GETRLIMIT) && defined(HAVE_SETRLIMIT)
 360 # define SET_STACK_SIZE
 361 #endif
 362 #ifdef SET_STACK_SIZE
 363 # include <sys/resource.h>
 364 extern struct rlimit stack_limit;
 365 #endif
 366
 367 struct floc
 368   {
 369     const char *filenm;
 370     unsigned long lineno;
 371   };
 372 #define NILF ((struct floc *)0)
 373
 374 #define STRING_SIZE_TUPLE(_s) (_s), (sizeof (_s)-1)
 375
 376 \f
 377 /* We have to have stdarg.h or varargs.h AND v*printf or doprnt to use
 378    variadic versions of these functions.  */
 379
 380 #if HAVE_STDARG_H || HAVE_VARARGS_H
 381 # if HAVE_VPRINTF || HAVE_DOPRNT
 382 #  define USE_VARIADIC 1
 383 # endif
 384 #endif
 385
 386 #if HAVE_ANSI_COMPILER && USE_VARIADIC && HAVE_STDARG_H
 387 const char *concat (unsigned int, ...);
 388 void message (int prefix, const char *fmt, ...)
 389               __attribute__ ((__format__ (__printf__, 2, 3)));
 390 void error (const struct floc *flocp, const char *fmt, ...)
 391             __attribute__ ((__format__ (__printf__, 2, 3)));
 392 void fatal (const struct floc *flocp, const char *fmt, ...)
 393                    __attribute__ ((noreturn, __format__ (__printf__, 2, 3)));
 394 #else
 395 const char *concat ();
 396 void message ();
 397 void error ();
 398 void fatal ();
 399 #endif
 400
 401 void die (int) __attribute__ ((noreturn));
 402 void log_working_directory (int);
 403 void pfatal_with_name (const char *) __attribute__ ((noreturn));
 404 void perror_with_name (const char *, const char *);
 405 void *xmalloc (unsigned int);
 406 void *xcalloc (unsigned int);
 407 void *xrealloc (void *, unsigned int);
 408 char *xstrdup (const char *);
 409 char *xstrndup (const char *, unsigned int);
 410 char *find_next_token (const char **, unsigned int *);
 411 char *next_token (const char *);
 412 char *end_of_token (const char *);
 413 void collapse_continuations (char *);
 414 char *lindex (const char *, const char *, int);
 415 int alpha_compare (const void *, const void *);
 416 void print_spaces (unsigned int);
 417 char *find_percent (char *);
 418 const char *find_percent_cached (const char **);
 419 FILE *open_tmpfile (char **, const char *);
 420
 421 #ifndef NO_ARCHIVES
 422 int ar_name (const char *);
 423 void ar_parse_name (const char *, char **, char **);
 424 int ar_touch (const char *);
 425 time_t ar_member_date (const char *);
 426
 427 typedef long int (*ar_member_func_t) (int desc, const char *mem, int truncated,
 428                                       long int hdrpos, long int datapos,
 429                                       long int size, long int date, int uid,
 430                                       int gid, int mode, const void *arg);
 431
 432 long int ar_scan (const char *archive, ar_member_func_t function, const void *arg);
 433 int ar_name_equal (const char *name, const char *mem, int truncated);
 434 #ifndef VMS
 435 int ar_member_touch (const char *arname, const char *memname);
 436 #endif
 437 #endif
 438
 439 int dir_file_exists_p (const char *, const char *);
 440 int file_exists_p (const char *);
 441 int file_impossible_p (const char *);
 442 void file_impossible (const char *);
 443 const char *dir_name (const char *);
 444 void hash_init_directories (void);
 445
 446 void define_default_variables (void);
 447 void set_default_suffixes (void);
 448 void install_default_suffix_rules (void);
 449 void install_default_implicit_rules (void);
 450
 451 void build_vpath_lists (void);
 452 void construct_vpath_list (char *pattern, char *dirpath);
 453 const char *vpath_search (const char *file, FILE_TIMESTAMP *mtime_ptr,
 454                           unsigned int* vpath_index, unsigned int* path_index);
 455 int gpath_search (const char *file, unsigned int len);
 456
 457 void construct_include_path (const char **arg_dirs);
 458
 459 void user_access (void);
 460 void make_access (void);
 461 void child_access (void);
 462
 463 void close_stdout (void);
 464
 465 char *strip_whitespace (const char **begpp, const char **endpp);
 466
 467 /* String caching  */
 468 void strcache_init (void);
 469 void strcache_print_stats (const char *prefix);
 470 int strcache_iscached (const char *str);
 471 const char *strcache_add (const char *str);
 472 const char *strcache_add_len (const char *str, unsigned int len);
 473 int strcache_setbufsize (unsigned int size);
 474
 475 /* Guile support  */
 476 int setup_guile (void);
 477
 478
 479 #ifdef  HAVE_VFORK_H
 480 # include <vfork.h>
 481 #endif
 482
 483 /* We omit these declarations on non-POSIX systems which define _POSIX_VERSION,
 484    because such systems often declare them in header files anyway.  */
 485
 486 #if !defined (__GNU_LIBRARY__) && !defined (POSIX) && !defined (_POSIX_VERSION) && !defined(WINDOWS32)
 487
 488 long int atol ();
 489 # ifndef VMS
 490 long int lseek ();
 491 # endif
 492
 493 #endif  /* Not GNU C library or POSIX.  */
 494
 495 #ifdef  HAVE_GETCWD
 496 # if !defined(VMS) && !defined(__DECC)
 497 char *getcwd ();
 498 # endif
 499 #else
 500 char *getwd ();
 501 # define getcwd(buf, len)       getwd (buf)
 502 #endif
 503
 504 #if !HAVE_STRCASECMP
 505 # if HAVE_STRICMP
 506 #  define strcasecmp stricmp
 507 # elif HAVE_STRCMPI
 508 #  define strcasecmp strcmpi
 509 # else
 510 /* Create our own, in misc.c */
 511 int strcasecmp (const char *s1, const char *s2);
 512 # endif
 513 #endif
 514
 515 #if !HAVE_STRNCASECMP
 516 # if HAVE_STRNICMP
 517 #  define strncasecmp strnicmp
 518 # elif HAVE_STRNCMPI
 519 #  define strncasecmp strncmpi
 520 # else
 521 /* Create our own, in misc.c */
 522 int strncasecmp (const char *s1, const char *s2, int n);
 523 # endif
 524 #endif
 525
 526 extern const struct floc *reading_file;
 527 extern const struct floc **expanding_var;
 528
 529 extern char **environ;
 530
 531 extern int just_print_flag, silent_flag, ignore_errors_flag, keep_going_flag;
 532 extern int print_data_base_flag, question_flag, touch_flag, always_make_flag;
 533 extern int env_overrides, no_builtin_rules_flag, no_builtin_variables_flag;
 534 extern int print_version_flag, print_directory_flag, check_symlink_flag;
 535 extern int warn_undefined_variables_flag, trace_flag, posix_pedantic;
 536 extern int not_parallel, second_expansion, clock_skew_detected;
 537 extern int rebuilding_makefiles, one_shell;
 538
 539 /* can we run commands via 'sh -c xxx' or must we use batch files? */
 540 extern int batch_mode_shell;
 541
 542 /* Resetting the command script introduction prefix character.  */
 543 #define RECIPEPREFIX_NAME          ".RECIPEPREFIX"
 544 #define RECIPEPREFIX_DEFAULT       '\t'
 545 extern char cmd_prefix;
 546
 547 extern unsigned int job_slots;
 548 extern int job_fds[2];
 549 extern int job_rfd;
 550 #ifndef NO_FLOAT
 551 extern double max_load_average;
 552 #else
 553 extern int max_load_average;
 554 #endif
 555
 556 extern char *program;
 557 extern char *starting_directory;
 558 extern unsigned int makelevel;
 559 extern char *version_string, *remote_description, *make_host;
 560
 561 extern unsigned int commands_started;
 562
 563 extern int handling_fatal_signal;
 564
 565
 566 #ifndef MIN
 567 #define MIN(_a,_b) ((_a)<(_b)?(_a):(_b))
 568 #endif
 569 #ifndef MAX
 570 #define MAX(_a,_b) ((_a)>(_b)?(_a):(_b))
 571 #endif
 572
 573 #ifdef VMS
 574 #  define MAKE_SUCCESS 1
 575 #  define MAKE_TROUBLE 2
 576 #  define MAKE_FAILURE 3
 577 #else
 578 #  define MAKE_SUCCESS 0
 579 #  define MAKE_TROUBLE 1
 580 #  define MAKE_FAILURE 2
 581 #endif
 582
 583 /* Set up heap debugging library dmalloc.  */
 584
 585 #ifdef HAVE_DMALLOC_H
 586 #include <dmalloc.h>
 587 #endif
 588
 589 #ifndef initialize_main
 590 # ifdef __EMX__
 591 #  define initialize_main(pargc, pargv) \
 592                           { _wildcard(pargc, pargv); _response(pargc, pargv); }
 593 # else
 594 #  define initialize_main(pargc, pargv)
 595 # endif
 596 #endif
 597
 598 #ifdef __EMX__
 599 # if !defined chdir
 600 #  define chdir _chdir2
 601 # endif
 602 # if !defined getcwd
 603 #  define getcwd _getcwd2
 604 # endif
 605
 606 /* NO_CHDIR2 causes make not to use _chdir2() and _getcwd2() instead of
 607    chdir() and getcwd(). This avoids some error messages for the
 608    make testsuite but restricts the drive letter support. */
 609 # ifdef NO_CHDIR2
 610 #  warning NO_CHDIR2: usage of drive letters restricted
 611 #  undef chdir
 612 #  undef getcwd
 613 # endif
 614 #endif
 615
 616 #ifndef initialize_main
 617 # define initialize_main(pargc, pargv)
 618 #endif
 619
 620
 621 /* Some systems (like Solaris, PTX, etc.) do not support the SA_RESTART flag
 622    properly according to POSIX.  So, we try to wrap common system calls with
 623    checks for EINTR.  Note that there are still plenty of system calls that
 624    can fail with EINTR but this, reportedly, gets the vast majority of
 625    failure cases.  If you still experience failures you'll need to either get
 626    a system where SA_RESTART works, or you need to avoid -j.  */
 627
 628 #define EINTRLOOP(_v,_c)   while (((_v)=_c)==-1 && errno==EINTR)
 629
 630 /* While system calls that return integers are pretty consistent about
 631    returning -1 on failure and setting errno in that case, functions that
 632    return pointers are not always so well behaved.  Sometimes they return
 633    NULL for expected behavior: one good example is readdir() which returns
 634    NULL at the end of the directory--and _doesn't_ reset errno.  So, we have
 635    to do it ourselves here.  */
 636
 637 #define ENULLLOOP(_v,_c)   do { errno = 0; (_v) = _c; } \
 638                            while((_v)==0 && errno==EINTR)