libiberty/xstrerror.c

   1 /* xstrerror.c -- jacket routine for more robust strerror() usage.
   2    Fri Jun 16 18:30:00 1995  Pat Rankin  <rankin@eql.caltech.edu>
   3    This code is in the public domain.  */
   4
   5 /*
   6
   7 @deftypefn Replacement char* xstrerror (int @var{errnum})
   8
   9 Behaves exactly like the standard @code{strerror} function, but
  10 will never return a @code{NULL} pointer.
  11
  12 @end deftypefn
  13
  14 */
  15
  16 #include <stdio.h>
  17
  18 #include "config.h"
  19 #include "libiberty.h"
  20
  21 #ifdef VMS
  22 #include <errno.h>
  23 #if !defined (__STRICT_ANSI__) && !defined (__HIDE_FORBIDDEN_NAMES)
  24 extern char *strerror PARAMS ((int,...));
  25 #define DONT_DECLARE_STRERROR
  26 #endif
  27 #endif  /* VMS */
  28
  29 #ifndef DONT_DECLARE_STRERROR
  30 extern char *strerror PARAMS ((int));
  31 #endif
  32
  33 /* If strerror returns NULL, we'll format the number into a static buffer.  */
  34
  35 #define ERRSTR_FMT "undocumented error #%d"
  36 static char xstrerror_buf[sizeof ERRSTR_FMT + 20];
  37
  38 /* Like strerror, but result is never a null pointer.  */
  39
  40 char *
  41 xstrerror (errnum)
  42      int errnum;
  43 {
  44   char *errstr;
  45 #ifdef VMS
  46   char *(*vmslib_strerror) PARAMS ((int,...));
  47
  48   /* Override any possibly-conflicting declaration from system header.  */
  49   vmslib_strerror = (char *(*) PARAMS ((int,...))) strerror;
  50   /* Second argument matters iff first is EVMSERR, but it's simpler to
  51      pass it unconditionally.  `vaxc$errno' is declared in <errno.h>
  52      and maintained by the run-time library in parallel to `errno'.
  53      We assume that `errnum' corresponds to the last value assigned to
  54      errno by the run-time library, hence vaxc$errno will be relevant.  */
  55   errstr = (*vmslib_strerror) (errnum, vaxc$errno);
  56 #else
  57   errstr = strerror (errnum);
  58 #endif
  59
  60   /* If `errnum' is out of range, result might be NULL.  We'll fix that.  */
  61   if (!errstr)
  62     {
  63       sprintf (xstrerror_buf, ERRSTR_FMT, errnum);
  64       errstr = xstrerror_buf;
  65     }
  66   return errstr;
  67 }