/* xstrerror.c -- jacket routine for more robust strerror() usage.
   Fri Jun 16 18:30:00 1995  Pat Rankin  <rankin@eql.caltech.edu>
   This code is in the public domain.  */

/*

@deftypefn Replacement char* xstrerror (int @var{errnum})

Behaves exactly like the standard @code{strerror} function, but
will never return a @code{NULL} pointer.

@end deftypefn

*/

#include <stdio.h>

#include "config.h"
#include "libiberty.h"

#ifdef VMS
#  include <errno.h>
#  if !defined (__STRICT_ANSI__) && !defined (__HIDE_FORBIDDEN_NAMES)
#    ifdef __cplusplus
extern "C" {
#    endif /* __cplusplus */
extern char *strerror (int,...);
#    define DONT_DECLARE_STRERROR
#    ifdef __cplusplus
}
#    endif /* __cplusplus */
#  endif
#endif  /* VMS */


#ifndef DONT_DECLARE_STRERROR
#  ifdef __cplusplus
extern "C" {
#  endif /* __cplusplus */
extern char *strerror (int);
#  ifdef __cplusplus
}
#  endif /* __cplusplus */
#endif

/* If strerror returns NULL, we'll format the number into a static buffer.  */

#define ERRSTR_FMT "undocumented error #%d"
static char xstrerror_buf[sizeof ERRSTR_FMT + 20];

/* Like strerror, but result is never a null pointer.  */

char *
xstrerror (int errnum)
{
  char *errstr;
#ifdef VMS
  char *(*vmslib_strerror) (int,...);

  /* Override any possibly-conflicting declaration from system header.  */
  vmslib_strerror = (char *(*) (int,...)) strerror;
  /* Second argument matters iff first is EVMSERR, but it's simpler to
     pass it unconditionally.  `vaxc$errno' is declared in <errno.h>
     and maintained by the run-time library in parallel to `errno'.
     We assume that `errnum' corresponds to the last value assigned to
     errno by the run-time library, hence vaxc$errno will be relevant.  */
  errstr = (*vmslib_strerror) (errnum, vaxc$errno);
#else
  errstr = strerror (errnum);
#endif

  /* If `errnum' is out of range, result might be NULL.  We'll fix that.  */
  if (!errstr)
    {
      snprintf (xstrerror_buf, sizeof xstrerror_buf, ERRSTR_FMT, errnum);
      errstr = xstrerror_buf;
    }
  return errstr;
}