src/port/strtof.c

   1 /*-------------------------------------------------------------------------
   2  *
   3  * strtof.c
   4  *
   5  * Portions Copyright (c) 2019-2025, PostgreSQL Global Development Group
   6  *
   7  *
   8  * IDENTIFICATION
   9  *        src/port/strtof.c
  10  *
  11  *-------------------------------------------------------------------------
  12  */
  13
  14 #include "c.h"
  15
  16 #include <float.h>
  17 #include <math.h>
  18
  19
  20 /*
  21  * Cygwin has a strtof() which is literally just (float)strtod(), which means
  22  * we can't avoid the double-rounding problem; but using this wrapper does get
  23  * us proper over/underflow checks. (Also, if they fix their strtof(), the
  24  * wrapper doesn't break anything.)
  25  *
  26  * Test results on Mingw suggest that it has the same problem, though looking
  27  * at the code I can't figure out why.
  28  */
  29 float
  30 pg_strtof(const char *nptr, char **endptr)
  31 {
  32         int                     caller_errno = errno;
  33         float           fresult;
  34
  35         errno = 0;
  36         fresult = (strtof) (nptr, endptr);
  37         if (errno)
  38         {
  39                 /* On error, just return the error to the caller. */
  40                 return fresult;
  41         }
  42         else if ((*endptr == nptr) || isnan(fresult) ||
  43                          ((fresult >= FLT_MIN || fresult <= -FLT_MIN) && !isinf(fresult)))
  44         {
  45                 /*
  46                  * If we got nothing parseable, or if we got a non-0 non-subnormal
  47                  * finite value (or NaN) without error, then return that to the caller
  48                  * without error.
  49                  */
  50                 errno = caller_errno;
  51                 return fresult;
  52         }
  53         else
  54         {
  55                 /*
  56                  * Try again. errno is already 0 here.
  57                  */
  58                 double          dresult = strtod(nptr, NULL);
  59
  60                 if (errno)
  61                 {
  62                         /* On error, just return the error */
  63                         return fresult;
  64                 }
  65                 else if ((dresult == 0.0 && fresult == 0.0) ||
  66                                  (isinf(dresult) && isinf(fresult) && (fresult == dresult)))
  67                 {
  68                         /* both values are 0 or infinities of the same sign */
  69                         errno = caller_errno;
  70                         return fresult;
  71                 }
  72                 else if ((dresult > 0 && dresult <= FLT_MIN && (float) dresult != 0.0) ||
  73                                  (dresult < 0 && dresult >= -FLT_MIN && (float) dresult != 0.0))
  74                 {
  75                         /* subnormal but nonzero value */
  76                         errno = caller_errno;
  77                         return (float) dresult;
  78                 }
  79                 else
  80                 {
  81                         errno = ERANGE;
  82                         return fresult;
  83                 }
  84         }
  85 }