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strtof.c
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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 */
29float
30pg_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}
float pg_strtof(const char *nptr, char **endptr)
Definition: strtof.c:30