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annotate lib/strtod.c @ 9821:18bab9955c43

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Document various strtod bugs, with some fixes. * doc/posix-functions/strtod.texi (strtod): Document bugs with "-0x", "inf", "nan", and hex constants. * doc/posix-functions/atof.texi (atof): Likewise. * modules/stdlib (Makefile.am): Support strtod. * m4/stdlib_h.m4 (gl_STDLIB_H_DEFAULTS): Likewise. * m4/strtod.m4 (gl_FUNC_STRTOD): Fit in stdlib framework, and detect additional strtod bugs. * lib/stdlib.in.h (rpl_strtod): Add declarations. * lib/strtod.c (strtod): Return -0.0 on negative underflow. Use bool where appropriate. Parse 'inf' and 'nan'. * tests/test-strtod.c: New file. * modules/strtod (Depends-on): Add stdbool, stdlib. (configure.ac): Turn on module indicator. * modules/strtod-tests: New module. Signed-off-by: Eric Blake <ebb9@byu.net>
author Eric Blake <ebb9@byu.net>
date Sat, 29 Mar 2008 13:50:21 -0600
parents bbbbbf4cd1c5
children fb687649f177
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
rev   line source
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1 /* Copyright (C) 1991, 1992, 1997, 1999, 2003, 2006, 2008 Free
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2 Software Foundation, Inc.
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3
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4 This program is free software: you can redistribute it and/or modify
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5 it under the terms of the GNU General Public License as published by
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6 the Free Software Foundation; either version 3 of the License, or
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7 (at your option) any later version.
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8
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9 This program is distributed in the hope that it will be useful,
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10 but WITHOUT ANY WARRANTY; without even the implied warranty of
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11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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12 GNU General Public License for more details.
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13
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14 You should have received a copy of the GNU General Public License
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15 along with this program. If not, see <http://www.gnu.org/licenses/>. */
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16
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17 #include <config.h>
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18
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19 #include <stdlib.h>
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20
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21 #include <ctype.h>
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22 #include <errno.h>
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23 #include <float.h>
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24 #include <math.h>
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25 #include <stdbool.h>
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26 #include <string.h>
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27
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28 /* Convert NPTR to a double. If ENDPTR is not NULL, a pointer to the
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29 character after the last one used in the number is put in *ENDPTR. */
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30 double
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31 strtod (const char *nptr, char **endptr)
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32 {
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33 const char *s;
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34 bool negative = false;
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35
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36 /* The number so far. */
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37 double num;
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38
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39 bool got_dot; /* Found a decimal point. */
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40 bool got_digit; /* Seen any digits. */
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41
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42 /* The exponent of the number. */
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43 long int exponent;
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44
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45 if (nptr == NULL)
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46 {
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47 errno = EINVAL;
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48 goto noconv;
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49 }
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50
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51 s = nptr;
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52
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53 /* Eat whitespace. */
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54 while (isspace ((unsigned char) *s))
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55 ++s;
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56
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57 /* Get the sign. */
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58 negative = *s == '-';
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59 if (*s == '-' || *s == '+')
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60 ++s;
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61
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62 num = 0.0;
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63 got_dot = false;
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64 got_digit = false;
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65 exponent = 0;
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66 for (;; ++s)
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67 {
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68 if ('0' <= *s && *s <= '9')
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69 {
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70 got_digit = true;
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71
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72 /* Make sure that multiplication by 10 will not overflow. */
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73 if (num > DBL_MAX * 0.1)
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74 /* The value of the digit doesn't matter, since we have already
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75 gotten as many digits as can be represented in a `double'.
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76 This doesn't necessarily mean the result will overflow.
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77 The exponent may reduce it to within range.
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78
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79 We just need to record that there was another
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80 digit so that we can multiply by 10 later. */
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81 ++exponent;
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82 else
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83 num = (num * 10.0) + (*s - '0');
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84
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85 /* Keep track of the number of digits after the decimal point.
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86 If we just divided by 10 here, we would lose precision. */
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87 if (got_dot)
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88 --exponent;
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89 }
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90 else if (!got_dot && *s == '.')
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91 /* Record that we have found the decimal point. */
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92 got_dot = true;
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93 else
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94 /* Any other character terminates the number. */
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95 break;
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96 }
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97
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98 if (!got_digit)
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99 {
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100 /* Check for infinities and NaNs. */
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101 if (tolower ((unsigned char) *s) == 'i'
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102 && tolower ((unsigned char) s[1]) == 'n'
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103 && tolower ((unsigned char) s[2]) == 'f')
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104 {
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105 s += 3;
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106 num = HUGE_VAL;
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107 if (tolower ((unsigned char) *s) == 'i'
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108 && tolower ((unsigned char) s[1]) == 'n'
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109 && tolower ((unsigned char) s[2]) == 'i'
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110 && tolower ((unsigned char) s[3]) == 't'
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111 && tolower ((unsigned char) s[4]) == 'y')
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112 s += 5;
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113 goto valid;
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114 }
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115 #ifdef NAN
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116 else if (tolower ((unsigned char) *s) == 'n'
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117 && tolower ((unsigned char) s[1]) == 'a'
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118 && tolower ((unsigned char) s[2]) == 'n')
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119 {
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120 s += 3;
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121 num = NAN;
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122 /* Since nan(<n-char-sequence>) is implementation-defined,
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123 we define it by ignoring <n-char-sequence>. A nicer
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124 implementation would populate the bits of the NaN
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125 according to interpreting n-char-sequence as a
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126 hexadecimal number, but the result is still a NaN. */
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127 if (*s == '(')
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128 {
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129 const char *p = s + 1;
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130 while (isalnum ((unsigned char) *p))
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131 p++;
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132 if (*p == ')')
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133 s = p + 1;
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134 }
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135 goto valid;
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136 }
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137 #endif
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138 goto noconv;
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139 }
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140
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141 if (tolower ((unsigned char) *s) == 'e')
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142 {
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143 /* Get the exponent specified after the `e' or `E'. */
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144 int save = errno;
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145 char *end;
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146 long int exp;
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147
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148 errno = 0;
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149 ++s;
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150 exp = strtol (s, &end, 10);
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151 if (errno == ERANGE && num)
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152 {
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153 /* The exponent overflowed a `long int'. It is probably a safe
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154 assumption that an exponent that cannot be represented by
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155 a `long int' exceeds the limits of a `double'. */
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156 if (endptr != NULL)
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157 *endptr = end;
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158 if (exp < 0)
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159 goto underflow;
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160 else
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161 goto overflow;
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162 }
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163 else if (end == s)
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164 /* There was no exponent. Reset END to point to
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165 the 'e' or 'E', so *ENDPTR will be set there. */
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166 end = (char *) s - 1;
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167 errno = save;
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168 s = end;
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169 exponent += exp;
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170 }
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171
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172 if (num == 0.0)
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173 goto valid;
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174
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175 /* Multiply NUM by 10 to the EXPONENT power,
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176 checking for overflow and underflow. */
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177
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178 if (exponent < 0)
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179 {
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180 if (num < DBL_MIN * pow (10.0, (double) -exponent))
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181 goto underflow;
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182 }
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183 else if (exponent > 0)
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184 {
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185 if (num > DBL_MAX * pow (10.0, (double) -exponent))
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186 goto overflow;
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187 }
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188
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189 num *= pow (10.0, (double) exponent);
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190
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191 valid:
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192 if (endptr != NULL)
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193 *endptr = (char *) s;
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194 return negative ? -num : num;
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195
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196 overflow:
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197 /* Return an overflow error. */
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198 if (endptr != NULL)
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199 *endptr = (char *) s;
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200 errno = ERANGE;
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201 return negative ? -HUGE_VAL : HUGE_VAL;
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202
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203 underflow:
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204 /* Return an underflow error. */
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205 if (endptr != NULL)
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206 *endptr = (char *) s;
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207 errno = ERANGE;
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208 return negative ? -0.0 : 0.0;
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209
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210 noconv:
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211 /* There was no number. */
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212 if (endptr != NULL)
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213 *endptr = (char *) nptr;
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214 errno = EINVAL;
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215 return 0.0;
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216 }