If the conversion fails, 0 is returned and errno is not set. It does the conversion from string to long, int, double, float, string, char, etc. The errno handling is clearly wrong, and some of the other typemaps correctly set errno0. This function resets errno before calling strtod so that you can reliably detect overflow and underflow. I would recommend to drop all float variables in your prog and replace them by double.
The atof function is provided mostly for compatibility with existing code. Since setting errno to erange is implementation defined in the case of underflow, there is actually no portable way to detect underflow. The strtod function converts the initial portion of the string pointed to by \a nptr to double representation. See also atof3, atoi3, atol3, strtol3, strtoul3 linux 20010607 strtod 3. Ill offer a more robust parsing a string into a double code that allows leadingtrailing whitespace taking into account the above 7. When testing for underflow, though, wont the test fail in some cases since errno may not necessary be set to erange in some implementations, as you indicated earlier. Besides, the str variable is retrieved correctly and clearly has value 222.
Aug 30, 2019 compliant solution snprintfnullif unknown, the length of the formatted string can be discovered by invoking snprintf with a null buffer pointer to determine the size required for the output, then dynamically allocating a buffer of sufficient size, and finally calling snprintf again to format the output into the dynamically allocated buffer. For floatingpoint conversion functions in the strtod and wcstod families, if an underflow occurs, whether errno acquires the value erange is implementationdefined. Until today, in the few cases where i needed something like this, it had been in simple programs which only i used, and where i didnt care about security, so i used the simple atoi however, today i needed to do that for a some more serious program, and i researched about the many different forms that are out there to go from a string to a number. If endptr is not a null pointer, the function also sets the value of endptr to point to the first character after the number. Since 0 can legitimately be returned on both success and failure, the calling program should set errno to 0 before the. The strtod, strtof, and strtold functions convert the initial portion of the string pointed to by nptr to double, float, and long double representation, respectively. The c standard only stipulates that underflow cannot return a value greater than the smallest positive double, and whether or not errno is set to erange is implementation defined 2. For the strtod, strtof, and strtold subroutines, if the value of the endpointer parameter is not char null, a pointer to the character that stopped the subroutine is stored in endpointer. However, the stdstrtof in the latest ndk stl looks fine to me and seems to be correctly used in this project. Aug 30, 2019 for floatingpoint conversion functions in the strtod and wcstod families, if an underflow occurs, whether errno acquires the value erange is implementationdefined. My code followed what i found in the linux man page on my system. If no conversion could be performed, strtod returns zero.
The errno handling is clearly wrong, and some of the other typemaps correctly set errno 0. There are only rare cases where float type is still appropriate e. If the correct value would cause underflow, zero is returned and erange is stored in. The numeric conversion function atof and those in the atoi family need not affect the value of errno. When i run it on suse linux enterprise server 11 sp2 or linux mint 17 qiana with an argument of 2. Public git conversion mirror of openbsds official cvs src repository. Set errno to zero before calling a library function. The strtod, strtof, and strtold functions convert the initial portion of the string pointed to by nptr to double, float, and long double representation, r. Another corner case is an empty string strtod returns 0 on empty string. This function recognizes in order an optional string of spaces, an optional base indicator 0 for octal, x or x for hexadecimal, and a string of digits.
If the correct value would cause underflow, the function returns a value whose magnitude is no greater than the smallest normalized positive number some library implementations may also set. By continuing to use pastebin, you agree to our use of cookies as described in the cookies policy. Name strtod, strtof, strtold convert ascii string to floatingpoint number synopsis. Or, if base is nonzero and less than 2, or greater than 36. Detect errors when converting a string to a number. Conversion errors are indicated by the pointer pointed to by the second argument being set to the same value as the first argument. Conforming to ansi c describes strtod, c99 describes the other two functions.
Rationale behind c library functions never setting errno to zero. The c standard mandates that no c standard library functions shall set errno to zero. For convenience, the following abbreviations are used in the following tables. Parses the cstring str interpreting its content as a floating point number according to the current locale and returns its value as a double. This program calls strtod on the first command line argument and prints the returned value. So i would say that there is a problem in your project setup outdated ndk, weird defines, wrong stl.
Detect and handle standard library errors sei cert. If the correct value would cause underflow, zero is returned. However, on suse linux enterprise server 11 sp3 with the same argument 2, errno is set to erange. But when i trying to run my program in windows i got a problem. This function is similar to the strtod function, except that it need not detect overflow and underflow errors. It only sets errno if there is an overflow or underflow during the conversion.
If the correct value would cause underflow, zero is returned and erange is stored in errno. I could understand it being useful for calling several functions, and only checking errno. If the correct value would cause underflow, the function returns a value whose magnitude is no greater than the smallest normalized positive number and sets errno to erange. The strtod function converts a character array to a floatingpoint number. If no conversion is performed, zero is returned and the value of nptr is stored in the location referenced by endptr. Rationale behind c library functions never setting errno. We use cookies for various purposes including analytics. If the conversion would cause an underflow, a properly signed value of 0 is returned and the errno global variable is set to erange.
The c library function double strtod const char str, char endptr converts the string pointed to by the argument str to a floatingpoint number type double. Governments and large corporations are using this incredible gift to their advantage every day. It returns the number of tokens successfully extracted from the string. The strtod, strtof, and strtold functions return the converted value, if any. There is actually an extensive cert advisory writeup that recommends always setting errno to 0 before a library call and checking its value after the call indicates a failure has occurred. For example, mathematical functions such as pow can easily outbound the range representable by a floating point variable, or functions such as strtod can encounter sequences of digits longer than the range representable values.
605 1508 458 502 978 108 636 966 1203 1360 165 143 201 897 892 1439 974 967 1387 1124 677 1081 1161 1159 895 1189 1481 190 170 1363 991 616 992 248 9 1092 1263 474 248 997 207 1480 203 668 795 1112 1168 316 1438