nan(), nanf(), nanl()
QNX SDP8.0C Library ReferenceAPIDeveloper
Return a quiet NaN
Synopsis:
#include <math.h>
double nan( const char *tagp );
float nanf( const char *tagp );
long double nanl( const char *tagp );
Arguments:
- tagp
- NULL, or an n-char sequence that identifies the contents of a NaN.
Library:
- libm
- The general-purpose math library.
- libm-sve
- A library that optimizes the code for ARMv8.2 chips that have Scalable Vector Extension hardware.
Your system requirements will determine how you should work with these libraries:
- If you want only selected processes to run with the SVE version, you can include both libraries in your OS image and use the -l m or -l m-sve option to qcc to link explicitly against the appropriate one.
- If you want all processes to use the SVE version, include libm-sve.so in your OS image and set up a symbolic link from libm.so to libm-sve.so. Use the -l m option to qcc to link against the library.
Note:
Compile your program with the -fno-builtin option to prevent the compiler from using a
built-in version of the function.
Description:
The nan(), nanf(), and nanl() functions convert the string pointed to by tagp into a quiet NaN, if available.
Calls to nan() are equivalent to calls to strtod(), as shown below:
| This call: | Is equivalent to: |
|---|---|
nan("n-char-sequence") |
strtod("NAN(n-char-sequence)", (char **) NULL) |
nan("") |
strtod("NAN()", (char **) NULL) |
nan(tagp), where tagp doesn't point to an
n-char sequence or an empty string
|
strtod("NAN", (char **) NULL) |
Note:
The QNX OS versions of these functions don't interpret n-char sequences, and
the results are equivalent to specifying NULL for tagp.
Calls to nanf() and nanl() are equivalent to the corresponding calls to strtof() and strtold().
Returns:
A quiet NaN, if available, corresponding to the string pointed to by tagp.
Classification:
| Safety: | |
|---|---|
| Cancellation point | No |
| Signal handler | Yes |
| Thread | Yes |
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