@node log2
@subsection @code{log2}
@findex log2

POSIX specification:@* @url{https://pubs.opengroup.org/onlinepubs/9799919799/functions/log2.html}

Gnulib module: log2 or log2-ieee
@mindex log2
@mindex log2-ieee

Portability problems fixed by either Gnulib module @code{log2} or @code{log2-ieee}:
@itemize
@item
This function is missing on some platforms:
FreeBSD 6.0, NetBSD 3.0, OpenBSD 3.8, Minix 3.1.8, AIX 5.1, Solaris 9, MSVC 9, Android 4.2.
@item
This function is only provided as a macro on some platforms:
Cygwin 1.5.x.
@item
This function returns slightly wrong values for exact powers of 2 on some platforms:
Cygwin 1.7.9.
@end itemize

Portability problems fixed by Gnulib module @code{log2-ieee}:
@itemize
@item
This function returns a wrong value for a negative argument on some platforms:
NetBSD 5.1, Solaris 10/x86_64.
@end itemize

Portability problems not fixed by Gnulib:
@itemize
@end itemize
