What about platforms like AVR? That would not be a good decision for
AVR since it is a harvard machine and cannot access data in ROM without
special operations.
On 7/27/2020 9:55 PM, Xiang Xiao wrote:
Hi all,
For example, here is isspace implementation:
# define isspace(c) \
((c) == ' ' || (c) == '\t' || (c) == '\n' || (c) == '\r' || \
(c) == '\f' || (c) == '\v')
The argument of c will evaluate 6 times, which make the following code suddenly
fail:
while (end != begin)
{
If (!isspace(*--end))
{
break;
}
}
But it work well with other libc implementation, because all other libc utilize
a table to classify the char type:
https://github.com/bminor/newlib/blob/master/newlib/libc/include/ctype.h#L97
https://github.com/bminor/glibc/blob/master/ctype/ctype.h#L197
and the argument only need evaluate once.
So my question is: can we implement ctype functions through table to improve
the compatibility?
Yes, the table need take more 256 bytes ROM space, but the complex expression
used in NuttX also bloat the code size, especially
considering ctype function is used very frequently.
Thanks
Xiang
