On 2023-05-05 16:22, Linus Torvalds wrote:
On Fri, May 5, 2023 at 1:08 PM Mathieu Desnoyers
<mathieu.desnoyers@xxxxxxxxxxxx> wrote:
The reason why I think the lvalue of a "=" operator can be argued to be
"special" is because it is simply invalid to apply many of the C
operators to an lvalue (e.g. +, -, /, ...),
Mathieu, you are simply objectively wrong.
See here:
#define m1(x) (x = 2)
#define m2(x) ((x) = 2)
and then try using the argument "a = b" to those macros.
Guess which one flags it as an error ("lvalue required") and which one does not?
I'm glad you are proving me wrong. So it was just a lack of imagination
on my end.
m2 is the only "good" one. Yes, m1 works in 99% of all cases in
practice, but if you want a safer macro, you *will* add the
parentheses.
So *STOP*ARGUING* based on an incorrect "lowest precedence" basis.
Even for the "lowest precedence" case, you have the *same* precedence.
Yes, your example clearly shows it.
The fact is, assignment is not in any way special operation in macros,
and does not deserve - and should absolutely not have - any special
"doesn't need parentheses around argument" rules.
Good point. You are right. So that strongly supports the parentheses
around use of parameters as lvalues. One less special-case to care
about, which is great.
Thanks,
Mathieu
--
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com
