16 Aug
2024
16 Aug
'24
12:32 a.m.
On Thu, 15 Aug 2024, Mike Katz wrote:
C has specific specifications for what is promoted
when and how. They are not
ambiguous just not known by many.
I worked for a C compiler company so I'm may be a bit more familiar with the
actual C specs and how the compiler works.
However, I totally agree with you. I heavily typecast and parenthesize my
code to avoid any possible ambiguity. Sometimes for the compiler and
sometimes for someone else reading my code.
I will readily concede that ANSI C has fewer problems with ambiguous code
than the K&R C that I learned.
But, for example, in:
X = foo() + bar();
has it been defined which order the functions of foo() and bar()
are evaluated? Consider the possibility that either or both alter
variable that the other function also uses.
(Stupidly simpe example, one function increments a variable, and the other
one doubles it)
As another example of code that I would avoid,
int x=1,y=1;
x = x++ + x++;
y = ++y + ++Y;
give 2, 3, 4, or 5?
is heavily dependent on exactly when the increments get done.
But, thorough careful typecasting, use of intermediate variables, etc. can
eliminate all such problems.
'course "optimizing compilers" can (but shouldn't) alter your code.
If you don't explicitly specify exactly what you want, "C gives you enough
rope to shoot yourself in the foot" (as Holub titled one of his books)
But, I've always loved how easily C will get out of the way when you want
to get closer to the hardware.
--
Grumpy Ol' Fred cisin(a)xenosoft.com