I have created before two threads about the weird semantics of
labeled block statements. In a word: putting a label before a
block means that block does not create a scope, and the variables
created inside that scope will "leak" to the outside of said
scope. I've found this to be problematic on several points:
1. No use case for this
2. You can accidentally break code by placing a label before a
block (but without meaning to label the actual block)
3. Deviates from C.
What kind of bothers me most is the combination 1 & 3: Why???
I've complained about this before, and the answer was: "According
to spec", but to the question "why are the specs like this", I
have yet to get an answer.
----------------
The reason I'm bringing this up (again), is that it bit me in the
ass very recently. According to TDPL:
"If a numeric expression compiles in the C language and also
compiles in D, its
type will be the same in both languages (note that not all C
expressions must be
accepted by D)."
Followed by
"Rule 1 makes things just a tad more complicated than they would
otherwise be, but D overlaps enough with C and C++ to inspire
people to simply copy and paste entire functions into D programs.
Now it’s all right if D occasionally refuses to compile certain
constructs for safety or portability reasons; but if it compiled
that 2000-line encryption package and ran it with different
results, life would definitely not be good for the hapless
victim."
So basically, this is saying "If your C code compiles in D,
you'll get the same result. I guarantee it :)"
Here's a (reduced) C program:
----
int i = 3;
void main()
{
{
int some_condition = 1;
if ( some_condition )
goto block_end;
/* dummy code */
} block_end:
{
int i = 7;
printf("%i", i);
}
printf("%i", i);
}
----
C prints: "70"
D prints: "77"
Oops!
I realize 99% of people don't use goto or labels too much, but
this doesn't mean it shouldn't be addressed. For me, D has been
about being a "smooth experience", and this makes so little sense
to me it infuriates me.
I don't see how this could help anyone, but I do see how it can
create bugs, and these kinds of cases are what D strives to
avoid. "Fixing" would probably break nothing.
-------------------
I'd like to make a push to get the specs changed in regards to
this. I'd like to get others' opinion on the matter, in
particular, if anybody can think of a rationale for the current
behavior. And if there is no rationale, how much support there is
for changing it. (in which case I'll file the corresponding ER).
