Re: Variable length arrays in debugger
Re: Variable length arrays in debugger
- Subject: Re: Variable length arrays in debugger
- From: Jim Ingham <email@hidden>
- Date: Wed, 1 Oct 2008 11:41:08 -0700
gcc doesn't emit any debug information that tells the size of variable
length arrays. If you think about it a bit, it would be kind of hard
to express, for instance you could do:
void
foo (int input)
{
int size
int array[size];
size += input;
// Now how do I figure out what the size of "array" is?
}
gcc would somehow have to express what range of code the variable
"size" actually still contained the size used for the array. Start
sketching more devious examples and you'll realize that's pretty hard
to do in general.
I already filed a bug with the compiler to express this somehow, but
given how tricky it would be to do they haven't done anything about
it. Feel free to file a bug - it's another vote to work on this...
Anyway, without any debug info there's not much the debugger can do to
present this array.
Jim
On Oct 1, 2008, at 11:25 AM, Sean McBride wrote:
On 10/1/08 11:16 AM, Howard Moon said:
I've noticed that debugger in Xcode 3.1.1 always shows variable
length arrays as "out of scope". If I change it to constant size
array it works as it supposed to.
I'm talking about this kind of things:
int size;
....
int array[size];
I'm ready to file a bug, but would like to figure before if I'm not
alone in this or may be there is some option needs to be enabled in
compiler (couldn't find anything though).
Is that an extension allowed in GCC? According to the C++ Standard,
arrays must have a compile-time constant size. Perhaps the Xcode
debugger assumes that rule to be the case, even if the compiler has
allowed it to compile?
It is part of C99. Maybe also in C++0x ?
--
____________________________________________________________
Sean McBride, B. Eng email@hidden
Rogue Research www.rogue-research.com
Mac Software Developer Montréal, Québec, Canada
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