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Re: [lambda] Segmentation fault in simple lambda program
On 08/03/2009 09:39 PM, John Freeman wrote:
* Instead of transforming:
*
* [&] { i = 1; j = 2; k = 3; };
*
* into
*
* [&i,&j,&k] { i = 1; j = 2; k = 3; };
*
* and thus storing three pointers to int, transform it into:
*
* [sp=enclosing-stack-pointer] { var-from-stack(i,sp) = 1;
* var-from-stack(j,sp) = 2;
* var-from-stack(k,sp) = 3; };
*
* and only store one pointer.
This is preferred for reference default captures, but I was not familiar
with stack pointer mechanics in GCC. I just wanted to get something
working first that could be improved later.
Have a look at the documentation at the beginning of tree-nested.c.
Having something so magic as an "enclosing stack pointer" got us into
a lot of trouble in the past. It's much better to be explicit about
things and create a struct to pop onto the stack of the caller.
Lets say you have
int i, j, k, l;
...
[&] { return i + j + k; }
...
[&] { return j + k + l; }
you'd create a
struct frame
{
int i,j,k,l;
};
frame f;
[&f] { return f.i + f.j + f.k; }
[&f] { return f.j + f.k + f.l; }
which is effectively what tree-nested.c does.
r~