alloca() portability

[Walter Bright]

In article <27634 at mimsy.umd.edu> chris at mimsy.umd.edu (Chris Torek) writes:
/There may be major correctness losses using alloca (as I wrote earlier,
/any optimizing compiler can easily produce failing object code from
/apparently-correct source code if that source code uses alloca).

You're right. I struggled with this problem for a while, until the
solution became obvious: make alloca() a 'magic' function, and have
the optimizations take it into account. I implemented this, and it
works fine (including in those cases you pointed out, and the cases
in the MSC manual where it says not to use it).

ANSI C allows other functions to be magic.

But the fact remains that if you wish to write maximally portable programs
you are better off avoiding alloca.