[M3devel] gratuitous platform differences?

[Jay]

I'm looking to add user thread support to the stuff I'm working on.
As part of this, I'm surveying various platform-specific code,
to find the commonality.
Some of this should be common Modula-3 code.
Where there are dealings with struct sigaction or sigset_t, the
code should be rewritten in C to avoid requiring other additional
platform-dependent code.
 

It seems to me that many of the differences are gratuitous.
 

Here are two:
 

 - some platforms unmap, or at least take away write access, to the
last page in the stack; and then remap it (or add back write access)
before disposing
  Now, I'm not going to move all ports to "my rewritten headers",
  just ones that I can test and are "somewhat active".
  In this case, I think that leads to all platforms being the same.
  So the question of "why not always do this?" doesn't matter.

 
 - Regarding disallow_sigvtalrm, allow_sigvtalrm, some platforms
  initialize the mask in the module's initializer, some recreate it
  for every call.
  Is there a reason for this?
  Creating it once is faster.
  But does require the initializer run early enough.
  And one would hope that the cached struct isn't too huge and memory wasting.
 

 To be safe, I could just provide two versions here, one that makes the mask
  over and over, one that does not.
 
 
 - Jay