[M3devel] a note on parse.c "GTY" use

[Jay K]

I am striving to have one parse.c be portable between gcc 4.5, gcc 4.2, and possibly gcc 4.3.
I already established 4.3/4.2 portability a year or so ago.


The main "indefinitely sticky" motivation is that Apple is only on 4.2 and they have a lot of changes.
  That I wouldn't want to merge.
We should imho, use their code for Darwin platforms, or at least Darwin/arm.
   Mainline FSF seems to work fine for Darwin/ppc/x86 so I'm not advocating change there.



"indefinitely sticky" meaning, not really indefinite, but we aren't in control.
Presumably they'll move up to a newer version but I have no idea when.



Granted, Modula-3/iphone/pod/pad is seemingly nowhere.
A year or so ago I ran cm3 on my iPhone, got the usual "unable to find cm3.cfg", which is
exactly what you want to see when all you have is cm3 and no config files or source, and got distracted after that :)


An alternate motivation would be if we want to more easily move between 4.3 and 4.5.
This one we are more control of. If 4.5 has a few problems on a few platforms, we can
decide to debug and fix, or use 4.3 selectively.
I don't forsee problems major here though.


"Much ado about not much" -- more background than conclusion:


Gcc has some internal garbage collector. You have to annotate your code a bit for it.

In gcc 4.2/4.3 you say:

struct foo GTY()) { int field; } and such


In 4.5 you say:
struct  GTY()) foo { int field; } and such


The thing that scans your code I don't think knows much C.
I wasn't not able use #ifdef to guide it to varying versions.


Therefore, I've isolated 4.3 vs. 4.5-specific uses of GTY to their own files.
It's just a few lines.
But it is not how you would structure the code if not for this goal of working with multiple versions.


Generally otherwise I'll use #ifdef and have src/m3makefile #define whatever.
 Possibly prepending to parse.c, yucky, but oh well.
A read only source tree is ideal, granted, but I do what I can..


GTY is presumably "garbabe collected type" or such.



 - Jay