[Axiom-developer] [#46 termio vs ptermio] additional information

[anonymous]

=========================================================================================
| Gabriel,
| 
| Steve Wilson points out that the CHANGELOG contains the lines:
| 
| 20041116 tpd src/clef/edible.c termios -> termio
| 20040730 sxw src/clef/edible.c termio -> termios
| 
| so it appears that on some systems we need termio and
| on others we need termios.

I see.  I can confirm that on GNU/Linux, and generally (recent) glibc
systems, one needs termios.  I also looked on solaris plateforms
(apparently currently not supported by axiom), one needs termios there
too. 
I guess that is something one would need to test for at configure time. 

| Steve believes that this is dead code because at the top
| of the file we see:
| 
| #ifdef unlikely
| ...
| #define logterm
| 
| and the termios code is protected by 
| #ifdef logterm

I can see that the fragment is guarded by 
  
   #ifdef logterm

but for some reasons that code is reached on my system (SuSE-9.0, 
with glibc-2.3.2).

GCC with the option -dM dumps macros that are defined.  I can confirm
that gcc -E -dM edible.c shows a line where logterm is defined.  More
precisely, I have the following

   [....]
   #define _SC_2_PBS_MESSAGE _SC_2_PBS_MESSAGE
   #define _GCC_SIZE_T 
   #define CEOT CEOF
   #define logterm 1  /* <===== here */
   #define __INO64_T_TYPE __UQUAD_TYPE
   #define _SC_AVPHYS_PAGES _SC_AVPHYS_PAGES
   #define _IO_LINKED 0x80
   [....]

so my gut feeling is that that macro gets defined as internal to some
system header files.  

That gut feeling turns out to be wrong, as replacing logterm with
AXIOM_LOGTERM throughout edible.c still leads to the same problem.
So I operated on a second assumption: the macro "unlikely" must have
been defined somewhere else.  Bingo!  With the help of gcc -E -dM, I
could spot

    [...]
    #define __KEY_T_TYPE __S32_TYPE
    #define sigev_notify_function _sigev_un._sigev_thread._function
    #define likely(x) __builtin_expect((x),1)   /* <==== here */
    #define FAPPEND O_APPEND
    #define _XOPEN_ENH_I18N 1
    [...] 
    #define F_ULOCK 0
    #define errno (*__errno_location ())
    #define unlikely(x) __builtin_expect((x),0) /* <=== here too */
    #define EL2NSYNC 45
    #define _IO_off64_t _G_off64_t
    [...]

I can't tell you right now which system header files define those
questionable macros (I know what they mean, but I don't see what they
are doing there).  It seems that some glibc-based systems have taken
the right to hijack those names.  
Maybe Axiom might prefer to spell its macros all in caps, and probably
prefixed with AXIOM_ ...
--
forwarded from http://page.axiom-developer.org/zope/mathaction/address@hidden