From: "A.Appleyard" <A DOT APPLEYARD AT fs2 DOT mt DOT umist DOT ac DOT uk>
To: DJGPP AT DELORIE DOT COM
Date: Tue, 26 Mar 1996 11:16:18 GMT
Subject: -O3 says that longjmp may clobber variables
Message-ID: <11D54ED67C1@fs2.mt.umist.ac.uk>

  I have a big djgpp program, that compiled with -Wall with no remarks. I
recently compiled it with -O3 -Wall, and got warnings of this type:-

  main.cc:33: warning: variable `class buffer * C' might be clobbered by
`longjmp' or `vfork'
  macros.cc:397: warning: variable `class val *const this' might be clobbered
by `longjmp' or `vfork'

  Broeker AT physik DOT rwth-aachen DOT de referred me to the `-W' node of gcc.info,
which advised me to put `volatile' before the affected variables, which I then
did (except with the warnings about `this'), and recompiled with -O3 -Wall.
The above warnings did not go away, but merely became this type:-

  main.cc:33: warning: variable `volatile class buffer * C' might be clobbered
by `longjmp' or `vfork'

  and many new warnings of this type appeared:-
  main.cc:38: warning: passing `volatile char *' as argument 1 of
`strcmp(const char *, const char *)' discards volatile

  And how do I put `volatile' before the `this' of a class member function?

  I also got this new warning:-
  main.cc:37: warning: assignment to `volatile char **' from `char **' adds
cv-quals without intervening `const'
  What is a cv-qual?