From: "Anthony.Appleyard" <MCLSSAA2 AT fs2 DOT mt DOT umist DOT ac DOT uk>
Organization:  Materials Science Centre
To: Eli Zaretskii <eliz AT is DOT elta DOT co DOT il>, DJGPP AT delorie DOT com
Date:          Mon, 16 Mar 1998 11:50:55 GMT
Subject:       Re: Clobbered
Reply-to: Anthony DOT Appleyard AT umist DOT ac DOT uk
CC: DJGPP AT delorie DOT com
Message-ID: <4AEC033B86@fs2.mt.umist.ac.uk>
Precedence: bulk

  On Fri, 13 Mar 1998, Anthony.Appleyard wrote:
> What the rules for deciding whether longjmp may `clobber' a particular local
> variable or a `*this'? (I never use vfork().)

  Eli Zaretski replied:-
> * A nonvolatile automatic variable might be changed by a call to `longjmp'.
> These warnings as well are possible only in optimizing compilation. ... The
> easiest solution is to declare the variable `volatile' (and have some
> sub-optimal optimization). ...

  In the affected program, one of the many `clobbered' complaints comes from
main():-
  main(int nargs,char**Arg){Subr*S; char*s,*t,*U,**arg; jmp_buf emacserror;
  int i,j,k,m,n,w,F; int ctrlc_old=__djgpp_set_ctrl_c(0); ...
  main.cc:49: warning: variable `volatile char * T' might be clobbered by
`longjmp' or `vfork'
    so I changed these two lines to this:-
  main(int nargs,char**Arg){Subr*S; char*s,*U,**arg; jmp_buf emacserror;
  int i,j,k,m,n,w,F; int ctrlc_old=__djgpp_set_ctrl_c(0); volatile char*T;

but this did not get rid of the warning but merely created two more warnings:-
  main.cc: In function `int main(int, char **)':
  main.cc:268: warning: passing `volatile char *' as argument 1 of
`strlen(const char *)' discards volatile
  main.cc:273: warning: passing `volatile char *' as argument 2 of
`strcpy(char *, const char *)' discards volatile
  main.cc:49: warning: variable `volatile char * T' might be clobbered by
`longjmp' or `vfork'