From: Joe Buck <jbuck@synopsys.com>
To: egcs@cygnus.com
Subject: Re: Strange warning (variable might be clobbered by `longjmp' or `vfork')
Date: Sun, 31 Aug 1997 23:12:29 -0000 [thread overview]
Message-ID: <9709010239.AA21568@beeblebrox-84.synopsys.com> (raw)
In-Reply-To: 199708312248.WAA11022@chestnut.cygnus.com
[ setjmp warnings with exceptions ]
> The warning is correct and useful. It warns for a situation where programs
> using setjmp may fail at runtime because of how setjmp works.
>
> This warning may be triggered for C++ programs using the setjmp/longjmp
> exception handling support. However, this is clearly a bug in the sjlj EH
> support. We should not remove a useful and correct warning to work around
> bugs in the EH support. We should fix the EH support.
It is not clear to me that it represents an actual bug (that is, that in
the execution of the programs where we've seen these messages, that any
flow is possible that accesses the automatic variables being warned about
after setjmp catches a longjmp. The compiler issues the warning because
it cannot prove this; it may be being overly conservative.
I am not enough of a backend wizard to answer this question definitively,
but I feel we must answer it before releasing this sucker. STL programs
with -O and -Wall spew loads of warnings.
For example, cd to egcs-97XXXX/libstdc++/tests and say
gcc -c -O -Wall tmap.cc
on sparc-sun-solaris2.5.1
You will get the following. (the msgs about lock_instance and member
initializers are fixed by a patch I sent in before). The "may be used
uninitialized" messages all go away if exceptions are disabled. Almost
any use of the STL map template will give these messages.
So, are they real (can the variables in question be used uninitialized,
and can longjmp clobber them)?
/u/jbuck/egcs/include/g++/alloc.h: In function `static void * __default_alloc_template ::allocate(unsigned int)':
In file included from /u/jbuck/egcs/include/g++/tree.h:55,
from /u/jbuck/egcs/include/g++/map.h:30,
from tmap.cc:1:
/u/jbuck/egcs/include/g++/alloc.h:394: warning: unused variable `class __default_alloc_template ::lock lock_instance'
/u/jbuck/egcs/include/g++/alloc.h: In function `static void __default_alloc_template ::deallocate(void *, unsigned int)':
/u/jbuck/egcs/include/g++/alloc.h:417: warning: unused variable `class __default_alloc_template ::lock lock_instance'
/u/jbuck/egcs/include/g++/tree.h: In method `rb_tree ,select1st >,int_less,__default_alloc_template >::rb_tree(const struct int_less & = Compare())':
/u/jbuck/egcs/include/g++/tree.h:460: warning: member initializers for `unsigned int rb_tree ,select1st >,int_less,__default_alloc_template >::node_count'
/u/jbuck/egcs/include/g++/tree.h:462: warning: and `struct int_less rb_tree ,select1st >,int_less,__default_alloc_template >::key_compare'
/u/jbuck/egcs/include/g++/tree.h:514: warning: will be re-ordered to match declaration order
/u/jbuck/egcs/include/g++/tree.h: In method `rb_tree ,select1st >,str_less,__default_alloc_template >::rb_tree(const struct str_less & = Compare())':
/u/jbuck/egcs/include/g++/tree.h:460: warning: member initializers for `unsigned int rb_tree ,select1st >,str_less,__default_alloc_template >::node_count'
/u/jbuck/egcs/include/g++/tree.h:462: warning: and `struct str_less rb_tree ,select1st >,str_less,__default_alloc_template >::key_compare'
/u/jbuck/egcs/include/g++/tree.h:514: warning: will be re-ordered to match declaration order
/u/jbuck/egcs/include/g++/tree.h: In method `struct __rb_tree_iterator ,pair &> rb_tree ,select1st >,int_less,__default_alloc_template >::__insert(struct __rb_tree_node_base *, struct __rb_tree_node_base *, const struct pair &)':
/u/jbuck/egcs/include/g++/tree.h:431: warning: `struct __rb_tree_node > * tmp' might be used uninitialized in this function
/u/jbuck/egcs/include/g++/tree.h:431: warning: variable `struct __rb_tree_node > * tmp' might be clobbered by `longjmp' or `vfork'
/u/jbuck/egcs/include/g++/tree.h:435: warning: `struct pair * p' might be used uninitialized in this function
/u/jbuck/egcs/include/g++/tree.h:435: warning: variable `struct pair * p' might be clobbered by `longjmp' or `vfork'
/u/jbuck/egcs/include/g++/algobase.h:554: warning: `void * place' might be used uninitialized in this function
/u/jbuck/egcs/include/g++/algobase.h:554: warning: variable `void * place' might be clobbered by `longjmp' or `vfork'
/u/jbuck/egcs/include/g++/tree.h:440: warning: `struct __rb_tree_node > * p' might be used uninitialized in this function
/u/jbuck/egcs/include/g++/tree.h:440: warning: variable `struct __rb_tree_node > * p' might be clobbered by `longjmp' or `vfork'
/u/jbuck/egcs/include/g++/tree.h:428: warning: `struct __rb_tree_node > * p' might be used uninitialized in this function
/u/jbuck/egcs/include/g++/tree.h:428: warning: variable `struct __rb_tree_node > * p' might be clobbered by `longjmp' or `vfork'
/u/jbuck/egcs/include/g++/alloc.h:218: warning: `void * p' might be used uninitialized in this function
/u/jbuck/egcs/include/g++/alloc.h:218: warning: variable `void * p' might be clobbered by `longjmp' or `vfork'
/u/jbuck/egcs/include/g++/alloc.h:411: warning: `void * p' might be used uninitialized in this function
/u/jbuck/egcs/include/g++/alloc.h:411: warning: variable `void * p' might be clobbered by `longjmp' or `vfork'
/u/jbuck/egcs/include/g++/tree.h:431: warning: `struct __rb_tree_node > * tmp' might be used uninitialized in this function
/u/jbuck/egcs/include/g++/tree.h:431: warning: variable `struct __rb_tree_node > * tmp' might be clobbered by `longjmp' or `vfork'
/u/jbuck/egcs/include/g++/tree.h:435: warning: `struct pair * p' might be used uninitialized in this function
/u/jbuck/egcs/include/g++/tree.h:435: warning: variable `struct pair * p' might be clobbered by `longjmp' or `vfork'
/u/jbuck/egcs/include/g++/algobase.h:554: warning: `void * place' might be used uninitialized in this function
/u/jbuck/egcs/include/g++/algobase.h:554: warning: variable `void * place' might be clobbered by `longjmp' or `vfork'
/u/jbuck/egcs/include/g++/tree.h:440: warning: `struct __rb_tree_node > * p' might be used uninitialized in this function
/u/jbuck/egcs/include/g++/tree.h:440: warning: variable `struct __rb_tree_node > * p' might be clobbered by `longjmp' or `vfork'
/u/jbuck/egcs/include/g++/tree.h:428: warning: `struct __rb_tree_node > * p' might be used uninitialized in this function
/u/jbuck/egcs/include/g++/tree.h:428: warning: variable `struct __rb_tree_node > * p' might be clobbered by `longjmp' or `vfork'
/u/jbuck/egcs/include/g++/alloc.h:218: warning: `void * p' might be used uninitialized in this function
/u/jbuck/egcs/include/g++/alloc.h:218: warning: variable `void * p' might be clobbered by `longjmp' or `vfork'
/u/jbuck/egcs/include/g++/alloc.h:411: warning: `void * p' might be used uninitialized in this function
/u/jbuck/egcs/include/g++/alloc.h:411: warning: variable `void * p' might be clobbered by `longjmp' or `vfork'
/u/jbuck/egcs/include/g++/tree.h: In method `struct __rb_tree_iterator ,pair &> rb_tree ,select1st >,str_less,__default_alloc_template >::__insert(struct __rb_tree_node_base *, struct __rb_tree_node_base *, const struct pair &)':
/u/jbuck/egcs/include/g++/tree.h:431: warning: `struct __rb_tree_node > * tmp' might be used uninitialized in this function
/u/jbuck/egcs/include/g++/tree.h:431: warning: variable `struct __rb_tree_node > * tmp' might be clobbered by `longjmp' or `vfork'
/u/jbuck/egcs/include/g++/tree.h:435: warning: `struct pair * p' might be used uninitialized in this function
/u/jbuck/egcs/include/g++/tree.h:435: warning: variable `struct pair * p' might be clobbered by `longjmp' or `vfork'
/u/jbuck/egcs/include/g++/algobase.h:554: warning: `void * place' might be used uninitialized in this function
/u/jbuck/egcs/include/g++/algobase.h:554: warning: variable `void * place' might be clobbered by `longjmp' or `vfork'
/u/jbuck/egcs/include/g++/tree.h:440: warning: `struct __rb_tree_node > * p' might be used uninitialized in this function
/u/jbuck/egcs/include/g++/tree.h:440: warning: variable `struct __rb_tree_node > * p' might be clobbered by `longjmp' or `vfork'
/u/jbuck/egcs/include/g++/tree.h:428: warning: `struct __rb_tree_node > * p' might be used uninitialized in this function
/u/jbuck/egcs/include/g++/tree.h:428: warning: variable `struct __rb_tree_node > * p' might be clobbered by `longjmp' or `vfork'
/u/jbuck/egcs/include/g++/alloc.h:218: warning: `void * p' might be used uninitialized in this function
/u/jbuck/egcs/include/g++/alloc.h:218: warning: variable `void * p' might be clobbered by `longjmp' or `vfork'
/u/jbuck/egcs/include/g++/alloc.h:411: warning: `void * p' might be used uninitialized in this function
/u/jbuck/egcs/include/g++/alloc.h:411: warning: variable `void * p' might be clobbered by `longjmp' or `vfork'
/u/jbuck/egcs/include/g++/tree.h:431: warning: `struct __rb_tree_node > * tmp' might be used uninitialized in this function
/u/jbuck/egcs/include/g++/tree.h:431: warning: variable `struct __rb_tree_node > * tmp' might be clobbered by `longjmp' or `vfork'
/u/jbuck/egcs/include/g++/tree.h:435: warning: `struct pair * p' might be used uninitialized in this function
/u/jbuck/egcs/include/g++/tree.h:435: warning: variable `struct pair * p' might be clobbered by `longjmp' or `vfork'
/u/jbuck/egcs/include/g++/algobase.h:554: warning: `void * place' might be used uninitialized in this function
/u/jbuck/egcs/include/g++/algobase.h:554: warning: variable `void * place' might be clobbered by `longjmp' or `vfork'
/u/jbuck/egcs/include/g++/tree.h:440: warning: `struct __rb_tree_node > * p' might be used uninitialized in this function
/u/jbuck/egcs/include/g++/tree.h:440: warning: variable `struct __rb_tree_node > * p' might be clobbered by `longjmp' or `vfork'
/u/jbuck/egcs/include/g++/tree.h:428: warning: `struct __rb_tree_node > * p' might be used uninitialized in this function
/u/jbuck/egcs/include/g++/tree.h:428: warning: variable `struct __rb_tree_node > * p' might be clobbered by `longjmp' or `vfork'
/u/jbuck/egcs/include/g++/alloc.h:218: warning: `void * p' might be used uninitialized in this function
/u/jbuck/egcs/include/g++/alloc.h:218: warning: variable `void * p' might be clobbered by `longjmp' or `vfork'
/u/jbuck/egcs/include/g++/alloc.h:411: warning: `void * p' might be used uninitialized in this function
/u/jbuck/egcs/include/g++/alloc.h:411: warning: variable `void * p' might be clobbered by `longjmp' or `vfork'
next reply other threads:[~1997-08-31 23:12 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
1997-08-31 23:12 Joe Buck [this message]
1997-09-01 12:09 ` Jim Wilson
1997-09-01 12:23 ` John Carr
1997-09-01 15:32 ` Strange warning (variable might be clobbered by `longjmp' or`vfork') Toon Moene
1997-09-02 9:52 ` Strange warning (variable might be clobbered by `longjmp' or Joe Buck
1997-09-02 11:50 ` Jim Wilson
1997-09-02 12:20 ` Joe Buck
1997-09-02 15:24 ` Jim Wilson
1997-09-02 19:15 ` Jeffrey A Law
1997-09-02 19:32 ` Richard Henderson
1997-09-02 20:05 ` Jeffrey A Law
1997-09-03 13:09 ` Richard Henderson
1997-09-01 13:48 ` Wrong debug info on pc-linux-gnu ? Oleg Krivosheev
1997-09-02 6:14 ` Bernd Schmidt
1997-09-03 2:29 ` Strange warning (variable might be clobbered by `longjmp' or `vfork') Andreas Schwab
1997-11-01 21:24 ` Jeffrey A Law
-- strict thread matches above, loose matches on Subject: below --
1997-08-31 22:48 Jim Wilson
1997-08-31 2:07 egcs 970828 and X11 on linux/x86 H.J. Lu
1997-08-31 18:57 ` Strange warning (variable might be clobbered by `longjmp' or `vfork') Kamil Iskra
1997-08-31 1:23 Jim Wilson
1997-11-01 21:16 ` Jeffrey A Law
1997-08-26 15:53 Mike Stump
1997-08-26 13:14 Tobias Ringstrom
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